Anesthesia for patients with head trauma.

Patients undergoing anesthesia soon after head trauma are at great risk for further neural damage during the anesthetic, especially if the head injury is severe or the anesthetic technique is suboptimal. Secondary complications of the anesthetic that are often lethal include hypoventilation, increases in ICP, airway obstruction, and brain-stem herniation. Anesthetic management of patients with head injury must include intravenous induction with barbiturates or narcotics, smooth endotracheal intubation, controlled ventilation with oxygen, and minimal amounts of inhalational agents. It is important to position the patient so that jugular veins are not occluded, in about 10 degrees head up position, and to avoid inducing patient coughing and straining. Recovery from anesthesia should be quiet and rapid, with the maintenance of a clear airway and the use of as little depressant medication post-operatively as possible. Oxygen should be provided.     

Pulmonary function in dogs after intercostal thoracotomy: comparison of morphine, oxymorphone, and selective intercostal nerve block

A thoracotomy was performed at the left 5th intercostal space in 24 dogs. Dogs were assigned to 4 groups of 6 dogs each. Postoperative analgesia was administered as follows: group 1--control, no analgesia; group II--morphine (0.5 mg/kg of body weight); group III--oxymorphone (0.1 mg/kg); group IV--selective intercostal nerve block with bupivacaine HC1. Respiratory rate, minute volume (VE), and arterial blood gases were measured during the recovery period. Ventilation-perfusion mismatch was estimated by calculation of the alveolar-arterial oxygen tension difference. Arterial carbon dioxide tension (Paco2) in the control and selective intercostal nerve block groups remained within the normal range and did not differ significantly (P less than 0.05) between groups. During the first 60 to 90 minutes after surgery, Paco2 tension was increased significantly (P less than 0.05) in the groups given morphine and oxymorphone. Hypoventilation in the groups given narcotics resulted from significant reductions (P less than 0.05) in the respiratory rate and VE and produced significant (P less than 0.05) respiratory acidosis and hypoxemia. Three dogs in the groups given narcotics had a panting response that resulted in increased respiratory rates and VE. This response did not improve alveolar ventilation in these dogs, which was evidenced by increased Paco2 values. Hypoventilation, respiratory acidosis, and hypoxemia in the groups given narcotics improved significantly with time, presumably because of drug clearance. Values for alveolar-arterial oxygen tension difference indicated moderate ventilation-perfusion mismatch secondary to anesthesia in all groups; however, significant differences (P less than 0.05) between the groups were not observed.     

Neuromuscular blocking agents in equine anesthesia

In summary, neuromuscular blocking agents can be used safely and to advantage in equine anesthesia. Muscle-relaxant use in equine anesthesia has been helped by the development of new relaxants such as atracurium, which has a reliable and reproducible duration of action. There are certain cases that benefit particularly by the use of relaxants but their use is not limited to these cases. These cases involve horses that experience persistent movement and hypotension during anesthesia, are undergoing ophthalmic or abdominal surgery or fracture repair, or are severely ill. Horses receiving muscle relaxants during anesthesia require mechanical ventilation, and neuromuscular blockade should be monitored with a peripheral-nerve stimulator.     

Results of the confidential enquiry into perioperative small animal fatalities regarding risk factors for anesthetic-related death in dogs

OBJECTIVE: To identify major risk factors associated with anesthetic-related death in dogs. DESIGN: Case-control study. ANIMALS: 148 dogs that died or were euthanized within 48 hours after undergoing anesthesia or sedation and for which anesthesia could not be reasonably excluded as a contributory factor (cases) and 487 control dogs that did not die within 48 hours after undergoing anesthesia or sedation (controls). PROCEDURES: Details of patient characteristics, preoperative evaluation and preparation, procedure, anesthetic and sedative agents used, monitoring, postoperative management, and personnel involved were recorded. Mixed-effects logistic regression modeling was used to identify factors associated with anesthetic-related death. RESULTS: An increase in physical status grade, urgency of the procedure, age, or intended duration of the procedure; a decrease in body weight; anesthesia for a major versus a minor procedure; and use of injectable agents for anesthetic induction and halothane for maintenance or use of inhalant anesthetics alone (compared with use of injectable agents for induction and isoflurane for maintenance) were associated with increased odds of anesthetic-related death. CONCLUSIONS AND CLINICAL RELEVANCE: The results suggested that specific factors could be associated with increased odds of anesthetic-related death in dogs. Knowledge of these factors should aid the preoperative assessment and perioperative management of dogs undergoing anesthesia and sedation.     

Anesthesia for severe mitral and tricuspid regurgitation.

Anesthesia for mitral or tricuspid regurgitation should be designed to maintain cardiac output by decreasing systemic and pulmonary vascular resistance to aortic and pulmonary outflow, respectively, and by carefully preserving venous return. A moderate increase in heart rate may be helpful with mitral regurgitation; bradycardia should be avoided. Isoflurane, halothane, or opioid anesthesia is preferred.     

Combined spinal-epidural anesthesia in a dog

OBJECTIVE: To report use of combined spinal epidural anesthesia for tail resection and surgical exploration of the pelvic canal and the perineal-pararectal area in a dog. ANIMAL: A 4-month-old, 13 kg male Collie dog. METHODS: Under inhalant anesthesia, an epidural catheter was threaded through a Tuohy needle at L5-L6. Then using a Whitacre spinal needle bupivacaine and fentanyl were administered in the subarachnoid space at L6-L7 level. Fifteen minutes later, morphine was administered epidurally. Bupivacaine and morphine were administered epidurally 4 hours after the subarachnoid injection. RESULTS: No cardiorespiratory response to surgical stimulation was observed. Postoperative analgesia was satisfactory, and the catheter was removed 30 hours later. No complications or neurologic sequelae occurred before discharge or were noted 10 days later. CONCLUSION: Combined spinal-epidural anesthesia provided excellent intraoperative anesthesia and perioperative analgesia in a dog undergoing surgery involving the pelvic canal. CLINICAL RELEVANCE: Combined spinal-epidural anesthesia can be performed in dogs, and its use should be considered in major surgeries caudal to the diaphragm, as the epidural catheter allows cranial extension of the block, providing excellent intraoperative anesthesia and perioperative analgesia.     

Digital semiological anesthesia in horses: technique and elements of interpretation

Digital semiological anesthesia in horses: Technique and elements of interpretation. Semiological anesthesia of the pes is used during examinations for lameness in horses. Recent research data on the distal digital, distal interphalangeal articular, and podotrochlear intrathecal nerve blocks indicate that they are less than specific when considered in isolation. They should be used in combination to localize pain in the pes. A positive response to anesthesia of the distal interphalangeal articulation could also indicate that the source of the pain was in the podotrochlear apparatus or the dorsal part of the sole. Podotrochlear anesthesia also anesthetizes the dorsal part of the sole and, later, the distal interphalangeal joint. Distal digital anesthesia affects a large palmar area of the hoof and extends dorsally. Overall, basic research provides little support for the practical uses of semiological blocks.     

Transcervical insemination techniques in the bitch.

The benefits of using endoscopic TCI for frozen semen come from being able to achieve the same or better results without the need and risks of general anesthesia and surgery. The ability to do all fresh and chilled inseminations this way will certainly improve conception rates without the owner having to make a decision about exposing their bitch to the risks of anesthesia and surgery. The other potential uses open up a whole new field for canine theriogenology. Above all, the client response to the technique is overwhelmingly positive. At times the learning process will be discouraging, but the end result is worth the effort. The endoscope should not be treated as something special for frozen semen insemination but should be used at every opportunity in order to develop experience and expertise in all situations.     

Standing musculoskeletal surgery.

Indications for performing orthopedic surgery on the standing horse include inability to tolerate general anesthesia, risk of worsening an injury during recovery from anesthesia, and cost. The surgeon should be aware that performing surgery in the standing horse can be more demanding and require more experience than the same procedures when the time and convenience of general anesthesia are available. Improved sedatives and analgesics have allowed more latitude because the horses now are more tolerant than when older agents were used. Common sense should be applied to each situation before the decision is made to do a procedure, because every horse and problem is unique.     

Anesthesia of the sighthound

The sighthounds are an ancient group of dog breeds that have been selectively bred for high-speed pursuit of prey by sight. Probably as a consequence of this selection process, these dogs have a number of idiosyncrasies that can potentially adversely affect their anesthetic management. These include (1) nervous demeanor which can lead to stress-induced clinical complications, such as hyperthermia; (2) lean body conformation with high surface-area-to-volume ratio, which predisposes these dogs to hypothermia during anesthesia; (3) hematological differences such as a higher packed cell volume and lower serum protein compared with other dog breeds which may complicate interpretation of preanesthetic blood work; (4) Impaired biotransformation of drugs by the liver resulting in prolonged recovery from certain intravenous anesthetics, especially thiopental; and increased risks of drug interactions. Safe anesthetic management of sighthounds should include sedative premedication and appropriate use of analgesic drugs to minimize perioperative stress. Thiopental, or any other thiobarbiturate, should not be used in these dogs. Propofol, ketamine/diazepam combination, and methohexital are recommended alternative intravenous anesthetics. Avoid coadministration of agents that inhibit drug biotransformation, such as chloramphenicol. Inhalation anesthesia using isoflurane is the preferred anesthetic maintenance technique. Core body temperature should be monitored closely and techniques to minimize hypothermia should be employed both during anesthesia and into the recovery period.     

Management of airway difficulties during induction of general anesthesia in an American miniature horse with dwarfism

This report describes previously unreported upper airway abnormalities encountered in a 5-month-old American miniature horse colt presented for elective surgery. Caution should be exercised when administering general anesthesia or heavy sedation to individuals of this breed that present with multiple congenital abnormalities.     

Anesthesia of the intensive-care patient

Mortality rates for healthy horses undergoing general anesthesia for routine procedures have been reported to range from 0.6% to 1.8%; these numbers increase as high as 5% when systemically ill horses are included in calculations. Anesthesia of intensivecare equine patients should first include critical assessment of the need for versus risk of anesthetic intervention. When general anesthesia cannot be avoided, the following measures should be considered and addressed throughout the perianesthetic period: preanesthetic assessment and cardiopulmonary stabilization, perianesthetic oxygen supplementation and ventilatory support, vigilant monitoring of the cardiopulmonary system, supportive therapy (ie, inotropic agents, fluids) to promote adequate cardiac output, use of perioperative adjunct systemic and/or regional agents to reduce inhalant requirements, close observation and assistance during recovery, and postoperative analgesia.     

Use of the Anderson Sling suspension system for recovery of horses from general anesthesia

OBJECTIVE: To describe a sling recovery system (Anderson Sling) for horses and to evaluate outcome of high-risk horses recovered from general anesthesia by a sling. STUDY DESIGN: Retrospective study. SAMPLE POPULATION: Horses (n=24) recovered from general anesthesia. METHODS: Complete medical and anesthetic records (1996-2003) for horses recovered from general anesthesia using the Anderson Sling system were evaluated retrospectively. Information retrieved included anesthetic protocol, surgical procedure, recovery protocol, recovery time, and quality of the recovery. Horses were recovered from anesthesia supported by the Anderson Sling in a standing position within a traditional padded equine recovery stall. RESULTS: Twenty-four horses had 32 assisted recoveries; 31 events were successful. No complications associated with the sling or recovery system protocol occurred. One horse was intolerant of the sling's support and was reanesthetized and recovered successfully using head and tail ropes. CONCLUSION: The Anderson Sling recovery system is an effective and safe way to recover horses that are at increased risk for injury associated with adverse events during recovery from general anesthesia. CLINICAL RELEVANCE: The Anderson Sling system should be considered for assisted recovery of equine patients from general anesthesia.     

Propofol: application in veterinary sedation and anesthesia

Propofol can be used for sedation, induction of anesthesia, and maintenance of anesthesia in small animal patients. In all these situations recovery from its effects is typically rapid and smooth. The drug should be administered slowly, intravenously, to minimize the negative cardiac and respiratory effects seen after rapid bolus administration. The currently available formulations do not contain preservatives, and sterile technique should be strictly followed during its use. Propofol can be used for induction of anesthesia in patients with preexisting disease with minimal delays in recovery. It does not cause excitement at low doses so is also useful for sedation of patients undergoing nonpainful procedures such as radiological examination. This review focuses on the diverse clinical applications for propofol in a small animal practice including indications, recommendations, and contraindications as well as a discussion of the controversies that surround its use.     

Idiopathic cecal rupture in foals after anesthesia for gastric endoscopy

Cecal rupture has been reported as a complication of tape-worm infestation or parturition in horses. Often it occurs with no apparent predisposing factors. Spontaneous rupture on the medial surface of the cecum occurred in 2 of 19 foals, 12 to 24 hours after gastric endoscopy. The sites of rupture were identical in both foals. Rupture occurred despite prior deworming, withholding of food and water before anesthesia, and care in induction of anesthesia and recovery. Surgeons should be aware of the potential of cecal rupture in horses anesthetized for elective surgery.     

Limited approach to the right flank for placement of a duodenostomy tube

A new enterostomy tube placement technique is described for provision of nutrients into the duodenum. Placement of the duodenostomy tube (d-tube) is performed through a limited right flank approach under sedation and local anesthesia. Seven client-owned animals (three dogs and four cats) requiring enteral nutritional support were selected for d-tube placement. Patients were fed via the d-tube for two to 28 days. Complications included discomfort when manipulating and exteriorizing the duodenum, discomfort with bolus feedings, local cellulitis, and tube site infection. All complications resolved without further incident. This technique should be considered in patients that are not good candidates for prolonged general anesthesia or esophageal or gastric feeding, or patients being mechanically ventilated.     

Cecal rupture in foals — 7 cases (1996–2006)

The objective of this study was to identify risk factors and describe clinical signs in 7 foals with cecal rupture; none of the foals survived. Six foals had undergone general anesthesia; 5 for orthopedic procedures. Six of the foals were receiving nonsteriod anti-inflammatory drugs. Most foals started showing colic signs on day 2 after surgery, preceded in 3 cases by dullness. Cecal rupture occurred between 4 hours and 2 days after the first signs of colic were noticed. Intestinal motility was decreased or absent in all foals for which it was recorded.Foals undergoing general anesthesia should be closely monitored for any sign of dullness, prolonged recumbency, reduced fecal output, and signs of abdominal discomfort for 3 days postoperatively, especially in cases following orthopedic surgery. If any of the above occurs, cecal impaction should be considered as a differential diagnosis. A prompt exploratory laparotomy may be a reasonable diagnostic option before the cecum ruptures with fatal consequences.     

The effects of perioperative hypothermia and the duration of anesthesia on postoperative wound infection rate in clean wounds: a retrospective study

OBJECTIVE: To determine the effects of hypothermia and duration of anesthesia on the infection rate in clean wounds in dogs and cats. STUDY DESIGN: Retrospective clinical study. SAMPLE POPULATION: Seven hundred seventy-seven dogs and cats undergoing clean surgical procedures. METHODS: Records of animals prospectively evaluated for postoperative wound infection were retrospectively evaluated for the prevalence of perioperative hypothermia. Body temperatures during the perioperative period and the duration of surgery and anesthesia were recorded. Data were analyzed to identify differences between animals with infected and uninfected wounds and multiple logistic regression modeling was used to evaluate the independent contribution of risk factors to the incidence of postoperative wound infection. RESULTS: No statistically significant differences were found in the analysis of temperature data between animals with infected and uninfected wounds. Duration of anesthesia was significantly greater in animals with wound infections (P = .01). Multiple logistic regression modeling identified duration of anesthesia as a risk factor for postoperative wound infection independent of the duration of surgery. CONCLUSIONS: In animals with clean surgical wounds, mild perioperative hypothermia is not a significant risk factor for postoperative wound infection. The duration of anesthesia, however, is a significant risk factor independent of the duration of surgery. CLINICAL RELEVANCE: To decrease the incidence of postoperative wound infection, the duration of anesthesia should be minimized. Surgical time, as well as the time required for ancillary diagnostic tests while under anesthesia should, therefore, be kept to a reasonable minimum.     

Cardiopulmonary effects of halothane anesthesia in cats

The cardiopulmonary effects of 2 planes of halothane anesthesia (halothane end-tidal concentrations of 1.78% [light anesthesia] and 2.75% [deep anesthesia]) and 2 ventilatory modes (spontaneous ventilation [SV] or mechanically controlled ventilation [CV]) were studied in 8 cats. Anesthesia was induced and maintained with halothane in O2 only, and each cat was administered each treatment according to a Latin square design. Cardiac output, arterial blood pressure, pulmonary arterial pressure, heart rate, respiratory frequency, and PaO2, PaCO2, and pH were measured during each treatment. Stroke volume, cardiac index, and total peripheral resistance were calculated. A probability value of less than 5% was accepted as significant. In the cats, cardiac output, cardiac index, and stroke volume were reduced by deep anesthesia and CV, although only the reduction attributable to CV was significant. Systemic arterial pressure was significantly reduced by use of deep anesthesia and CV. Respiratory frequency was significantly lower during CV than during SV. Arterial PO2 was significantly decreased at the deeper plan of anesthesia, compared with the lighter plane. At the deeper plane of anesthesia, arterial PCO2 and pulmonary arterial pressure were significantly lower during CV than during SV. The deeper plane of halothane anesthesia depressed cardiopulmonary function in these cats, resulting in hypotension and considerable hypercapnia. Compared with SV, CV significantly reduced circulatory variables and should be used with care in cats. Arterial blood pressure was judged to be more useful for assessing anesthetic depth than was heart rate or respiratory frequency.     

Anesthesia and Analgesia in Rabbits and Rodents

Rabbits and rodents are popular pets and are often presented to veterinarians for evaluation and medical treatment. Anesthesia in exotic pets is required for many diagnostic and surgical procedures and is associated with a higher perioperative risk in rabbits and rodents when compared with dogs and cats. Inhalation anesthetic agents are commonly used as the sole source of anesthesia in small rodents, whereas injectable agents in combination with inhalation anesthesia are often used for rabbits and larger rodents. Analgesia is an important component of exotic pet medicine. Although it may be difficult to recognize signs of pain in companion exotic mammals, adequate pain management should always be provided. Opioid and nonsteroidal antiinflammatory drugs are the analgesic medications of choice, but others should be considered (e.g., local anesthetic agents). This article provides an update of the current literature regarding anesthesia and analgesia in rabbits and rodents.