Comparison of arterial pressure waveform analysis with the lithium dilution technique to monitor cardiac output in anesthetized dogs     

Chen HC  Sinclair MD  Dyson DH  McDonell WN  Sears WC 《American journal of veterinary research》2005,66(8):1430-1436

OBJECTIVE: To assess agreement between arterial pressure waveform-derived cardiac output (PCO) and lithium dilution cardiac output (LiDCO) systems in measurements of various levels of cardiac output (CO) induced by changes in anesthetic depth and administration of inotropic drugs in dogs. ANIMALS: 6 healthy dogs. PROCEDURE: Dogs were anesthetized on 2 occasions separated by at least 5 days. Inotropic drug administration (dopamine or dobutamine) was randomly assigned in a crossover manner. Following initial calibration of PCO measurements with a LiDCO measurement, 4 randomly assigned treatments were administered to vary CO; subsequently, concurrent pairs of PCO and LiDCO measurements were obtained. Treatments included a light plane of anesthesia, deep plane of anesthesia, continuous infusion of an inotropic drug (rate adjusted to achieve a mean arterial pressure of 65 to 80 mm Hg), and continuous infusion of an inotropic drug (7 microg/kg/min). RESULTS: Significant differences in PCO and LiDCO measurements were found during deep planes of anesthesia and with dopamine infusions but not during the light plane of anesthesia or with dobutamine infusions. The PCO system provided higher CO measurements than the LiDCO system during deep planes of anesthesia but lower CO measurements during dopamine infusions. CONCLUSIONS AND CLINICAL RELEVANCE: The PCO system tracked changes in CO in a similar direction as the LiDCO system. The PCO system provided better agreement with LiDCO measurements over time when hemodynamic conditions were similar to those during initial calibration. Recalibration of the PCO system is recommended when hemodynamic conditions or pressure waveforms are altered appreciably.  相似文献   

Postoperative effects of anesthesia and surgery on resting energy expenditure in horses as measured by indirect calorimetry          下载免费PDF全文

Antonio M. Cruz  Nathalie Cot  Wayne N. McDonell  Raymond J. Geor  Brian A. Wilson  Gabrielle Monteith    Ronald Li 《Canadian journal of veterinary research》2006,70(4):257-262

In this study, we aimed to define the effects of anesthesia and surgery on the resting energy expenditure of horses in experimental conditions. Six horses were used in a longitudinal study with 2 study periods: before and after anesthesia and surgery. Every horse underwent a standard 90-min ventral midline exploratory laparotomy. Oxygen uptake (VO2) and carbon dioxide output (VCO2) were measured, with the use of a closed-circuit spirometry system, on 5 consecutive days immediately before and after the surgery. In 3 consecutive 5-min periods each day, the expired air was collected in a Collins spirometer. Samples of the expired gas were drawn from the spirometer through a drying column into O2 and CO2 analyzers. Resting energy expenditure was calculated as [(VO2 STPD*3.94) + (VCO2 STPD*1.11)]*1.44. This study showed that anesthesia and ventral midline exploratory laparotomy in experimental conditions increase the postoperative caloric demand in horses by an average of 1.0 Mcal/d, which represents approximately a 10% increase (P = 0.03). Additional studies in critically ill horses after surgery are needed to determine their caloric needs and to optimize their nutritional management.  相似文献   

Pharmacokinetics and toxic effects of lithium chloride after intravenous adminstration in conscious horses     

Hatfield CL  McDonell WN  Lemke KA  Black WD 《American journal of veterinary research》2001,62(9):1387-1392

OBJECTIVE: To determine the pharmacokinetics and toxic effects associated with IV administration of lithium chloride (LiCl) to conscious healthy horses. ANIMALS: 6 healthy Standardbred horses. PROCEDURE: Twenty 3-mmol boluses of LiCl (0.15 mmol/L) were injected IV at 3-minute intervals (total dose, 60 mmol) during a 1-hour period. Blood samples for measurement of serum lithium concentrations were collected before injection and up to 24 hours after injection. Behavioral and systemic toxic effects of LiCl were also assessed. RESULTS: Lithium elimination could best be described by a 3-compartment model for 5 of the 6 horses. Mean peak serum concentration was 0.561 mmol/L (range, 0.529 to 0.613 mmol/L), with actual measured mean serum value of 0.575 mmol/L (range, 0.52 to 0.67 mmol/L) at 2.5 minutes after administration of the last bolus. Half-life was 43.5 hours (range, 32 to 84 hours), and after 24 hours, mean serum lithium concentration was 0.13+/-0.05 mmol/L (range, 0.07 to 0.21 mmol/L). The 60-mmol dose of LiCl did not produce significant differences in any measured hematologic or biochemical variables, gastrointestinal motility, or ECG variables evaluated during the study period. CONCLUSIONS AND CLINICAL RELEVANCE: Distribution of lithium best fit a 3-compartment model, and clearance of the electrolyte was slow. Healthy horses remained unaffected by LiCl at doses that exceeded those required for determination of cardiac output. Peak serum concentrations were less than steady-state serum concentrations that reportedly cause toxic effects in other species.  相似文献   

Effect of protective padding on forelimb intracompartmental muscle pressures in anesthetized horses     

W A Lindsay  P J Pascoe  W N McDonell  M L Burgess 《American journal of veterinary research》1985,46(3):688-691

Wick catheters were used to measure intracompartmental muscle pressures (ICMP) within the long heads of the triceps brachii and extensor carpi radialis muscles of 8 horses maintained under halothane anesthesia while their breathing was controlled by intermittent positive-pressure ventilation. Blood gas, cardiac output, and blood pressure determinations were monitored to maintain a stable plane of anesthesia. The horses were positioned in left lateral recumbency and were placed sequentially on each of 4 contact surfaces for 1 hour. The 4 surfaces used for each horse were concrete, foam rubber, air dunnage bag, and a water mattress. Hematologic and biochemical determinations were made before and 24 hours after anesthesia. All horses recovered from the anesthesia. One horse had forelimb lameness for 36 hours after anesthesia, which was clinically diagnosed as a myoneuropathy. The ICMP values were markedly elevated in the muscle bellies of the lower limb of all horses. Supporting the horse on a water mattress caused the least dramatic pressure elevation and foam caused the most. The triceps muscle and, to a lesser extent, the extensor carpi radialis muscle of the lower limb are at risk of ischemia in anesthetized horses because the ICMP may exceed the critical closing pressure of 30 mm of Hg required for capillary blood flow.  相似文献   

Comparison of three methods for cardiac output determination in cats   总被引：5，自引：0，他引：5  

D H Dyson  D G Allen  W N McDonell 《American journal of veterinary research》1985,46(12):2546-2552

Cardiac output (CO) was measured in sodium pentobarbital-anesthetized cats over a wide range of blood flow rates. In 10 cats, CO was measured simultaneously, using Fick determination and thermodilution techniques. Echocardiography was used to estimate contractility of the heart by measuring percentage change in minor diameter and velocity of circumferential fiber shortening. These indices were compared with CO by the other techniques. Echocardiographic equations used for CO determination in man were evaluated for reliability in the cat. Thermodilution and Fick determination correlated best with low CO (r = 0.89) and less with intermediate (r = 0.69) and high (r = 0.75) CO. Percentage change in minor diameter and velocity of circumferential fiber shortening correlated with thermodilution measurements of the cardiac index (r = 0.71 and r = 0.84, respectively). The value of echocardiography for CO estimation was questionable, using existing equations. Fick determination of CO was more inconsistent and was more prone to technical error than was thermodilution.  相似文献   

Histopathologic alterations induced in the lungs of sheep by use of alpha2-adrenergic receptor agonists     

Celly CS  Atwal OS  McDonell WN  Black WD 《American journal of veterinary research》1999,60(2):154-161

OBJECTIVE: To study effects of central- and peripheral-acting alpha2-adrenergic receptor agonists on lung parenchyma, platelets, and pulmonary intravascular macrophages (PIM) of sheep. ANIMALS: 12 healthy mature female sheep. PROCEDURE: Group-1 (control, n = 2) sheep received 5 ml of physiologic saline solution IV and were euthanatized 3 minutes later. Sheep of group 2 (n = 8) received xylazine (150 microg/kg of body weight, IV), then 2 sheep each were euthanatized 3, 10, or 60 minutes, or 12 hours later. Sheep (n = 2) of group 3 were given ST-91 (30 microg/kg, IV), then were euthanatized 3 minutes later. Immediately after euthanasia, the lungs were fixed intratracheally and tissue was obtained for light and electron microscopy after 1 hour. RESULTS: Pulmonary parenchymal damage or morphologic alterations in PIM and platelets were not evident in control sheep. Three minutes after xylazine administration, morphologic changes in PIM were appreciable. After 10 minutes, extensive damage to the capillary endothelium and alveolar type-I cells, intra-alveolar hemorrhage, and interstitial and alveolar edema were evident. Most PIM had complete internalization of the surface coat. Similar changes were seen 60 minutes after xylazine administration; however, by 12 hours, morphologic features of PIM and lung parenchyma were almost completely restored. Evidence of PIM activation, obvious damage to capillary endothelium, and extensive pulmonary edema also were evident 3 minutes after ST-91 administration. CONCLUSIONS: XYLAZINE induces severe pulmonary parenchymal damage when administered at clinical sedative doses in sheep; morphologic changes in PIM within 3 minutes after administration of these drugs are substantial; and platelet aggregation is not apparent.  相似文献   

Effects of acepromazine or dexmedetomidine on fentanyl disposition in dogs during recovery from isoflurane anesthesia          下载免费PDF全文

Stephanie Keating  Carolyn Kerr  Wayne McDonell  Alexander Valverde  Ron Johnson  Heather Knych  Andrea Edginton 《Veterinary anaesthesia and analgesia》2016,43(1):35-43

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Cardiorespiratory effects of a cardioselective muscarinic antagonist in anesthetized horses     

FJ Teixeira Neto  WN McDonell  W Black  S Durongphongtorn 《Veterinary anaesthesia and analgesia》2003,30(2):111-112

Treatment of bradycardia in horses has been historically ignored because of the motility depressant effects of nonselective antimuscarinics. This study evaluated the cardiopulmonary effects of a cardioselective (M2) muscarinic antagonist, methoctramine (MET), in anesthetized horses. In a previous in vitro study, we determined that supraphysiological doses of MET were necessary to inhibit acetylcholine‐induced longitudinal jejunal smooth muscle contractions in this species. Six adult horses were allocated to two treatments in a randomized complete block design. Anesthesia was induced with xylazine/ketamine, and maintained with halothane (1% end‐tidal) and a constant infusion of xylazine (1 mg kg^?1 hour^?1) under mechanical ventilation. Invasive hemodynamic variables were monitored at baseline (approximately 45 minutes after induction) and for 120 minutes after MET or saline (control) had been injected. MET was titrated at 10‐minute intervals (10 µg kg^?1 IV) until the heart rate (HR) increased at least 30% above the baseline, or a maximum cumulative dose of 30 µg kg^?1 had been injected. A person blinded to the treatment evaluated recovery scores and monitored intestinal auscultation until 24 hours after the end of anesthesia using previously published methods. Cardiovascular parameters were analyzed by anova followed by a Dunnet's test, and nonparametrical data were analyzed by a Mann–Whitney U‐test (p < 0.05). Values were mean ± SEM unless otherwise stated. MET significantly increased HR from baseline to 120 minutes post‐injection (from 29 ± 1 to 36 ± 2 beats minute^?1 at 20 minutes). Thermodilution cardiac output (CO) and mean arterial pressure (MAP) were increased from baseline to 75 minutes post‐MET injection (from 13.9 ± 0.8 to 19.4 ± 2.0 L minute^?1 for CO at 20 minutes, and from 82 ± 3 to 103 ± 5 mm Hg for MAP at 20 minutes). Recovery characteristics and bowel auscultation scores did not differ among the groups. The return to at least 75% of the maximum auscultation score occurred at 10 (8–18) hours [median (range)] for controls and at 9 (8–12) hours for MET. It was concluded that MET increased HR and improved hemodynamic function during halothane/xylazine anesthesia with no apparent effect on return to full‐bowel motility, as assessed by auscultation. Accordingly, M2 muscarinic antagonists might be represented as a safer alternative to treat intraoperative bradycardia in horse.  相似文献   

Evaluation of the wick catheter as used to measure intracompartmental muscle pressure in equine muscle     

W N McDonell  P J Pascoe  W A Lindsay  M L Burgess 《American journal of veterinary research》1985,46(3):684-687

The use of the wick catheter to measure intracompartmental muscle pressure in equine muscle was documented. The presence of muscle compartments involving the extensor carpi radialis muscle and the long head of the triceps brachii was demonstrated by anatomic dissection and radiographic technique. The wick catheter was capable of accurately measuring pressures within both of these compartments. Furthermore, the wick catheter was sensitive to pressure changes resulting from external compression of muscle compartments. Manipulation of systemic blood pressure and PaCO2 in 1 anesthetized horse did not affect intracompartmental muscle pressure.  相似文献   

Comparative hemodynamic effects of halothane and halothane-acepromazine at equipotent doses in dogs.   总被引：4，自引：2，他引：2       下载免费PDF全文

C J Boyd  W N McDonell    A Valliant 《Canadian journal of veterinary research》1991,55(2):107-112

The purpose of this study was to compare the cardiovascular effects of halothane when used alone at increasing doses (1.2, 1.45 and 1.7 minimum alveolar concentration, MAC) to those produced with equipotent doses of halothane after potentiation of the anesthetic effect with acepromazine (ACP) sedation (45% reduction of halothane MAC). Six healthy mature dogs were used on three occasions. The treatments were halothane and intramuscular (IM) saline (1.0 mL), halothane and ACP (0.04 mg/kg IM), or halothane and ACP (0.2 mg/kg IM). Anesthesia was induced and maintained with halothane in oxygen and the dogs were prepared for the collection of arterial and mixed venous blood and for the determination of heart rate, systolic, diastolic and mean arterial pressure, mean pulmonary arterial pressure (PAP), central venous pressure and cardiac output. Following animal preparation the saline or ACP was administered and positive pressure ventilation instituted. Twenty-five minutes later the dogs were exposed to the first of three anesthetic levels, with random assignment of the sequence of administration. At each anesthetic level, measurements were obtained at 20 and 35 min. Calculated values included cardiac index, stroke index, left ventricular work, systemic vascular resistance, arterial oxygen content, mixed venous oxygen content, oxygen delivery and oxygen consumption. Heart rate was significantly higher with halothane alone than with both halothane-ACP combinations and was significantly higher with high dose ACP compared to low dose ACP. Systolic and mean blood pressures were lowest with halothane alone and highest with 0.2 mg/kg ACP, the differences being significant for each treatment. Oxygen uptake and PAP were significantly lower in dogs treated with ACP. It was concluded that ACP does not potentiate the cardiovascular depression that accompanies halothane anesthesia when the resultant lower dose requirements of halothane are taken into consideration.  相似文献