Search PubMed⌕ Search

Biomedical subjects

E Ornstein

Publications and source records attributed to E Ornstein.

At least 73 records · Page 4Linked to original sources
PubMed1991

A comparison of cerebral blood flow reactivity to CO2 during halothane versus isoflurane anesthesia for carotid endarterectomy.

The effects of isoflurane or halothane on cerebral blood flow (CBF) reactivity to changes in arterial carbon dioxide tension (PaCO2) during carotid endarterectomy were compared using the intravenous method of 133Xe-CBF determination. Patients, aged 65 +/- 3 yr (mean +/- SE), received O2 and N2O (1:1) and either 0.75% isoflurane (n = 7) or 0.5% halothane (n = 7). Patient demographic and clinical data were similar for both groups and followed the expected strata of patients with ischemic cerebrovascular disease. Measurements were made during the period of temporary bypass shunting. In the isoflurane group, increasing PaCO2 from 33.3 +/- 1.4 to 43.4 +/- 1.3 mm Hg resulted in a significant (P less than 0.05) increase in CBF from 21 +/- 1 to 35 +/- 4 mL.100 g-1.min-1. In the halothane group, increasing PaCO2 from 31.1 +/- 1 to 39.4 +/- 1.6 mm Hg resulted in a significant increase in CBF from 26 +/- 3 to 37 +/- 3 mL.100 g-1.min-1. Mean CBF reactivity to changes in PaCO2 (mL.100 g-1.min-1.mm Hg-1) was 1.74 +/- 0.39 for isoflurane and 1.78 +/- 0.4 for halothane (not significant), corresponding to a relative change of 4.8% +/- 0.8% and 5.2% +/- 1.3% per mm Hg, respectively. There is no significant difference between halothane and isoflurane in their effects on CO2 reactivity in the mildly hypocapnic to normocapnic range.

Aged↗
PubMed1990

Pharmacokinetics of sufentanil in the elderly surgical patient.

The effect of age on the distribution and elimination of sufentanil was studied in seven elderly (77 +/- 5 yr, mean +/- SD) and seven younger (41 +/- 15 yr) neurosurgical patients. Following a single IV bolus of sufentanil 2 micrograms.kg-1 multiple arterial samples were obtained at timed intervals and plasma concentrations of sufentanil were measured by radioimmunoassay. Pharmacokinetic variables were calculated from the derived compartmental models. The initial volume of distribution was significantly smaller in the elderly patients (310 +/- 109 ml.kg-1 vs 491 +/- 112 ml.kg-1 mean +/- SD). Elimination half-lives, plasma clearances, and total volumes of distribution were similar for elderly and younger subjects. Six of seven elderly patients required administration of naloxone at the termination of surgery to achieve an adequate rate of ventilation (greater than eight breaths.min-1) while only one younger patient required antagonism of ventilatory depression. The authors believe that age-related differences in the action of sufentanil cannot be accounted for by the observed differences in the initial volume of distribution. It is concluded that alterations in pharmacodynamics appear to be of greater importance in the prolonged opioid effect seen in the elderly.

Adult↗
PubMed1990

The effect of arteriovenous malformation resection on cerebrovascular reactivity to carbon dioxide.

To investigate the cerebral hemodynamic changes associated with obliteration of arteriovenous malformations (AVMs), we studied 26 patients undergoing total microsurgical AVM resection during isoflurane and N2/O2 anesthesia. Detectors were placed 5 to 6 cm from the margin of the lesion and in a homologous contralateral position. Cerebral blood flow (CBF) was measured using the intravenous xenon-133 technique before and after AVM resection, during both hypocapnia and normocapnia at each stage. Intraoperative changes in CBF were related to a risk score system based on the patient's history and preoperative angiograms. Seven otherwise healthy patients undergoing spinal surgery were studied to control for anesthetic effects. Patient demographic and clinical data for the AVM group conformed to the expected strata of a large AVM population. The CBF increased after excision (22 +/- 1 ml/100 g/min before excision to 30 +/- 2 ml/100 g/min after excision; mean +/- SE, n = 25, P less than 0.002) without a hemispheric difference. CO2 reactivity increased slightly after excision (4.2 +/- 0.3% change/mm Hg before excision to 4.7 +/- 0.3% change/mm Hg after excision; n = 14, P less than 0.02). The baseline CBF and CO2 reactivity were not different from the control group. There was a weak correlation between the risk score and the percentage of change in the ipsilateral CBF, with a trend for the patients with the lowest risk to have the lowest CBF changes after resection. There was no relationship between CO2 reactivity and risk grade. None of the patients awoke from anesthesia with unexpected neurological deficits. The highest CBF increases were associated with postoperative brain swelling in one patient and fatal intracerebral hemorrhage in another. Both patients had normal CO2 reactivity before excision. One patient suffered postoperative intracerebral hemorrhage, attributable to technical problems, and had no increase in CBF. We conclude that, with an acute increase in the arteriovenous pressure gradient (and cerebral perfusion pressure) that results from shunt obliteration, there is an immediate global effect of AVM resection to increase CBF. Cerebrovascular reactivity to CO2 remains intact both before and after excision.

Adult↗
PubMed1990

The equivalence of anesthetic regimens with respect to plasma glucose elevation during cerebrovascular surgery.

Hyperglycemia, even if mild, is known to aggravate neuronal damage from cerebral ischemia. In order better to define the influence of currently used anesthetic techniques on plasma glucose levels during cerebrovascular surgery, we examined serial plasma glucose values during 43 carotid endarterectomies (CEA) and 19 intracranial arteriovenous malformation (AVM) resections. CEA patients (aged 67.6 +/- 1.4 years and weighing 76.4 +/- 2.3 kg, mean +/- SEM) received N2O in O2 and either isoflurane (ISO) (n = 14), halothane (n = 8), fentanyl (n = 10), or sufentanil (n = 11). Plasma glucose was compared at 1.12 +/- 0.05 h (stage 1), 2.08 +/- 0.07 h (stage 2), and 3.12 +/- 0.1 h (stage 3) after induction of anesthesia. AVM patients received ISO and N2O in O2. Plasma glucose was compared 2.32 +/- 0.14 h (stage 1) and 6.25 +/- 0.34 h (stage 2) after induction of anesthesia (surgical stage). Glucose was determined by the hexokinase method. In the CEA cases, progressively elevated plasma glucose levels were associated with successive surgical stage (114 +/- 6, 122 +/- 6, and 138 +/- 6 mg/dl). The seven CEA patients that carried the diagnosis of diabetes mellitus tended to have higher glucose levels but they did not differ significantly from nondiabetic patients. The AVM patients (aged 35.7 +/- 2.3 years and weighing 71.1 +/- 2.9 kg) were all nondiabetic. They were significantly younger than the CEA patients and each received dexamethasone intraoperatively. In these patients, there was a significant effect (p <0.04) of surgical stage to increase plasma glucose (115 +/- 10 vs. 126 +/- 10 mg/dl). For CEA, the anesthetic techniques examined do not differ significantly in their influence on plasma glucose levels, but all techniques were associated with a gradual increase in plasma glucose levels intraoperatively, even in nondiabetic patients. Compared to the group of younger AVM patients, glucose elevation was more pronounced in the elderly CEA patients. We conclude that intraoperative monitoring of plasma glucose may be useful in elderly patients during prolonged neurovascular procedures.

Journal Article↗
PubMed1990

Pharmacokinetics and pharmacodynamics of edrophonium in elderly surgical patients.

The effect of age (over 70 yr) on the pharmacokinetics and pharmacodynamics of edrophonium was evaluated in seven patients aged 76-87 yr and in seven patients aged 27-57 yr. When elderly patients were compared with younger controls, the elderly exhibited a statistically significant decreased plasma clearance (5.9 +/- 2 versus 12.1 +/- 4 mL.kg-1.min-1) and a prolonged elimination half-life (84.2 +/- 17 versus 56.6 +/- 16 min). Pharmacodynamically, a higher concentration of edrophonium is required in elderly patients to produce the same effect as in the younger controls. This observation may be explained in part by changes in neuromuscular transmission that are a function of the aging process. In addition, even though plasma concentrations were significantly greater at every sampling point in the elderly than the younger group, there was no difference between either the maximum duration or the total duration of action of edrophonium in the two groups. The maximum duration of action of edrophonium in both groups was very brief (1.3-2.2 min). These results contrast with a previous study of the anticholinesterases neostigmine and pyridostigmine, in which the action of these drugs was significantly prolonged in elderly patients. Explanations for the observed differences between edrophonium and other anticholinesterases may relate to differences in chemical structure and the possibility that edrophonium produces antagonism of neuromuscular blockade by a different mechanism than neostigmine or pyridostigmine.

Adult↗
PubMed1989

Pharmacokinetics of sufentanil in neurosurgical patients undergoing hyperventilation.

The pharmacokinetics of sufentanil were determined in 11 hypocapnic (arterial PCO2 2.9-3.7 kPa) and seven normocapnic (arterial PCO2 5.3-6.0 kPa) neurosurgical patients. Following a single i.v. bolus of sufentanil 4 micrograms kg-1, multiple arterial samples were obtained at timed intervals and plasma concentration of sufentanil was measured by radioimmunoassay. Calculation of the pharmacokinetic parameters from the derived compartmental models demonstrated an increased total volume of distribution of sufentanil in hypocapnic patients (mean 5427 (SD 1866) ml kg-1 v. 3518 (1097) ml kg-1; P less than 0.05) in the control patients and a more prolonged elimination half-life (232 (60) min v. 143 (51) min; P less than 0.01). The increased distribution of sufentanil with hyperventilation was probably caused by an increased proportion of opioid in the nonionized state.

Adult↗
PubMed1989

A comparison of the cerebral hemodynamic effects of sufentanil and isoflurane in humans undergoing carotid endarterectomy.

Prompted by reports of potentially deleterious cerebral vasodilation by the synthetic opioid sufentanil, the authors compared the effects of either isoflurane/N2O and sufentanil/N2O on cerebral blood flow (CBF), arteriovenous difference in oxygen content (AVDO2), and CBF reactivity to changes in PaCO2 during carotid endarterectomy. Cerebral blood flow was measured using the iv method of 133-Xe CBF determination and AVDO2 was measured using systemic arterial-jugular venous oxygen content differences. Patients, age 68 +/- 1 yr (mean +/- SE), received either isoflurane (n = 10), 0.75% in O2 and N2O, 1:1; or sufentanil (n = 10), 1.5-2 micrograms/kg bolus and then 0.2-0.3 micrograms.kg-1.h-1 infusion in addition to O2 and N2O, 2:3. Measurements were made immediately before carotid occlusion, and then at two levels of PaCO2 (approximately 32 and 42 mmHg) after insertion of a temporary in-dwelling bypass shunt. Prior to carotid occlusion, there was no significant difference in CBF (ml.100 g-1.min-1) between patients receiving isoflurane (22 +/- 3) or sufentanil (20 +/- 2). Similarly, there was no difference in AVDO2 (vol-%) between isoflurane (4.5 +/- 0.7) and sufentanil (5.4 +/- 0.8) groups. Using a two-way ANOVA design with anesthetic as the between-group factor and elevation of PaCO2 as the within-group repeated measure, there was a significant effect of hypercarbia to increase CBF (P less than 0.0001) and decrease AVDO2 (P less than 0.001). The product of AVDO2 and CBF, which reflects cerebral metabolic oxygen consumption, remained constant (P = 0.364).(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1989

Cerebral blood flow and metabolism in patients undergoing anesthesia for carotid endarterectomy. A comparison of isoflurane, halothane, and fentanyl.

The effects of isoflurane, halothane, and fentanyl on cerebral blood flow (CBF) and cerebral metabolic rate for oxygen (CMRO2) during anesthesia prior to carotid endarterectomy were compared using the intravenous method of 133-Xenon CBF determination. Patients, mean (+/- SE) age 68 +/- 2, received either isoflurane (N = 16), 0.75% in O2 and N2O, 50:50; halothane (N = 11), 0.5% in O2 and N2O, 50:50; or fentanyl (N = 10), 5-6 micrograms/kg bolus and then 1-2 micrograms.kg-1.h-1 infusion in addition to O2 and N2O, 40:60. Measurements were made immediately before carotid occlusion. Mean (+/- SE) CBF (ml.100 g-1.min-1) was 23.9 +/- 2.1 for isoflurane, 33.8 +/- 4.8 for halothane, and 19.3 +/- 2.4 for fentanyl. CMRO2 (ml.100 g-1.min-1) was available from 22 patients and was 1.51 +/- 0.28 for isoflurane (N = 7), 1.45 +/- 0.24 for halothane (N = 6), and 1.49 +/- 0.21 for fentanyl (N = 9). Although CBF was greater during halothane than during isoflurane or fentanyl anesthesia (p less than 0.05), there were no demonstrable differences in CMRO2 among the 3 agents. We conclude that choice of anesthetic agent for cerebrovascular surgery with comparable anesthetic regimens should not be made on the basis of "metabolic suppression." During relatively light levels of anesthesia, vasoactive properties of anesthetics are more important than cerebral metabolic depression with respect to effects on the cerebral circulation.

Aged↗
PubMed1988

Electroencephalographic monitoring for ischemia during carotid endarterectomy: visual versus computer analysis.

In a retrospective study, we compared the use of computer-generated spectral electroencephalographic descriptors with a neurologist's interpretation of raw EEG data. Data were collected from patients undergoing carotid endarterectomy and anesthetized with isoflurane in nitrous oxide and oxygen. The EEG was recorded on magnetic tape during the period immediately before and after occlusion. These tapes were then analyzed off-line using a computer to generate averaged changes in 18 spectral descriptors. A strip-chart of raw EEG before and after the carotid occlusion was interpreted by a neurologist, who assigned changes in the EEG following occlusion to one of four visual inspection groups, depending on the severity of change. A descriptive examination of the distribution of changes in spectral descriptors revealed that no single descriptor adequately reflected the neurologist's interpretation of the raw EEG. Using data from 20 patients, the percent change from preocclusion to postocclusion values for total power, spectral edge frequency, spectral variance, and log spectral variance was examined. Only for the visual inspection group judged by the electroencephalographer to have the most severe ischemic change was there a significant difference in total power and log spectral variance. Although computer-processed EEG devices are of value as trending devices for detecting visual patterns associated with inadequate cerebral perfusion, single descriptors in this study did not consistently reflect a neurologist's diagnosis of ischemia. Single descriptors of spectral EEG analysis may not be sufficient to use as alarm variables in the recognition of cerebral ischemia.

Brain Ischemia↗
PubMed1988

A controlled trial of esmolol for the induction of deliberate hypotension.

Twenty-five patients scheduled for lumbar fusion or cerebrovascular surgery were enrolled in an open label treatment controlled study comparing blood pressure and heart rate responses during deliberate hypotension with either esmolol or nitroprusside during steady-state N2O/isoflurane anesthesia. The first 5 patients were empirically assigned to the esmolol group; the remaining 20 patients were randomized to receive either esmolol or nitroprusside. The target of 15% reduction in mean arterial pressure (MAP) from baseline determined during anesthesia was attained with esmolol 195 +/- 10 micrograms/kg/min (mean +/- SEM) for the group (n = 15) or nitroprusside 1.9 +/- 0.3 micrograms/kg/min for the nitroprusside group (n = 10). Nitroprusside use was associated with a 15.9 +/- 5.3% increase in heart rate compared to a 12.1 +/- 2.2% decrease in the esmolol group (p = 0.0001 between groups). Upon termination of the hypotensive infusions, nitroprusside patients had a MAP increase of 13.9 +/- 5.5% above baseline (p less than 0.05 compared to prehypotension) while the 7.4 +/- 3.5% increase in the esmolol group was not statistically significant. Although 30% of nitroprusside patients overshot their baseline MAP by more than 25%, no esmolol patients had this degree of rebound. One esmolol patient had a brief period of atrial premature contractions. No patient in either group suffered any adverse reaction to hypotension. It is concluded that in moderate doses esmolol is a safe and effective hypotensive agent during isoflurane anesthesia, with no reflex tachycardia and no significant potential for rebound hypertension. A MAP reduction of 30% from preanesthesia baseline was readily obtained with this combination.

Adrenergic beta-Antagonists↗
PubMed1988

Rapid monitoring of intraoperative cerebral blood flow using 133Xe.

This study examined the feasibility of rapid rCBF monitoring using 133Xe as a tracer during operative procedures. We compared the initial slope index derived from two bicompartmental and one monocompartmental physiological models. The single-compartment model requires only 3 min of monitoring, whereas the bicompartmental models, thought to be more reliable, require 11 min of clearance. Data were collected from 26 patients undergoing carotid endarterectomy. Approximately 20 mCi of 133Xe in saline was injected i.v. for up to five measurements per patient, for a total of 117 measurements. The robustness of the regression for the three parameters (r = 0.781-0.99, p less than 0.0001) suggests that the three parameters are closely related. This is supported by similarity of the slopes of the regression lines (between 0.944 and 1.25) and the mean +/- SD of the three rCBF models (24.9-27.5 +/- 12.0-14.3 ml 100 g-1 min-1). Similar results were obtained for individual detectors, despite the expected higher variability. For intraoperative use in surgical procedures in which physiological conditions may change rapidly and i.v. injections of tracer must be used, a rCBF index that quickly and accurately reflects flow conditions is useful. Our data suggest that the single-compartmental Wyper index may be used to provide information about cerebral perfusion that is as accurate and robust as bicompartmental models, but requires only one-quarter of the data collection time.

Cerebrovascular Circulation↗
PubMed1988

133Xe blood flow monitoring during arteriovenous malformation resection: a case of intraoperative hyperperfusion with subsequent brain swelling.

Measurement of regional cerebral blood flow (rCBF) using the i.v. 133Xe technique was carried out during resection of a right temporooccipital arteriovenous malformation (AVM) with ipsilateral middle and posterior cerebral arterial supply. Intraoperatively, a rCBF detector was in place over the right frontotemporal area, about 5 to 6 cm from the border of the AVM. Anesthesia was 0.75% isoflurane in oxygen and nitrous oxide. After dural exposure, the rCBF was 27 ml/100 g/min at a pCO2 of 29 mm Hg and a mean arterial pressure (MAP) of 90 mm Hg. The pCO2 was then elevated to 40 mm Hg, and the rCBF was increased to 55 ml/100 g/min at a MAP of 83 mm Hg. After AVM removal, the rCBF rose to 50 ml/100 g/min at a pCO2 of 27 mm Hg and a MAP of 75 mm Hg. The pCO2 was elevated to 33 mm Hg and the rCBF increased to 86 ml/100 g/min at a MAP of 97 mm Hg. During skin closure, the rCBF was 94 ml/100 g/min at a pCO2 of 26 mm Hg and a MAP of 97 mm Hg. The patient was neurologically normal postoperatively except for a mild, new visual field defect. After 2 to 3 days, the patient gradually developed lethargy, confusion, and nausea with relatively normal blood pressure. An angiogram revealed residual enlargement of the posterior cerebral artery feeding vessel. Computed tomography showed edema extending from the area of AVM resection as far as the frontal region, producing a significant midline shift anteriorly. Intraoperative rCBF monitoring revealed significant hyperperfusion after AVM resection, which was associated with signs and symptoms of the normal perfusion pressure breakthrough syndrome.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

Pharmacodynamics of vecuronium and atracurium in the obese surgical patient.

The effect of obesity on the duration of action of the nondepolarizing muscle relaxants atracurium and vecuronium was studied in 28 neurosurgical patients. In obese patients given vecuronium (0.1 mg/kg), the time to go from 5 to 25% of recovery of twitch response was statistically significantly longer (14.6 +/- 7 minutes, mean +/- SD) than it was in nonobese control patients (6.9 +/- 2 minutes). Similarly, with vecuronium times for recovery from 25 to 75% were longer (33 +/- 15 minutes) in obese patients than in control patients (13.2 +/- 2 minutes), as was time to 75% recovery, 82 +/- 30 minutes in obese patients, 50 +/- 9 minutes in controls. In contrast, obese patients given atracurium (0.5 mg/kg) exhibited no difference in recovery indexes or recovery times when compared to control patients of normal weight. The prolonged duration of action of vecuronium in obese patients is most likely related to impaired hepatic clearance and/or an overdose effect with recovery occurring during the distribution phase. That the duration of action of atracurium is not prolonged in the obese is believed due to this relaxant's not depending on organ function for elimination.

Adult↗
PubMed1988

Duration of action of neostigmine and pyridostigmine in the elderly.

This study was undertaken to assess differences between young and elderly patients with respect to the duration of antagonism of metocurine neuromuscular blockade by neostigmine (NEO) or pyridostigmine (PYR). Patients were given either NEO (seven elderly and ten young) or PYR (seven elderly and eight young) and received nitrous oxide in oxygen (60:40) and 1 MAC halothane. Neuromuscular transmission was assessed by using evoked compound electromyography. Metocurine 0.1 mg/kg was given, followed by a continuous infusion to achieve 90% reduction in baseline single twitch height. After at least 30 minutes, either NEO (0.07 mg/kg) or PYR (0.14 mg/kg) and atropine (0.02 mg/kg) were given IV. After injection of NEO or PYR, the duration of maximal response (DOMR) was recorded. Mean (+/- SE) ages were 38 +/- 5 and 68 +/- 2 years in the two groups of patients receiving PYR. In the elderly, PYR significantly prolonged DOMR compared to younger patients (35.3 +/- 8.2 vs 14.4 +/- 4.2 minutes, respectively). The mean ages in the two groups of patients receiving NEO were 41.5 +/- 4 and 72 +/- 2 years. The elderly group demonstrated a significant increase in the DOMR compared to younger patients (32 +/- 10 vs 11 +/- 2 minutes, respectively). It is concluded that, compared to younger patients, the duration of action of NEO and PYR in the aged patient is prolonged.

Adult↗
PubMed1987

The effect of phenytoin on the magnitude and duration of neuromuscular block following atracurium or vecuronium.

Patients chronically receiving anticonvulsants have been reported to be resistant to the long-acting competitive neuromuscular blockers. This study examines the effects of atracurium and vecuronium on 100 neurosurgical patients; 50 receiving chronic phenytoin therapy (group I) and 50 controls (group II). During O2/N2O/halothane anesthesia, five patients in each group were given a bolus of vecuronium 0.1 mg/kg, and a different five patients in each group were given atracurium 0.5 mg/kg, to produce neuromuscular blockade in excess of 95%. The time to maximum blockade and the recovery from atracurium was unaffected by phenytoin therapy. Recovery from vecuronium was enhanced in the phenytoin group, as demonstrated by the recovery index, defined as the time required for recovery from 25-75% of the control neuromuscular response (7.9 +/- 2.2 min compared with 17.8 +/- 5.1 min in controls, P less than 0.005). Similarly, the total duration of neuromuscular blockade, defined as recovery to 90% of control response, was significantly shorter in the phenytoin group (31.9 +/- 6.0 min compared with 69.7 +/- 12.9 min in controls, P less than 0.001). The remaining 40 patients from each group were given a preselected dose of either vecuronium (0.02-0.06 mg/kg) or atracurium (0.10-0.25 mg/kg) during anesthesia with O2/N2O/fentanyl, to generate dose-response curves for the relaxants. Using analysis of covariance, the slopes and elevations for atracurium were found to be essentially identical in the two groups; as were the calculated ED50 and ED95. Patients receiving chronic phenytoin therapy were resistant to vecuronium-induced neuromuscular blockade. With vecuronium, the dose-response curves for the two groups were parallel; the curve for phenytoin patients was shifted to the right.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗