Laryngotracheal lesions following routine orotracheal intubation in the horse.

Sequelae of routine orotracheal intubation under clinical conditions were characterised in 38 healthy horses presented at three veterinary medical teaching hospitals. Four of these were necropsied and their tissues studied histologically. To minimise variation, 30 mm id cuffed silicone endotracheal tubes or Cole cuffless tubes were used in all patients. Fibreoptic endoscopic examination of upper respiratory and tracheal areas was accomplished pre-intubation, immediately post extubation and after 24 h. Endoscopy revealed that intubation was associated with laryngeal and/or tracheal lesions in all horses. Observations included abundant tracheal mucus, epithelial ecchymoses, basement membrane haemorrhage and mucus covered diphtheritic membrane plaques. Histological examination of lesions from the upper respiratory system of the four necropsied horses confirmed that the damage was comparable to that associated with tracheal intubation and reported in other species.

Pharmacokinetics of thiamylal in cats.

Pharmacokinetics of thiamylal were determined after 13.2 mg of thiamylal/kg of body weight was administered IV to 6 healthy cats. Blood samples were obtained for 12 hours. Disposition of thiamylal best conformed to 2 multicompartmental models, a 2-compartment (n = 1) and a 3-compartment (n = 5) open pharmacokinetic model. The pharmacokinetic values were calculated for the overall best-fitted model, a mixed 2- and 3-compartmental model. The first or rapid distribution half-life was 1.91 minutes and a second, or slower, distribution half-life was 26.51 minutes. The elimination half-life was 14.34 hours. The apparent volume of distribution was 3.61 +/- 1.8463 L/kg, whereas the apparent volume of the central compartment was 0.46 +/- 0.2034 L/kg, and the total clearance was 0.135 +/- 0.0616 L/kg/h.

Pharmacokinetics of etomidate in cats.

Pharmacokinetic variables of etomidate were determined after IV administration of etomidate (3.0 mg/kg of body weight). Blood samples were collected for 6 hours. Disposition of this carboxylated imidazole best conformed to a 2- (n = 2) and a 3- compartment (n = 4) open pharmacokinetic model. The pharmacokinetic values were calculated for the overall best-fitted model, characterized as a mixed 2- and 3-compartmental model. The first and most rapid distribution half-life was 0.05 hour and a second distribution half-life was 0.35 hour. Elimination half-life was 2.89 hours, apparent volume of distribution was 11.87 +/- 4.64 L/kg, apparent volume of distribution at steady state was 4.88 +/- 2.25 L/kg, apparent volume of the central compartment was 1.17 +/- 0.70 L/kg, and total clearance was 2.47 +/- 0.78 L/kg/h.

Evaluation of five common induction protocols by comparison of hemodynamic responses to surgical manipulation in halothane-anesthetized horses.

OBJECTIVE: To determine whether hemodynamic responses of halothane-anesthetized horses undergoing surgical procedures depended on anesthetic induction protocols used, and to determine whether hemodynamic responses to surgical manipulation could be detected. DESIGN: Prospective experimental study without controls. ANIMALS: 36 clinically normal horses. PROCEDURE: Horses were allotted to 5 groups according to anesthetic induction protocol: acepromazine/guaifenesin/thiamylal, acepromazine/guaifenesin/ketamine, xylazine/guaifenesin/thiamylal, xylazine/guaifenesin/ketamine, and xylazine/diazepam/ketamine. Anesthesia was maintained with halothane. Hemodynamic measurements and blood gas values were obtained prior to the start of surgery, during surgery, and after surgery. RESULTS: Few differences in hemodynamic measurements existed between horses in which anesthesia was induced by 5 anesthetic induction protocols, whether prior to the start of surgery or for pooled values for all 3 measurement periods. Hemodynamic responses to surgical manipulation were marked and included increased mean arterial pressure and systemic vascular resistance, and decreased cardiac index and oxygen delivery. CLINICAL IMPLICATIONS: Choice of anesthetic induction protocol has little impact on hemodynamic function during surgery in halothane-anesthetized horses. Surgical stimulation may increase blood pressure, but does not improve cardiac index or oxygen delivery.

Effect of intravenous administration of fluids on packed cell volume, blood pressure, and total protein and blood glucose concentrations in healthy halothane-anesthetized dogs.

OBJECTIVE: To determine the effects of IV administration of fluids on PCV, serum total protein and blood glucose concentrations, and systolic arterial pressure in healthy anesthetized dogs undergoing elective surgical procedures. DESIGN: Prospective, randomized controlled trial. ANIMALS: 70 clinically normal dogs. PROCEDURE: Dogs received i.v. administration of 0, 5, 10, or 15 mL/kg of body weight/h of a polyionic crystalloid solution or 5% dextrose in water. Blood samples were collected before and after administration of medication, prior to anesthetic induction, after anesthetic induction, at the end of the surgical procedure, and 2 hours after surgery to determine PCV and serum total protein and blood glucose concentrations. Blood pressure was measured before and after anesthetic induction and at the end of the surgery. RESULTS: There were not any significant differences in PCV, total protein concentration, or systolic arterial pressure among treatment groups. Hyperglycemia developed in dogs receiving 5% dextrose in water, but resolved 2 hours after discontinuing administration of fluids. CLINICAL IMPLICATIONS: Intravenous administration of fluids may not be necessary to maintain normal blood pressure in young, healthy dogs undergoing elective surgery.

A comparison of the haemodynamic effects of propofol and isoflurane in pregnant ewes.

The purpose of this study was to compare the effects of inhaled isoflurane and a constant infusion of propofol on maternal haemodynamics and uterine arterial and umbilical venous flows in pregnant ewes. Late term pregnant ewes (n = 5) were randomly assigned to receive either inhaled isoflurane or an intravenous infusion of propofol for 1 h, each on separate occasions. Maternal systemic arterial, right atrial and pulmonary arterial blood pressures, cardiac index, systemic vascular resistance index, stroke volume index, heart rate, and uterine arterial and umbilical venous flows were determined over the 1 h period of each treatment. Data were analysed using an univariate analysis of variance for repeated measures performed on the ranks of the data. Propofol anaesthetized ewes had significantly higher heart rate (P = 0.0040), mean arterial pressure (P = 0.0003) and cardiac index (P = 0.0475) compared to isoflurane anaesthetized ewes. There were no significant differences in uterine arterial flows, umbilical venous flows, or other measured variables. Continuous propofol infusions maintain maternal haemodynamics at significantly higher levels than does inhaled isoflurane, while uterine arterial and umbilical venous flows do not differ significantly.

Treatment of low arterial oxygen tension in anesthetized horses with clenbuterol.

Clenbuterol (0.8 microgram/kg intravenously) was administered to 10 anesthetized horses with an abnormally low PaO2 (less than 90 mm Hg) despite controlled ventilation with an oxygen-rich gas mixture. Results were compared with those from 10 controls to which no clenbuterol was given and in which conventional methods to increase PaO2 were ongoing. Horses treated with clenbuterol had higher PaO2 values for at least 90 minutes. Clenbuterol was associated with increased heart rate and profuse sweating. Clenbuterol can be administered intravenously to increase the PaO2 of mechanically ventilated horses that have low arterial oxygen tension while under inhalation anesthesia. Further studies are warranted to define more precisely the circumstances under which clenbuterol may be used safely.

Complications and mortality associated with anesthesia in dogs and cats.

The complications and mortality associated with anesthesia of dogs and cats in a university teaching hospital were determined. During one year, 2,556 dogs and 683 cats were anesthetized by the anesthesia service. Hypotension occurred in 179 (7%) dogs and 58 (8.5%) cats. Cardiac dysrhythmias occurred in 64 (2.5%) dogs and 12 (1.8%) cats. Transfusions were required in 31 (1.2%) dogs. Hypercapnea occurred in 33 (1.3%) dogs and one (less than 1%) cat. Hypoxemia occurred in 14 (0.5%) dogs. Anesthetic complications, as defined, occurred in 12.0% of dogs and 10.5% of cats, while deaths associated with the perianesthetic period occurred in 0.43% of dogs and 0.43% of cats.

Hemodynamic responses of horses to anesthesia and surgery, before and after administration of a low dose of endotoxin.

Seven horses, which were part of an investigation of the effect of endotoxin administration on vascular reactivity, were anesthetized on two separate occasions for surgical excision of 4-cm sections of palmar digital artery and vein. On the first occasion, the horses were given an infusion of 1 L 0.9% NaCl solution intravenously (i.v.) just before induction of anesthesia (control); on the second occasion, the horses received an infusion of 1 L 0.9% NaCl containing Escherichia coli endotoxin, 0.1 microgram/kg (endotoxin). On both occasions, anesthesia was induced with xylazine, guaifenesin, and ketamine, and maintained with halothane in oxygen. Hemodynamic measurements were made with the horses under anesthesia immediately before beginning surgery (period 1), during skin incision (period 2), during dissection and excision of the vessels (period 3), during skin suturing (period 4), and after completion of surgery during bandaging (period 5). Hemoglobin concentration and mixed venous oxygen content were greater at all periods in horses that received endotoxin. Otherwise, there were no significant differences in hemodynamic parameters between control horses and horses administered endotoxin before beginning surgery (period 1). During surgery and bandaging, horses administered endotoxin had significantly higher heart rate (periods 3, 4, and 5), cardiac index (periods 3, 4, and 5), and oxygen delivery (periods 2, 3, 4, and 5) than did control horses, and mean arterial blood pressure (period 2) and systemic vascular resistance (periods 2, 3, 4, and 5) were less than in control horses. Compared with period 1, surgical stimulation in control horses was associated with increased mean arterial blood pressure and systemic vascular resistance (periods 2, 3, 4, and 5), but cardiac index and oxygen delivery were decreased (periods 3, 4, and 5).(ABSTRACT TRUNCATED AT 250 WORDS)