Before Admission

Before the horse is admitted to the hospital, the person responsible for the admission needs to consider:

• Admission time: booking a time slot for admissions may be wise. This ensures there are sufficient staff and time to admit the patient correctly and allow clients enough time to ask relevant questions [1].
  
• Medical history: make sure that all relevant medical history is attached to the admission documents so that all staff are aware of previous conditions that may affect the GA [4].
  
• Accommodation: ensure the horse has been allocated a suitable stable for their condition. There are many considerations to make when thinking about stabling:
  
  
  
  • Do they need to be near the recovery suite?
    
  • Will they require a stable in the intensive care unit (ICU)?
    
  • Are they stallions and therefore require a stable away from mares?
    
  • Do they need company?
  
  
• Admission documents: some practices now send out the basic documentation before the patient’s arrival; if this is the case, the client’s understanding should be checked thoroughly.
  
• Understanding the procedure: it is vital that the person responsible for the admission understands the procedure that is taking place so they can answer any questions the client may have [5].

Admission

Upon arrival, the client should be greeted in a friendly, welcoming way to ensure they feel comfortable. When admitting any patient, it is essential that the client does not feel rushed or unwelcome; this is especially relevant for surgical admission, as clients may be apprehensive about the procedure. The RVN must acknowledge why the client has come to the hospital, as the client will want to know that their horse will be cared for by the best team of people. When admitting horses, it is generally good practice to place the horse in a selected stable and then take the client to a quiet area away from the horse. This will reduce the chances of the client being distracted by the horse and will help them focus on the admission process. The admission process should include the following:

• Passport: The horse’s passport should be checked for several things:
  
  
  
  • Part II of Section IX is signed, ensuring that the horse is not eligible to enter the human food chain [6]. This information should be recorded on the practice computer system.
    
  • The microchip: this should be scanned and compared with the number in the passport, ensuring the correct horse is admitted. There has also been an increase in the number of people using one horse’s insurance against multiple horses meaning they only need one insurance policy for multiple horses that look the same. For this reason, all horses should have a microchip scanned at admission [7].
  
  
• Admission questionnaire: on admission, there should be some form of questioning to ensure that the horse is cared for in the best possible way. This questionnaire may have been sent to the owner before arrival; however, it should be checked with the owner to ensure no mistakes are made. The Ability Model assessment form is a good document to use for this. Please see Chapter 13 for further information.

Questions should include the following:

• 
  
  
  
  • – The horse’s usual diet: this can then be matched as closely as possible while the horse is at the practice. Some practices may require owners to bring food with them to ensure the horses’ diet stays the same, and some clients may prefer to do this regardless of practice policy.
    
  • – The horse’s typical routine: how is the horse kept at home? Is it used to being stabled?
    
  • – Current work level: finding out what type of work the horse is in and used for is essential to understanding the horse. If the horse is coming straight off the racecourse and is fit for racing, sudden changes to this could impact both its mental and physical well‐being.
    
  • – Vaccination and worming status: the horse’s vaccination status must be known. Some owners may not have kept their horse’s vaccinations up to date. When admitting a surgical patient, the horse must be up to date with tetanus. If the horse is not up to date with tetanus, it should receive a dose of antitoxin and start a course of tetanus vaccinations. It is also important to know the worming history of the horse, as this may have an impact on the GA if they have a heavy worm burden [8].
    
  • – The horse’s temperament: what is the typical character of the horse? Is the horse ordinarily quiet? Do they have behavioural problems? Does the horse get stressed in a stable? This is important, especially in the surgical patient, as if this is not known, it is hard to judge the horse post‐operatively [9].
    
  • – Behaviour: what is the horse’s behaviour like? Are they likely to bite, kick or rear? Could they cause harm to members of staff or other inpatients that get too close?
    
  • – Allergies: does the horse have any allergies that could cause issues while hospitalised? This is especially important if there are drug allergies, such as an allergy to penicillin.
    
  • – Relevant history: does the horse have any relevant history that is unknown to the practice?
    
  • – Concurrent illnesses that may affect the anaesthetic: for example, chronic lung infections, severe equine asthma (formally known as recurrent airway obstruction or RAO) or exertional rhabdomyolysis (see Chapters 10 and 13).
    
  • – Is the horse used to wearing a bit and a bridle?: it is good practice to handle unknown horses with a bridle, so identifying if a horse can wear a bridle is important.
    
  • – Contact details of the client: there must be correct contact details for the client so they can be contacted regarding their horse. It is also important to ensure the client has details about the practice and understands how to contact the practice out of hours.

• Consent – For full details on consent, see Chapter 3. It may be the responsibility of the RVN to gain consent for surgical procedures; this should come after the vet has had an in‐depth conversation regarding the procedure and associated risks [10]. Although an RVN can gain consent from a client, the overall responsibility for informed consent lies with the vet. Consent for an anaesthetic must be obtained from the owner or someone acting on the owner’s behalf [10]. Before the owner signs the consent form, they should be fully informed of the potential consequences of anaesthesia/surgery and its potential risks. The surgical outcome should be discussed at length, so the owner is fully informed of the risks of the surgery and the risks that the anaesthetic may pose to the horse. The owner should have time to process whether they would like to proceed [10]. The vet should determine whether the client has processed the information and is fully informed of the potential risks.
  
• GA risks are covered in detail in Chapter 10; however, the primary considerations include the risk of myopathy, neuropathy and fracture following the GA. Myopathies and neuropathies are caused by long periods of recumbency, compression of the nerves and muscles and poor perfusion. The most common myopathy occurs when the triceps muscle is not pulled forward adequately when the horse is in lateral recumbency. Generally, myopathies are more painful for the patient due to ischaemic muscle damage. Neuropathies occur due to nerve compression, stretch, contusion, or transection, which can occur following surgical trauma or patient positioning compression of the nerve. This can happen if the patient is put into an abnormal position under GA, for example, overextension of the limbs; neuropathies are not as obviously painful as a myopathy but can still cause lameness and an inability to move the affected limb [11].
  
• Labelling: once all paperwork is complete, the horse should have identity tags attached to its headcollar and put into the mane. This will ensure that the horse can be identified correctly. All items left with the horse should be clearly labelled to ensure that they are not misplaced.
  
• Weight: anaesthetic doses are calculated based on body weight. Therefore, obtaining an accurate weight for the patient before GA is important. The most accurate way to do this is to use an electronic weighbridge. If a weighbridge is unavailable, a weigh tape can be used, but these do not tend to be as accurate, so they are less ideal [12].

Post‐Admission

After the client leaves, a complete clinical examination should occur; this may be done by an RVN or vet, depending on practice policy. All clinical parameters should be assessed (see Chapter 17). Emphasis should be put on the cardiovascular and respiratory systems. The musculoskeletal system should also be assessed to check for pre‐existing lameness. If the initial assessment highlights any areas of concern, these should be investigated prior to anaesthesia. This may require further diagnostic tests to be performed, such as electrocardiography (ECG), radiography, ultrasonography, haematology and biochemistry. The decision to perform further diagnostic tests will be at the discretion of the case vet. Blood samples may be taken for haematology to check for any underlying diseases and ensure the horse is fit for a GA.

Typically, equine patients being admitted for surgery are admitted the day before surgery; this allows the horse time to settle and adjust to the surroundings; some horses will have travelled long distances or maybe unsettled travellers. Admission, the day before surgery, also ensures that the practice has time to carry out the necessary preoperative checks. However, this may not be the case for several reasons:

• The horse is an emergency
  
• The client does not want the horse to stay or cannot afford for the horse to stay for extra time
  
• Practice policy
  
• A minor procedure that does not require the horse to be admitted to the practice for a more extended period

Minor Surgery

Minor surgery generally includes minimally invasive surgeries with a low risk to the patient’s health and welfare. This may be performed under standing sedation or GA [13].

Common minor surgeries may include:

• Sarcoid removal
  
• Standing splint bone removal
  
• Keratoma removal
  
• Pedal bone scrap

Standing Surgery

Standing surgery is a procedure that is performed under local anaesthesia and standing sedation. Procedures using this technique can be classified as minor, but some are also major surgeries [13].

Common standing surgeries include:

• Urogenital: cystotomy to remove uroliths
  
• Laparoscope: ovariectomy (removal of ovary/ovaries), nephrosplenic space closure, nephrectomy (removal of kidney), cryptorchidectomy (removal of a retained testicle – this can be performed standing or under GA via a laparoscopic technique if the testicle is in the abdomen)
  
• Upper airway and sinus surgery: tieback and or Hobday, sinus trephination, sinus flap
  
• Skin mass removal: melanoma removal, sarcoid removal, lumpectomy
  
• Orthopaedic: splint bone removal, lag screw placement, joint flush
  
• Dentistry: tooth removal, minimal invasive transbuccal extraction (MTE)

GA

A GA is carried out for any surgeries that require the horse to be fully unconscious for the procedure; for more information on GA, refer to Chapter 10. Horses carry a high mortality rate compared to humans and small animals; because of this, a GA must be used only when necessary to carry out a procedure [11].

Common surgeries completed under GA include [12]:

• Tenoscopy: keyhole surgery entering a tendon sheath
  
• Arthroscopy: keyhole surgery entering a joint space
  
• Fracture repair: bone repair using screws and/or plates
  
• Annular ligament desmotomy (ALD): the cutting of the ligament to create more room for the tendon to move
  
• Penile surgery: partial or complete resection
  
• Castration: removal of testicles

When preparing for any surgical procedures, it is important that the RVN is organised and understands the procedure that is due to happen; the following should be considered for all surgeries:

• Pain management: managing pain in horses can be difficult and varies from breed to breed. Certain breeds of horses and donkeys are more likely to mask signs of pain due to their nature as prey animals. It is useful to use multimodal analgesia for procedures. This usually involves the use of non‐steroidal anti‐inflammatory drugs (NSAIDs) and opioids, depending on the procedure. Pain scoring can be a valuable tool to use in the perioperative period. Each practice will have a specific pain scoring method to assess a patient’s pain level; the pain scoring should be derived from a validated system; all staff members must use the same system. Pain scoring can ensure that a patient’s pain level is managed sufficiently. If the pain score is high and the level of pain relief is insufficient, the RVN’s job is to highlight this to the vet [11].
  
• Antibiotics: the use of antibiotics prior to surgery is a controversial subject; there are now many routine surgeries that may not require antibiotics, especially clean surgeries such as arthroscopies. The use of antibiotics for surgical cases will always be a practice‐led discussion and should factor in the practice’s infection rates and the best evidence base available; this should be reviewed regularly, as well as looking at protocols for patient preparation and surgical cleaning, using resources such as The British Equine Veterinary Association (BEVA) ProtectMe toolkit, can also help with this decision‐making process [14] (see Chapter 6 for more information).
  
• Equipment: all surgical instrumentation and equipment should be prepared in advance depending on the surgery and requirements of the vet (see Chapter 11 for more information). The RVN should check that any auxiliary equipment is working and that all surgical equipment is sterilised prior to the surgery commencing [4].
  
• Communication: with any surgery, good communication is essential. The RVN is part of a large surgery team, and all team members should have good lines of communication to prevent human errors from occurring [9] (see Chapter 2 for more information).

Once all these points have been discussed as a team and a surgical plan has been created, the horse can be prepared for surgery. This will include the following:

Starvation

The starvation of surgical patients is a much‐debated topic, with some guidance set at starving for 6–12 hours prior to surgery. After the patient has metabolised the anaesthetic drugs, food is slowly introduced post‐anaesthetic. Traditionally, starving equine patients before GA has been suggested to reduce diaphragmatic splinting and vena cava compression by an otherwise full gastrointestinal tract (GIT) [11]. This reduction during recumbency (particularly dorsal recumbency) is hoped to preserve pulmonary functional residual capacity (FRC), alveolar ventilation and venous return during GA [11]. However, there is a lack of evidence to support the starvation of equine patients prior to GA. Evidence suggests that starving horses increases circulating catecholamines (catecholamines are important in stress responses [15], and high levels can cause high blood pressure or hypertension). Another reason for not starving prior to GA is that it may increase the chance of post‐operative ileus and/or caecal impactions. This has led to some hospitals now not having a starvation period. Specific, evidence‐based guidelines for the starvation of equine patients prior to GA are not available at the time of writing. However, the following guidance can be considered when deciding on a starvation protocol [11]:

• Access to clean, fresh water should be allowed up until the time of premedication.
  
• Restricting access to concentrates and large meals of forage for around four to six hours prior to premedication might be prudent as a starting point to limit gut fill and the development of tympany. This may contribute to limiting increases in intra‐abdominal pressure.
  
• It is difficult to justify restriction for patients who have true ab lib access to grazing or conserved or ensiled forages.
  
• Allowing access to food right up until the point of premedication would require a thorough mouthwash, especially if an endotracheal tube is to be placed.
  
• Alternatively, access to food could be restricted one to two hours prior to anaesthesia. This may help to address the problem of food in the oral cavity while mitigating against the detrimental effects of restricting food intake.

If access to food is to be restricted, the patient should be put in a stable containing nonedible bedding such as shavings or cardboard. Whichever starvation protocol is used within the practice, there are some instances where starvation is generally avoided regardless [12]:

• Foals: foals should not be starved as they could become dehydrated and hypoglycaemic, and this could cause complications during and after surgery.
  
• Donkeys and some native pony breeds: these patients carry a high risk of hyperlipemia. When these types stop eating, i.e. are starved, their body goes into a state of ‘negative energy balance’ (more energy is used up than is being taken in). When this happens, the body tries to use stored fat deposits as a source of energy [16]. This results in free fatty acids circulating to the liver to be converted to glucose for use by the body. Control of this system is hormonal and should get shut down again. However, donkeys and small ponies cannot efficiently turn off this fat release, and fat levels soon build up in the circulation. Fat levels can be measured by testing the blood for triglycerides. Large amounts of fat cause the liver and kidneys to degenerate and fail, and eventually, all the organs in the body fail. The result is irreversible organ damage and death [17].

Table 12.1 identifies some possible advantages and disadvantages of starvation versus non‐starvation of equine patients before a GA. As previously stated, there are arguments for either, which should be decided upon using the best evidence‐based practice and statistics available [12].

Some surgeries require starvation to facilitate access to the surgical site, for example, a cystotomy. Under GA, the patient may need to be put into the Trendelenburg position (this is a term used to describe when the horse’s head is lower than the body) to access the bladder. Other surgeries will require extended periods of starvation to enable a procedure to take place. Patients undergoing elective laparoscopy may be required to have a starvation period of between 24 and 48 hours [12]. This reduces the ingesta in the colon and cecum, allowing the surgeon access to the upper caudal abdomen.

It is vital to remember that horses do not require water removal before a GA.

Shoe Removal and Foot Preparation

Shoes should be removed before GA to reduce the risk of injury to the patient and to protect the floor of the knockdown box from damage. The feet must then be pared and thoroughly scrubbed clean and, after induction, covered with rectal sleeves prior to hoisting into the theatre to prevent contamination [3]. If shoe removal is not possible, the shoes can be taped up with adhesive tape before induction.

Scrupulous preparation is essential for surgery involving the foot or a structure close to the foot [3]. Bacterial numbers can be significantly reduced by removing the superficial hoof surface, for example, paring the feet with a hoof knife, applying a povidone‐iodine scrub and using a 24‐hour povidone‐iodine soak. However, bacterial populations can persist after these disinfection techniques [4]. Chlorhexidine gluconate could be considered for pre‐surgical foot preparation, as chlorhexidine has a residual activity against bacteria and is not inactivated by organic material, unlike povidone‐iodine. This, along with paring the feet before surgery, could be a useful and effective cleaning technique, although there is currently no empirical evidence to support this. Regardless of the cleaning technique, a foot dressing should be applied after cleaning, then covered with an empty drip bag, and secured with an adhesive bandage to keep the area clean and dry [3].

Grooming

The horse should be groomed thoroughly to prevent contamination of the theatre. Some horses, especially those with long coats and feathers, may require bathing to facilitate asepsis [3]. The mane should be plaited if long, and the tail should be tied up and covered with a bandage or rectal sleeve.

Site Identification

The surgical site must be identified with the vet before surgery and documented in the relevant places according to practice policy. Best practice may include having standard operating procedures (SOPs) for routine procedures. Diagrams and explanations of the clipping and prepping process could be provided to ensure this is standardised throughout the hospital to minimise human error.

Clippers

When using clippers for surgical skin preparation and intravenous (IV) catheter placement, the recommended blade size is 40. Previously, it was thought that 50 blades were suitable as they clipped the hair closer to the skin. However, these blades can clip too closely to the skin, sometimes resulting in post‐operative skin abrasions and acute dermatitis.

When clipping the patient, the blades must be flat to the skin and used gently. Clipping too vigorously can damage the skin, causing abrasions that increase the risk of bacterial colonisation from bacteria such as Staphylococcus aureus; this type of bacteria is commonly found in normal skin and only causes an issue if the skin becomes damaged [12].

Clipper blades must be cleaned between patients to prevent cross‐contamination. Diseases such as dermatophytosis (ringworm) and lice are easily passed from patient to patient by inadequate cleaning and disinfection of clipper blades. The clipper blade cleaner used must be fungicidal, virucidal and bactericidal, and act as lubrication for the clipper blades. If the blades are not adequately lubricated, they can cause excess tissue drag and damage the patient’s skin. Blades must be changed frequently, as blunt blades can cause skin trauma. Clipper blades should be sent off regularly for routine sharpening [1].

The surgical site should be clipped as much as possible before GA to minimise anaesthetic time. Equine patients are not ideal candidates for GA due to their large size. Clipping the day before surgery is considered controversial; some research suggests that the skin trauma caused by clipping causes residual skin bacteria to come to the surface and increases the risk of a surgical site infection (SSI). The hair protects the patient’s skin surface, often shielding it from dirt [18]. Removing the hair the day before surgery and leaving the skin open to a contaminated, stable environment may lead to an increased risk of an SSI. However, it has also been suggested that clipping the night before and the minimal risk this poses to SSIs is outweighed by the benefits of reducing anaesthetic time. When the patient is clipped, will depend on individual practice policies, which should be linked to the best available evidence‐based research [19].

When clipping for a surgical procedure, there should be a circumference of at least 5–10 cm around the patient’s surgical site where possible. In some instances, such as young Thoroughbreds that are going to the horse sales, a smaller clip patch or none at all may be required to ensure that it is less visible when the horse is sold; this may be requested by the owners/trainers; this is a decision to be made by the vet.

IV Catheter Placement

Vascular access should be secured before any equine patient is anaesthetised [2]. This ensures that the anaesthetist has consistent IV access throughout the procedure, and this increases the safety of the patient and all theatre personnel. A wide‐bore catheter is usually placed around the time of premedication. Please see Chapter 17 for further information on IV catheter placement. The catheter should be placed into the left jugular vein if the horse is positioned in dorsal recumbency or the uppermost vein if the horse is positioned in lateral recumbency [3].

Tail Bandaging

The application of a tail bandage aids in reducing microorganisms and contaminants entering the surgical theatre space; it also helps to ensure the tail does not contaminate the surgical site when moving the horse out of the theatre at the end of surgery and when recovering. Tail bandages come in a range of types. They can be a reusable, clean tail bandage, crepe bandage or self‐adhesive bandage; whichever is chosen, it should be appropriately placed so that it does not interfere with the blood supply to the tail [2].

Mouth Cleansing

Rinsing the horse’s mouth is vital to prevent the patient from aspirating food material during endotracheal tube placement [3]. A large dental syringe can be used for this, and the water should be warm. Mints or a small amount of mint oil can be added to the water to flavour it and make it more palatable to the patient. This will make the experience more positive for the patient.

Padded Headcollar

A leather padded headcollar should be applied to equine patients prior to induction. Leather is less likely to cause trauma, such as friction burns, when compared to nylon‐webbing material [2]. The padding on the headcollar protects the superficial nerves near bony prominences from the metal rings on the headcollar. This helps to reduce the chance of the patient developing facial paralysis following anaesthesia. However, removal of the headcollar following induction is the only way to prevent this entirely.

Surgical Safety Checklist (SSC)

The World Health Organization (WHO) has encouraged the use of SSCs to decrease errors and increase teamwork and communication in surgery [20]. Several human studies have shown a significant reduction in surgical‐related morbidity and mortality (between 43% and 62%) following the implementation of and adherence to SSCs. These SSCs are designed to minimise/erase human factors (human factors are those things that affect an individual’s performance). Research by Oxtoby et al. [21] suggests that 80% of adverse events are primarily related to human factors. Factors that the use of an SSC may eliminate include [22]:

• Operating on the incorrect horse or incorrect limb
  
• Having the horse positioned in an incorrect way
  
• Having the wrong surgical kit
  
• Not having a surgeon present
  
• Severe allergic reaction

The benefits of an SSC may arise from the opportunity for the team to pause for a moment and communicate in a busy setting, which encourages the sharing of collective responsibility within the surgical team. An SSC should be a simple checklist of instructions that are carried out at three intervals throughout the surgical period and should include the following considerations [20]:

Before the horse is induced:

• Has the identity been confirmed?
  
• Has consent for the procedure been obtained?
  
• Is the surgeon aware?
  
• Is the site clipped?
  
• Has the patient had its pre‐op drugs?
  
• Has the patient been groomed?
  
• Have the feet been cleaned?
  
• Has the mouth been washed?
  
• Has the tail bandage been applied?
  
• Any allergies?
  
• Any expected issues with intubation?

Before skin incision:

• All staff members identify themselves with name and role
  
• Confirm the patient’s name and procedure
  
• To the surgeon:
  
  
  
  • Are there any extras required?
    
  • How long will the procedure take?
    
  • Are there any concerns regarding blood loss?
  
  
• To the anaesthetist
  
  
  
  • Do you have any concerns with the anaesthetic?
  
  
• Nursing team
  
  
  
  • Has the equipment been sterilised?
    
  • Are there any known equipment issues?

Before the patient goes into recovery:

• Verbal communication of the procedure taking place
  
• Completion of the swab and instrument count verbalised
  
• For any samples taken during surgery, the patient details and test requirements should be read aloud
  
• Whether any equipment issues need addressing
  
• The verbalisation of the recovery and treatment plan [11]

A SSC should always be read aloud with the whole room pausing to listen and answer when appropriate; just using it as a tick list is not appropriate. If one person ticks these during the surgery, it will not prevent adverse events from happening. For more information on human factors or SSCs, please refer to VetLed and the WHO [22, 23].

Sedation Considerations

Sedation prior to GA is covered in detail in Chapter 10. Commonly used sedative drugs include the following:

• Alpha 2 agonists:
  
  
  
  • Xylazine
    
  • Romifidine
    
  • Detomidine
  
  
• Opioids:
  
  
  
  • Morphine
    
  • Butorphanol (counteracts morphine)
  
  
• Phenothiazines:
  
  
  
  • Acepromazine

A deeper level of sedation is usually required for standing surgery due to the horse being conscious. The surgeon may have to get themselves in dangerous positions to operate. Different sedation protocols are needed for different procedures, and the right sedation for the right procedure must be selected. A sedation plan should be made when discussing the procedure with the surgeon [15]. A combination of IV, intramuscular and constant‐rate infusions may be used. Xylazine is rarely used in standing surgery, as it is short‐acting, so it does not give a good enough level and depth of sedation even for short procedures [15].

Constant‐Rate Infusion (CRI)

For any procedures that are going on for some time or that use loud, noisy equipment, a CRI is typically a good method of administering sedation. It is created using a bag of saline spiked with a sedative (typically detomidine). It allows for a continuous delivery system of sedation to the patient to keep the patient on a level sedation plane without the patient transitioning between light and deep sedation, which can be a problem with ‘top‐up’ sedation. CRIs are administered IV and require the following preparation [15]:

• IV catheter placement
  
• 500 ml bag of saline
  
• Giving set
  
• Detomidine 0.1–0.6 ug/kg (1.25 ml per bag) rate; 1 drop/s
  
• Xylazine 0.69 mg/kg, rate; 3 drops/s (if requested by the vet for use)

Local Anaesthesia

Local anaesthesia is essential for many surgeries; using anaesthesia locally in the area that is being operated on can reduce the amount of analgesia used, reduce the chance of wind‐up or a chronic pain state developing and ensure that the horse has a more comfortable post‐operative experience. It can also make a standing procedure safer for the surgeon as the horse cannot feel discomfort during the surgery. Types of local anaesthesia used include [15]:

• Nerve blocks: local anaesthetic is injected around a nerve or neurovascular bundle to remove the sensation to a particular area; the area should always be checked to make sure that desensitisation has occurred before the surgery starts [15].
  
• Line block: subcutaneous lidocaine is injected along the incision site. Relatively straightforward, it is often used when the surgical site is away from a nerve or nerve bundle. The block can be easier on the animal if a longer needle is inserted through the last injection site.
  
• Ring block: a specific type of field block. The entire limb is encircled with subcutaneous local anaesthetic to reach all nerves in the limb.
  
• Regional IV blocks: a tourniquet is placed on the limb, and local anaesthetic is injected into a vessel below the tourniquet. The local anaesthetic is diluted to the level that it pushes out of the vasculature and into the tissues [15].

Types of Local Anaesthetic

The most common local anaesthetics used are as follows [15]:

• Mepivacaine hydrochloride (Intra‐Epicaine)
  
• Bupivacaine hydrochloride (Marcaine)
  
• Prilocaine hydrochloride (Citanest)
  
• Lidocaine hydrochloride (Lignol)

Lidocaine with adrenaline is not for use in the skin as it has a vasoconstrictive effect and can cause tissue necrosis. Lidocaine with adrenaline increases the duration of anaesthesia; when used for local infiltration, its vasoconstrictive effect is an added benefit as it provides a bloodless operating field. Because of this, it is more commonly used in laparoscopic surgeries for desensitising internal structures and local infiltration during sinus surgery, throat surgery and perineal surgery [12].

When preparing local anaesthesia for a procedure, the correct type should be selected to prevent errors from developing. More information can be found in Chapter 10.

Epidural Anaesthesia

Epidural anaesthesia is most commonly used in standing procedures for rectovaginal fistula repairs in mares post‐foaling and any procedures in the perianal area. The caudal epidural space is most frequently used; it is found by lifting the tail, creating a divot that can be palpated. Xylazine is the preferred drug for perineal analgesia; its analgesic effect lasts longer than detomidine and romifidine and is thought to last around 2.5 hours [24]. Morphine can be used for an epidural but is more commonly used to manage severe pain or painful long‐term procedures. A long‐term epidural can be achieved by placing an epidural catheter into the caudal epidural space. If using an epidural in horses, it is important not to overdose as this can affect the sensory and motor function of the hindlimbs [12]. It is important for RVNs to know the landmarks for this procedure when assisting the vet, as they will be involved with patient preparation. Figure 12.1 shows the different areas where an epidural can be placed; the first position is between the sixth lumbar vertebrae L6 and the first sacral dorsal spinous process S1; this is used for catheter placement for continuous caudal epidural anaesthesia (technically demanding, infrequently performed). The second position is between the first and second coccygeal vertebrae (C1 and C2). Needle placement for caudal anaesthesia perpendicular direction. Once the needle is inserted, anaesthesia administration can occur, or a catheter can be introduced over 10–30 cm into the epidural space. After placement of the catheter, the needle can be removed and the catheter can be secured to the skin [24].

Scrubbing patterns

The Circular Scrub Technique (Target or Bullseye)

Also known as the singular or concentrative pattern, historically, RVNs have used the circular scrub technique, which has often been favoured in the veterinary profession. Some evidence suggests the back‐and‐forth technique is superior to the circular scrub technique. This will vary on the particular area of the patient being prepared.

The circular motion technique starts with a centre point (where the incision is to be made) and moves outwards away from the centre point in a circular motion to the clipped edge. Once the edge is reached, or the swab is contaminated, it must be discarded [27].

Excessive pressure is unnecessary and will abrade the skin, causing inflammation and the incision may be more prone to healing complications if the dermal layer is compromised. It will also cause the native skin microbes to rise to the surface.

Figure 12.2 shows the two scrub patterns used in the equine patient when preparing for a surgical procedure [27].

Skin Preparation for Wounds

This section will concentrate on preparing wounds for surgical procedures. For information on preparing wounds that do not require surgery, please see Chapter 13. Hydrogels are helpful to place into the wound to prevent further dirt, hair and contaminants from tracking deep into the wound when clipping and prepping around the area as it creates a barrier and rehydrates the wound. A hydrogel protects the wound, keeps it moist and aids wound healing [12]. PI can be used for preparing contaminated, chronic and acute wounds as it has a broad antimicrobial spectrum, lack of resistance, efficacy against biofilms and is tolerated well [30].

If appropriate, a PI solution can be used on contaminated wounds; iodine scrub should only be used on intact skin. This can be difficult when preparing a large area of skin with wounds and intact skin. The PI scrub is used to lift the dirt and grease from the skin; without its use, the preparation of the area can take longer. When preparing two separate areas due to intact skin and multiple wounds, the wound should be covered with sterile saline‐soaked swabs, and then intact skin should be prepped with PI scrub [30]. This is then rinsed with sterile saline, and then the skin and wounds are prepared with a PI solution. PI has low cytotoxicity compared to CG, which has high cytotoxicity. The PI solution can be used to cleanse contaminated wounds before closure. A ratio for wound irrigation of PI solution (10%) should be applied in a 0.1–0.2% concentration. s. PI 7.5% scrub contains detergent and is unsuitable for cleansing wounds [31].

Saline is widely used for cleansing clean wounds and is often preferred due to its isotonic nature, which makes it non‐toxic to tissues. This characteristic helps maintain cellular integrity and prevents additional tissue damage during wound care. Unlike tap water, saline does not contain various compounds that might irritate the wound or disrupt the osmotic balance.

In contrast, tap water can be beneficial for the initial cleaning phase of heavily contaminated wounds. Its abundance and cost‐effectiveness make it a practical choice for flushing out debris and contaminants. However, tap water should be used cautiously because it is not isotonic and may contain minerals and other substances. After the initial decontamination with tap water, switching to an isotonic solution like saline is advisable to promote optimal healing conditions and avoid potential tissue irritation.

It’s important to note that tap water should only be used when a constant supply of potable drinking water is available, ensuring it is free from harmful microorganisms. The primary advantage of tap water lies in its affordability and ready availability, making it a convenient option for the initial management of contaminated wounds [31].

Skin Marking

Sometimes, it is necessary to mark the surgery site with staples preoperatively. If this needs to be done, the skin should be clipped, shampooed rinsed and an initial skin prep should be carried out before staple insertion. The staples are then included in the skin preparation for surgical site preparation. Care should be taken when scrubbing, as it is easy to loosen the staples [12].

Bacterial Colonisation

Recolonisation of the surgical site will gradually occur after antiseptic preparation. The time this takes will depend on several factors, including, but not limited to, antiseptic preparation used, length of surgery time and type of drape. It is essential to know how these factors can affect the efficacy of the products used, as re‐colonisation will increase the chance of SSIs. The occurrence of an SSI can cause major post‐operative problems for a patient and can be caused by the patient, the surgical team, as well as the environment [30]. To minimise this risk, correct surgical attire must be worn when scrubbing a patient (see Chapter 11 for more information). RVNs should remain bare below the elbows, and hats and masks should be worn from the point of scrubbing to the end of closure to minimise airborne microorganisms from staff.

SSIs have various causes staphylococcus aureus is the most common bacteria associated with SSIs and is derived from the patients own skin flora.[12]. If the patient’s skin is damaged from excessive scrubbing or clipping, this encourages bacteria to come to the surface, and increases the risk of a SSI developing. Plastic drapes are more likely to increase the risk of SSIs; however, iodophor‐impregnated incise films are thought to reduce the risk, having shown fewer colonies of bacteria developing in the studies conducted [30]. Hair shafts and sweat glands go deep within the dermis; the longer a surgical site is left covered by a drape, the more likely the patient is to sweat and cause bacteria to resurface from the hair shaft or sweat gland. It is almost impossible to penetrate deep within the hair follicles. Prepping the surgical site just before the incision is made helps to prevent SSIs. If alcohol is used as a rinsing agent, it must be allowed to dry before the surgical incision is made. If diathermy or a laser is being used, alcohol should be avoided as it can cause burns [25].

Physiology of Wound Healing

Wound healing is broken down into four stages: haemostasis, inflammatory, proliferation and maturation; these stages occur in an overlapping sequence of events that result in the repair of the damaged tissue. The healing process is initiated as soon as the injury occurs [12].

• Phase 1: haemostasis (cessation of bleeding): This phase happens immediately following the injury and is completed in hours. The first response of the body to the initial injury is to stop the flow of blood. The blood vessels constrict to help reduce the blood flow, and then platelets stick together to help seal the break in the wall of the blood vessel. Strands of fibrin adhere to the platelets and start to form a clot, and this clot helps to reduce blood loss.
  
• Phase 2: inflammatory: Occurs during the first 6–8 hours following injury [1]. The inflammatory phase begins shortly after the initial injury when the blood vessels leak transudate, which causes localised swelling. Activation of platelets and the presence of fibrin in the blood clot attracts neutrophils to the area [2]. The neutrophils function to clear up bacteria, necrotic tissue and foreign material. Neutrophils release inflammatory mediators that, in turn, attract macrophages into the tissue [2]. The macrophages perform the final stage of debridement before the next stage begins.
  
• Phase 3: proliferation: This phase normally occurs from day three following [1]. Granulation tissue develops at this stage to fill in the wound bed. Healthy granulation tissue is bright red in colour and even in appearance. Fibroblasts lay down a collagen matrix, and endothelial cells lay down new blood vessels (angiogenesis). Epithelial cells migrate over the top of the wound in a process known as epithelialisation. The wound starts to contract at this stage, and this process alone can close the wound by up to 30% [2]. Gradually, collagen fibres and scar tissue are laid down, and the wound progresses to the next stage.
  
• Phase 4: maturation: This phase occurs from 14 days after injury and can last for 12 months [1]. A collagen framework is laid down where a new dermal matrix is formed [3]. Fibroblasts help to improve tensile strength by remodelling the dermal tissues. Granulation tissue matures into scar tissue, and re‐epithelisation occurs [3]. This scar tissue is the body’s natural way of healing from an injury; however, it has only 80% of the original tissue tensile strength one‐year post‐injury [3].

Healing Times of Different Tissues

The basic physiology of wound healing remains the same for various tissue types: haemostasis, inflammation followed by proliferation and maturation. However, the length of time may differ considerably for the type of damaged tissue and the extent to which that tissue has been affected. Muscles and tendons generally take longer to heal due to the structural demands that are placed on them. These tissues require healing to a high level of strength and function. Muscle tissue should heal quickly, and immobilisation can help to allow strength to develop in the scar tissue [2]. The healing process for tendon and ligament injuries is slow, and rushing this process will only cause delays to the whole healing process. A tailored rehabilitation programme will often be needed for these types of injuries. Tissues in the GIT, urinary and reproductive tract heal more rapidly than the skin. The colon has the slowest healing time compared to the urinary bladder, which heals the fastest [2]. RVNs must understand the healing times of different tissues to ensure that rehabilitation plans and nursing care are tailored to the individual patient and are as effective as possible. Table 12.2 shows the average healing times for different tissue types; these times can be affected by external factors such as age, health status and SSIs [25].

Wound Healing Complications

RVNs should carefully monitor any wound, be it surgical or otherwise, for complications. Factors to look out for include [32]:

• Excessive amounts of purulent exudate.
  
• Erythema (reddening) of the skin edges and surrounding area
  
• Oedema (swelling) of the wound and the surrounding area
  
• Haematoma
  
• Pain on palpation

The wound should be assessed carefully and treated accordingly if any of these factors are identified.

Types of Wounds

Wound types can be divided into open or closed wounds [12].

Classification of Wounds

A wound can be classified as follows:

• Clean wounds: these are the simplest of wounds, providing no complications occur. Clean wounds are created under aseptic conditions. For example, surgical incisions produced via scalpel blade causing minimal tissue damage. These ‘clean’ wounds do not enter body cavities such as the respiratory, gastrointestinal, or urogenital tracts.
  
• Clean‐contaminated wounds: surgical incisions made into one of the body cavities mentioned previously are classified as ‘clean‐contaminated’ wounds. Although these wounds are prepared under the same aseptic conditions as clean wounds, the entry into one of the tracts introduces a level of contamination, making them fall into the ‘clean‐contaminated’ category.
  
• Contaminated wounds: wounds obtained via accident, or a traumatic event are classed as ‘contaminated’. These wounds often have a degree of environmental debris within them, for example, mud in a laceration wound on a tarsus.
  
• Dirty wounds: dirty wounds are those that are infected and exude purulent material. Traumatic ‘contaminated’ wounds can fall into this category if improper initial treatment is not sought.

Understanding the type and classification of the wound being dealt with is essential, as this has implications for the equipment and methods required for treatment.

Wound Closure Methods

The classification of the wound will impact the best management approach. There are different types of wound closure. These are as follows:

• Primary closure or first intention healing is the best choice of closure for clean wounds. Wounds closed by primary closure must be free from foreign material to give the wound the best chance of healing without complication [12].
  
• Delayed primary closure can be used for contaminated wounds which benefit from initial lavage and debris removal and then given a few days for any inflammation and swelling to reduce. The wound would then be closed after further lavage and possible debridement, generally done before the granulation process commences. Please see Chapter 13 for more information on wound lavage and debridement.
  
• Secondary closure can be used to surgically close wounds that have been left to develop a healthy granulation bed.
  
• Second intention healing is where wounds are not surgically closed but left to heal by granulation tissue formation and contraction. This method is often used for large wounds over areas of high movement, for example, the gluteal or pectoral muscles [3].

Many factors could cause a delay in wound healing; some of these complications can derive from the patient itself, for example, self‐mutilation, systemic disease or other factors such as surgical complications, infection or poor wound management. The RVN plays a significant role in monitoring and assessing the progress of the wound during the healing process; it is essential to recognise complications as they arise to allow for a change in management as soon as possible, should it be required. Please see Chapter 13 for more information on the factors that delay healing [12].

Drains

Drains can be a helpful addition in wound management and healing in wounds where excess fluid accumulation is anticipated, predisposing the patient to seroma formation or where the infection is present, and drainage is beneficial. However, close monitoring and post‐operative care are essential in ensuring the selected drain works correctly and, therefore, does not adversely affect the wound healing process [12]. Equine patients occasionally present with large, traumatic, open wounds, which can create large areas of dead space. Dead space develops between tissues after the disruption of subcutaneous connective tissues. This is undesirable because the fluid that typically fills this void provides a prime medium for bacterial growth [4]. Drains are often used in these situations to prophylactically reduce the chances of excess fluid accumulation. A drain should be sutured proximally, traverse the wound and exit through a small incision separate from the wound [3].

Types of Drains

Drains are classified by their action, which is either passive or active [5]. Passive drains use gravity and capillary action to allow fluid to drain freely from the wound. Active drains require ‘active’ suction to remove fluid or exudate. An active drain can be intermittently drained via a syringe or a chamber‐like device for continuous drainage. Table 12.3 shows the different drains available for use in equine patients, the mechanisms by which they work and the advantages and disadvantages of each.

Figure 12.3 shows a Penrose drain on the left and a Jackson‐Pratt drain on the right. Figure 12.4 shows a Jackson–Pratt drain placed in a large wound surgically repaired under GA.

Management of Drains

As mentioned previously, drains require careful post‐operative monitoring and care. Things to monitor for are as follows [12]:

• Pain
  
• Increased exudate
  
• Swelling around the drain insertion
  
• Patient interference

Drains should be checked daily to ensure that they are still working correctly and are still patent. They should also be cleaned daily. During cleaning, the drain should be moved slightly to break any seal formed between the drain, the exudate and the surrounding skin [3].

Drains, although often placed to prevent problems, may occasionally cause further complications such as:

• Some patients may react to some of the materials drains are made of, for example, latex.
  
• Bacteria may migrate up the drain lumen and contaminate the healing wound.
  
• Exudate draining freely from passive drains can cause skin scalding and irritation if the area below is not kept clean and dry. A barrier cream or emollient can be applied as necessary to help prevent this secondary complication.
  
• Where possible, the drain should be bandaged in place with a sterile dressing to absorb fluid from the end of the drain [2].

If complications of drains are not identified and addressed promptly, the outcome of the wound healing and, therefore, the patient’s comfort and healing time can be significantly impacted.

Timing of drain removal is essential, as premature removal of the drain will be counterproductive unless complications have been encountered. Drains should not be left in situ for an excessive length of time. Drains are usually left in place for 24–48 hours but longer if drainage persists [3]. Active drains allow for a more precise assessment of drainage reduction. In comparison, passive drains rely on a subjective visual assessment of drainage reduction and improved exudate appearance. When the drain is removed, the skin suture is cut and the drain is pulled out swiftly [2]. It is important to pull the drain out in the correct direction, for example, with gravity, to avoid pulling the most contaminated end of the drain back through the wound.

Passive drains
Type of drain	Material	Action and function	Advantage	Disadvantage
Gauze drains	Fine mesh gauze	Gravity Capillary action	Economical Step‐by‐step removal	Adherence of fibrin clots to gauze Risk of gauze fraying
Latex Penrose drain	Soft, pliable latex	Gravity Capillary action Mostly extraluminal drainage	Economical Many applications	Kinks easily Not applicable in body cavities No suction possible, collapse It may facilitate ascending infection
Silicone Penrose drain	Soft, pliable, nonreactive silicone	Capillary action Mainly extraluminal drainage	Minimal tissue irritation Use in latex‐sensitive patients Radiodense marker	Not applicable in body cavities No suction possible
Rubber tube drains	Red Rubber	Gravity Capillary action	Because of relative stiffness, it is rarely compressed or occluded Suction possible	Increased foreign body reaction
Sheet drain (‘well [wave] drain’)	Waved sheet of stiff red rubber	Gravity Capillary action	Because of relative stiffness, it is rarely compressed or occluded Can be cut to size	Increased foreign body reaction
Flexi‐drain	12 parallel joined silicone tubes of 3‐mm diameter	Gravity Capillary action	Good drainage along the tubes where they join Suction possible Can be cut to size	Mainly extraluminal drainage
Active drains
Type of drain	Material	Action and function	Advantage	Disadvantage
Redon drain	Round, multi‐fenestrated polyvinyl chloride (PVC) with non‐fenestrated extension tube	Intraluminal drainage	Excellent for evacuation of fluids from body cavities No collapse Used for lavage and drainage	Stiff Fenestrations may occlude
Jackson‐Pratt drain	Flat silastic, multi‐fenestrated drain with a non‐fenestrated extension	Intraluminal drainage	Excellent for evacuation of fluids from body cavities Minimal tissue irritation	Expensive The suction function is only possible when implanted in an airtight space
Blake drain	Round or flat pliable silastic drain with longitudinal slits and protected spaces with a non‐slit extension	Drainage through the longitudinal slits	Multifaceted slits reducing the risk of occlusion Minimal tissue irritation Radiodense marker No collapse possible	Expensive Voluminous The suction function is only possible when implanted in an airtight space
Trocar catheter	Round, multi‐fenestrated tube Inserted with blunt trocar into body cavity	Drainage of body cavity Intraluminal drainage	Minimal tissue irritation Used for fluid drainage and lavage	Relatively easy dislodgement and interruption of adequate drainage Occlusion

Skin Grafts

Bone Structure and the Response to Injury

Figure 12.5 shows the structure of an equine long bone; for more information on the structure and function of bone, see Chapter 4. However, this figure can be used as a reference point throughout this section.

Bone structure can renew and remodel to repair its surface; this is called bone activation. Bone can regenerate itself rather than healing through the production of scar tissue like a tissue wound [1]. Once the bone structure has healed, it can resume 100% of its former strength again. The three main components of bone include:

• Bone osteogenic cells (osteoblasts, osteoclasts and osteocytes)
  
• Organic matrix (collagen)
  
• Minerals

Cortical bones are characterised by their compact structure and higher density levels, compared with cancellous bone, which is less dense and features a more porous composition[33].

Anatomical Orientation of a Fracture

Anatomical terms are often used to describe the location of a fracture:

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