Topic:Anesthesia
Anesthesia in horses involves the administration of drugs to induce a temporary loss of sensation or consciousness, facilitating surgical procedures and other medical interventions. This complex process requires a deep understanding of equine physiology and pharmacology to ensure the safety and well-being of the animal. Anesthesia in horses can be challenging due to their size, temperament, and unique anatomical and physiological characteristics. Common anesthetic agents used in equine practice include inhalants like isoflurane and sevoflurane, as well as injectable drugs such as ketamine and xylazine. The management of anesthesia in horses also involves careful monitoring of vital signs and the use of supportive measures to prevent complications such as hypotension, hypoventilation, and post-anesthetic myopathy. This page compiles peer-reviewed research studies and scholarly articles that explore the techniques, advancements, and clinical outcomes associated with anesthesia in equine medicine.
Glyceryl guaiacolate in equine anaesthesia. GG is a useful sedative and anaesthetic agent in horses. Used
alone, or in conjunction with barbiturates, it produces a un-
iformly smooth recovery from anaesthesia.
The need to infuse large volumes to obtain the desired effect is
a disadvantage ofthis agent. Few critical studies have been made
on the short and long term effects of administration of GG to
horses. Its pharmacology and clinical use are described and
indicate that it is a safe and useful drug.
Increased plasma bromide concentration in the horse after halothane anesthesia. A long-lasting increase of the plasma bromide concentration was found in 25 horses after clinical halothane anesthesia. The plasma bromide concentration was significantly (P less than 0.005) increased at the end of anesthesia. In 18 horses, peak values were reached between 48 and 72 hours after anesthesia. Eighteen days after horses had been anesthetized, the plasma bromide concentration remained significantly (P less than 0.005) increased. Significant correlation was not found between the total dose of halothane and the plasma bromide concentration. In 1 horse reanesthetized with halothane 4 ...
Surgical approach for medial meniscectomy in the horse. After preliminary studies on cadavers, a surgical approach was developed for removal of the medial meniscus, offering maximal exposure and minimal trauma to the articular surfaces of the medial tibial plateau and femoral condyle. Medial meniscectomy was then performed on 10 clinically normal horses that had been given general anesthesia. Nine horses were euthanatized at intervals of 1 to 6 months, and the joints were evaluated grossly and histologically. (One horse will be examined 1 year after surgery). Medial meniscus tears were diagnosed in 5 horses; medial meniscectomy was done on 4 horses...
Infective arthritis of the elbow joint in horses. Six horses were found to have infective arthritis of one elbow joint. The history, and presence of a small wound on the lateral aspect of the elbow suggested the condition was trauma induced. Two horses recovered following joint lavage under general anaesthesia and antibiotic therapy. The joint changes found post mortem in the others were characteristic of an infective arthritis.
Evaluation of xylazine, guaifenesin, and ketamine hydrochloride for restraint in horses. A combination of intramuscular xylazine plus intravenous guaifenesin and ketamine hydrochloride was evaluated as a method for chemical restraint and casting of the adult horse. This drug combination provided safe and rapid induction of the horse and uneventful recovery from lateral recumbency. Cardiopulmonary function remained within base-line values for the adult horse, although cardiac output, arterial blood pressure, and arterial partial pressure of oxygen were decreased from base-line values. Xylazine, guaifenesin, and ketamine hydrochloride provided safe induction to general anesthesia wi...
Potency of halothane-N20 in the horse. The minimal alveolar concentration (MAC) of halothane which just prevented purposeful movement in response to electrical stimulation was determined in 11 young, healthy, unpremedicated horses breathing oxygen (O2) or nitrous oxide (N2O) and O2. Ventilation was controlled during these MAC studies. The arterial PO2 was always greater than 90 mm of Hg and the average PaCO2. range was 36 to 40 mm of Hg. The MAC for halothane in O2 was 0.93 vol %. Alveolar N2O concentrations of 25% and 50% reduced the halothane MAC about 12% and 25%, respectively. In 8 of these horses, the cardiovascular effects of...
Short term immobilization in the horse with ketamine CHl and promazine HCl combinations. Combinations of promaxine HCl and ketamine HCl were used to produce short term dissociative anaesthesia in the horse under normal clinical conditions. Premedication with 1 mg/kg promazine HCl followed 5 min later by a rapid i.v. injection of 2 mg/kg ketamine HCl, induced dissociative anaesthesia of 16 +/- 1 min. When 1 mg/kg promazine HCl and a 2 mg/kg ketamine HCl were given simultaneously by rapid i.v. injection, a state of dissociative anaesthesia was induced with a mean duration of 17.1 +/- 2 min. Both treatments permitted minor surgery in the horse.
Priapism after sedation, neuroleptanalgesia and anaesthesia in the horse. The paper reports 6 cases of priapism with subsequent protrusion and paresis after neuroleptanalgesia and anaesthesia in horses. Five were ultimately treated by amputation of the penis but the sixth horse is responding satisfactorily to conservative treatment at the time of writing. Causative factors, preventive measures and possible methods of treatment are discussed.
Cardiovascular effects of halothane in the horse. Cardiovascular effects of venous alveolar concentrations of halothane in oxygen were studied in 8 young, healthy horses under conditions of constant arterial carbon dioxide tension. The alveolar concentration of halothane was expressed as a multiple of the minimal alveolar concentration (MAC) which was known for each animal. Increasing alveolar halothane concentrations to MAC 2.0 resulted in a progressive and significant (P less than 0.05) decline in systemic arterial pressure and left ventricular work. Cardiac output decreased between MAC 1.0 and MAC 2.0 as a result of a significant (P less t...
General anesthesia in pleasure horses. Anesthetic management of the pleasure horse consists of the appropriate selection and administration of pre-anesthetic medications including anticholinergics, tranquilizers and narcotics followed by appropriate techniques of anesthetic induction. The anesthetic induction must vary somewhat for the pleasure horse practice since many of the procedures are completed on farms and ranches. As a result the inducing of anesthesia will frequently be with the same agent which will be used to maintain anesthesia. Noticeably will be the reduction and duration of anesthesia and surgical time. The inductio...
Recovery from anaesthesia in ponies: a comparative study of the effects of isoflurane, enflurane, methoxyflurane and halothane. The duration and quality of recovery after separate 2 hour anaesthetic periods with equipotent alveolar concentrations of isoflurane, enflurane, halothane and methoxyflurane were evaluated in experimental ponies. Recovery was shortest after isoflurane anaesthesia, followed by enflurane, halothane and finally methoxyflurane, although standing was achieved more rapidly after enflurane than after isoflurane. This sequence of recovery times was compatible with the respective solubilities of the 4 agents. The smoothest recovery was obtained after isoflurane anaesthesia, followed by methoxyflurane, ...
Regional blood flow to the stomach and small intestine in ponies. Studies on regional blood flow to the stomach and small intestine were performed in 9 anesthetized ponies. Carbonized microspheres (15 +/- 5 micron in diameter) labeled with 85Sr were injected into the left atrium to determine blood flow distribution. In 4 ponies, the regional flows to mucosal-submucosal layers of the stomach and the small intestine were also measured. The nonglandular region of the stomach received the least blood per 100 g of tissue, and the duodenum received the greatest. The regional blood flow to the duodenum was significantly higher than that to the glandular stomach reg...
Rate of change of halothane concentration in a large animal circle anesthetic system. The slow rate of change of inspired halothane concentration which results in a conventional large animal circle anesthetic delivery system when low carrier gas flow rates are used was confirmed, using a model system. To obtain a 63% change in inspired halothane concentration in the 32-L large animal circle anesthetic machine at fresh gas inflow rates of 3, 6, and 12 L/minute required 10.7, 5.3, and 2.7 minutes, respectively. At a given inflow rate, increasing the rebreathing bag size from 20 to 40 L prolonged the time for equilibration between the gas flowing into the anesthetic circuit and th...
Radiological protection in equine radiography and radiotherapy. The principles of radiological protection are summarised and consideration is then given to problems, which may confront the equine practitioner, in the fulfillment of these principles during diagnostic radiography of the limbs, head, and spine of the horse. The place of anaesthesia in such procedures is discussed and the special problems associated with therapeutic radiography of the horse are considered.
Studies on left ventricular isotonic function in conscious and anaesthetized ponies. The effects of thiopentone-halothane and thiopentone-ether anaesthesia on left ventricular isotonic function were assessed in Welsh Mountain ponies from measurements of left ventricular stroke work, minute work, stroke power, mean ejection rate and tension-time index.
All of these variables were affected similarly during anaesthesia, an initial marked reduction being followed by a progressive return towards control levels in the later stages of anaesthesia. Quantitative differences between the effects of each agent were evident, the depression which occurred during halothane anaesthesia bei...
Enflurane, halothane, and isoflurane potency in horses. The minimal alveolar concentration of anesthetic required to prevent gross purposeful movement in response to electrical stimulation of oral mucous membranes was determined in horses for 3 agents. Equipotent concentrations of enflurane were 2.12 volumes %; of halothane, 0.88 volumes %; and of isoflurane, 1.31 volumes +. The alveolar concentration required to produce at least 60 seconds of apnea was also determined for these agents. From these data and the minimal alveolar concentration information, anesthetic indices were determined for each agent. The indices for enflurane, halothane, and iso...
Flow rates from an intermittent positive pressure breathing-anesthetic delivery apparatus for horses. Inspiratory flow rates were measured and compared in an equine intermittent positive pressure breathing-anesthesia delivery apparatus powered by a positive phase ventilator, a positive-negative phase ventilator, and a modified positive phase ventilator with automatic flow acceleration at driving pressures of 2,600, 4,400, and 5,200 mm of Hg (50, 85, and 100 psi). The last-named apparatus consistently produced the highest flows for a given ventilator setting and driving pressure. Regardless of the unit used, the greater driving pressures and high ventilator range settings produced the greatest ...
Body position and mode of ventilation influences arterial pH, oxygen, and carbon dioxide tensions in halothane-anesthetized horses. Effects of body position and type of ventilation were determined on arterial blood gases (PaO2, PaCO2) and pH during and immediately following clinical halothane anesthesia in 36 young, physically conditioned horses. Horses in dorsal recumbency had a lower PaO2 than did similarly breathing horses in a lateral position. Predictably controlled positive-pressure ventilation inproved arterial oxygenation and permitted maintenance of a normal PaCO2. Most horses, regardless of type of ventilation and operative body positioning, were hypoxemic in the immediate postanesthetic period.
Evaluation of xylazine and ketamine hydrochloride for anesthesia in horses. The cardiopulmonary effects resulting from the combination of xylazine and ketamine hydrochloride were evaluated in the adult horse. Xylazine (1.1 mg mg/kg) administered intravenously prior to or simultaneously with ketamine hydrochloride (2.2 mg/kg; intravenous) provided excellent analgesia and light anesthesia in all horses. Cardiac output, arterial blood pressure, pulmonary arterial pressure, central venous pressure, and pulmonary arterial wedge pressure remained within normal limits for the adult horse. Evidence of respiratory acidosis developed with time during the anesthetic period. Indu...
Portal vein anomaly and hepatic encephalopathy in a horse. Periodic episodes of diffuse central nervous system disease occurred in a yearling Thoroughbred gelding that had a history of frequent respiratory tract disease and stunted growth. Hepatic encephalopathy was diagnosed on the basis of history, clinical signs, prolonged bromsulphalein clearance, and increased blood ammonia content. Because of the poor prognosis and recurrent clinical signs the horse was euthanatized. Necropsy revealed an arteriovenous anomaly and thrombosis of the portal vein. Histologically, there was diffuse primary astrocytosis of the brain.