Surgery of the Reproductive Tract in Lamoids

CHAPTER 124 Surgery of the Reproductive Tract in Lamoids



Surgery of the reproductive tract in camelids includes most of the elective procedures as well as therapeutic surgical techniques considered for other domestic species. As the practice of theriogenology in lamoids has developed in recent years more information has become available on the specific considerations in reproductive surgeries in llamas and alpacas pertaining to anesthesia, surgical approach choices, and pre- and postoperative management. The objective of this chapter is to review the most important reproductive surgeries in lamoids, including laparoscopic techniques.



GENERAL CONSIDERATIONS


As for any surgery, complete physical examination and assessment of the patient should be performed whenever it is possible and is a necessity in compromised patients. This assessment should include at least determination of packed cell volume, total protein, complete cell count (CBC), and fibrinogen. Serum biochemistry may be indicated in some patients (geriatric, depressed, or severely compromised patients), which may require fluid therapy. A jugular vein catheter should be placed in any compromised animal. Elective surgeries should be deferred if the animal shows clinical signs of illness. An accurate estimation of body weight is very important for calculation of medication (sedatives and anesthetics) dosage.


For minor elective surgeries, fasting for 12 hours and water deprivation for 6 to 8 hours is recommended before anesthesia. For more involved surgeries such as ovariectomy or ovariohysterectomy and laparoscopic techniques, food and water should be withheld for 24 and 12 hours before surgery, respectively.


During anesthesia, the most commonly encountered problems in camelids are bradycardia, excessive salivation, bloat, regurgitation, and aspiration. In the recumbent animal the poll of the recumbent camelid should be elevated by 10 cm above the rostral portion of the oral cavity to prevent pooling of regurgitated material in the pharynx and allow the excess saliva to run down freely. Bradycardia can be managed by administration on atropine (0.02 mg/kg IV or 0.04 mg/kg IM). Excessive saliva or regurgitated material may be removed by suction. Placement of nasogastric tube may help to reduce bloating.


Presurgical antimicrobials are commonly used by several practitioners.



ANALGESIA AND ANESTHESIA


Healthy subjects are generally easy to anesthetize in the field. Problems arise when the patient is compromised. For these compromised patients injectable anesthesia may not be the most appropriate choice, and gas anesthesia in a hospital setup should be considered.



Local Anesthesia


The most common local anesthesia used in reproductive surgery is epidural anesthesia and local blocks. Although lumbosacral epidural anesthesia has been described by some authors, it is rarely used because it causes muscle weakness and presents the risk of cranial spread to T10-11. Epidural anesthesia is generally performed in the sacrococcygeal space or between the first and second coccygeal vertebrae and provides perineal analgesia without locomotion compromise. The intervertebral space is easily identified by palpation while moving the tail up and down. The skin is shaved and aseptically prepared. An 18-gauge, 1.5-inch needle is placed on dorsal midline with the bevel facing cranially and at a 60-degree angle to the tail head. The hub of the needle is filled with the solution and advanced until the solution is pulled into the epidural space.


The duration of analgesia depends on the drug used. In the case of 2% lidocaine (0.2 mg/kg with a maximum of 1 ml per 50 kg of body weight), onset of analgesia is seen 5 minutes after administration and lasts about 1 hour to 1½ hours. Administration of xylazine (0.1 mg/kg) provides up to 3 hours of anesthesia and the association of xylazine and lidocaine provides up to 6 hours of analgesia.


Local blocks are usually performed for abdominal surgeries with lidocaine 2% HCl. It is generally recommended to dilute this drug to 1% using isotonic bicarbonate or saline. The total dose should not exceed 4.4 mg/kg body weight (1 ml of 2% lidocaine per 5 kg of BW) to prevent lidocaine toxicity.



Sedation and Tranquilization


Sedation of the patient is accomplished easily by administration of the drug of choice intramuscularly. The most commonly used sedatives in lamoids are the alpha-2 agonists xylazine and medetomidine1 (Table 124-1). Llamas are more sensitive to these sedatives than alpacas. Analgesia and sedation are increased by combination with butorphanol. Acepromazine is occasionally used for sedation but should be avoided in compromised animals because of its hypotensive effects and lack of reversal agents.




General Anesthesia


An association that works well in the field for anesthesia lasting 20 to 30 minutes consists of a combination of xylazine (100 mg/ml), ketamine (1000 mg/10 ml), and butorphanol (10 mg/ml). This mixture is administered intramuscularly at the dose of 1 ml/50 lb in llamas and 1 ml/50 lb plus an additional milliliter for alpacas. In pregnant animals, this association can be used for induction at half dose or with xylazine (0.05–0.1 mg/lb SQ or IM) + butorphanol (0.03–0.06 mg/lb IM).


The most commonly used induction agent is ketamine. This drug has minimal effect on the cardiovascular system, does not depress reflexes, and provides some analgesia. The major problem is that it causes muscle rigidity and increased salivation. It is better used in combination with xylazine, xylazine and butorphanol, diazepam, or guaifenesin to improve muscle relaxation (see Table 124-1).


In pregnant animals (correction of uterine torsion or cesarean section), anesthesia is generally induced with propofol (3.5 mg/kg IV) and diazepam (0.5 mg/kg IV) or guaifenesin and maintained with isoflurane in oxygen.2 These drugs have minimal effect of the neonate. Propofol is rapidly redistributed and metabolized and diazepam has minimal placental transfer. Isoflurane is rapidly eliminated, making it well suited for cesarean section in most species.


In field practice and for rapid surgeries in healthy subjects the combination ketamine/xylazine is sufficient. The combination of butorphanol (0.1 mg/kg), xylazine (0.2 mg/kg), and ketamine (1.5 mg/kg IV) provides approximately 20 minutes of useful anesthesia for surgical procedures such as castration and testicular biopsy. I prefer to administer this combination IM. Ketamine may cause profound respiratory depression.


Triple drip (ketamine/xylazine/guaifenesin) can be administered to effect for longer duration surgeries, but anesthesia time should not exceed 1 hour. Maintenance of anesthesia can be accomplished by halothane or isoflurane in oxygen.


During recovery, the patient should be placed in sternal recumbency as soon as possible following surgery. The neck and head should be supported to prevent injury. Reversal agent should be administrated if the patient is still too sedated (see Table 124-1).



SURGERY OF THE MALE REPRODUCTIVE TRACT


Surgical procedures in the male lamoids include castration and vasectomy as well as procedures to relieve urolithiasis such as urethrotomy and tube cystomy.



Castration


Castration is the most commonly performed elective surgery in camelids. As for many species castration is indicated to prevent aggressive behavior and eliminate nondesirable males from the genetic pool. Castration may also be indicated in cases of testicular diseases.



Castration of the Normal Male


Much debate is ongoing about the most appropriate age for castration of lamoids. This is due to the effect of castration before puberty on bone growth and predisposition to arthritis. Castration at early age has been shown to delay closure of the long-bone physes, resulting in tall, straight-legged geldings and a predisposition to early onset of degenerative osteoarthritis. It is recommended that male lamoids be castrated no earlier than 15 months of age for alpacas and 18 months for llamas.3


Precastration considerations include thorough examination for testicular descent, lesions, and scrotal and testicular adhesions as well as evaluation of the male temperament. Presurgical administration of tetanus toxoid vaccination and antimicrobial therapy is recommended. Procaine penicillin G is generally given at 22,000 U/kg before castration and daily for 3 days.


Two techniques are used for castration of the male lamoid: scrotal and prescrotal. Prescrotal technique requires more time to complete, but is more esthetic and less painful.3,4



Scrotal technique.


This technique is performed on the male either in the standing position or in lateral recumbency.5,6 It is the author’s preference to use the standing procedures on llamas and lateral recumbency in alpacas as the latter tend to cush, which makes manipulation and surgery very difficult and presents a risk for contamination. For standing castration sedation and analgesia is obtained by using butorphanol alone with local scrotal and testicular infiltration of lidocaine5 or by administration of a combination of butorphanol and xylazine. Some practitioners prefer administration of an epidural, but this is generally not necessary. For recumbent patient castration a combination xylazine/ketamine or xylazine/ketamine/butorphanol is indicated. Local anesthesia of the scrotum is provided by injection of 1 to 2 ml of lidocaine 2% as a line block along the raphe median.


The technique is not different from that described for other species. The scrotum is prepared for aseptic surgery and an incision is made along the most ventral aspect of the scrotum by holding the testicle firmly into the scrotum to make the scrotal skin tight (Fig. 124-1). The extent of the incision is determined by the size of the testicles and is generally continued until the testicle and its envelopes protrude under pressure from the skin incision. The testicle is exteriorized and held with a towel clamp while the testicular cord is gently stripped from fat and connective tissue using a piece of gauze (Fig. 124-2). The testicle is removed using an emasculator (adult llamas) or after transfixation ligation of the spermatic cord with No. 0 chromic gut (llamas) or No. 2-0 polyglactin 910 (young llamas and alpacas) (Fig. 124-3).






Prescrotal technique.


This approach requires the animal to be in a dorsal recumbency position under general anesthesia.4 The animal is maintained in a frog-leg position by means of ropes or straps. Strict aseptic technique is critical to prevention of infection. The skin is incised on the ventral midline immediately cranial to the ventral base of the scrotum.


In the llama a 5-cm skin incision is located 2 to 3 cm cranial to the scrotum. The left testis is moved cranially by digital pressure, and a skin incision is made directly over it. The skin and subcutaneous tissues are incised to expose the parietal vaginal tunic. The tissue surrounding the tunic is bluntly dissected to free the testis and spermatic cord, which are then retracted out of the incision. The cord is ligated proximally using No. 2 chromic gut suture material and sharply incised distal to the ligature. The contralateral testis is exteriorized through the same skin incision by manipulation into the cranial position and under the penis using digital pressure and blunt dissection and incised in the same manner. Subcutaneous fascia is closed with absorbable suture (No 3-0 polyglecaprone or No. 2-0 polydioxanone) placed in a simple continuous pattern. The skin is closed with the same absorbable suture material in a continuous subcuticular fashion.


Postoperative care for castration includes antimicrobial therapy and confinement in a small pen for 24 hours. Topical antiseptic and fly spray are indicate under farm conditions. The animal should be observed for excessive bleeding or swelling, exudative discharge due to infection, and difficulty urinating. However, postcastration complications are rare, and excessive bleeding can be managed by scrotal packing with gauze. It is important to warn the client that some males may continue displaying copulatory activity even after castration.



Castration of the Cryptorchid Male


Cryptorchidism is relatively rare in lamoids but has been reported in llamas, alpacas, and vicunas. There are very few reports on surgical removal of the retained testis. Two approaches can be utilized: parainguinal approach7 or a laparoscopic approach (see under laparoscopic surgery).


The parainguinal cryptorchidectomy approach requires the animal to be in dorsal recumbency under general anesthesia. The inguinal area is prepared and draped for aseptic surgery. The inguinal canal is located by palpation and a 1-cm skin incision is made medial to the caudal border of the external inguinal ring and extended cranially 3 to 4 cm. The incision is continued carefully through all tissue layers into the peritoneum. The abdominal cavity is entered using two fingers and the retained testicle is identified by palpation of the area around the incision. The cryptorchid testicle lies usually just lateral to the vaginal ring. Once identified the testicle is grasped and brought up to the incision site. The spermatic cord is ligated with 2-0 polyglactin 910 and resected. The internal abdominal oblique muscle is closed with 0 polyglactin 910 in a continuous pattern. The fascia of the external abdominal oblique muscle is closed with 1 polyglactin 910 in a simple interrupted or simple continuous pattern. A subcuticular closure is provided by 2-0 polyglactin 910 in a simple continuous pattern, which apposed the skin edges. Postoperative care includes limited exercise and antimicrobial therapy for 5 days.



Vasectomy


Vasectomy is mainly used for the preparation of teasers for the induction of ovulation in camelidae for the purpose of scientific studies. However, because of its esthetic advantages some breeders may opt for this technique rather than castration to sterilize males that are undesirable for reproduction.3


Vasectomy can be performed in the llama in a sitting or standing position after sedation, but the dorsal recumbency is the preferred position in alpacas. The scrotal skin is prepared by clipping and surgical scrubbing. Surgical drapes are placed around the scrotum. A 2- to 4-cm vertical scrotal skin incision is made slightly medial on the cranial surface of the neck of the spermatic cord. The spermatic cord is freed by blunt dissection and exteriorized with the help of hemostatic forceps (Fig. 124-4). The vas deferens can be easily identified by palpation or visually by its white color and the presence of adjacent vein and artery. The vas deferens is exteriorized using forceps or a spay hook through a small nick made in the vaginal tunic. A 3-cm portion of the vas deferens is removed after ligating each end (Fig. 124-5). The vaginal tunic does not need to be sutured. The skin is sutured, and the same procedure is repeated on the other side. Excised tissue should be submitted for histologic confirmation.




Another approach to vasectomy is to make the incision near the inguinal canal. This technique provides an easier identification of the vas deferens, particularly in individuals that have a short testicular cord. A subcuticular suture provides closure of the surgical site. Alternatively, a 2-cm segment of the ductus deferens may be excised via standard laparoscopy using a forceps scissors8 (see discussion of laparoscopic surgery).



SURGERY OF THE FEMALE REPRODUCTIVE TRACT



Cesarean Section


Cesarean section is indicated if vaginal delivery is impossible. The most common causes of dystocia requiring cesarean section include failure of cervical dilation, uterine torsion, and fetal malpresentation. In alpacas, delivery by cesarean section may be indicated even if the fetus is dead because of the difficulty of manipulation and procedures such as fetotomy. Damage to the cervix or uterus is more likely to occur when trying to force manipulation of the fetus because of inadequate space or cervical dilation. The decision to proceed with a cesarean section should be made relatively quickly in order to improve the chances of fetal and maternal survival. If the size of the dam precludes transvaginal palpation, immediate cesarean section should be chosen.9


The health and degree of compromise of the parturient female and the fetus should be assessed. I recommend placing a jugular vein catheter in all females presented for dystocia. Females presenting with cardiovascular shock, dehydration, and hypotension should receive crystalloid fluids and nonsteroidal anti-inflammatory drugs. Presentation, position, and posture of the fetus may be determined by vaginal or rectal palpation. It is preferable to perform these examinations after epidural anesthesia. Viability of the fetus may be determined by transabdominal ultrasonography. However, in many cases there is no time to proceed with fetal evaluation.


Two approaches are utilized for cesarean section in lamoids: the ventral midline approach and the left paralumbar approaches.9,10



Ventral Midline Approach


The ventral midline approach has been suggested as the preferred approach for alpacas and llamas. This allows simple access to the abdominal cavity and complete exteriorization of the uterus with minimal hemorrhage. Anesthesia is generally induced with propofol and diazepam (0.5 mg/kg IV) or guaifenesin. Although some have used halothane, maintenance of anesthesia is usually provided by isoflurane in oxygen.11 The patient is placed in dorsal recumbency and the ventral midline is prepared aseptically. A midline celiotomy incision (25 cm in alpacas and 35 to 40 cm in llamas) is made through the skin, subcutaneous fat, cutaneus trunci muscle, and linea alba from the cranial border of the mammary gland extending cranially (Fig. 124-6). The uterus is identified by direct palpation and exteriorized from the abdomen.11


Sep 3, 2016 | Posted by in SUGERY, ORTHOPEDICS & ANESTHESIA | Comments Off on Surgery of the Reproductive Tract in Lamoids
Premium Wordpress Themes by UFO Themes