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Biomedical subjects

K W Hinchcliff

Publications and source records attributed to K W Hinchcliff.

At least 109 records · Page 6Linked to original sources
PubMed1993

Fluids, electrolytes, and bicarbonate.

In an attempt to enhance performance, primarily by delaying the onset of fatigue, a variety of formulations of fluids, electrolytes, and sodium bicarbonate are administered to performance horses. Some current practices of fluid and electrolyte supplementation are well justified; others have no basis to support their use. In addition, occasional combined administration of certain agents (i.e., furosemide and sodium bicarbonate) can have detrimental effects on performance.

Animals↗
PubMed1993

Plasma constituents during incremental treadmill exercise in intact and splenectomised horses.

Six intact and 6 splenectomised mares were given an incremental exercise test on a treadmill to examine the fluid and electrolyte changes associated with exercise and the role of the spleen in these changes. Blood samples were obtained at rest and at the end of each 1-min step of the test. Exercise at 7 m/sec caused significant (P < 0.05) increases in plasma osmolality (intact, +9.9%; splenectomised, +6.2%), plasma protein concentration (intact, +15.8%; splenectomised, +11.4%), and plasma K+ concentration (intact 46%; splenectomised, +57%). Plasma Na+ concentration did not increase significantly (P > 0.05) in either group (intact = 2.7%; splenectomised, = 3.5%). This appears to be the first record of substantial changes of these constituents during short-term exercise, even before the onset of visible sweat losses. The changes in the concentration of plasma protein suggest that short-term exercise causes a decrease in plasma volume. The changes in the concentration and content of sodium suggest that this is an isotonic shift of fluid. The increase in plasma potassium concentration appears to be due to haemoconcentration as well as an increase in the content of potassium within the vascular compartment.

Animals↗
PubMed1993

Role of decreased plasma volume in hematocrit alterations during incremental treadmill exercise in horses.

Six intact (IN) and six splenectomized (SP) mares were subjected to an incremental exercise test to examine the role of decreases in plasma volume (PV) in the changes in hematocrit (Hct) normally seen with exercise. Each horse underwent an incremental exercise test in which it ran on a treadmill up a fixed incline of 6 degrees. The test started at a speed of 4 m/s, and speed was increased 1 m/s each min until heart rate reached a plateau. Blood samples were obtained at rest and at the end of the 4, 5, 6, and 7 m/s steps of the exercise test. Resting PV was greater (P < 0.05) in the IN group (28.6 +/- 0.5 liters) compared with SP horses (22.7 +/- 2.2 liters). Exercise produced a significant increase in Hct in both groups of horses; however, the increases were greater (P < 0.05) at all exercise intensities in IN compared with SP horses. Hct increased rapidly during the first step (4 m/s) in the exercise test in the IN animals. After this, Hct increased slowly in IN horses, and values for the 5, 6, and 7 m/s steps paralleled the changes observed in the SP horses. Corrected Hct values were then used to calculate the relative change in PV. Exercise produced a significant decrease in PV in both groups of horses; however, there were no differences (P > 0.05) between the groups when IN horses (-13 +/- 3 and -18 +/- 2%) were compared with SP horses (-14 +/- 4 and -17 +/- 4%) at the 6 and 7 m/s steps of the exercise test.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Splenectomy alters blood pressure response to incremental treadmill exercise in horses.

Six intact (IN) and five splenectomized (SP) mares were subjected to an incremental exercise test to examine the effects of splenectomy on blood pressure responses during exercise. During the test the horses ran up a 6 degree grade on a treadmill set at an initial speed of 4 m/s. Speed was increased 1 m/s every 1 min until heart rate (HR) reached a plateau. Hemodynamic data were collected continuously and analyzed for the last 18 s of the 4, 5, 6, and 7 m/s steps of the exercise test. There were no differences (P > 0.05) between the groups for resting means for any parameter measured in the study. HR increased (P < 0.05) in both groups of horses during exercise with significantly greater HR in the SP horses during the first two steps of the test. There were no differences (P > 0.05) in maximal HR between the groups. Right atrial pressure (RAP) did not change during exercise in the SP horses; however, it did increase 20 mmHg (493%, P < 0.05) in the IN horses. Right ventricular pressure (RVP) increased (P < 0.05) during exercise with no differences (P > 0.05) between the groups. Right ventricular maximum change in pressure over time increased (P < 0.05) in a similar fashion in both groups of animals. Mean arterial pressure (MAP) increased 29 mmHg (30%, P < 0.05) in SP horses, reaching a plateau by the 5 m/s step of the test.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Effects of cocaine on incremental treadmill exercise in horses.

Four mature horses were used to test the effects of two doses (50 and 200 mg) of intravenously administered cocaine on hemodynamics and selected indexes of performance [maximal heart rate (HRmax), treadmill velocity at HRmax, treadmill velocity needed to produce a blood lactate concentration of 4 mmol/l, maximal mixed venous blood lactate concentration, maximal treadmill work intensity, and test duration] measured during an incremental treadmill test. Both doses of cocaine increased HRmax approximately 7% (P < 0.05). Mean arterial pressure was 30 mmHg greater (P < 0.05) during the 4- to 7-m/s steps of the exercise test in the 200-mg trial. Neither dose of cocaine had an effect on the responses to exertion of right atrial pressure, right ventricular pressure, or maximal change in right ventricular pressure over time. Maximal mixed venous blood lactate concentration increased 41% (P < 0.05) with the 50-mg dose and 75% (P < 0.05) with the 200-mg dose during exercise. Administration of cocaine resulted in decreases (P < 0.05) in the treadmill velocity needed to produce a blood lactate concentration of 4 mmol/l from 6.9 +/- 0.5 and 6.8 +/- 0.9 m/s during the control trials to 4.4 +/- 0.1 m/s during the 200-mg cocaine trial. Cocaine did not alter maximal treadmill work intensity (P > 0.05); however, time to exhaustion increased by approximately 92 s (15%; P < 0.05) during the 200-mg trial.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Effect of furosemide and weight carriage on energetic responses of horses to incremental exertion.

The effect of furosemide-induced weight loss on the energetic responses of horses to running was examined in a 3-way crossover study. Eight 2- to 3-year-old Standardbred mares received, in random order, 10 ml of saline solution 4 hours before running on a treadmill (control trial, C); or, during 2 trials, 1 mg of furosemide/kg of body weight, i.v., 4 hours before running. During one of the trials when the horses received furosemide, they carried weight equal to that lost over the 3.75 hours after furosemide administration while running (furosemide-loaded, FL), and during the other trial they did not carry weight equal to that lost after furosemide administration (furosemide-unloaded, FU). Horses performed an incremental exercise test on a treadmill during which rates of oxygen consumption (VO2) and carbon dioxide production (VCO2) were measured, respiratory exchange ratio was calculated, and blood samples were collected for determination of mixed venous plasma lactate concentration and arterial and mixed venous oxygen saturation. Furosemide treatment caused significantly (P < 0.001) greater weight loss than did saline administration; mean +/- SEM weight loss (exclusive of fecal loss) was 1.6, 8.8, and 10.2 kg (SEM = 2.0) for C, FL, and FU trials, respectively. The speed at which peak VO2 was achieved was 9.31, 9.56, and 9.50 (SEM = 0.16) m/s, respectively, time to fatigue was 547, 544, and 553 (SEM = 26) seconds, respectively, and the highest speed attained was 10.3, 10.2, and 10.2 (SEM = 0.2) m/s, respectively. Mean peak rate of oxygen consumption was 130.7, 129.6, and 129.6 (SEM = 1.9) ml/min/kg, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Pedicle skin flaps in ponies: viable length is related to flap width.

The relationship between pedicle flap width and viable length was characterised for skin flaps of the flank in ponies. Four dorsally based, pedicle type skin flaps of 20 cm in length and 3, 6, 9 or 12 cm in width were created in a random sequence on one flank in each of 10 ponies. Flap survival length was assessed by skin texture and appearance, depilation of hair and wound healing at 14 days after surgery. There was considerable variation between animals in the viable length of flaps of the same width; however, a significant difference in the viable length of flaps of different widths was detected (P = 0.002). The viable length of the 3 cm flaps was significantly different from that of the 12 cm flaps (9.69 +/- 1.1 cm vs 12.97 +/- 1.0 cm, mean +/- se P less than 0.05). There was a positive correlation between flap width and viable length (r2 = 0.141, P = 0.017). There was no effect of flap order (cranial to caudal positioning relative to the other flaps) on viable length (P = 0.286). The results of this study demonstrate a significant relationship between flap width and viable length, confirming a previously unsupported assumption that flap width and viable length are related. These findings suggest that the clinician should employ broad pedicles when using local flaps to reconstruct skin defects on the flank of the horse.

Animals↗
PubMed1992

Arterial-venous difference in atrial natriuretic peptide concentration during exercise in horses.

Six nontrained mares were subjected to steady-state, submaximal treadmill exercise to examine the effect of exercise on the plasma concentration of atrial natriuretic peptide (ANP) in arterial, compared with mixed venous, blood. Horses ran on a treadmill up a 6 degree grade for 20 minutes at a speed calculated to require a power equivalent to 80% of maximal oxygen uptake (VO2MAX). Arterial and mixed venous blood samples were collected simultaneously from the carotid and pulmonary arteries of horses at rest and at 10 and 20 minutes of exercise. Plasma was stored at -80 C and was later thawed; ANP was extracted, and its concentration was determined by radioimmunoassay. Exercise caused significant (P < 0.05) increases in arterial and venous plasma ANP concentrations. Mean +/- SEM arterial ANP concentration increased from 25.2 +/- 4.4 pg/ml at rest to 52.7 +/- 5.2 pg/ml at 10 minutes of exercise and 62.5 +/- 5.2 pg/ml at 20 minutes of exercise. Mean venous ANP concentration increased from 24.8 +/- 4.3 pg/ml at rest to 67.2 +/- 14.5 pg/ml at 10 minutes of exercise and 65.3 +/- 13.5 pg/ml at 20 minutes of exercise. Significant differences were not evident between arterial or mixed venous ANP concentration at rest or during exercise, indicating that ANP either is not metabolized in the lungs or is released from the left atrium at a rate matching that of pulmonary metabolism.

Animals↗
PubMed1992

Plasma renin activity and aldosterone and vasopressin concentrations during incremental treadmill exercise in horses.

Six untrained mares were subjected to incremental treadmill exercise to examine exercise-induced changes in plasma renin activity (PRA) and plasma aldosterone (ALDO) and plasma arginine vasopressin (AVP) concentrations. Plasma renin activity, ALDO and AVP concentrations, and heart rate (HR) were measured at each step of an incremental maximal exercise test. Mares ran up a 6 degree slope on a treadmill set at an initial speed of 4 m/s. Speed was increased 1 m/s each minute until HR reached a plateau. Plasma obtained was stored at -80 C and later was thawed, extracted, and assayed for PRA and ALDO and AVP values by use of radioimmunoassay. Exercise caused significant increase in HR from 40 +/- 2 beats/min (mean +/- SEM) at rest to 206 +/- 4 beats/min (HRmax) at speed of 9 m/s. Plasma renin activity increased from 1.9 +/- 1.0 ng/ml/h at rest to a peak of 5.2 +/- 1.0 ng/ml/h at 9 m/s, paralleling changes in HR. Up to treadmill speed of 9 m/s, strong linear correlations were obtained between exercise intensity (and duration) and HR (r = 0.87, P less than 0.05) and PRA (r = 0.93, P less than 0.05). Heart rate and PRA reached a plateau and did not increase when speed was increased from 9 to 10 m/s. Plasma ALDO concentration increased from 48 +/- 16 pg/ml at rest to 191 +/- 72 pg/ml at speed of 10 m/s. Linear relation was found between exercise intensity (and duration) and ALDO concentration (r = 0.97, P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Aldosterone↗
PubMed1991

Gossypol pharmacokinetics in mid-lactation Brown Swiss dairy cows.

A bolus equivalent to 450 ppm (dosage based on average feed intake for lactating dairy cows of similar mass) of gossypol was administered orally to three Brown Swiss dairy cows in mid lactation daily for a 7-day treatment period. Blood samples were taken during a 2-day pretreatment period, the 7-day treatment period and a 6-day recovery period. The serum recovered from the cows was stored at -20 degrees C until analysis for extractable gossypol content. The highest concentration of gossypol (a mean of 0.53 microgram/ml serum) was attained in all the cows on day 6 of the treatment period, indicating that a steady-state condition had been reached before the end of the treatment period. The gossypol concentrations then gradually declined during the 6-day recovery period but never fell to the zero baseline. The cows exhibited terminal elimination half-lives of 67, 67.5 and 40 h. Gossypol elimination was best described by a bi-exponential decay curve in two cows and a mono-exponential decay curve in the remaining cow.

Absorption↗
PubMed1991

Ruminant pharmacology.

Aspects of drug disposition, metabolism, and toxicity in the ruminant animal are discussed, and illustrative examples are provided. The effects of the reticulo-rumen on drug disposition in the ruminant are highlighted.

Animals↗
PubMed1991

Clinical examination of the respiratory system.

Aspects of a detailed examination of the respiratory system of the horse with suspected respiratory system disease are described. This review includes discussions of the terminology of signs associated with respiratory system disease; radiographic examination of the upper and lower airways and thorax; nuclear scintigraphy; percutaneous and endoscopic tracheal aspiration; bronchoalveolar lavage; electromyography; blood gas analysis; and pleuroscopy and pleural fluid examination.

Animals↗
PubMed1991

Furosemide-induced changes in plasma and blood volume of horses.

The effect of furosemide administration (1 mg/kg body weight, i.v.) on plasma and blood volumes in 6 intact and 4 splenectomized horses was measured using Evans blue dye dilution, hematocrit, and hemoglobin and plasma total solids concentrations. Body weight decreased by 33.6 +/- 3.3 and 33.7 +/- 0.8 g/kg 4 h after furosemide administration to intact and splenectomized mares, respectively. Plasma volume, estimated by Evans blue dye dilution, was reduced by 8.3 +/- 3.3% (mean +/- SE) 4 h after furosemide administration. The reduction in plasma volume was first detectable 5-10 min after furosemide administration and was greatest 15-30 min (13.0 +/- 0.8%) after dosing. This study demonstrates that furosemide produces significant and rapid reductions in plasma volume in horses. These decreases in plasma volume only partially resolve 4 h after furosemide administration.

Animals↗
PubMed1991

Renal tubular function in horses during submaximal exercise.

Exercise-induced changes in renal function were examined during steady-state submaximal treadmill exercise in six unfit mares. Horses were randomly assigned to either an exercise or parallel control (no exercise) trial on day 1 and the alternate trial 1 wk later. The mares ran on a treadmill, set at a 6 degrees incline, for 1 h at 55-60% of maximal heart rate. Exercise significantly (P less than 0.05) increased plasma osmolality, plasma [K+], urine flow (+ 45%), Na+ excretion (+ 371%), K+ excretion (+ 57%), osmotic clearance (+ 32%), Na+ clearance (+ 391%), K+ clearance (+ 33%), and fractional Na+ excretion (+ 320%) and significantly decreased plasma [Cl-], Cl- excretion (-46%), Cl- clearance (-41%), and fractional Cl- excretion (-47%). Glomerular filtration rate, fractional K+ excretion, and free water clearance did not change during exercise. Atrial natriuretic peptide increased during exercise from 11 +/- 1 pg/ml at rest to a peak of 40 +/- 9 pg/ml (264%, P less than 0.05) at 40 min. Increases in plasma renin activity (66%, P less than 0.05) were accompanied by increases in plasma aldosterone concentration (760%, P less than 0.05). Vasopressin concentration increased (P less than 0.05) steadily over the 60-min period of exercise. It was concluded that, in horses, submaximal exercise-induced increases in urine flow and sodium excretion are associated with a concurrent increase in the plasma concentration of atrial natriuretic peptide.

Animals↗
PubMed1991

Cardiovascular effects of xylazine and detomidine in horses.

The cardiovascular effects of xylazine and detomidine in horses were studied. Six horses were given each of the following 5 treatments, at 1-week intervals: xylazine, 1.1 mg/kg, IV; xylazine, 2.2 mg/kg, IM; detomidine, 0.01 mg/kg, IV; detomidine, 0.02 mg/kg, IV; and detomidine, 0.04 mg/kg, IM. All treatments resulted in significantly decreased heart rate, increased incidence of atrioventricular block, and decreased cardiac output and cardiac index; cardiac output and cardiac index were lowest following IV administration of 0.02 mg of detomidine/kg. Mean arterial pressure was significantly reduced for various periods with all treatments; however, IV administration of 0.02 mg of detomidine/kg caused hypertension initially. Systemic vascular resistance was increased by all treatments. Indices of ventricular contractility and relaxation, +dP/dt and -dP/dt, were significantly depressed by all treatments. Significant changes were not detected in stroke volume or ejection fraction. The PCV was significantly reduced by all treatments. Respiratory rate was significantly decreased with all treatments, but arterial carbon dioxide tension did not change. Arterial oxygen tension was significantly decreased briefly with the 3 IV treatments only.

Analgesics↗