Chemical restraint for surgery in the standing horse.

Chemical restraint can be a useful pharmacologic tool to assist the veterinarian performing surgery in the standing horse. The agents discussed impose minimal adverse side effects and are considered relatively safe when administered in the doses described. Acetylpromazine, the most widely used tranquilizer, produces mild sedation but no analgesia. The use of tranquilizers for surgical procedures requires the combined use of either a local anesthetic technique or a sedative-hypnotic or opiate to provide analgesia. Sedative-hypnotics such as xylazine and detomidine or opiates such as morphine and butorphanol are commonly used. The sedative-hypnotics also can induce deep CNS depression and may be sufficient alone for many procedures. Opiates may be used to supplement the analgesia produced by sedative-hypnotics or provide analgesia to the tranquilized horse. Opiates are not useful alone because of their potential to cause CNS excitement in the horse. The combination of detomidine and butorphanol is probably the most effective drug combination to facilitate painful surgery in the standing horse.     

Sedation and chemical restraint in the dog and cat

Small animal patients must often undergo veterinary procedures that are painful or distressful, for which judicious use of sedatives or other agents with anesthetic or analgesic properties can be useful. If the degree of sedation is profound enough, such "chemical restraint" may be employed to provide immobilization for radiographs or minor surgical procedures. The choice of agents to be used will depend upon the physiologic state and cooperative nature of the patient and the desired endpoint, ie, anxiolysis versus deep sedation with analgesia. This report discusses important features of patient assessment, preparation, equipment needs, consideration of the types of procedures for which sedation is useful, and recovery considerations. A brief review is included of the useful effects and contraindications for the various agents employed, and doses for each are listed. Algorithms are presented for a given category of patient, leading the practitioner through a decision making strategy to arrive at examples of sedation or chemical restraint protocols that are commonly found to be effective by the author.     

Neuromuscular blocking agents.

In summary, with proper vigilance, neuromuscular blocking agents can be used safely in anesthetized equine patients to optimize conditions for certain surgical procedures. By appropriate use of neuromuscular monitoring techniques and reversal agents, residual blockade and muscle weakness should be avoided, allowing the horse to recover to standing without difficulty. Research is ongoing to develop the ideal muscle relaxant, one that has a rapid onset, predictable duration and recovery times, and negligible hemodynamic effects. As newer agents become available, they should be evaluated for their suitability for use in equine patients.     

Regional anesthesia

Organ toxicity from local anesthetic agents is rare. This makes these agents an attractive option in the high-risk patient. Complications associated with local anesthetics are related to overdosage. Overdosage with local anesthetic agents administered epidurally may cause motor paralysis and hind-limb weakness. Systemic signs of local anesthetic overdosage include changes in central nervous system activity (excitement or depression), muscle tremors, and hypotension. Because the dose required to produce these effects in the horse is high (12 mg/kg), this complication is uncommon. Few side effects and low cost justify the use of local anesthetic techniques in equine practice.     

Restraint

The object of restraint is to limit, restrict, and keep under control the animal's movement while performing different procedures. The author discusses the importance of evaluating the horse and its owner prior to employing any type of restraint, various concepts of restraint, and examples of situations in which restraint may be required.     

Role of prokinetic drugs for treatment of postoperative ileus in the horse

All horses undergoing coeliotomy for an acute abdominal crisis are at risk of developing ileus and should receive therapy aimed at promoting gastrointestinal function by restoring fluid and electrolyte balance. Adequate analgesia and prevention against peritonitis, bacteraemia and endotoxaemia should be provided. Horses that at the time of surgery have a strangulating or non-strangulating small intestinal obstruction should be considered to be at greater risk of developing a persistent ileus that is refractory to treatment than those horses with lesions involving the large intestine. In horses considered to be at greater risk of developing a persistent ileus, the use of prokinetic agents should be considered. Agents that may be used to improve gastrointestinal motility include adrenergic receptor antagonists, cholinergic agonists, benzamides, dopamine antagonists, macrolide antimicrobials, opiate receptor agonists and antagonists, somatostatin analogues and local anaesthetics. There are limited studies into the use of these agents in the horse. Until further research provides more information on motility disorders following intestinal surgery and the efficacy of prokinetic agents in this species, only selective use of some of these drugs can be recommended.     

Retrospective analysis of detomidine infusion for standing chemical restraint in 51 horses

Objective To assess the effectiveness of a detomidine infusion technique to provide standing chemical restraint in the horse. Design Retrospective study. Animals Fifty‐one adult horses aged 9.5 ± 6.9 years (range 1–23 years) and weighing 575 ± 290.3 kg. Methods Records of horses presented to our clinic over a 3‐year period in which a detomidine infusion was used to provide standing chemical restraint were reviewed. Information relating to the types of procedure performed, duration of infusion, drug dosages and adjunct drugs administered was retrieved. Results Detomidine was administered as an initial bolus loading dose (mean ± SD) of 7.5 ± 1.87 µg kg^?1. The initial infusion rate was 0.6 µg kg^?1 minute^?1, and this was halved every 15 minutes. The duration of the infusion ranged from 20 to 135 minutes. Twenty horses received additional detomidine or butorphanol during the procedure. All horses undergoing surgery received local anesthesia or epidural analgesia in addition to the detomidine infusion. A wide variety of procedures were performed in these horses. Conclusions Detomidine administered by infusion provides prolonged periods of chemical restraint in standing horses. Supplemental sedatives or analgesics may be needed in horses undergoing surgery. Clinical relevance An effective method that provides prolonged periods of chemical restraint in standing horses is described. The infusion alone did not provide sufficient analgesia for surgery and a significant proportion of animals required supplemental sedatives and analgesics.     

Iron metabolism

Extract

The introduction of chemical restraint into horse practice brought significant advantages in handling fearful and fractious animals as well as allowing the practitioner to carry out procedures which would normally arouse considerable resistance from the equine patient. Phenothiazine derivatives were widely used for these purposes prior to the introduction of xylazine hydrochloride, a drug which was synthesised in Germany in 1962 by Bayer, A. G., Leverkusen, tested underthe code name Bayer Va 1470 and marketed under the trade name Rompun. In view of the increasing use of xylazine in equine practice it seems worth-while to review the literature on the pharmacological action and clinical use of this agent in horses.     

The effect of aging on immune responses.

Although vaccine manufacturers make no specific recommendations regarding the vaccination of older horses and ponies, the similarities in age-induced immunologic changes between human beings and equids suggests that similar vaccination recommendations should be followed. The need for vaccination of the older horse depends, of course, on the relative risk of exposure for the individual horse. Particular care should be taken when using attenuated vaccine products because these live agents may pose a unique risk to the older individual. Immunization with inactivated agent vaccines is likely to be safer. In general, annual vaccination against equine influenza virus infection, tetanus, rabies, and encephalomyelitis viruses is warranted.     

Kick injuries of veterinarians during examination and treatment of horses: a retrospective study in Switzerland

The risk of injury to veterinarians treating horses is high, particularly when performing painful procedures. The present retrospective study investigated this risk, including the frequency and severity of kick injuries, by submitting questionnaires to 700 veterinary practitioners in Switzerland. Evaluation of 216 completed questionnaires revealed that the frequency of kick injuries was affected by the professional experience of the veterinarian, veterinarians being an owner of a horse, the season, the type of procedure, the percentage of equine patients in the practice population, the treatment location (stall, pasture) and chemical restraint of the patient. Severe injuries incurred by veterinarians in recent years were few in number and the result of a number of unfortunate circumstances, which included hurried procedures due to time restraints and unforeseen events that frightened the patient. The risk factors derived from the full statistical model are the percentage of equine patients in the practice population, the treatment location, the type of procedure and chemical restraint of the patient. Using this information, it should be feasible to reduce the risk of injuries. Sedation of horses undergoing painful procedures, choosing a safe treatment location and caution on the part of the veterinarian are advised to reduce the number of injuries.     

Nasogastric Intubation as Health and Safety Risk in Equine Practice—A Questionnaire

Placing a nasogastric tube can be a life-saving act for a horse but is considered an occupational hazard for veterinarians. An online questionnaire was performed to assess and specify potential risks. 123 equine veterinarians completed the survey, and the majority admitted using the mouth to handle the end of the nasogastric tube (sucking or blowing air) and having accidentally swallowed or aspirated stomach content or medications. This can potentially lead to aspiration pneumonia or pneumonitis. Mineral oil seems to be especially dangerous as aspiration may be asymptomatic at the beginning and lipoid pneumonitis may develop. Furthermore, 60% of responders would also handle the tube with their mouth if the horse was presented with fever and diarrhea or reflux formation, which might be affected by Salmonella sp. or Clostridium difficile producing toxins. The fact that nasogastric tubes are rarely being disinfected increases the risk of infection. 50% of veterinarians would use their mouth to suck or blow air into the tube during nasogastric intubation, even if the patient was presented with suspected poisoning. Rodenticide zinc phosphide is particularly dangerous as its breakdown product is a highly toxic gas. Inhalation leads to serious symptoms in humans, including pulmonary edema and neurological signs. Alternatives to mouth use (lavage, big syringe, or suction pump) when passing a tube should be considered, especially if a patient is presented with duodenitis—proximal jejunitis, diarrhea, or suspected poisoning. Awareness needs to be raised among veterinarians that nasogastric intubation is an extremely hazardous occupational practice.     

Narcotic analgesics, their detection and pain measurement in the horse: a review

Narcotic analgesics produce pharmacological effects by interacting with specific opiate receptors. At least five major types of opiate receptors have been recognised. These include mu (morphine) and kappa (ethylketazocine) receptor types. Narcotic analgesics which interact with mu receptors produce locomotor and autonomic stimulation at doses that produce little or no analgesia. Therefore, use of these drugs as analgesics in equine medicine has not been very satisfactory. Theoretical considerations suggested that the role of kappa agonists in equine analgesia be investigated. Using a pure kappa agonist, U-50, 488H, good analgesia was produced in the horse with little or no locomotor stimulation or autonomic effects. These data suggest that kappa agonists may be superior analgesics for clinical use in the horse. On the other hand, the locomotor stimulant effects of mu agonist analgesics enable their use as illegal medications. Specifically, these agents produce a good running response, signs of central nervous stimulation and analgesia, all potentially useful effects in a racehorse. Regulatory control of most narcotic analgesics can be obtained by high performance thin layer chromatographic screening. However, effective screening for the fentanyls and small doses of etorphine can only be achieved by use of immunoassay.     

Ethical equitation: Capping the price horses pay for human glory

Ethical equitation is nowadays coming into sharp focus in equestrian culture. Concerns surround the ethics of sports based on controlling an animal's locomotory responses and in using animals such as horses in sport in general. Anthropomorphically labeled misinterpretations of the responses of trained horses, such as the use of terms like “mad,” “lazy,” “keen,” and “stubborn,” may be detrimental to optimal equine welfare. Similarly, the concept of the “equine athlete” may imply an ill-informed teleological explanation of the motives of the horse in sport. Despite problems in identifying the happy horse, rewarding optimal welfare and the absence of critical stress responses in performance horses is an important step forward.Horse racing is the source of many welfare concerns because of the use of the whip and the physical dangers to horses involved in hurdle racing and steeplechasing. The use of the whip in racing is controversial and, because it does not always lead to acceleration, problematic. There is a pressing need for learning theory to be adopted in all equestrian pursuits, because such an approach would obviate the need for whips, punishment, and the use of fear in escape learning. In other disciplines, practices such as hyperflexion and soring have a significant potential to compromise the welfare of the horse in sport.The future of horse sports should involve abandoning the mandatory use of primitive control devices, such as curb bits, that have a real potential to cause harm. International governing bodies and national equestrian federations ought to proceed with removing any requirements to use curb bits and judges should reward riders who use the most humane control devices at the higher levels of competition.Finally, horse breeding should also be scrutinized under an ethical spotlight. Selecting horses on the basis of temperament has inherent risks, including lowered motivation of riders and trainers to refine their training skill set, which may also lead to significant wastage. Pure breeding risks the health and welfare of horses owing to increases in homozygous deleterious genes expressing themselves.     

A review of topical therapy for skin infections with bacteria and yeast

Background – Cutaneous infections with bacteria and yeasts are common in small animal practice. Treatment with systemic antibiotics or antifungal agents may not be ideal, because of the increasing development of multiresistant organisms, the cost and the possible adverse effects. Topical antimicrobials may be used as adjunctive therapy to systemic treatment or as sole therapy instead of systemic treatment. Objective – This literature review evaluated studies on topical antimicrobial treatment of skin infections. Methods – In vitro and in vivo studies evaluating topical antimicrobial agents were identified using a number of electronic and manual searches of textbooks and articles. Studies were evaluated, and the evidence for or against the use of the topical agents was extracted. Results – There is good evidence for the efficacy of chlorhexidine and, to a lesser degree, benzoyl peroxide in canine bacterial skin infections. There is limited evidence for the efficacy of silver sulfadiazine and medical honey against bacterial skin infections in the dog, and for the efficacy of hydrogen peroxide and stannous fluoride in the horse. Good evidence supports the use of a combination of chlorhexidine and miconazole in dogs with cutaneous Malassezia infections. There is insufficient evidence to recommend any other topical therapy for use in cutaneous infections. Conclusions and clinical importance – Although many antimicrobial topicals are marketed in veterinary dermatology, the efficacy has been reported for only a minority of agents. Randomized controlled trials evaluating various topical treatments are therefore urgently needed.     

Pharmacology and therapeutics in donkeys

Therapeutics are often administered to donkeys based on dosage and intervals recommended for horses because very few drugs have donkey‐specific label indications. Yet differences between donkeys and horses in drug distribution, metabolism and elimination have been noted for most therapeutic agents studied. These differences can be partially explained by the donkey's unique physiology. Since their ancestors evolved in a desert environment, the modern donkey exhibits qualities that allow them to tolerate dehydration better than the horse and recover more quickly from its effects. Fluid balance and body water compartment partitioning differ from the horse and may have implications regarding drug distribution. Since donkeys are preferential browsers, differences in diet may have influenced evolutionary differences in metabolic disposition of drugs. It is important to acknowledge these differences when designing dose regimes for donkeys based on horse protocols in order to avoid either lack of efficacy or toxicity.     

Anesthetic considerations for the geriatric patient

The geriatric patient presents an anesthetic challenge due to the physiologic alterations that occur during aging. The geriatric patient usually has an increased number of disease processes and does not possess the functional organ reserve capabilities compared to a younger patient. The geriatric patient seems more susceptible to the cardiopulmonary depressant effects of the preanesthetic and anesthetic agents in common use and, due to decreased hepatic function and other factors, may have a delayed recovery from these drugs. The preanesthetic and anesthetic drugs chosen for a geriatric patient will depend on that particular patient's physiologic status, the procedure to be done, and the experience of the veterinarian. Adequate fluid and monitoring support should always be provided for the geriatric patient.     

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.     

Restraint and anaesthesia of primates

The methods available for the restraint and anaesthesia of captive primates are discussed, emphasising the differences between the techniques for primates and those for other mammals; the importance of humane methods of physical restraint is emphasised. The agents available for chemical restraint and surgical anaesthesia are considered in terms of their ease of administration, the dose rate required, speed of induction and recovery, analgesic properties, muscle relaxation and side effects. New agents are available which are potentially useful in primates.     

The use of intravenous lipid emulsion as an antidote in veterinary toxicology

Objective – To review the use of IV lipid emulsion (ILE) for the treatment of toxicities related to fat‐soluble agents; evaluate current human and veterinary literature; and to provide proposed guidelines for the use of this emerging therapy in veterinary medicine and toxicology. Data Sources – Human and veterinary medical literature. Human Data Synthesis – Human data are composed mostly of case reports describing the response to treatment with ILE as variant from mild improvement to complete resolution of clinical signs, which is suspected to be due to the variability of lipid solubility of the drugs. The use of ILE therapy has been advocated as an antidote in cases of local anesthetic and other lipophilic drug toxicoses, particularly in the face of cardiopulmonary arrest and unsuccessful cardiopulmonary cerebral resuscitation. Veterinary Data Synthesis – The use of ILE therapy in veterinary medicine has recently been advocated by animal poison control centers for toxicoses associated with fat‐soluble agents, but there are only few clinical reports documenting successful use of this therapy. Evidence for the use of ILE in both human and veterinary medicine is composed primarily from experimental animal data. Conclusions – The use of ILE appears to be a safe therapy for the poisoned animal patient, but is warranted only with certain toxicoses. Adverse events associated with ILE in veterinary medicine are rare and anecdotal. Standard resuscitation protocols should be exhausted before considering this therapy and the potential side effects should be evaluated before administration of ILE as a potential antidote in cases of lipophilic drug toxicoses. Further research is waranted.     

Ultrasonographic examination of the distal limb of cattle.

Ultrasonography has proven its worth in both small animal and equine musculoskeletal work. It allows visualization of soft tissue that is not possible with anything barring magnetic resonance imaging. In bovine practice, ultrasound has been used to great effect in reproductive work and has also shown itself to be of value in the evaluation of the thorax, abdomen, and the udder. Ultrasound examination of the bovine limb is certainly feasible because of the availability of small portable and affordable equipment. The restraint necessary is dependent on the animal. Cattle, because of their size and inherent dislike of restraint, pose a challenge for ultrasonographic examination. However, if proper restraint is used, it seems possible that ultrasonography may become a helpful tool in the evaluation of soft tissue injuries. It should prove to provide valuable information that may be used to offer better advice with regard to treatment and prognosis.