摘要:

The sensitivities of current monitoring methods for detection of air embolism were compared in eight anesthetized dogs. Air was infused at controlled rates of 0.001 and 0.005 ml. k−1.min−1for 1 min; 0.01, 0.05, 0.1, 0.2, and 0.4 ml.kg−1for 6 min; and 5 ml. kg−1bolus injection. Based on the mean quantity of air infused to elicit a positive response, the monitors could be placed into three significantly different sensitivity groups. Transesophageal echocardiography (TEE) and precordial Doppler ultrasound were the most sensitive monitoring methods detecting 0.19 and 0.24 ml. kg−1of air, respectively. TEE detected air during six infusions in which the Doppler failed to do so. The next most sensitive group of monitoring methods included pulmonary artery pressure (PAP), end-tidal CO2(Ptco2), arterial oxygen tension (Pao2), and transcutaneous oxygen tension (Ptco2). The mean quantity of air infused to elicit a positive response in this group of monitors ranged from 0.61 to 0.76 ml. kg−1. The response of Ptco2, Pao2, PETco2, and PAP equally reflected the quantity of air infused. The least-sensitive group of methods included arterial and transcutaneous carbon dioxide tension and systemic arterial blood pressure. These data indicate that TEE is more sensitive than Doppler ultrasound and that PAP, PETco2, and Ptco2are equally sensitive in detecting venous air embolism in the dog.

ISSN:0003-3022    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

Transcutaneous oxygen tension (Ptco2) and transcutaneous carbon dioxide tension (Ftcco2) were monitored in 60 patients undergoing neurosurgical procedures. Twenty-six patients were in the sitting position and underwent routine monitoring for air embolism. Seventeen episodes of air embolism were diagnosed by precordial Doppler ultrasound or transesophageal echocardiography, and the Ptco2decreased early during the course of each episode. The mean Ptco2decrease was 48 ± 35 mmHg. During ten episodes the end-tidal carbon dioxide tension (PETco2) decreased but only after the Ptco2had already begun to decrease. Ptcco2increased during air embolism but PETco2changes preceded the change in PtCco2by 1–2 min. Transcutaneous values during air embolism were verified with simultaneous arterial blood gas values during six air embolism episodes. A strong positive correlation was found between transcutaneous and arterial oxygen and carbon dioxide tensions. Correcting the Ptcco2by the patient's baseline Ptcco2/Paco2ratio, Ptcco2monitoring correctly reflected hypocarbia, normocarbia, and hypercarbia in 92% of the-cases. Ptco2monitoring was useful in detecting venous air embolism and may respond sooner than PETco2. Ptcco2monitoring was not useful as an early detector of air embolism.

ISSN:0003-3022    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

The effects of iv succinylcholine (SCh) on the electroencephalogram (EEG), cerebral blood flow (CBF), cerebral metabolic rate (CMRo2), intracranial pressure (ICP), central venous pressure (CVP), and mean arterial pressure (MAP) were tested in halothane-anesthetized dogs. Six dogs were maintained at 0.87 ‡ 0.00% (mean ‡ SE) expired halothane (1.0 MAC) and received both SCh 1.0 mg. kg−1and lactated Ringer's solution placebo 0.05 ml. kg−1. Fasciculations began 24 ‡ 4 s after iv SCh. Fasciculations were followed by immediate EEG arousal in five of six dogs and increases in CBF in all six. Average CBF was 151 ‡ 14% of control for the 0–15 min measurement period and 127 ‡ 7% of control for the 15–30 min period. Both were significantly greater than pre-SCh control values and placebo group values. Peak CBF of 177 ‡ 19% of control occurred 3 min after iv SCh and was accompanied by a peak ICP of 435 ‡ 131% of control. ICP values were significantly different between SCh and placebo treatments only during the periods of greatest CBF (1 to 5 min after iv SCh). Average Paco2values after iv SCh were significantly greater than pre-SCh control values and placebo values during each 15-min measurement interval. Average Paco2was 116 ± 2% of control during the 0–15 min measurement period, 114 ± 2% of control during the 15–30 min period, and 109 ± 1% of control during the 30–45 min period. CVP, MAP, and CMRo2did not significantly change after iv SCh. In two dogs maintained at 1.32 ± 0.01% expired halothane (1.5 MAC), SCh 1.0 mg. kg−1produced Paco2changes comparable with those in dogs maintained at 1.0 MAC halothane without comparable changes in CBF, ICP, or EEG. In an additional two dogs receiving pancuronium 0.2 mg.kg−1and 1.0 MAC halothane, SCh had no meaningful effect on any variable measured. The authors conclude that iv SCh increased ICP in the dog secondary to increases in CBF. They hypothesize that the CBF increases are related primarily to SCh-induced increases in afferent muscle spindle activity and secondarily to increases in Paco2.

ISSN:0003-3022    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

In order to assess the interaction between halothane and verapamil on the cardiovascular system, mongrel dogs were instrumented so that the following measurements could be made awake and under the influence of the drugs: aortic, left ventricular, and left atrial blood pressures; myocardial segment length shortening; heart rate and rhythm; and coronary, carotid, and renal blood flows. The effect of two infusion doses of verapamil (3 μg.kg−1.min−1and 6 μg. kg−1after 200 μg.kg−1bolus) were examined awake. On a different day in the same dogs, two concentrations of halothane (1.2-low and 2.4-high % end-tidal) and the effect of the two infusion doses of verapamil during low and high halothane were studied. Thirty minutes of either infusion dose of verapamil produced only heart rate and electrocardiographic P-R interval increases in conscious dogs. Halothane produced dose-related decreases in mean aortic pressure, left ventricular maximum rate of tension development (dP/dt), and segment length shortening and increases in heart rate and left atrial pressure. Carotid blood flow was increased by low halothane concentrations and returned to control with high halothane concentrations. There were no significant changes in coronary or renal blood flow produced by halothane. Verapamil infusion during low halothane concentration produced minimal effects. However, both the 3 and 6 μg.kg−1. min−1verapamil doses further depressed hearts already depressed by the high concentrations of halothane and decreased renal and carotid blood flows. Verapamil plasma levels were significantly higher during both low and high halothane concentrations than when the same dose was given to the same dogs awake. The authors conclude that: 1) the predominant effect of the combination of halothane and verapamil was from halothane; 2) halothane alters the pharmacokinetics of intravenous verapamil, resulting in marked increases in plasma verapamil levels when compared with the same dose awake; 3) verapamil infusion is well tolerated during low concentrations of halothane, but the combination of high halothane concentrations and verapamil produces profound cardiovascular depression.

ISSN:0003-3022    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

The effects of enflurane and isoffurane on the cardiovascular system and cellular calcium kinetics are somewhat different. Consequently, the interaction with the calcium channel blocking drug, verapamil, may also differ. In order to compare the anesthetics, the authors studied the effects of two infusion doses of verapamil (which produced plasma levels of 90 and 180 ng. ml−1) on cardiovascular dynamics and regional blood flow in awake dogs. On two other days, in the same dogs, the effects of approximately 1.1 and 2 MAC enflurane and isoflurane were first studied and then the same verapamil dose regimens while the same anesthetic concentrations were maintained. Verapamil produced only increases in heart rate and the P-R interval in the awake animal. The high dose of both anesthetics markedly decreased mean aortic pressure and left ventricular rate of tension development (dP/dt), and increased heart rate. However, only enflurane also decreased myocardial segment length shortening and increased left atrial pressure. Neither anesthetic alone affected coronary or renal blood flow, while both increased carotid blood flow at the low dose. Verapamil infusion during 1.2 MAC enflurane was more depressant than during 1.2 MAC isoflurane, but the combination of verapamil with 2 MAC concentration of both anesthetics was equally depressant. Both doses of both anesthetics increased plasma verapamil levels compared with the same verapamil dosing regimen awake. When these results are compared with those previously reported for halothane, the effects of verapamil during all three anesthetics are more similar than different. All anesthetics increased plasma verapamil levels at both doses of verapamil, and verapamil was profoundly depressant to the cardiovascular system during high concentrations of all three anesthetics. However, because of a tendency for increased incidence of sinus arrest and bradycardia and more hemodynamic depression during enflurane, the authors conclude that intravenous verapamil is better tolerated during low-dose isoflurane and halothane anesthesia than during comparable concentrations of enflurane anesthesia in healthy dogs.

ISSN:0003-3022    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

Changes in cerebral blood flow (CBF) in response to changes in Pa were measured by intraaortic injection of133Xe in 12 patients during hypothermic (23–30°C) cardiopulmonary bypass. In each patient, CBF was determined at two randomly ordered levels of Paco2obtained by varying the rate of gas inflow into the pump oxygenator (Group I, n = 6) or by varying the percentage of CO2added to the gas inflow (Group II, n = 6). Nasopharyngeal temperature, mean arterial pressure, pump-oxygenator flow, and hematocrit were maintained within a narrow range. In group I, a Paco2(uncorrected for body temperature) of 36± 4 mmHg (mean ± SD) was associated with a CBF of 13 ± 5 ml.100 g−1·min−1, while a Paco2of 42 ± 4 mmHg was associated with a CBF of 19± 10 ml · 100 g−1·min−1. In group II, a Paco2of 47 ± 3 mmHg was associated with a CBF of 20± 8 ml. 100 g−1·min−1, and a Paco2of 53± 3 mmHg was associated with a CBF of 26 ± 9 ml. 100 g−1·min−1. Within group I, the difference in CBF was significant (p < 0.05); within group II, the difference in CBF was significant at the P < 0.002 level. All CBF measurements were lower than those reported for normothermic, unanesthetized subjects of similar age. The response of the cerebral circulation to changes in CO2tension was well-maintained during hypothermic cardiopulmonary bypass. CBF increased by an average of 1.07 ± 1.19 (SD) ml. 100 g−1·min−1·mmHg−1increase in temperature-uncorrected Paco2in Group I, and by 1.05 ± 0.54 ml · 100 g−1·min−1· mmHg−1increase in group II.

ISSN:0003-3022    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

Inspiratory mechanical loads were applied to the airway continuously for 5 min in healthy young adult volunteers maintained in a near steady-state of halothane anesthesia 1.1 MAC. The loads, both flow resistive and elastic in nature, had been selected to reduce the first loaded tidal volume approximately 10, 30, or 50%—these being designated “small,” “medium,” and “large” loads, respectively. The actual magnitudes of resistive load were 8 ± 1, 21 ± 3, and 48 ± 6 cmH2O.1−1s, and of elastic load 6 ± 1, 18 ± 1, and 41 ± 5 cmH2O. 1−1(means ± SEM). All loads caused an immediate reduction of ventilation proportional to the size of the load. This was followed by a gradual recovery of ventilation toward control values over approximately 2 min and then nearly stable ventilation for the rest of the loading period. Respiratory frequency was unchanged throughout. At 5 min of loading, ventilation and Pco2had been nearly steady for 3 min and O2uptake and CO2output at the airway were unchanged from control, suggesting the establishment of a near steady respiratory state. With the small and medium loads of both types, ventilation and Paco2in this near steady-state were not detectably different from control. With the large loads, however, ventilation was significantly reduced and Paco2slightly increased. The end-expiratory position of the chest wall and the relative contributions of the rib cage and abdomen-diaphragm to ventilation, as estimated by antereroposterior chest wall magnetometers, were not consistently altered by any load. The small elastic loads reduced the “effective” intrinsic elastance at the end of the loading period. Loading did not increase the ratio of dead space to tidal volume (VD/VT) or the alveolar-arterial oxygen tension difference (P(A-a)o2). It is concluded that in healthy young humans anesthetized with halothane, steady-state compensation for inspiratory flow-resistive loads up to about 21 cmH2O.1−1s and inspiratory elastic loads up to 18 cmH2O · 1−1is virtually complete. Ventilatory compensation for these loads is due to nonchemical mechanisms, which in the case of small elastic loads reduce intrinsic elastance and thereby improve the performance of the ventilatory pump.

ISSN:0003-3022    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

In rats with chronically implanted intrathecal catheters, high concentrations of morphine (3 μl of 50 mg/ml: 150 μg) yielded a reliable and striking syndrome of pain behavior that involved intermittent bouts of biting and scratching at the dermatomes innervated by levels of the spinal cord proximal to the catheter tip. In addition, during intervals between bouts of agitation, the animals displayed a clear, marked hyperesthesia where an otherwise innocuous stimuli (brush stroke) evoked significant signs of discomfort and consequent aggressive behavior. These effects were exaggerated rather than reversed by high doses of naltrexone. The effect, perfectly mimicked by a considerably lower dose of morphine-3-glucuronide (15 μg) or the glycine antagonist strychnine (30 μg), was not produced by equimolar concentrations of sodium sulfate, glucuronide, methadone, or sufentanil. In halothane-anesthetized cats, light brushing of the hindpaw and tail or low-intensity stimulation of the sciatic nerves resulted in prominent elevations in blood pressure and pupil diameter following the intrathecal administration of high concentrations (50 mg/ml; 0.1 ml) of morphine sulfate. This effect, exaggerated by naloxone, was produced by a lower concentration of intrathecal morphine-3-glucuronide (5 mg/ml; 0.1 ml) but not by intrathecal saline. These results suggest the possibility that the effects of high doses of morphine may be characterized by a nonopiate receptor-mediated effect that alters the coding of sensory information in the spinal cord. The authors speculate that high concentrations of spinal opiates, as may be employed in tolerant terminal-cancer patients, could exert an action that physiologically antagonizes the analgesic effects otherwise mediated by the action of morphine on the spinal opiate receptor.

ISSN:0003-3022    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

The effects of halothane and isoflurane on regional cerebral blood flow (CBF) were studied in 18 New Zealand White rabbits anesthetized with nitrous oxide (N2O) and morphine sulfate (MS) at three different levels of Paco2.CBFwas measured using the hydrogen clearance technique. Monitored variables were intracranial pressure (ICP), central venous pressure, heart rate, mean arterial pressure, electroencephalogram, arterial blood gases, end-tidal (ET) volatile anesthetic, and ET CO2. Addition of 1 MAC halothane to the N2O/MS background anesthetic caused flow to increase significantly in all three regions studied (cortex, dorsal hippocampus, white matter) at all three levels of Paco2(low: 20–25 mmHg; normal: 35–40 mmHg; high: 50–55 mmHg). Addition of 1 MAC isoflurane to the background anesthetic caused CBF to decrease significantly in all regions during hypocapnia. During normocapnia, CBF was unchanged with the addition of 1 MAC isoflurane in all regions and during hypercapnia, CBF increased significantly only in the dorsal hippocampus following addition of 1 MAC isoflurane to the MS/ N2O background anesthetic. Volatile anesthetic administration was associated with significant, although small, increases in ICP at all Paco2levels. We conclude that 1 MAC concentrations of halothane and isoflurane have opposite effects on CBF when added to a N2O/ MS anesthetic during hypocapnia and that the effects of isoflurane on regional CBF are dependent on Paco2in rabbits under the anesthetic conditions of this experiment.

ISSN:0003-3022    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

Acute renal failure develops insidiously in the presence of normal urine output and vital signs. A prospective study was carried out to find whether renal impairment can be detected in the immediate postoperative period and to determine the renal function test best predicting the development of renal dysfunction. Forty patients with multiple trauma who required more than 10 units of blood and had a systolic blood pressure less than 80 mmHg on admission were studied.Creatinine clearance (Ccr), free-water clearance (CH2O), fractional excretion of Na+, blood urea nitrogen (BUN), urine flow rate, and vital signs were measured and compared in seven patients who developed renal dysfunction within a week of trauma (Group 1) and 33 patients who maintained normal renal function (Group 2). In all Group 1 patients Ccr remained less than 25 ml/min and CH2Ogreater than −15 ml/h for 6 h following surgery. None of the Group 2 patients had Ccr less than 25 ml/min for longer than 4 h following surgery. However, CH2Ovalues were greater than −15 ml/h in 15 of the 33 Group 2 patients during the first 24 postoperative hours.Ccr values less than 25 ml/min were present, despite normal urine flow rate and blood pressure, in patients who subsequently developed renal dysfunction. Patients who have Ccr values less than 25 ml/min within 6 h following trauma and surgery may develop renal dysfunction, and some of them may proceed to acute renal failure. CH2Owas not as good a predictor of development of renal dysfunction as Ccr.

ISSN:0003-3022    

出版商:OVID    

年代:1986

数据来源: OVID