Developments in management of the newborn foal in respiratory distress 2: Treatment

New developments in therapy for foals in respiratory distress are discussed. Therapy is based on preservation of the foal's life by maintenance of a patent airway, resuscitation with fluids and warmth, provision of humidified oxygen to raise the fractional concentration of inspired oxygen sufficient to avoid hypoxia and provision of ventilatory support when hypercapnia becomes critical. Ventilatory support described includes assisted and controlled ventilation, positive end expiratory pressure, continuous positive airway pressure and intermittent mandatory ventilation. The aims of these techniques are discussed together with their associated indications, disadvantages and complications. Secondary therapy includes coupage, airway hygiene, drug therapy and stress management. Knowledge of equine neonatology is limited in comparison with human neonatology. More information in basic physiology and pharmacology relating to equine neonatology is needed and the efficacy of various modes of therapy must be evaluated.

Developments in management of the newborn foal in respiratory distress 1: Evaluation

Developments in evaluation of newborn foals with respiratory distress are discussed. Major causes of respiratory distress are outlined and discussed in terms of the similar respiratory signs exhibited by foals with this clinical syndrome. History, physical examination, clinical pathology, chest radiography and blood gas analyses are discussed as important elements of the evaluation of the condition of these foals. Foals with respiratory disease are grouped into three major categories on the basis of clinical signs and arterial blood gas profiles. The evaluation of foals with respiratory distress is designed not only to reach an accurate diagnosis of the aetiology but also to define the foal's need for respiratory support.

Postural influence on systemic blood pressure, gas exchange, and acid/base status in the term-pregnant bitch during general anesthesia

Effects of positioning on certain physiologic parameters were done in 7 term-pregnant bitches during general anesthesia. Five positions (right and left lateral recumbency, right and left 10 degrees to 15 degrees tilt toward lateral recumbency, and dorsal recumbency) were examined. Anesthesia was induced with thiamylal sodium and was maintained with halothane and nitrous oxide in oxygen. Direct arterial blood pressure, arterial blood gases, pH, base excess, heart rate, respiratory rate, and a lead II ECG were recorded from the bitches during each position. Effects of positioning for each bitch during general anesthesia were reexamined after the bitch weaned its pups; therefore, each bitch served as its own control. Maternal posture had no significant (P less than 0.05) effect on any measured parameters in bitches before or after parturition. Pregnancy had a significant (P less than 0.05) effect on every parameter, except heart rate. Pregnant bitches had a lower systolic blood pressure, lower Pao2, lower PCV, higher PaCO2, higher respiratory rate, and a more severe acidosis than did the bitches after parturition. Seemingly, supine hypotension did not occur in anesthetized term pregnant bitches (9 to 16 kg). Tilting the bitch 10 degrees to 15 degrees toward right or left lateral recumbency or true lateral recumbency was not preferable to dorsal recumbency for doing cesarean sections using general anesthesia.

Fatal interaction between thiamylal sodium and a proprietary antidiarrheal preparation in the dog

A drug interaction involving thiamylal sodium and a proprietary antidiarrheal preparation caused fatal ventricular fibrillation in a dog. Trials involving 4 dogs were conducted to recreate the interaction, and 1 of the 4 dogs died after ventricular fibrillation developed. The nature of the interaction was hypothesized to be mediated through the anticholinergic drug diphemanil methylsulfate, producing an autonomic imbalance.

Tissue composition and halothane solubility in the horse

The halothane muscle/gas partition coefficients at 37 degrees C for 26 samples of eight different muscles from four horses were found to depend significantly on the fat content of the muscle sample with a regression coefficient of 1.913 (SEM 0.109) per per cent ether-extractable fat content. The blood/gas partition coefficients in 24 horses showed a significant dependence on plasma triglyceride concentration (regression coefficient 0.00084 (SEM 0.00033) per mg dl-1), an insignificant positive dependence on plasma free and total cholesterol concentration and, in a multiple regression analysis, a negative dependence of borderline significance on packed cell volume (regression coefficient -0.01 (SEM 0.005) per per cent p.c.v.).

Solubility of halothane in equine tissues at 37 degrees C

The solubilities of halothane at a concentration of 0.77% v/v in 5% carbon dioxide in air at 37 degrees C were determined for a variety of equine tissues. The mean values for the tissue/gas partition coefficients for visceral tissue taken from 36 horses were 5.42 for whole brain, 4.82 for grey matter, 7.41 for white matter, 4.18 for myocardium, 2.76 for lung, 8.51 for liver, 3.21 for kidneys, 2.66 for gastrointestinal tract, 1.77 for blood and 2.45 for spleen. The mean coefficients for eight different muscles taken from 23 horses ranged from 2.43 for extensor carpi radialis to 4.91 for psoas major. The values obtained were, with the exception of liver and brain, consistently lower than values in the literature for rabbit, dog, man and ox. Statistical analysis indicated that the condition of a horse was important in determining the solubility of halothane in its liver and muscles. The type of sex of a horse appeared to be important only in respect of the solubility of halothane in the gastrointestinal tract.

Distribution of cardiac output in anaesthetised horses

The radioactive microsphere method was used to determine the distribution of cardiac output in six anaesthetised ponies. Simultaneous measurements of cardiac output allowed calculation of the tissue perfusions (ml/min/100 g). Allowing for the fact that measurements were carried out on animals under halothane anaesthesia and which had respiratory acidosis, the results were comparable with published values for other species.

Body composition of the horse

Seventeen horses were dissected and their organs and tissues weighed. The results of these dissections are presented together with comparisons of the data with that already available in the literature. Predictive equations for organs and tissue weights are also given which were derived by comparison of linear and allometric regression models using 4 different body weight indices.

The density of equine tissue at 37 degrees C

The density of the following equine tissues was measured: white and grey brain matter, myocardium, lung parenchyma, liver, spleen, gastrointestinal tract and contents, renal medulla and cortex, muscle, fat, tendon and bone. Statistical analysis indicated that there were highly significant differences in the values for density between horses and between tissues within horses. Values for density of eight different muscles were obtained for 18 horses and these were shown to differ highly significantly between horses and between muscles within horses. The values for splenic density differed highly significantly between those for knackery killed horses and for the barbiturate killed post morten room horses.