Monitoring patient vital signs should begin during triage and continue well through the postoperative recovery phase. Each patient will require continued evaluation based on its affected organ system or systems.
Types of Trauma
Common ocular traumas include proptosed globes, corneal lacerations, or foreign bodies. It is essential for any trauma patient that the cardiovascular system be stabilized prior to having general anesthesia induced. In addition, normal intraocular pressure must be preserved to avoid further damage to the affected eye. (Techniques for ophthalmological procedures are discussed in Chapter 19.)
Tracheal trauma, although not very common in small animals, can be caused by bite wounds, impaled objects, vehicular accidents, diagnostic procedures such as transtracheal wash, misguided jugular venipuncture attempts, over inflation of and/or excessive movement of endotracheal tubes while in the trachea (especially in the feline patient and during dentistry procedures), and improper use of rigid stylets during endotracheal intubation (Fig. 29.2).
Crushing or nonpenetrating wounds may be caused by blunt force trauma or choke collars. These patients may present with subcuticular emphysema or in a state of collapse and cyanosis if there is sufficient obstruction of the airway. While a rapid prep is performed for a tracheostomy, oxygen may be delivered by inserting a large-bore catheter or needle directly into the lumen of the trachea distal to the obstruction. Injuries not causing life-threatening obstructive compromise may be stabilized and supplemented with oxygen via a tight-fitting mask or oxygen hood if the patient’s overall assessment indicates that there is no current or preexisting organ dysfunction and if the patient is not in an anxious state due to the stress of attempting to ventilate adequately.
Approximately one-third of the patients with blunt forelimb or hindlimb trauma additionally incur thoracic injury. Pulmonary lesions usually continue to worsen within 24–36 hours. Thoracic traumas include the following:
Preoxygenation of any patient with known or suspected pulmonary lesions can be achieved with a tight-fitting mask and should ideally be left on for 5 minutes prior to induction. Even flow by oxygen is advantageous if the patient is stressed by a mask. Small dogs and cats in severe respiratory distress may decompensate even with minimal handling. The use of an oxygen cage or an induction chamber while gathering the necessary supplies to immediately capture the airway will provide an oxygen rich environment.
Burn injuries/smoke inhalation
The presence of soot in the nostrils, facial burning and dyspnea should hasten the responder’s effort to initiate lifesaving measures. The immediate concerns with these patients will be protection of the airway, venous access, fluid resuscitation, and pain management. A sterile endotracheal tube (low pressure high volume cuff) lubricated with sterile lidocaine gel should be used. Propofol, thiopental, etomidate, benzodiazepines, and inhalant agents do not provide any analgesia. Patients should be provided with 100% oxygen at the earliest possible moment. Pain management could include adjunctive agents such as lidocaine and ketamine along with an opioid. Opioids can cause dose-dependent respiratory depression so careful monitoring is necessary following administration.
Burn patients are often presented with the additional trauma of smoke inhalation. Dermal burns seen in human medicine appear to have inflammatory cells sequester in the lungs thus causing more pulmonary edema than simple smoke inhalation (Carrol and Martin 2007). Regardless of the extent and severity of the burns, once the primary patient survey has been completed analgesia should be provided (Fig. 29.3). These patients should always be assessed while providing supplemental oxygen, and the pronecessary equipment to capture the airway should be nearby in case sudden need arises.
Hypovolemia in these patients is due to the fluid loss at the site of injury as well as vasoconstriction. Keep in mind that with the fluid loss, decreased protein contributes not only to decreased oncotic pressure but renders greater availability of the analgesic agents because the majority of the agents used are protein bound. It is ideal to start with 1/4 to 1/2 dose of the agent and titrate to effect.
Blunt force trauma
Blunt force abdominal trauma may involve several organs as in splenic/liver ruptures, kidney/bladder rupture or avulsion or bowel perforation.
Penetrating wounds are more easily recognized but do not always reveal the damage to underlying body systems. Impaled objects should be stabilized until the patient has been fully evaluated, and body systems should be supported until diagnostics have been performed.
Bite wounds can cause penetrating wounds as well as crushing/tearing injuries. Bite wounds may actually penetrate a body cavity, thus allowing a portal for bacterial infection.
Before premedicating any trauma patient, take into consideration the analgesic agents previously administered during the triage/assessment period, the cardiovascular stability of the patient and the effect of the agent on all body systems. As previously mentioned, the trauma patient may require decreased dosages of analgesics due to altered physiological response. Titrating to effect is usually the best plan. Consider the procedure to be performed and the anticipated pain associated with the surgery when making drug selections. Anesthesia should be designed to incorporate multiple agents, thus decreasing the adverse effects of any sole agent. Ideally, these agents should have the ability to be antagonized or reversed should the need arise. The goal with premedication should be to provide analgesia as well as decrease the amount of induction agent required.
Anticholinergics may or may not be indicated and should not be “routine” because there is no “routine” with a traumatized individual. Anticholinergics will increase heart rate, thus increasing cardiac workload and oxygen consumption. If there is an underlying systolic dysfunction, an anticholinergic can decrease myocardial perfusion by decreasing diastolic filling time due to an increased heart rate.
Agents capable of increasing intracranial/intraocular pressure such as ketamine should be avoided in those patients with cranial and or ocular trauma.
In many fragile trauma patients a neuroleptanalgesic may be the best option for induction (Table 29.1). Combining an opioid with a benzodiazepine tranquilizer provides a safe, titratable protocol that is gentle on the cardiovascular and pulmonary systems. Many critical patients can be intubated under this protocol in a calm, quiet atmosphere. Both the opioid and the benzodiazepine can be antagonized if necessary. At the very least, a neuroleptanalgesic technique will drastically reduce the amount of additional induction agent needed to get the patient intubated. If additional drug is needed, a low dose of propofol may be added to allow for intubation. Propofol can cause profound respiratory depression and/or apnea and can cause myocardial depression and subsequent decrease in cardiac output and arterial blood pressure. Propofol’s side effects must be considered prior to its use.