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1.
A crossover study design was used to investigate the dose-related effects of sevoflurane at end-tidal concentrations of 2.2 to 4.4 per cent on the respiratory rate, blood gases, heart rate, arterial blood pressure and ocular signs of chickens during spontaneous and controlled ventilation. The mean (sd) carbon dioxide partial pressure (PaCO2) increased as the concentration of sevoflurane increased, and was 86 (29) mmHg at an end-tidal concentration of 4.4 per cent during spontaneous ventilation, but was maintained between 29 and 42 mmHg during controlled ventilation. The heart rate increased as the concentration of sevoflurane increased during spontaneous ventilation, but did not change during controlled ventilation. Sevoflurane decreased arterial blood pressure during both spontaneous and controlled ventilation, but a dose-dependent decrease in arterial blood pressure was observed only during controlled ventilation. The mean arterial blood pressure at an end-tidal concentration of 4.4 per cent was significantly higher during spontaneous ventilation than during controlled ventilation. Controlled ventilation prevented the increases in PaCO2 and heart rate that were observed during spontaneous ventilation. The decrease in arterial blood pressure during spontaneous ventilation was less than that during controlled ventilation, possibly owing to the effects of hypercapnia.  相似文献   

2.
The purpose of this study was to investigate the cardiopulmonary influences of sevoflurane in oxygen at two anaesthetic concentrations (1.5 and 2 MAC) during spontaneous and controlled ventilation in dogs. After premedication with fentany-droperidol (5 microg/kg and 0.25 mg/kg intramuscularly) and induction with propofol (6 mg/kg intravenously) six dogs were anaesthetized for 3 h. Three types of ventilation were compared: spontaneous ventilation (SpV), intermittent positive pressure ventilation (IPPV), and positive end expiratory pressure ventilation (PEEP, 5 cm H2O). Heart rate, haemoglobin oxygen saturation, arterial blood pressures, right atrial and pulmonary arterial pressures, pulmonary capillary wedge pressure and cardiac output were measured. End tidal CO2%, inspiratory oxygen fraction, respiration rate and tidal volume were recorded using a multi-gas analyser and a respirometer. Acid-base and blood gas analyses were performed. Cardiac index, stroke volume, stroke index, systemic and pulmonary vascular resistance, left and right ventricular stroke work index were calculated. Increasing the MAC value during sevoflurane anaesthesia with spontaneous ventilation induced a marked cardiopulmonary depression; on the other hand, heart rate increased significantly, but the increases were not clinically relevant. The influences of artificial respiration on cardiopulmonary parameters during 1.5 MAC sevoflurane anaesthesia were minimal. In contrast, PEEP ventilation during 2 MAC concentration had more pronounced negative influences, especially on right cardiac parameters. In conclusion, at 1.5 MAC, a surgical anaesthesia level, sevoflurane can be used safely in healthy dogs during spontaneous and controlled ventilation (IPPV and PEEP of 5 cm H2O).  相似文献   

3.
OBJECTIVE: To determine hemodynamic effects of 3 concentrations of sevoflurane in cats. ANIMALS: 6 cats. PROCEDURE: Cats were anesthetized with sevoflurane in oxygen. After instruments were inserted, end-tidal sevoflurane concentration was set at 1.25, 1.5, or 1.75 times the individual minimum alveolar concentration (MAC), which was determined in another study. Twenty-five minutes were allowed after each change of concentration. Heart rate; systemic and pulmonary arterial pressures; central venous pressure; pulmonary artery occlusion pressure; cardiac output; body temperature; arterial and mixed-venous pH, PCO2, PO2, oxygen saturation, and hemoglobin concentrations; PCV; and total protein and lactate concentrations were measured for each sevoflurane concentration before and during noxious stimulation. Arterial and mixed-venous bicarbonate concentrations, cardiac index, stroke index, rate-pressure product, systemic and pulmonary vascular resistance indices, left and right ventricular stroke work indices, PaO2, mixed-venous partial pressure of oxygen (PVO2), oxygen delivery, oxygen consumption, oxygen-extraction ratio, alveolar-to-arterial oxygen difference, and venous admixture were calculated. Spontaneous and mechanical ventilations were studied during separate experiments. RESULTS: Mode of ventilation did not significantly influence any of the variables examined. Therefore, data from both ventilation modes were pooled for analysis. Mean arterial pressure, cardiac index, stroke index, rate-pressure product, left ventricular stroke work index, arterial and mixed-venous pH, PaO2, and oxygen delivery decreased, whereas PaCO2, PVO2, and mixed-venous partial pressure of CO2 increased significantly with increasing doses of sevoflurane. Noxious stimulation caused a significant increase in most cardiovascular variables. CONCLUSIONS AND CLINICAL RELEVANCE: Sevoflurane induces dose-dependent cardiovascular depression in cats that is mainly attributable to myocardial depression.  相似文献   

4.
OBJECTIVE: To determine hemodynamic and metabolic effects of IV infusion of ATP-MgCl2 combination and maximal safe IV infusion rate in conscious horses. ANIMALS: 6 adult female horses. PROCEDURE: All horses received an IV infusion of ATP-MgCl2 combination, beginning at a rate of 0.05 mg of ATP/kg of body weight/min, which was increased by 0.05 mg/kg/min increments at 10-minute intervals until a rate of 1.0 mg/kg/min was achieved. Data were collected prior to the start of the infusion, at the end of each infusion rate, and at 15-minute intervals for the next hour after discontinuation of the infusion. Measured or calculated hemodynamic variables included cardiac output, cardiac index, heart rate, stroke volume, systemic and pulmonary arterial pressures, and systemic and pulmonary vascular resistances. Arterial blood gas tensions, CBC, plasma biochemical profiles, urine volume and specific gravity, and selected clinical signs of disease also were evaluated. RESULTS: Intravenous infusion of ATP-MgCl2 significantly increased cardiac output, decreased systemic vascular resistance, and caused mild pulmonary hypertension. Magnitude of the hemodynamic alterations was dependent on rate of infusion. Maximal safe infusion rate for these horses was 0.3 mg/kg/min. All horses became lethargic, and their appetites diminished during the infusion; 5 horses had mild signs of abdominal discomfort. Flank sweating was observed in all horses as infusion rate increased. Urine volume and specific gravity and hematologic, biochemical, and arterial blood gas alterations were detected during and after infusion. CONCLUSIONS AND CLINICAL RELEVANCE: Intravenous administration of ATP-MgCl2 in healthy, conscious, adult horses caused various metabolic and hemodynamic alterations that were without appreciable detrimental effects.  相似文献   

5.
OBJECTIVE: To evaluate the effect of changing the mode of ventilation from spontaneous to controlled on the arterial-to-end-tidal CO2 difference [P(a-ET)CO2] and physiological dead space (VD(phys)/VT) in laterally and dorsally recumbent halothane-anesthetized horses. STUDY DESIGN; Prospective, experimental, nonrandomized trial. ANIMALS: Seven mixed breed adult horses (1 male and 6 female) weighing 320 +/- 11 kg. METHODS: Horses were anesthetized in 2 positions-right lateral and dorsal recumbency-with a minimum interval of 1 month. Anesthesia was maintained with halothane in oxygen for 180 minutes. Spontaneous ventilation (SV) was used for 90 minutes followed by 90 minutes of controlled ventilation (CV). The same ventilator settings were used for both laterally and dorsally recumbent horses. Arterial blood gas analysis was performed every 30 minutes during anesthesia. End-tidal CO2 (PETCO2) was measured continuously. P(a-ET)CO2 and VD(phys)NT were calculated. Statistical analysis included analysis of variance for repeated measures over time, followed by Student-Newman-Keuls test. Comparison between groups was performed using a paired t test; P < .05 was considered significant. RESULTS: P(a-ET)CO2 and VD(phys)/VT increased during SV, whereas CV reduced these variables. The variables did not change significantly throughout mechanical ventilation in either group. Dorsally recumbent horses showed greater P(a-ET)CO2 and VD(phys)/VT values throughout. PaCO2 was greater during CV in dorsally positioned horses. CONCLUSIONS AND CLINICAL RELEVANCE: Changing the mode of ventilation from spontaneous to controlled was effective in reducing P(a-ET)CO2 and physiological dead space in both laterally and dorsally recumbent halothane-anesthetized horses. Dorsal recumbency resulted in greater impairment of effective ventilation. Capnometry has a limited value for accurate estimation of PaCO2 in anesthetized horses, although it may be used to evaluate pulmonary function when paired with arterial blood gas analysis.  相似文献   

6.
Cardiovascular effects of halothane in the horse   总被引：3，自引：0，他引：3  
Cardiovascular effects of venous alveolar concentrations of halothane in oxygen were studied in 8 young, healthy horses under conditions of constant arterial carbon dioxide tension. The alveolar concentration of halothane was expressed as a multiple of the minimal alveolar concentration (MAC) which was known for each animal. Increasing alveolar halothane concentrations to MAC 2.0 resulted in a progressive and significant (P less than 0.05) decline in systemic arterial pressure and left ventricular work. Cardiac output decreased between MAC 1.0 and MAC 2.0 as a result of a significant (P less than 0.05) decrease in stroke volume. Heart rate, total peripheral resistance, pulmonary artery pressure, hematocrit, plasma protein concentration, arterial oxygen tension, and arterial pH remained constant over the same range of anesthetic dosages. Continuation of anesthesia, spontaneous ventilation, and the accompanying rise in arterial carbon dioxide tension and electrical stimulation of the horse's oral mucous membranes produced varying degrees of stimulation of cardiovascular function at MAC 1.5.  相似文献   

7.
OBJECTIVE: To determine the minimum anesthetic concentration for sevoflurane and effects of various multiples of minimum anesthetic concentration on arterial pressure and heart rate during controlled ventilation in chickens. STUDY DESIGN: Prospective experimental study. ANIMALS: Seven healthy chickens, 6 to 8 months old, weighing 1.6 to 3.4 kg. METHODS: A rebreathing, semiclosed anesthetic circuit was used. Anesthesia was induced by mask with sevoflurane in oxygen. Each chicken was endotracheally intubated, then controlled ventilation was started and the end-tidal CO2 partial pressure was maintained at 30 to 40 mm Hg. Body temperature was maintained at 39.5 degrees to 41.0 degrees C. The inspired and end-tidal sevoflurane concentration were monitored with a multigas monitor. Minimum anesthetic concentration was determined as the minimal end-tidal sevoflurane concentration which prevented gross purposeful movement in response to clamping a toe for 1 minute. After the determination, the cardiovascular effects of sevoflurane at 1.0, 1.5, and 2.0 times the minimum anesthetic concentration were determined. RESULTS: The minimum anesthetic concentration for sevoflurane was 2.21% + 0.32% (mean +/- SD). Mean arterial pressure and heart rate at minimum anesthetic concentration were 84 +/- 13 mm Hg and 150 +/- 58 beats/min, respectively. There was a dose-dependent decrease in arterial pressure. The heart rate did not change significantly over the range 1 to 2 x minimum anesthetic concentration. No cardiac arrhythmias developed throughout the experiments. CONCLUSIONS AND CLINICAL RELEVANCE: The minimum anesthetic concentration for sevoflurane in chickens was within the range of minimum alveolar concentration reported in mammals. When the concentration of sevoflurane is increased during controlled ventilation in chickens, decrease in arterial pressure should be expected.  相似文献   

8.
The anesthetic potency and cardiopulmonary effects of sevoflurane were compared with those of isoflurane and halothane in goats. The (mean +/- SD) minimal alveolar concentration (MAC) was 0.96 +/- 0.12% for halothane, 1.29 +/- 0.11% for isoflurane, and 2.33 +/- 0.15% for sevoflurane. Cardiopulmonary effects of sevoflurane, halothane and isoflurane were examined at end-tidal concentrations equivalent to 1, 1.5 and 2 MAC during either spontaneous or controlled ventilation (SV or CV). During SV, there were no significant differences in respiration rate, tidal volume and minute ventilation between anesthetics. Dose-dependent decreases in both tidal volume and minute ventilation induced by halothane were greater than those by either sevoflurane or isoflurane. Hypercapnia and acidosis induced by sevoflurane were not significantly different from those by either isoflurane or halothane at 1 and 1.5 MAC, but were less than those by halothane at 2 MAC. There was no significant difference in heart rate between anesthetics during SV and CV. During SV, all anesthetics induced dose-dependent decreases in arterial pressure, rate pressure product, systemic vascular resistance, left ventricular minute work index and left ventricular stroke work index. Systemic vascular resistance with isoflurane at 2 MAC was lower than that with sevoflurane. During CV, sevoflurane induced dose-dependent circulatory depression (decreases in arterial pressure, cardiac index, rate pressure product, systemic vascular resistance, left ventricular minute work index and right ventricular minute work index), similar to isoflurane. Halothane did not significantly alter systemic vascular resistance from 1 to 2 MAC.  相似文献   

9.
Eighty-five thoroughbred racehorses with various types of fracture were subjected to arthroscopic surgery (44 horses) or internal fixation (41 horses) under sevoflurane anesthesia. The mean end-tidal sevoflurane concentration during anesthesia ranged from 2.5 to 2.8%. PaCO2 was maintained between 50 and 65 mmHg by controlled ventilation. The mean arterial blood pressure was maintained above 65 mmHg by infusion of dobutamine and fluids, however, heart rate significantly increased with time. Recovery from anesthesia was calm and smooth in almost all cases. No apparent complication was observed during and after anesthesia in all cases. Therefore, sevoflurane anesthesia is considered to be safe and useful for orthopedic surgery in racehorses.  相似文献   

10.
OBJECTIVE: To compare the effects of spontaneous breathing and mechanical ventilation on haemodynamic variables, including muscle and skin perfusion measured with laser Doppler flowmetery, in horses anaesthetized with isoflurane. STUDY DESIGN: Prospective controlled study. ANIMALS: Ten warm-blood trotter horses (five males, five females). Mean mass was 492 kg (range 420-584 kg) and mean age was 5 years (range 4-8 years). MATERIALS AND METHODS: After pre-anaesthetic medication with detomidine (10 microg kg(-1)) anaesthesia was induced with intravenous (IV) guaifenesin and thiopental (4-5 mg kg(-1) IV) and maintained using isoflurane in oxygen. The horses were positioned in dorsal recumbency. In five animals breathing was initially spontaneous (SB) while the lungs of the other five were ventilated mechanically using intermittent positive pressure ventilation (IPPV). Total anaesthesia time was 4 hours with the ventilatory mode changed after 2 hours. During anaesthesia, heart rate (HR) cardiac output (Qt) stroke volume (SV) systemic arterial blood pressures (sAP), and pulmonary arterial pressure (pAP) were recorded. Peripheral perfusion was measured in the semimembranosus and gluteal muscles and on the tail skin using laser Doppler flowmetry. Arterial (a) and mixed venous (v) blood gases, pH, haemoglobin concentration [Hb], haematocrit (Hct), plasma lactate concentration and muscle temperature were measured. Oxygen content, venous admixture (s/Qt) oxygen delivery (DO(2)) and oxygen consumption (VO(2)) were calculated. RESULTS: During mechanical ventilation, HR, sAP, pAP, Qt, SV, Qs/Qt and PaCO(2) were lower and PaO(2) was higher compared with spontaneous breathing. There were no differences between the modes of ventilation in the level of perfusion, DO(2), VO(2), [Hb], (Hct), or plasma lactate concentration. After the change from IPPV to SB, left semimembranosus muscle and skin perfusion improved, while muscle perfusion tended to decrease when SB was changed to IPPV. Low-frequency flow motion was seen twice as frequently during IPPV compared with SB. CONCLUSIONS: Mechanical ventilation impaired cardiovascular function compared with SB in horses during isoflurane anaesthesia. Muscle and skin perfusion changes occurred with ventilation, although further studies are needed to elucidate the underlying mechanisms.  相似文献   

11.
OBJECTIVE: To measure the effects of isoflurane end-tidal concentration and mode of ventilation (spontaneous vs controlled) on intracranial pressure (ICP) and cerebral perfusion pressure (CPP) in horses. ANIMAL: adult horses of various breeds. PROCEDURES: Anesthesia was induced and maintained with isoflurane in O2 in 6 healthy, unmedicated, adult horses. Using a subarachnoid strain gauge transducer, ICP was measured. Blood gas tensions and carotid artery pressures also were measured. Four isoflurane doses were studied, corresponding to the following multiples of the minimum alveolar concentration (MAC): 1.0 MAC, 1.2 MAC, 1.4 MAC, and 1.6 MAC. Data were collected during controlled ventilation and spontaneous ventilation at each dose. RESULTS: increasing isoflurane end-tidal concentration induced significant dose-dependent decreases in mean arterial pressure (MAP) and CPP but no change in ICR Hypercapnic spontaneous ventilation caused significant increases in MAP and ICR compared with normocapnic controlled ventilation; no change in CPP was observed. CONCLUSIONS AND CLINICAL RELEVANCE: Hypercapnia likely increases cerebral blood flow (CBF) by maintaining CPP in the face of presumed cerebral vasodilation in healthy anesthetized horses. The effect of isoflurane dose on CBF however, remains unresolved because it depends on the opposing influences of a decrease in CCP and cerebral vasodilation.  相似文献   

12.
The hemodynamic, respiratory, and behavioral effects, as well as the pharmacokinetic properties of methocarbamol, were determined in horses. Heart rate, cardiac output, arterial and venous blood pressures, respiratory rate, and arterial blood gases did not change after IV methocarbamol (4.4, 8.8, 17.6 mg/kg) administration. There were no signs of behavior modification or ataxia observed. Analysis of plasma concentration time data indicated that the disposition of methocarbamol may be dose-dependent. Clearance and steady-state volume of distribution decreased as the dose increased. Plasma concentrations of guaifenesin, a metabolite of methocarbamol, were never greater than 0.5% of the plasma concentration of methocarbamol.  相似文献   

13.
BACKGROUND: Small volume resuscitation has been advocated as a beneficial therapy for endotoxemia in horses but this therapy has not been investigated in a prospective manner. The objective of this study was to determine the cardiopulmonary effects of small-volume resuscitation using hypertonic saline solution (HSS) plus Hetastarch (HES) during experimental endotoxemia in anesthetized horses. HYPOTHESIS: Treatment of horses with induced endotoxemia using HES-HSS does not alter the response of various cardiopulmonary indices when compared to treatment with either small- or large-volume isotonic crystalloid solutions. ANIMALS: Eighteen healthy horses were randomly assigned to 1 of 3 groups. Anesthesia was maintained with halothane. Endotoxemia was induced by administering 50 microg/kg of Escherichia coli endotoxin IV. The horses were treated over 30 minutes with 15 mL/kg of balanced polyionic crystalloid solution (control), 60 mL/kg of balanced polyionic crystalloid solution (ISO), or 5 mL/kg of HSS followed by 10 mL/kg of HES (HSS-HES). METHODS: Prospective randomized trial. RESULTS: Cardiac output (CO) after endotoxin infusion increased significantly (P < .05) from baseline in all groups, whereas mean central venous pressure increased significantly (P < .05) in the ISO group only. Mean pulmonary artery pressure increased from baseline (P < .05) in horses treated with isotonic fluids and HSS-HES. There was no effect of treatment with HSS-HES on CO, systemic vascular resistance (SVR), mean arterial pressure, blood lactate concentrations, or arterial oxygenation. CONCLUSIONS AND CLINICAL IMPORTANCE: The use of HSS-HES failed to ameliorate the deleterious hemodynamic responses associated with endotoxemia in horses. The clinical value of this treatment in horses with endotoxemia remains unconfirmed.  相似文献   

14.
The hemodynamic effects of high arterial carbon dioxide pressure (PaCO2) during anesthesia in horses were studied. Eight horses were anesthetized with xylazine, guaifenesin, and thiamylal, and were maintained with halothane in oxygen (end-tidal halothane concentration = 1.15%). Baseline data were collected while the horses were breathing spontaneously; then the horses were subjected to intermittent positive-pressure ventilation, and data were collected during normocapnia (PaCO2, 35 to 45 mm of Hg), moderate hypercapnia (PaCO2, 60 to 70 mm of Hg), and severe hypercapnia (PaCO2, 75 to 85 mm of Hg). Hypercapnia was induced by adding carbon dioxide to the inspired gas mixture. Moderate and severe hypercapnia were associated with significant (P less than 0.05) increases in aortic blood pressure, left ventricular systolic pressure, cardiac output, stroke volume, maximal rate of increase and decrease in left ventricular pressure (positive and negative dP/dtmax, respectively), and median arterial blood flow, and decreased time constant for ventricular relaxation. These hemodynamic changes were accompanied by increased plasma epinephrine and norepinephrine concentrations. Administration of the beta-blocking drug, propranolol hydrochloride, markedly depressed the response to hypercapnia. This study confirmed that in horses, hypercapnia is associated with augmentation of cardiovascular function.  相似文献   

15.
OBJECTIVE: To quantitate effects of dose of sevoflurane and mode of ventilation on cardiovascular and respiratory function in horses and identify changes in serum biochemical values associated with sevoflurane anesthesia. ANIMALS: 6 healthy adult horses. PROCEDURE: Horses were anesthetized twice: first, to determine the minimum alveolar concentration (MAC) of sevoflurane and second, to characterize cardiopulmonary and serum biochemical responses of horses to 1.0, 1.5, and 1.75 MAC multiples of sevoflurane during controlled and spontaneous ventilation. Results-Mean (+/- SEM) MAC of sevoflurane was 2.84 +/- 0.16%. Cardiovascular performance during anesthesia decreased as sevoflurane increased; the magnitude of cardiovascular depression was more severe during mechanical ventilation, compared with spontaneous ventilation. Serum inorganic fluoride concentration increased to a peak of 50.8 +/- 7.1 micromol/L at the end of anesthesia. Serum creatinine concentration and sorbitol dehydrogenase activity reached their greatest values (2.0 +/- 0.8 mg/dL and 10.2 +/- 1.8 U/L, respectively) at 1 hour after anesthesia and then returned to baseline by 1 day after anesthesia. Serum creatine kinase, aspartate aminotransferase, and alkaline phosphatase activities reached peak values by the first (ie, creatine kinase) or second (ie, aspartate aminotransferase and alkaline phosphatase) day after anesthesia. CONCLUSIONS AND CLINICAL RELEVANCE: Sevoflurane causes dose-related cardiopulmonary depression, and mode of ventilation further impacts the magnitude of this depression. Except for serum inorganic fluoride concentration, quantitative alterations in serum biochemical indices of liver- and muscle-cell disruption and kidney function were considered clinically unremarkable and similar to results from comparable studies of other inhalation anesthetics.  相似文献   

16.
The authors investigated the cardiovascular effects of low doses of nitroprusside, dobutamine, and phenylephrine and a beta-adrenergic blocking dose of propranolol in conscious, healthy horses with and without prior atropine administration. A parasympathetic blocking dose of atropine produced significant increases in heart rate and arterial pressures, and decreased stroke volume, ejection fraction, pulse pressure, and right-ventricular end-diastolic pressure and volume. Cardiac output was not changed by atropine administration. Nitroprusside reduced arterial pressures to a greater extent in atropinized horses but increased heart rate in both atropinized and non-atropinized horses. Dobutamine increased mean arterial pressure in both non-atropinized and atropinized horses but increased heart rate, diastolic arterial pressure, and systemic vascular resistance only in atropinized horses. Propranolol did not affect any of the hemodynamic variables that were measured. Phenylephrine, in the presence of beta-adrenergic blockade, increased mean arterial pressure and reduced cardiac output. This study showed that low doses of nitroprusside, dobutamine, and phenylephrine produce significant hemodynamic effects in conscious, healthy horses and that these effects are modified by prevailing parasympathetic tone.  相似文献   

17.
Cardiovascular and respiratory responses to variable PaO2 were measured in 6 horses anesthetized only with halothane during spontaneous (SV) and controlled (CV) ventilation. The minimal alveolar concentration (MAC) for halothane in oxygen was determined in each spontaneously breathing horse prior to establishing PaO2 study conditions--mean +/- SEM, 0.95 +/- 0.03 vol%. The PaO2 conditions of > 250, 120, 80, and 50 mm of Hg were studied in each horse anesthetized at 1.2 MAC of halothane and positioned in left lateral recumbency. In response to a decrease in PaO2, total peripheral resistance and systolic and diastolic arterial blood pressure decreased (P < 0.05) during SV. Cardiac output tended to increase because heart rate increased (P < 0.05) during these same conditions. During CV, cardiovascular function was usually less than it was at comparable PaO2 during SV (P < 0.05). Heart rate, cardiac output, and left ventricular work increased (P < 0.05) in response to a decrease in PaO2, whereas total peripheral resistance decreased (P < 0.05). During SV, cardiac output and stroke volume increased and arterial blood pressure and total peripheral resistance decreased with duration of anesthesia at PaO2 > 250 mm of Hg. During SV, minute expired volume increased (P < 0.05) because respiratory frequency tended to increase as PaO2 decreased. Decrease in PaCO2 (P < 0.05) also accompanied these respiratory changes. Although oxygen utilization was nearly constant over all treatment periods, oxygen delivery decreased (P < 0.05) with decrease in PaO2, and was less (P < 0.05) during CV, compared with SV, for comparable PaO2 values.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

18.
The effects of 3 commonly used dosages (0.3, 0.5, and 1.1 mg/kg of body weight, IV) of xylazine on ventilatory function were evaluated in 6 Thoroughbred geldings. Altered respiratory patterns developed with all doses of xylazine, and horses had apneic periods lasting 7 to 70 seconds at the 1.1 mg/kg dosage. Respiratory rate, minute volume, and partial pressure of oxygen in arterial blood (PaO2) decreased significantly (P less than 0.001) with time after administration of xylazine, but significant differences were not detected among dosages. After an initial insignificant decrease at 1 minute after injection, tidal volume progressively increased and at 5 minutes after injection, tidal volume was significantly (P less than 0.01) greater than values obtained before injection. Partial pressure of carbon dioxide in arterial blood (PaCO2) was insignificantly increased. After administration of xylazine at a dosage of 1.1 mg/kg, the mean maximal decrease in PaO2 was 28.2 +/- 8.7 mm of Hg and 22.2 +/- 4.9 mm of Hg, measured with and without a respiratory mask, respectively. Similarly, the mean maximal increase in PaCO2 was 4.5 +/- 2.3 mm of Hg and 4.2 +/- 2.4 mm of Hg, measured with and without the respiratory mask, respectively. Significant interaction between use of mask and time was not detected, although the changes in PaO2 were slightly attenuated when horses were not masked. The temporal effects of xylazine on ventilatory function in horses should be considered in selecting a sedative when ventilation is inadequate or when pulmonary function testing is to be performed.  相似文献   

19.
OBJECTIVE: To characterize alterations in systemic and local colonic hemodynamic variables associated with IV infusion of ATP-MgCl2 in healthy anesthetized horses. ANIMALS: 12 adult horses. PROCEDURE: Six horses were given ATP-MgCl2, IV, beginning at a rate of 0.1 mg of ATP/kg of body weight/min with incremental increases until a rate of 1.0 mg/kg/min was achieved. The remaining 6 horses were given an equivalent volume of saline (0.9% NaCl) solution over the same time period. Colonic and systemic hemodynamic variables and colonic plasma nitric oxide (NO) concentrations were determined before, during, and after infusion. RESULTS: Infusion of ATP-MgCl2 caused a rate-dependent decrease in systemic and colonic vascular resistance, principally via its vasodilatory effects. A rate of 0.3 mg of ATP/kg/min caused a significant decrease in systemic and colonic arterial pressure and colonic vascular resistance without a significant corresponding decrease in colonic arterial blood flow. Consistent alterations in NO concentrations of plasma obtained from colonic vasculature were not detected, despite profound vasodilatation of the colonic arterial vasculature. CONCLUSIONS AND CLINICAL RELEVANCE: Results revealed that IV infusion of ATP-MgCl2 may be beneficial in maintaining colonic perfusion in horses with ischemia of the gastrointestinal tract, provided a sufficient pressure gradient exists to maintain blood flow.  相似文献   

20.
OBJECTIVE: To determine the effect of sevoflurane on cardiac energetic and hemodynamic parameters in ferrets. ANIMALS: 7 healthy domesticated ferrets. PROCEDURE: Sevoflurane was used as the sole anesthetic agent for general anesthesia in ferrets. Standard midline laparotomy and median sternotomy were performed to permit instrumentation. Myocardial blood flow was determined by use of colored microsphere technology. Measurements and blood samples were obtained at 1.25%, 2.5%, and 3.75% expired concentration of sevoflurane. RESULTS: A dose-dependent decrease in arterial blood pressure, left ventricular pressure, systemic vascular resistance, aortic flow, and dp/dt (an index of contractility) was detected as expired concentration of sevoflurane increased. Heart rate, central venous pressure, coronary vascular resistance, myocardial oxygen extraction ratio, and tau (the time constant of relaxation) were unchanged. Cardiac external work decreased, as did myocardial oxygen consumption, causing increased cardiac efficiency at higher concentrations of sevoflurane. CONCLUSIONS AND CLINICAL RELEVANCE: Sevoflurane caused minimal and predictable cardiovascular effects in ferrets without increasing myocardial metabolic demands. Data obtained from this study have not been previously reported for a species that is being commonly used in cardiovascular research. These findings also support use of sevoflurane as a safe inhalant anesthetic in ferrets for clinical and research settings.  相似文献   

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