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Biomedical subjects

W W Muir

Publications and source records attributed to W W Muir.

At least 19 recordsLinked to original sources
PubMed1998

Evaluation of a portable clinical analyzer in a veterinary hospital setting.

OBJECTIVE: Evaluation of a portable clinical analyzer for determination of blood gas tensions, electrolyte and glucose concentrations, and Hct in a hospital setting. DESIGN: Prospective study. ANIMALS: 50 dogs, 50 cats, and 28 horses, all clinically normal. PROCEDURE: Blood samples were analyzed on a portable clinical analyzer to determine concentrations of sodium, potassium, chloride, BUN, glucose, and ionized calcium and values of Hct, pH, PCO2, and PO2. Values obtained were compared with those obtained from the same blood samples, using a standard automatic analyzer (serum sodium, potassium, chloride, BUN, and glucose concentrations), a cell counter (Hct), a blood gas analyzer (pH, PCO2, PO2), and a calcium-pH analyzer (ionized calcium). Bias (mean difference between values obtained on the same sample by different methods) and variability (SD of differences) were determined for all values. Data were also subjected to Deming regression analysis. RESULTS: Correlation coefficients were > 0.90 for all values except potassium and ionized calcium concentrations. Bias and variability were within clinically acceptable limits (+/- 2 SD) for all but potassium, ionized calcium, and glucose concentrations and Hct. Species-dependent variability was observed for glucose concentration and Hct. CLINICAL IMPLICATIONS: Most differences between values obtained with the portable clinical analyzer and standard clinical laboratory systems could be accounted for by differences in type of sample tested (blood vs serum). The portable clinical analyzer is suitable for point-of-care analysis in critical care situations and for routine blood biochemical analysis when extensive laboratory support is unavailable.

Animals↗
PubMed1998

Cell trafficking, mediator release, and articular metabolism in acute inflammation of innervated or denervated isolated equine joints.

OBJECTIVES: To describe the acute cellular response, inflammatory mediator release, and effect on chondrocyte metabolism of interleukin 1 beta (IL-1 beta) in isolated innervated or denervated equine metacarpophalangeal joints. ANIMALS: One metacarpophalangeal joint of 24 adult horses. PROCEDURES: The metacarpophalangeal joint was isolated for 6 hours in a pump-perfused, auto-oxygenated, innervated or denervated metacarpophalangeal joint preparation. Isolated joints were assigned to 4 groups: control, control-denervated, inflamed, and inflamed-denervated, and inflammation was induced by intra-articular injection of IL-1 beta. Synovial fluid was collected for cytologic examination and determination of IL (IL)-1 beta, (IL-6), prostaglandin E2 (PGE2), and substance P (SP) values. Synovial membrane was immunostained with SP and nerve-specific enolase (NSE) antibodies. Cartilage was collected for determination of proteoglycan (PG) synthesis and degradation. RESULTS: IL-1 beta induced significant neutrophilic leukocytosis in synovial and synovial membrane. IL-1 beta concentration and returned to baseline by 5.5 hours, but IL-6 concentration significantly increased throughout the study. Total SP content was significantly higher in inflamed joints. There was a significant increase in 24- and 48-hour PG degradation in inflamed innervated joints. CONCLUSION: Cellular response to IL-1 beta was rapid and sustained; joint clearance of IL-1 beta was rapid, and endogenous production of IL-1 beta did not follow. The IL-6 and PGE2 concentrations significantly increased, and SP content was increased in association with inflammation but not denervation. A degradative response of cartilage of IL-1 beta was observed, and was enhanced by innervation. This model was useful for investigation of the articular response to acute inflammation and the influence of denervation in modulating this response.

Animals↗
PubMed1998

Cardiorespiratory effects of sevoflurane, isoflurane, and halothane anesthesia in horses.

OBJECTIVE: To determine and compare cardiorespiratory and recovery effects of sevoflurane, isoflurane, and halothane in horses. ANIMALS: 8 clinically normal horses (4 mares, 4 geldings), 5 to 12 years old. PROCEDURE: Inhalation anesthesia was maintained for 90 minutes with sevoflurane, isoflurane, or halothane. Anesthesia depth was maintained at 1.5 minimum alveolar concentration of halothane, isoflurane, and sevoflurane, then was reduced at 30 and 60 minutes. A surgical plane of anesthesia was reinduced by administration of ketamine or thiopental or by increasing the fractional inspired concentration of sevoflurane. Cardiovascular and pulmonary variables were recorded and compared among inhalation anesthetics. Recovery was monitored, and subjective assessment of recovery quality was performed. RESULTS: Hemodynamic and pulmonary indices during sevoflurane anesthesia were similar to those of isoflurane. Cardiac output and systemic arterial pressure decreased less during sevoflurane and isoflurane anesthesia than during halothane anesthesia. After 90 minutes, cardiac output was greater for sevoflurane and isoflurane, respectively, compared with halothane. Mean arterial pressure was similar for all three anesthetic agents. Respiratory rate for sevoflurane and isoflurane was less than that for halothane. This apparent respiratory depression correlated with greater increase in PaCO2 and decreased pH when sevoflurane and isoflurane were compared with halothane. Recovery from sevoflurane anesthesia was qualitatively similar and superior to recovery from isoflurane and halothane, respectively. Time to standing did not differ significantly between sevoflurane and isoflurane, but was shorter than halothane. CONCLUSIONS: Sevoflurane induced cardiorespiratory effects that were comparable to those of isoflurane and halothane. Cardiac output was greater and respiratory rate was less than that for halothane at 1.5 MAC. Sevoflurane anesthesia was characterized by good control of anesthesia depth during induction, maintenance, and recovery. Recovery time after sevoflurane anesthesia was comparable to that for isoflurane, and recovery was smooth and controlled in a manner consistent with recovery from halothane.

Anesthesia, Inhalation↗
PubMed1998

Systemic and colonic venous plasma biochemical alterations in horses during low-flow ischemia and reperfusion of the large colon.

The purpose of this study was to determine the effects of low-flow ischemia and reperfusion (I-R) of the large colon on 16 systemic venous (SV) and colonic venous (CV) plasma biochemical variables in horses. Horses (n = 24) were randomly allocated to 3 groups: sham-operated (n = 6), 6 h ischemia (n = 9), and 3 h ischemia followed by 3 h reperfusion (n = 9). SV and CV heparinized blood was collected at 0, 1, 3, 3.25, 4, and 6 h. The SV-CV difference was calculated for each variable. The SV, CV, and SV-CV difference for albumin, total protein, and calcium decreased significantly (P < 0.05) across time in horses of all groups, but there were no differences among groups. SV phosphorous was significantly increased from baseline (BL) at 1 to 6 h in horses of all groups, but there were no differences among groups. CV phosphorous was significantly greater than BL from 1 to 6 h in group-2 horses and from 1 to 3 h in group-3 horses. SV potassium was not different among groups, but was significantly higher at 6 h, compared with BL in horses of all groups. CV potassium was significantly greater than BL from 1 to 6 h in horses of groups 2 and 3. SV glucose was greater at 6 h compared with all previous times in horses of all groups, but there were no difference among groups. CV glucose was significantly lower than BL and group-1 values in horses of groups 2 and 3 during ischemia, but returned to BL during reperfusion in group-3 horses. CV anion gap was significantly greater and SV-CV anion gap was significantly more negative in horses of groups 2 and 3, compared with group-1 horses during ischemia. The biologic relevance of these alterations is unknown, but they may contribute to histopathologic, hemodynamic, and metabolic alterations characteristic of low-flow I-R. Alternatively, these alterations may simply reflect colonic injury sustained during I-R. Results suggest that the colon utilizes glucose as a fuel and generates acid anions during low-flow ischemia. Increased CV phosphorous and potassium during I-R likely occurs as a result of leakage of intracellular stores subsequent to cellular damage.

Alkaline Phosphatase↗
PubMed1998

Respiratory depression and apnea induced by propofol in dogs.

OBJECTIVE: To determine the maximal i.v. administered dose of propofol that would not induce a serious adverse event in nonsedated dogs. ANIMALS: 6 clinically normal dogs (3 males and 3 females) between 8 and 12 months old and weighing between 8.8 and 11.3 kg. PROCEDURE: Propofol was administered i.v. at an initial dosage of 6.5 mg/kg of body weight at a rate of 20 mg/10 s. Subsequent doses were incrementally increased by 2.5 mg/kg (eg, second dose: 9 mg/kg) and separated by a minimum of 3 days. This procedure was repeated until a dose that induced a serious respiratory, cardiovascular, or neurologic adverse effect was determined. RESULTS: Apnea was determined to be the serious adverse effect for all dogs. Duration of apnea varied between dogs, but increased in a dose-dependent manner at dosages > 14 mg/kg. CONCLUSIONS: Respiratory depression and apnea are the most likely adverse effects induced by i.v. administration of propofol to dogs. Propofol administered i.v. at a rate of 20 mg/kg/10 s induces minimal cardiovascular depression at dosages in excess of the apneic dosage. CLINICAL RELEVANCE: Respiratory depression and apnea should be expected as potential adverse effects after i.v. administration of propofol to dogs, particularly when administered at rapid rates of infusion.

Anesthetics, Intravenous↗
PubMed1998

Accuracy of noninvasive oxyhemoglobin saturation, end-tidal carbon dioxide concentration, and blood pressure monitoring during experimentally induced hypoxemia, hypotension, or hypertension in anesthetized dogs.

OBJECTIVE: To determine reliability of noninvasive methods of arterial oxyhemoglobin saturation (SpO2), end-tidal CO2 concentration (PEtCO2), and blood pressure (BP) determination during periods of hypoxemia and systemic arterial BP perturbations. ANIMALS: 7 healthy, conditioned dogs weighing 19 to 22 kg. PROCEDURE: 3 pulse oximeters, 2 capnometers, and 2 oscillometric BP monitors were used to measure oxygen-carrying capacity of the blood, heart rate, ventilatory status and arterial BP changes during hypoxemia, and altered arterial BP. Pulse oximeter-derived SpO2 and PEtCO2 were determined during rapidly induced plateaus of hypoxia (decreased fractional in-spired oxygen concentration [FiO2]) and altered systemic arterial BP. A lead-II ECG was used to monitor heart rate. RESULTS: Pulse oximetry provided an accurate assessment of fractional oxyhemoglobin saturation (SaO2) at SpO2 > 70%. As SaO2 decreased from 70%, the magnitude of the SpO2 error increased (20% error at SpO2 < 30%). The PEtCO2, was accurate at PaCO2, ranging from 30 to 55 +/- 5 mm of Hg under all experimental conditions. When PaCO2 was > 55 mm of Hg, both capnometers produced values that were as much as 20 mm of Hg less than the corresponding PaCO2. Mean BP was least dependent on pulse wave quality, consistently underestimating mean arterial BP by approximately 10 mm of Hg. CONCLUSIONS AND CLINICAL RELEVANCE: The pulse oximeters tested provided an accurate estimation of SaO2 at SpO2 > 70%. A PEtCO2 value > 55 mm of Hg may represent hypercapnia that is more profound than indicated. Systolic BP determinations were most accurate during hypotensive states and least accurate during hypertension. Diastolic BP measurements were generally more accurate during hypertension than normotension. Accuracy is not appreciably affected by hypotension resulting from vasodilation or blood loss. The tendency to underestimate systemic arterial BP should not interfere with trend detection during unstable clinical conditions.

Anesthesia, General↗
PubMed1998

Influence of atipamezole on effects of midsacral subarachnoidally administered detomidine in mares.

OBJECTIVE: To examine effects of atipamezole on detomidine midsacral subarachnoidally-induced analgesia, cardiovascular and respiratory activity, head ptosis, and position of pelvic limbs in healthy mares. ANIMALS: 10 healthy mares. PROCEDURE: Using a randomized, blinded, crossover study design, mares received detomidine (0.03 mg/kg of body weight, diluted in 3 ml of CSF) midsacral subarachnoidally, followed by atipamezole (0.1 mg/kg [test]) or sterile saline (0.9% NaCl) solution (control), i.v. 61 minutes later and saline solution (3 ml, midsacral subarachnoidally) on a separate occasion, at least 2 weeks later. Analgesia was determined by lack of sensory perception to electrical stimulation at the perineal dermatome and no response to needle-prick stimulation extending from the coccygeal to T15 dermatomes. Arterial acid-base (pH, standard bicarbonate, and base excess values), gas tensions (PO2, PCO2), PCV, total solids concentration, heart and respiratory rates, rectal temperature, and arterial blood pressure were determined, and mares were observed for sweating and urination. Mean scores of perineal analgesia, head ptosis, position of pelvic limbs, and cardiovascular and respiratory data were compared for the 3-hour test period. RESULTS: Subarachnoidally administered detomidine induced perineal analgesia (mean +/- SD onset, 9.0 +/- 4.6 minutes; duration, 130 +/- 26 minutes), marked head ptosis, moderate changes in pelvic limb position, cardiovascular and respiratory depression, sweating in analgesic zones, and diuresis. Intravenously administered atipamezole significantly reduced mean scores of detomidine-induced perineal analgesia, head ptosis, pelvic limb position, sweating and diuresis; partially antagonized detomidine-induced bradycardia; and did not effect detomidine-induced bradypnea. CONCLUSIONS AND CLINICAL RELEVANCE: Most effects of midsacral subarachnoidally administered detomidine, except bradycardia and bradypnea, were reversed by atipamezole (0.1 mg/kg, i.v.), indicating that most of the actions of detomidine were mediated via activation of alpha2-adrenergic receptors.

Acid-Base Equilibrium↗
PubMed1998

Vascular and transsynovial forces of the isolated stationary equine joint.

OBJECTIVE: To provide quantitative assessment of forces affecting filtration of synovial fluid in response to incremental changes in arterial and venous hemodynamics. ANIMALS: 7 clinically normal adult horses. PROCEDURE: Using a stationary, isolated metacarpophalangeal joint preparation, blood flow (Qa[cir]), tissue perfusion, arterial pressure (Pa[cir]), venous pressure (Pv[cir]), transsynovial fluid flow, total vascular resistance, vascular compliance, and tissue compliance were evaluated before and after arterial and venous pressure manipulations. At isogravimetric conditions, pre- and postcapillary resistance and ratios, osmotic reflection coefficient (sigma[d]), capillary pressure, net filtration pressure, and transitional microvascular pressure were determined. RESULTS: Synovial tissue blood flow was similar before, immediately after, and 3.5 hours after joint isolation. The sigma(d) for the joint was low, owing to the high oncotic pressure of synovial fluid at filtration-independent states. Transsynovial flow occurred in preference to lymph flow because of the high permeability of synovial tissue (low sigma[d]). Synovial fluid production and transfluid flow (synovium weight gain) increased at Pa(cir) > 200 mm of Hg, indicating a threshold phenomenon for synovial filtration. Net filtration pressure > 6 mm of Hg is needed to effect an increase in synovial fluid flow, and pressure of approximately 11 mm of Hg is necessary to increase lymphatic flow. Vascular compliance in the joint was low, but increased markedly with Pv(cir). Vascular and tissue compliance increased with increased Pa(cir). Vascular compliance changes caused by increased arterial pressure were minimal, compared with those caused by increased venous pressure owing to the greater elastance of arteries and the larger muscular arterial wall. CONCLUSION: This isolated joint preparation permitted evaluation of codependent hemodynamic, microvascular, and transsynovial flow responses to hemodynamic manipulations. Synovial tissue permeability was markedly affected by increased vascular forces altering filtration pressures toward synovial fluid production.

Animals↗
PubMed1998

Cardiorespiratory effects of low-flow and closed circuit inhalation anesthesia, using sevoflurane delivered with an in-circuit vaporizer and concentrations of compound A.

OBJECTIVES: To determine the concentrations of sevoflurane and compound A (a degradation product of sevoflurane) in the anesthetic circuit when sevoflurane was delivered with an in-circuit vaporizer, and to determine the cardiorespiratory effects of sevoflurane in dogs. ANIMALS: 6 mixed-breed dogs. PROCEDURE: In-circuit vaporizers were connected to the inspiratory limb of a circle rebreathing system connected to a ventilator. A reservoir bag was attached to the Y-piece connector to act as an artificial lung, and sevoflurane concentrations in the anesthetic circuit were measured at vaporizer settings of 1, 3, 5, 7, and 10 and oxygen flow rates of 250 and 500 ml/min. Cardiorespiratory effects of sevoflurane were determined in dogs while they were breathing spontaneously, during controlled ventilation, and during closed circuit anesthesia. Concentrations of compound A were determined by means of gas chromatography with flame ionization. RESULTS: The concentration of sevoflurane in the anesthetic circuit increased with vaporizer setting and time. For oxygen flow rates of 250 and 500 ml/min, vaporizer settings between 5 and 7 and between 7 and 10, respectively, produced sevoflurane concentrations closest to values reported to produce surgical anesthesia in dogs. Significant differences were not observed in cardiorespiratory variables with time or among anesthetic conditions. Concentrations of compound A in the anesthetic circuit were less than values reported to produce renal toxicoses and death in rats. CONCLUSION: Results suggested that sevoflurane can be administered to nonsurgically stimulated dogs, using an in-circuit vaporizer and low (< 15 ml/kg/min) oxygen flow rates, without causing significant cardiorespiratory depression or clinically important concentrations of compound A.

Anesthesia, Closed-Circuit↗
PubMed1998

Comparison of anion gap and strong ion gap as predictors of unmeasured strong ion concentration in plasma and serum from horses.

OBJECTIVE: To compare the accuracy of anion gap (AG) and strong ion gap (SIG) for predicting unmeasured strong ion concentration in plasma and serum from horses. ANIMALS: 6 well-trained Standardbred horses undergoing high-intensity exercise (experimental study) and 78 horses and ponies that underwent i.v. administration of lactic acid or endotoxin, and endurance, submaximal, or high-intensity exercise. PROCEDURE: Anion gap was calculated as AG = (Na+ + K+) - (Cl- + HCO3-), and SIG was calculated, using the simplified strong ion model, whereby SIG (mEq/L) = 2.24 x total protein (g/dl)/(1 + 10(6.65-pH)) - AG. The relation between AG or SIG and plasma lactate concentration was evaluated, using linear regression analysis. RESULTS: Linear relations between plasma lactate concentration and AG and SIG were strong for the experimental study (r2 = 0.960 and 0.966, respectively) and the published studies (r2 = 0.914 and 0.925, respectively). The following relations were derived: AG = 1.00 x plasma lactate + 10.5; SIG = 0.99 x plasma lactate + 2.8. An AG > 15 mEq/L indicated an increased unmeasured anion concentration, whereas a SIG < -2 mEq/L indicated an increased unmeasured strong anion concentration. CONCLUSIONS AND CLINICAL RELEVANCE: Anion gap and SIG can be used to predict plasma lactate concentration in horses. AG is accurate and clinically useful for estimating unmeasured strong ion concentration in horses with total protein concentrations within or slightly outside reference range, whereas SIG is more accurate in horses with markedly abnormal total protein concentrations and those of various ages and with various concentrations of albumin, globulin, and phosphate.

Acid-Base Equilibrium↗
PubMed1998

Local hemodynamics, permeability, and oxygen metabolism during acute inflammation of innervated or denervated isolated equine joints.

OBJECTIVES: To determine oxygen metabolism, permeability, and blood flow in isolated joints in response to interleukin 1beta (IL-1beta) and contribution of innervation. SAMPLE POPULATION: One metacarpophalangeal (MCP) joint of 24 adult horses. PROCEDURE: The MCP joint was isolated for 6 hours in a pump-perfused, auto-oxygenated, innervated or denervated preparation. Isolated joints were assigned to the following 4 groups: control, control-denervated, inflamed, and inflamed-denervated, and inflammation was induced by intra-articular injection of IL-1beta. Circuit arterial and venous pressures, flows, and blood gas tensions, synovial fluid production, and intra-articular pressure were measured. Total vascular resistance; oxygen delivery, consumption, and extraction ratio (ER); and permeability surface area product were calculated. Synovial membrane blood flow was determined at 0, 60, and 330 minutes. Synovial membrane wet-to-dry ratio was obtained, and permeability to macromolecules was determined by intra-articular injection of Evans blue albumin and fluorescein isothiocyanate-conjugated dextran. RESULTS: Oxygen delivery and synovial membrane blood flow progressively increased but were not different among groups. Oxygen consumption and ER significantly increased in inflamed joints, as did intraarticular pressure and synovial fluid production. Inflamed joints had greater wet-to-dry ratio. Albumin permeability significantly increased in the villous synovial membrane of the inflamed groups, and dextran permeability was increased in the innervated groups, with a trend toward increased permeability in inflamed groups. CONCLUSION: Inflammation significantly increased oxygen demand, which was initially met by increased ER. Permeability to small molecules was increased with inflammation; innervation increased permeability to large molecules. Use of an isolated joint model enabled documentation of the physiologic responses of the joint to acute inflammation.

Albumins↗
PubMed1997

Use of yohimbine to reverse prolonged effects of xylazine hydrochloride in a horse being treated with chloramphenicol.

A 1-year-old Standardbred gelding had received xylazine hydrochloride (0.75 to 1.00 mg/kg [0.34 to 0.45 mg/lb] of body weight, IV) during 2 surgeries for debridement of a wound. The horse was given chloramphenicol (55 mg/kg [25 mg/lb], PO, q 6 h) for 5 days, and was anesthetized a third time with xylazine (0.75 mg/kg, IM). Five hours after administration of xylazine, the horse remained markedly sedated and had clinical signs of gaseous distention of the large bowel (bloat) requiring trocharization. Administration of yohimbine (0.03 mg/kg [0.01 mg/lb], i.v.) eliminated signs of sedation within 5 minutes. Moderate flatulence developed, and gastrointestinal sounds could be heard within all 4 abdominal quadrants within 15 minutes of yohimbine administration. The remainder of recovery was unremarkable. Xylazine induces bradycardia and decreases gastrointestinal motility in addition to causing sedation, muscle relaxation, and analgesia. Chloramphenicol can inhibit oxidase activity of cytochrome P-450 and inhibit metabolism and elimination of drugs such as xylazine.

Anesthesia, Intravenous↗
PubMed1997

Evaluation of a hypertonic saline-dextran solution for treatment of dogs with shock induced by gastric dilatation-volvulus.

OBJECTIVE: To test the hypothesis that small volumes of hypertonic saline-dextran (HSD) solution can be used to effectively resuscitate dogs in shock induced by gastric dilatation-volvulus (GDV), and, compared with administration of large volumes of lactated Ringer's solution (LRS), can be used to limit the overall volume of fluid needed for resuscitation. DESIGN: Prospective, clinical study. ANIMALS: 15 dogs with GDV-induced shock. PROCEDURE: Initially, HSD solution (5 ml/kg of body weight) or LRS (60 to 90 ml/kg) was administered. All dogs then received a maintenance administration (20 ml/kg/h) of LRS. Cardiorespiratory, blood gas, and serum biochemical analyses were performed over a 4-hour period after initiation of treatment. RESULTS: Systolic arterial and central venous pressures and plasma volume increased more rapidly in dogs in the HSD + LRS group. The cumulative dose of fluids administered to dogs in the HSD + LRS group was significantly less than that administered to dogs in the LRS group. Serum sodium and chloride concentrations and osmolality increased significantly in dogs in the HSD + LRS group, but not in dogs in the LRS group. Ventricular arrhythmias were detected in both groups of dogs, but did not appear to be induced by either form of fluid therapy. CLINICAL IMPLICATIONS: Administration of HSD rapidly restored cardiorespiratory function and induced resuscitation equivalent to administration of large volumes of LRS. Use of HSD solutions to treat dogs in GDV-induced shock may be more efficient than use of isotonic fluids. Administration of HSD solution was not associated with noticeable complications.

Animals↗
PubMed1997

Effect of intravenous anesthetics on inward rectifier potassium current in rat and human ventricular myocytes.

BACKGROUND: Inhibition of the inward rectifying potassium current (I(K1)) may cause cardiac dysrhythmias by decreasing resting membrane potential or prolonging action potential. METHODS: The effects of thiopental, ketamine, and propofol on I(K1) conductance were evaluated in rat ventricular myocytes. The effect of thiopental on I(K1) conductance was also evaluated in human ventricular myocytes. Currents were recorded using the nystatin-perforated whole-cell patch-clamp technique (holding potential, -50 mV; test potentials, -140 to -40 mV). Pipette solution contained 130 mM KCl, 5 mM MgCl2, 5 mM HEPES, and 5 mM EGTA,pH 7.2. Bath solution (32 degrees C) contained 134 mM NaCI, 4 mM KCl, 1 mM MgCl2, 1 mM CaCl2, 0.3 mM CdCl2, 5 mM HEPES, and 5 mM d-glucose,pH 7.4. Drug concentrations examined encompassed the range of clinically relevant unbound plasma concentrations. Currents were normalized for cell capacitance. Conductance was calculated as current density/delta mV from -140 to -100 mV. Analysis of variance was used to test for changes in conductance as a function of drug concentration. RESULTS: Thiopental reduced I(K1) conductance in a concentration-dependent manner (P < 0.0001). Thiopental-induced changes in I(K1) conductance in rat ventricular myocytes were fit to an inhibitory E(max) model, with a median inhibitory concentration of 10.5 microM. The effect of thiopental on I(K1) conductance in human ventricular cells was comparable to that observed in rat ventricular myocytes. Neither ketamine nor propofol altered I(K1) conductance. CONCLUSIONS: Thiopental reduces I(K1) conductance in a concentration-dependent manner at clinically relevant concentrations in both rat and human ventricular myocytes.

Anesthetics, Intravenous↗
PubMed1997

Cardiorespiratory and metabolic effects of walking, standing, and standing with a splint during the recuperative period from maximal exercise in horses.

OBJECTIVE: To determine the effects of walking, standing, or standing with a splint on 1 forelimb on rate of recuperation of horses after a brief, intense bout of exercise. ANIMALS: 6 adult Thoroughbreds (435 to 542 kg). PROCEDURE: Horses were preconditioned by exercise on a treadmill to establish a uniform level of fitness. Once fit, the treadmill speed causing each horse to exercise at 120% of its maximal oxygen consumption was determined and was used in simulated races at 14-day intervals. Horses were instrumented for collection of arterial and mixed venous blood samples for measurement of acid-base status, concentrations of metabolites, and cardiopulmonary indices. The horses were exercised at a speed inducing 120% of their maximal oxygen consumption until fatigued or for a maximum of 2 minutes. Three recuperative interventions were evaluated: walking at 1.8 m/s for 30 minutes, then standing for the remainder of the 90-minute trial; standing stationary for 90 minutes; and standing stationary for 90 minutes with a splint on the right forelimb. RESULTS: Walking significantly increased cardiac output during the recuperative phase and hastened recovery of normal acid-base status and return of blood lactate concentration to baseline values. CONCLUSION: Limiting movement of horses during the recuperative period delays recovery from maximal exercise. Most measured indices returned to baseline by 60 minutes after exercise. All measured cardiopulmonary indices returned to baseline values by 90 minutes after exercise. CLINICAL RELEVANCE: Horses that are not allowed to walk during recuperation from exercise may have a prolonged recovery period.

Acid-Base Equilibrium↗
PubMed1996

Evaluation of a survey of the diplomates of the American College of Laboratory Animal Medicine on use of analgesic agents in animals used in biomedical research.

OBJECTIVE: To determine the analgesic agents administered to animals frequently used in biomedical research. DESIGN: Telephone survey. SAMPLE POPULATION: Diplomates of the American College of Laboratory Animal Medicine. PROCEDURE: 200 of 429 active diplomates listed in the 1993 directory of the American College of Laboratory Animal Medicine were selected at random for telephone interviews. Diplomates were asked to identify the species that they cared for and the dosages, dosing intervals, and routes of administration for analgesic agents. RESULTS: 90 of 200 (45%) diplomates completed the survey. Twenty-two analgesic agents were identified for use in 472 applications in 16 species. Opioid analgesics were the most frequently selected agents, with buprenorphine hydrochloride and butorphanol being most frequently used. Intramuscular and subcutaneous routes of administration were used most frequently. CLINICAL IMPLICATIONS: Among diplomates of the American College of Laboratory Animal Medicine, opioids are the most frequently selected agents used to induce analgesia in animals used in biomedical research. Dosages and dosing intervals used vary widely among animals of various species as well as for animals in each species.

Analgesics↗
PubMed1996

Evaluation of a hypertonic sodium chloride/dextran solution for treatment of traumatic shock in dogs.

OBJECTIVE: To compare the efficacy of 7% NaCl solution (hypertonic saline) in 6% dextran 70 solution (HSD) with that of lactated Ringer's solution (LRS) for treatment of dogs in traumatic shock. DESIGN: Prospective, randomized, clinical study. ANIMALS: 16 traumatized adult dogs with clinical signs of shock. PROCEDURE: Physical, hemodynamic, blood gas, and clinical chemistry measurements were performed prior to treatment. Initial treatment consisted of HSD (n = 8) or LRS (n = 8) administered as a bolus (5 ml/kg of body weight, IV) over a 3-minute period, followed by administration of additional LRS and other treatments to restore hemodynamic and physical criteria to within reference limits. Measurements were repeated for 3 hours after initial treatment. The volumes of LRS and HSD administered were recorded hourly. Degree of injury was scored by using a trauma severity index. RESULTS: Dogs responded similarly to the treatments, and all but 3 dogs survived to be discharged. The amount of fluid administered to dogs in the HSD group over the final 2 hours of the study was significantly less than that administered to the dogs in the LRS group. Serum sodium concentration and osmolality of the dogs in the HSD group were not significantly greater than those values in the LRS group. Bradyarrhythmias were observed in 2 dogs in the HSD group. CLINICAL IMPLICATIONS: Hypertonic sodium chloride/dextran solution is safe and effective for resuscitating dogs in traumatic shock. Seven percent NaCl in 6% dextran 70 may reduce the need for isotonic fluids in the hours after initial resuscitation.

Accidents, Traffic↗