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Biomedical subjects

C I Dunlop

Publications and source records attributed to C I Dunlop.

At least 19 recordsLinked to original sources
PubMed1999

Cardiopulmonary measurements in dogs undergoing gastropexy without gastrectomy for correction of gastric dilatation-volvulus.

OBJECTIVE: To measure cardiopulmonary variables, including cardiac index, in dogs with naturally acquired gastric dilatation-volvulus (GDV). DESIGN: Prospective clinical study. ANIMALS: 6 dogs with GDV. PROCEDURE: In addition to typical medical and surgical management of GDV, the dorsal metatarsal and pulmonary arteries and right atrium of the dogs were catheterized to obtain cardiopulmonary measurements before and during anesthesia and surgery. RESULTS: All dogs underwent gastropexy but none required gastrectomy. Mean cardiac index and mean arterial blood pressure for this small population of dogs with GDV were not significantly different from those reported for clinically normal awake or anesthetized dogs. CONCLUSIONS AND CLINICAL RELEVANCE: Dogs with naturally acquired GDV without gastric necrosis may not have the classic characteristics, including decreased cardiac index and hypotension, of hypovolemic circulatory shock.

Animals↗
PubMed1998

Monitoring adequacy of ventilation by capnometry during thoracotomy in dogs.

OBJECTIVE: To determine whether end-tidal partial pressure of carbon dioxide (PETCO2) was a reliable estimate of PaCO2 in dogs undergoing thoracotomy. DESIGN: Case series. ANIMALS: 18 dogs that underwent thoracotomy. PROCEDURE: PaCO2 and PETCO2 were measured shortly after induction of anesthesia, while dogs were breathing spontaneously; 5 minutes prior to initial skin incision, while dogs were receiving intermittent positive-pressure ventilation (IPPV); 5, 30, and 60 minutes after the thoracic cavity was opened, while dogs were receiving IPPV; and after the thoracic cavity was closed and evacuated, when dogs were again breathing spontaneously. For each period, arterial-end-tidal difference in partial pressure of carbon dioxide (PaCO2-PETCO2) was compared with PaCO2-PETCO2 for the preceding period. RESULTS: Significant changes in PaCO2-PETCO2 from one period to the next were not detected except when values obtained 5 minutes after the thoracic cavity was opened were compared with values obtained 5 minutes before incision. The PaCO2-PETCO2 was not constant for individual dogs. CLINICAL IMPLICATIONS: PETCO2 was not a reliable indicator of adequacy of ventilation during thoracotomy in these dogs, because it differed greatly from PaCO2, and PaCO2-PETCO2 was not consistent.

Animals↗
PubMed1998

Cardiopulmonary effects of anesthesia induced and maintained with isoflurane in cats.

OBJECTIVE: To determine the cardiopulmonary effects of anesthesia induced and maintained with isoflurane (ISO) in cats. ANIMALS: 8 healthy cats between 1 and 5 years old. PROCEDURE: Anesthesia was induced with ISO in oxygen. Two anesthetic depths were maintained in each cat; mean alveolar concentrations (MAC) were 1.3 and 2.0 times MAC. Ventilation was either spontaneous or controlled. Each cat received each treatment combination according to a Latin square design. Cardiopulmonary measurements were made after 20 minutes of constant conditions with each combination of anesthetic depth and ventilatory mode. RESULTS: Cardiac index was not different between ISO doses, but 2.0 MAC ISO reduced arterial blood pressure and total peripheral resistance. Cardiac index and systolic arterial blood pressure were reduced by controlled ventilation. The PaCO2 and pulmonary artery pressure were highest in association with 2.0 MAC ISO during spontaneous ventilation. Changes in pHa were attributable to changes in PaCO2. CONCLUSIONS: 2.0 MAC ISO causes hypotension and hypercapnia; however, cardiac index is maintained. Hypercapnia may be abolished with controlled ventilation, but at the expense of reduced cardiac index. 1.3 MAC ISO results in minimal cardiopulmonary depression, especially when healthy cats are allowed to breathe spontaneously. CLINICAL RELEVANCE: Hypoventilation associated with untoward physiologic responses to 2.0 MAC may be overcome with controlled ventilation, but results in marked reduction in cardiovascular performance; thus, use of 2.0 MAC ISO should be avoided in cats.

Anesthetics, Inhalation↗
PubMed1996

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.

Acepromazine↗
PubMed1994

Cardiopulmonary effects of three prolonged periods of isoflurane anesthesia in an adult elephant.

An adult 3,500-kg female African elephant was anesthetized 3 times for treatment of subcutaneous fistulas over the lateral aspect of each cubitus (anesthesia 1 and 2) and for repair of a fractured tusk (anesthesia 3). Lateral recumbency and anesthesia were achieved with etorphine (anesthesia 1 and 2) or etorphine and azaperone (anesthesia 3). The elephant's trachea was intubated and anesthesia was maintained by use of isoflurane and oxygen delivered via 2 standard large animal anesthesia machines joined in parallel. The range of total recumbency time was 2.4 to 3.3 hours. Breathing and heart rates, systemic arterial pressure, rectal temperature, PaO2, pH, and end-tidal gases were monitored. After administration of etorphine, measurements were made while the air-breathing elephant was recumbent, then every 5 minutes (cardiovascular) or 15 minutes (blood gases) after commencement of administration of isoflurane and oxygen. Tachycardia and hypertension were detected after administration of etorphine, but heart rate and systemic arterial pressure decreased to within normal ranges after administration of isoflurane and oxygen. The elephant remained well oxygenated while anesthetized and breathing a high oxygen mixture. The elephant had an uneventful recovery from each anesthesia.

Anesthesia↗
PubMed1994

Anesthesia and sedation of foals.

Physiologic similarities and differences between foals and adult horses, including response to pain, cardiopulmonary function, ability to compensate for dehydration and hemorrhage, and response to anesthetic drugs, are considered in this article. Preanesthetic evaluation, choice of anesthetic drugs, technique, and monitoring support requirements through to anesthetic recovery are based on these physiologic considerations. Anesthetic techniques discussed include drugs for premedication, parenteral or inhalational anesthetic induction, and maintenance using inhalational and parenteral anesthesia. Where possible, the cardiopulmonary response of foals to individual anesthetic drugs or a combination of them is provided.

Anesthesia, General↗
PubMed1994

Cardiopulmonary effects of positioning pregnant cows in dorsal recumbency during the third trimester.

The uterine hemodynamic response to maternal positioning in dorsal recombency was evaluated in 7 conscious pregnant cows during the third trimester. Anesthetic or sedative drugs were not administered. Uterine artery flow was measured, using a previously implanted ultrasonic flow probe. Catheters implanted in the uterine artery and vein were used for measurement of blood pressure and for blood sample collections. Heart rate, systemic arterial pressure, uterine arterial blood flow, arterial and venous oxygen and carbon dioxide tensions, and pH were measured in cows in standing position. Cows were cast with ropes and positioned in dorsal recumbency, then measurements were repeated at 15 and 30 minutes. Compared with standing measurements, dorsal recumbency caused 50% increase in heart rate and 44% increase in arterial blood pressure. Uterine artery flow did not change significantly. Despite increased ventilation, arterial oxygenation was reduced during dorsal recombency. There were minimal differences between measurements at 15 and 30 minutes of dorsal recumbency.

Animals↗
PubMed1993

Biochemical and haematological changes following prolonged halothane anaesthesia in horses.

Six healthy horses were anaesthetised with halothane (1.2 times the horse minimal alveolar concentration) in oxygen for more than 12 hours. Serum bilirubin, aspartate aminotransferase, alkaline phosphatase and L-iditol dehydrogenase values were significantly (P < 0.05) increased for up to nine days after anaesthesia. These changes suggest an anaesthesia related liver dysfunction. Creatine kinase increased to an average of more than 1400 IU litre-1 24 hours after anaesthesia and this change is indicative of muscle cell disruption. Renal-associated biochemical results, (that is serum creatinine and inorganic phosphate concentrations) were significantly increased transiently and are indicative of reduced renal function during and immediately after anaesthesia. Plasma concentrations of eicosanoids (6-keto-PGF1a, PGF2a, PGE and thromboxane) following anaesthesia were not different from preanaesthetic values. The magnitude of liver and muscle cell related increases in serum enzyme activities resulting from prolonged halothane anaesthesia was in excess of that previously reported for anaesthesia of shorter duration.

Anesthesia, Inhalation↗
PubMed1993

Cardiopulmonary and behavioral responses to computer-driven infusion of detomidine in standing horses.

Cardiopulmonary and behavioral responses to detomidine, a potent alpha 2-adrenergic agonist, were determined at 4 plasma concentrations in standing horses. After instrumentation and baseline measurements in 7 horses (mean +/- SD for age and body weight, 6 +/- 2 years, and 531 +/- 48.5 kg, respectively), detomidine was infused to maintain 4 plasma concentrations: 2.1 +/- 0.5 (infusion 1), 7.2 +/- 3.5 (infusion 2), 19.1 +/- 5.1. (infusion 3), and 42.9 +/- 10 (infusion 4) ng/ml, by use of a computer-controlled infusion system. Detomidine caused concentration-dependent sedation and somnolence. These effects were profound during infusions 3 and 4, in which marked head ptosis developed and all horses leaned heavily on the bars of the restraining stocks. Heart rate and cardiac index decreased from baseline measurements (42 +/- 7 beats/min, 65 +/- 11 ml.kg of body weight-1.min-1) in linear relationship with the logarithm of plasma detomidine concentration (ie, heart rate = -4.7 [loge detomidine concentration] + 44.3, P < 0.01; cardiac index = -10.5 [loge detomidine concentration] + 73.6, P < 0.01). Second-degree atrioventricular block developed in 5 of 7 horses during infusion 3, and in 6 of 7 horses during infusion 4. Mean arterial blood pressure increased significantly from 118 +/- 11 mm of Hg at baseline to 146 +/- 27 mm of Hg at infusion 4. Similar responses were observed for mean pulmonary artery and right atrial pressures. Systemic vascular resistance (baseline, 182 +/- 28 mm of Hg.ml-1.min-1.kg-1) increased significantly during infusions 3 and 4 (to 294 +/- 79 and 380 +/- 58, respectively). (ABSTRACT TRUNCATED AT 250 WORDS)

Analgesics↗
PubMed1993

Effects of ephedrine on cardiovascular function and oxygen delivery in isoflurane-anesthetized dogs.

The hemodynamic effects of 2 dosages of ephedrine were studied in 6 dogs anesthetized with isoflurane only (end-tidal concentration equivalent to 1.5 times minimum alveolar concentration). Following instrumentation, baseline (time 0) measurements included heart rate (HR), respiratory rate, mean arterial blood pressure (MAP), cardiac output, and blood gas tensions. Cardiac index (CI), stroke volume (SV), systemic vascular resistance (SVR), arterial oxygen content (CaO2), and oxygen delivery and consumption (DO2 and VO2, respectively) were calculated. Three dogs were given ephedrine IV at a dosage of 0.1 mg/kg of body weight, and 3 dogs were given ephedrine IV at a dosage of 0.25 mg/kg. Measurements were recorded at 5, 10, 15, 30, and 60 minutes. Each dog then received the alternate dosage of ephedrine, and measurements were again recorded at the same intervals. Effects of ephedrine varied with dosage. Neither dosage was associated with significant changes in pH, PaO2, PaCO2, VO2, or respiratory rate. Ephedrine at a dosage of 0.1 mg/kg caused transient significant increases in MAP, CI, SV, CaO2, and DO2, significant decreases in HR and SVR, and a late, slight decrease in CaO2. Ephedrine at a dosage of 0.25 mg/kg caused a greater and more prolonged increase in MAP, as well as increases in CI, SV, and SVR, and a decrease in HR. The higher dosage of ephedrine also caused a pronounced increase in hemoglobin concentration and CaO2, resulting in a 20 to 35% increase in DO2 throughout the 60-minute experiment.

Anesthesia↗
PubMed1993

Circulatory and respiratory responses of spontaneously breathing, laterally recumbent horses to 12 hours of halothane anesthesia.

Cardiovascular and respiratory changes that accompany markedly long periods (12 hours) of halothane anesthesia were characterized. Eight spontaneously breathing horses were studied while they were positioned in left lateral recumbency and anesthetized only with halothane in oxygen maintained at a constant end-tidal concentration of 1.06% (equivalent to 1.2 times the minimal alveolar concentration for horses). Results of circulatory and respiratory measurements during the first 5 hours of constant conditions were similar to those previously reported from this laboratory (ie, a time-related significant increase in systemic arterial blood pressure, cardiac output, stroke volume, left ventricular work, PCV, plasma total solids concentration, and little change in respiratory system function). Beyond 5 hours of anesthesia, arterial blood pressure did not further increase, but remained above baseline. Cardiac output continued to increase, because heart rate significantly (P < 0.05) increased. Peak inspiratory gas flow increased significantly (P < 0.05) in later stages of anesthesia. There was a significant decrease in inspiratory time beginning at 4 hours. Although PaO2 and PaCO2 did not significantly change during the 12 hours of study, PVO2 increased significantly (P < 0.05) and progressively with time, beginning 6 hours after the beginning of constant conditions. Metabolic acidosis increased with time (significantly [P < 0.05] starting at 9 hours), despite supplemental IV administered NaHCO3. Plasma concentrations of eicosanoids: 6-keto-prostaglandin F1 alpha (PGF1 alpha, a stable metabolite of PGI2), PGF2 alpha, PGE, and thromboxane (TxB2, a stable metabolite of TxA2) were measured in 5 of the 8 horses before and during anesthesia. Significant changes from preanesthetic values were not detected. Dynamic thoracic wall and lung compliances decreased with time.

Anesthesia, Inhalation↗
PubMed1992

The case for rebreathing circuits for very small animals.

The objections to using adult circle systems on very small patients include increased resistance to breathing, mechanical dead space, and slow equilibration times. These objections warrant consideration before assuming that nonrebreathing systems have an inherent advantage for patients between 3 and 10 kg. The cost of anesthesia and the time taken to establish a desired anesthetic level are as important in determining which system to use for small animal patients. Based on the current evidence, it is acceptable to use adult circle rebreathing systems on healthy patients as small as 3 kg.

Anesthesia, Closed-Circuit↗
PubMed1992

Evaluation of the Doppler ultrasonic method of measuring systolic arterial blood pressure in cats.

The accuracy of the Doppler technique for indirect systolic blood pressure measurement was assessed in 16 anesthetized cats. Eight cats were anesthetized with isoflurane and 8 were anesthetized with halothane. Anesthetic depth and mode of ventilation were varied to obtain a wide range of arterial blood pressure. A Doppler transducer was placed on the palmer surface of the left forelimb over the common digital branch of the radial artery to detect blood flow, and a blood pressure monitoring cuff with a width 37% the limb circumference was placed half way between the elbow and the carpus. To enable direct arterial pressure measurements, the left femoral artery was catheterized and the blood pressure waveforms recorded simultaneously. Systolic blood pressure measured by use of the Doppler ultrasonic technique was significantly lower than that obtained from the femoral artery catheter. Using linear regression, we determined a clinically useful calibration adjustment for Doppler indirect blood pressure measurement in cats: femoral systolic pressure = Doppler systolic pressure + 14 mm of Hg.

Animals↗
PubMed1992

Cardiopulmonary responses to experimentally induced gastric dilatation in isoflurane-anesthetized dogs.

Gastric dilatation was experimentally induced in 6 anesthetized dogs maintained with constant-dose isoflurane in oxygen. An intragastric balloon was used to distend the stomach with a constant 30 mm of Hg pressure for 3.5 hours. The PaCO2 was maintained between 35 and 45 mm of Hg, using intermittent positive-pressure ventilation. Cardiopulmonary measurements prior to stomach distension (baseline) were compared with measurements taken during 0.1, 0.5, 1.0, 1.5, 2.5, and 3.5 hours of stomach distension by analyzing the change from baseline in a randomized-block analysis with each dog as a block. After distending the stomach, cardiac index increased (P less than 0.01) from 1.5 to 3.5 hours. Stroke volume did not change, thus the increase in the cardiac index was attributable to an increase in heart rate. During inflation, increases were observed in systemic arterial, pulmonary arterial, and right atrial pressure. Respiratory frequency was unchanged; however, to maintain PaCO2 constant, it was necessary to progressively increase peak airway pressure. Although PaO2 tended to decrease during gastric dilation, the dogs were never hypoxemic. These results indicate that when our methods are used to maintain a constant anesthetic dose of isoflurane in oxygen, an observed increase in cardiovascular performance is expected. This differs from other studies in anesthetized dogs that have shown reduction in cardiovascular performance following gastric dilatation.

Anesthesia, Inhalation↗