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Biomedical subjects

E Ornstein

Publications and source records attributed to E Ornstein.

At least 55 records · Page 3Linked to original sources
PubMed1994

Relational themes in the inpatient community meeting.

The authors present a model of psychiatric inpatient community meetings run as large group interpretive psychotherapy. They developed this model in part from Gill's notion that patients attach plausible meanings to therapist behavior based on the patient's characteristic and stereotypical ways of experiencing relationships. The model provides a framework for the description of 11 clinically derived "unconscious relational configurations" that can frequently be detected as organizing "relational themes" of community meetings. The authors present two clinical vignettes in which staff detect these themes and interpret them together with the defenses against them. They then discuss the prominent negative affective valence that characterizes the "unconscious relational configurations."

Ego↗
PubMed1994

A computer simulation of the haemodynamic effects of intracranial arteriovenous malformation occlusion.

To study the effect of AVM occlusion on cerebrovascular haemodynamics, a simplified model was simulated consisting of a feeding artery supplying a capillary bed in parallel with a fistula-like malformation, both emptying into a draining vein. An electrical circuit analogue of the physiologic system was developed using lumped proximal and distal pressure dependent resistances, and capacitors representing vascular compliance. Autoregulation was introduced as a pressure varying precapillary arteriolar resistance. Equations derived from the circuit model were simulated using a graphical modeling program. The model successfully simulates phenomena angiographically observed during embolization procedures. Fistula pressure is shown to rapidly fall following proximal AVM occlusion, in contrast to a marked rise seen with distal occlusion, which is associated with biphasic flow into and out of the fistula and the arterial feeder. The model predicts an increase in capillary pressure and capillary flow which, depending on the magnitude of the flow increase and the state of autoregulation, may result either in reversal of ischaemia or hyperperfusion injury. Vascular overload is predicted in the absence of autoregulation. There is, however, little potential for vascular overload when autoregulation is intact. The model represents a first step in the mathematical characterization of the phenomenon of hyperperfusion following AVM occlusion.

Arterial Occlusive Diseases↗
PubMed1994

Arteriovenous malformation draining vein physiology and determinants of transnidal pressure gradients. The Columbia University AVM Study Project.

Arteriovenous malformation (AVM) draining vein pressure (DVP) may have an influence on both the natural history of the disease and treatment outcome. The purposes of this study were to assess the relationship between DVP and other clinical and physiological variables and to characterize the transmission of arterial pressure across the AVM nidus. DVP measurements were carried out during elective AVM resection with isoflurane/nitrous oxide anesthesia with arterial carbon dioxide pressure of approximately 30 mm Hg. The gradient between the right atrium and operative measurement site was noted. Pre-excision feeding mean arterial pressure and DVP were measured with a 26-gauge needle simultaneously with systemic mean arterial pressure and central venous pressure (CVP). DVP was tested with systemic mean arterial pressure increased to approximately 20 mm Hg with phenylephrine or CVP increased with a Valsalva maneuver. Finally, preresection and postresection DVP values were compared. Relative to the site of measurement, DVP was 7 +/- 5 mm Hg at a CVP of -4 +/- 5 mm Hg (n = 45). There was no influence of presentation, presence of deep venous drainage, size, location, or prior embolization on DVP. In 19 patients, DVP decreased (8 +/- 4 to 5 +/- 3; P < 0.05) whereas CVP increased from pre- to postresection (-4 +/- 5 to -2 +/- 5; P < 0.05). For the phenylephrine challenge (n = 11), there was no difference (P = 0.84) between the delta DVP (2 +/- 1 mm Hg) and the delta CVP (2 +/- 3 mm Hg).(ABSTRACT TRUNCATED AT 250 WORDS)

Arteriovenous Malformations↗
PubMed1993

Desflurane and isoflurane have similar effects on cerebral blood flow in patients with intracranial mass lesions.

BACKGROUND: Before desflurane is advocated for patients undergoing neurosurgical procedures, it is necessary to determine the effect of desflurane on cerebral blood flow (CBF). In this study, CBF values are compared between desflurane and isoflurane at two doses. In addition, CBF reactivity to CO2 and the effect of prolonged exposure were compared between the two agents. METHODS: Cerebral blood flow measurements with intravenous 133Xe were performed in 24 patients undergoing craniotomy for mass lesions, randomized to receive either isoflurane or desflurane in oxygen and air. Cerebral blood flow was determined at 1 and 1.5 MAC concentrations at PaCO2 of 25 mmHg in the absence of surgical stimulation. Intraoperatively, with 1.25 MAC anesthesia, CBF was determined at target PaCO2 of 25 and 35 mmHg. In 15 patients, an additional measurement at 1.25 MAC was made before closure. RESULTS: At 1.0 MAC, mean +/- SD CBF values for the desflurane and isoflurane groups were 18 +/- 2 and 20 +/- 3 ml x 100 g-1 x min-1, respectively. At 1.5 MAC, CBF values were the same for the two anesthetics; 17 +/- 3 ml x 100 g-1 x min-1 for isoflurane and 19 +/- 4 ml.100 g-1 x min-1 for desflurane. During 1.25 MAC anesthesia, there were no differences between groups, with CO2 reactivity 1.3 +/- 1.2 ml x 100 g-1 x min-1 x mmHg-1 for desflurane and 1.6 +/- 0.6 ml.100 g-1 x min-1 x mmHg-1 for isoflurane. There was no demonstrable decrease in CBF with prolonged exposure to either agent. CONCLUSIONS: Desflurane and isoflurane are similar in terms of absolute CBF, the response to increasing doses, and the preservation of CO2 reactivity.

Adult↗
PubMed1993

Pharmacokinetics and pharmacodynamics of rocuronium (Org 9426) in elderly surgical patients.

The effects of age on the pharmacokinetic and pharmacodynamic responses to rocuronium (Org 9426) were studied in 20 elderly (> 70 yr) and 20 younger control patients (< 60 yr) during N2O/O2, fentanyl anesthesia. The onset times were the same for both the elderly and younger control group, but the duration of action of rocuronium was significantly prolonged in the elderly patients. Elderly patients, when compared with the younger, also exhibited a significant decrease in plasma clearance (3.67 +/- 1.0 vs 5.03 +/- 1.5 mL.kg-1.min-1, mean +/- SD) and volume of distribution (399 +/- 122 vs 553 +/- 279 mL/kg, mean +/- SD). During the recovery phase of paralysis, no significant difference was seen in the log plasma concentration versus twitch tension response relationship between 20% and 80% paralysis in young and elderly patients receiving rocuronium. The differences in action of rocuronium between the elderly and younger groups can be fully explained by the observed differences in the distribution and elimination of rocuronium between the two groups. The decreased total body water and decreased liver mass which normally accompany aging are likely explanations for the pharmacokinetic changes found in the elderly in this study. We conclude that the action of rocuronium is prolonged in patients aged more than 70 yr because of decreased elimination of the drug.

Adult↗
PubMed1993

Pressure autoregulation is intact after arteriovenous malformation resection.

The loss of autoregulatory control of cerebral perfusion to changes in perfusion pressure in tissue remote from an arteriovenous malformation (AVM) has been proposed as the mechanism underlying "normal perfusion pressure breakthrough." This study is the first direct test of this mechanism. Studies were performed during the resection of moderate to large AVMs in 25 patients undergoing 28 procedures under isoflurane anesthesia. Cerebral blood flow (CBF) was measured (xenon-133 method) in the hemisphere adjacent to the nidus before resection after dural exposure (pre), after AVM removal before dural closure at spontaneous systemic blood pressure (post), and, finally, with the mean arterial pressure increased by 20 mm Hg, using phenylephrine (post-BP). AVM resection resulted in a significant enhancement of perfusion in the adjacent hemisphere (30 +/- 2 vs. 25 +/- 1 ml/100g/min, P < 0.01), but no further increase of CBF occurred during increased perfusion pressure (30 +/- 2 ml/100g/min). One patient suffered a postoperative hemorrhage and another developed intraoperative brain swelling during the course of the resection that necessitated staging the procedure. These two patients had the highest increases in CBF, but intact pressure autoregulation. Preserved autoregulation to increased mean arterial pressure after resection does not support a hemodynamic mechanism for the observed increase in CBF from before the resection to after the resection. Pathological events, however, do appear to be related to increases in hemispheric perfusion.

Adolescent↗
PubMed1992

Pharmacokinetics and pharmacodynamics of vecuronium in the obese surgical patient.

The effect of obesity on the disposition and action of vecuronium was studied in 14 surgical patients. After induction of anesthesia with thiopental and maintenance of anesthesia by inhalation of nitrous oxide and halothane, seven obese patients (93.4 +/- 13.9 kg, 166% +/- 30% of ideal body weight, mean +/- SD) and seven control patients (60.9 +/- 12.3 kg, 93% +/- 6% of ideal body weight) received 0.1 mg/kg of vecuronium. Plasma arterial concentrations of muscle relaxant were determined at 1, 3, 5, 10, 15, 20, 30, 45, 60, 90, 120, 150, 180, 210, 240, 300, and 360 min by a spectrofluorometric method. Simultaneously, neuromuscular blockade was assessed by stimulation of the ulnar nerve and quantification of thumb adductor response. Times to 50% recovery of twitch were longer in the obese than in the control patients (75 +/- 8 versus 46 +/- 8 min) as were 5%-25% recovery times (14.9 +/- 4.0 versus 10.0 +/- 1.7 min) and 25%-75% recovery times (38.4 +/- 13.8 versus 16.7 +/- 10.3 min). However, vecuronium pharmacokinetics were similar for both groups. When the data were calculated on the basis of ideal body weight (IBW) for obese and control patients, total volume of distribution (791 +/- 303 versus 919 +/- 360 mL/kg IBW), plasma clearance (4.65 +/- 0.89 versus 5.02 +/- 1.13 mL.min-1.kg IBW-1), and elimination half-life (119 +/- 43 versus 133 +/- 57 min) were not different between groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Pharmacokinetics and pharmacodynamics of pipecuronium bromide (Arduan) in elderly surgical patients.

The neuromuscular response to pipecuronium bromide (Arduan), 70 micrograms/kg, was studied in 20 elderly (greater than 70 yr) and 10 younger patients (less than 60 yr) during nitrous oxide, fentanyl, and droperidol anesthesia. The adductor pollicis response to single 0.2-ms supramaximal pulses was recorded. Although all younger patients were completely paralyzed, 2 of 20 elderly patients did not attain 90% paralysis. Onset time in the elderly was prolonged (6.9 +/- 2.6 vs 4.3 +/- 1.5 min, P less than 0.02). Spontaneous recovery was similar in both groups, with 75% recovery occurring at 133 +/- 52 min in the elderly and 146 +/- 46 min in the younger patients. The pharmacokinetic variables were similar for the two groups, and pharmacodynamic analysis revealed a similar sensitivity at the neuromuscular junction. The pharmacologic actions of pipecuronium in otherwise healthy patients do not differ between young and elderly adults.

Aged↗
PubMed1992

Effects of hypocarbia on the pharmacodynamics of sufentanil in humans.

Descriptors of power and frequency derived from power spectral analysis of the electroencephalogram (EEG) were used to determine the effects of low-dose sufentanil (0.1 micrograms/kg) on brain activity. The effects of hypocarbia alone and of hypocarbia with sufentanil in patients receiving a N2/O2 (70%:30%) anesthetic were also studied. Hypocarbia alone caused changes in most EEG descriptors from both the anterior (F3-C3) and posterior (P3-O1) EEG montages. All EEG descriptors in both hypocarbic and normocarbic patients significantly changed when sufentanil was administered, reflecting a shift of power into the lower frequency ranges. When the anterior EEG montages from the two groups that received sufentanil were compared, the delta power band, spectral edge 50 (median power frequency), and the relative power in the delta power band divided by the alpha plus beta power bands [D/(A + B)] in the hypocarbic group exhibited a significantly greater shift of power into the lower frequency range. It is concluded that (a) power spectral analysis is a sensitive measure of the effects of hypocarbia and small doses of sufentanil on the brain; (b) the power spectral analysis descriptors--delta power band, spectral edge 50, and [D/(A + B)]--are statistically the most sensitive to EEG changes induced by sufentanil; and (c) hypocarbia intensifies patient EEG response to sufentanil, as judged by changes in EEG descriptors.

Adult↗
PubMed1991

Metabolism of desflurane and isoflurane to fluoride ion in surgical patients.

The metabolism of isoflurane and the investigational volatile anaesthetic desflurane to fluoride ion was examined in 25 surgical patients. The patients were randomly assigned to four groups, to receive isoflurane or desflurane at either 0.65 MAC or 1.25 MAC. Anaesthesia was induced in all patients with thiopentone and midazolam and included nitrous oxide 60% in addition to the volatile agent. Blood was drawn before induction and at the end of the operation for determination of serum fluoride ion concentration. Plasma fluoride ion concentrations increased (+ 1.36 +/- 0.93 microM, P less than 0.01) in patients receiving isoflurane but were unchanged (-0.13 +/- 0.50 microM) in patients receiving desflurane. Metabolic release of fluoride ion is less with desflurane than with isoflurane during administration of the anaesthetics to surgical patients, and is unlikely to be of clinical significance.

Adult↗
PubMed1991

Cerebral blood flow reactivity to changes in carbon dioxide calculated using end-tidal versus arterial tensions.

We retrospectively examined arerial and end-tidal estimations of CO2 tension used to calculate cerebrovascular reactivity in 68 anesthetized patients. CBF was measured using the intravenous 133Xe technique at mean +/- SD PaCO2 values of 28.2 +/- 5.2 and 38.8 +/- 4.8 mm Hg. The correlation between all PaCO2 and end-tidal PCO2 (PetCO2) values was y = 0.85x - 0.49 (r = 0.93, p = 0.0001). There was a moderate correlation between age and the difference between PaCO2 and PetCO2 (y = 0.11x + 0.79; r = 0.73, p = 0.0001). Cerebrovascular reactivity to changes in CO2 (ml 100 g-1 min-1 mm Hg-1) was similar (p = 0.358) when calculated by using either PaCO2 (1.9 +/- 0.8) or PetCO2 (1.8 +/- 0.8) and highly correlated (y = 0.86x + 0.23; r = 0.91, p = 0.0001). The CBF response to changes in CO2 tension can be reliably estimated from noninvasive measurement of PetCO2.

Adult↗
PubMed1991

Desflurane and isoflurane in surgical patients: comparison of emergence time.

In order to examine the clinical potential of desflurane (difluoromethyl-1-fluoro-2,2,2-trifluoroethyl ether) in humans, a randomized, controlled study was designed to compare time of emergence from anesthesia in patients undergoing elective surgery under desflurane anesthesia to that of patients under isoflurane anesthesia. Twenty-eight patients were randomly divided into four groups. Group 1 received isoflurane 0.65 MAC; group 2, desflurane 0.65 MAC; group 3, isoflurane 1.25 MAC; and group 4, desflurane 1.25 MAC. Anesthesia was induced with sodium thiopental, and N2O 60% was added to the volatile agent. Mean anesthetic exposure times (min [mean +/- SD]) were 108 +/- 49 in group 1, 132 +/- 46 in group 2, 147 +/- 74 in group 3, and 166 +/- 71 in group 4, with no significant differences between groups. The times from discontinuation of anesthetic gases until patients opened their eyes and squeezed the investigator's hand in response to a command were averaged and recorded as "emergence time." Emergence time was significantly less with desflurane than with isoflurane given at the same MAC. Patients receiving isoflurane 0.65 MAC responded to commands 15.6 +/- 4.3 min after discontinuation of the anesthetic; patients in the desflurane 0.65 MAC group responded in 8.8 +/- 2.7 min (P less than 0.01). Emergence time for isoflurane 1.25 MAC was 30.0 +/- 11.0 min; for desflurane 1.25 MAC it was 16.1 +/- 6.0 min (P less than 0.05). Our results confirm that emergence from desflurane anesthesia is more rapid than from isoflurane.

Adult↗
PubMed1991

Thiopental effect on cerebral blood flow during carotid endarterectomy.

To investigate the effect of thiopental on cerebral blood flow (CBF) during carotid endarterectomy, five patients receiving isoflurane-N2O anesthesia were studied. During the period of temporary bypass shunting, a baseline CBF was measured using i.v. Xe washout, and global CBF was calculated from the mean of 10 detectors. Thiopental was given in a dose sufficient (mean 4.5, range 2.6-5.8 mg/kg) to result in burst-suppression on the electroencephalogram (EEG) of approximately 1:1 duration and CBF was measured again. Data were compared using repeated measures analysis of variance. Thiopental significantly reduced mean (+/-SE) CBF (ml/100 g/min) from 37 +/- 6 to 18 +/- 2 (p <0.02). Corresponding PaCO2 (mm Hg) values were 42.8 +/- 1.2 and 41.2 +/- 1.6 and mean systemic blood pressure (mm Hg) was 101 +/- 3 and 100 +/- 6, respectively (NS). Mean % change in CBF was 48 +/- 5 (range 32-62%). There was no relationship between the dose administered and the change in CBF. During steady-state anesthesia, a small dose of thiopental capable of suppressing EEG resulted in a profound reduction in CBF.

Journal Article↗
PubMed1991

Deliberate hypotension in patients with intracranial arteriovenous malformations: esmolol compared with isoflurane and sodium nitroprusside.

Thirty patients undergoing resection of arteriovenous malformations with deliberate hypotension were randomized to receive 1 of 3 hypotensive agents. Anesthesia was maintained with isoflurane and nitrous oxide in all patients. Mean arterial pressure was reduced 20% to 60-65 mm Hg with use of either isoflurane (less than or equal to 4%), sodium nitroprusside (less than or equal to 8 micrograms.kg-1.min-1), or esmolol (less than or equal to 24 mg/min). Esmolol was associated with a decrease in cardiac output from 6.2 +/- 1.3 to 3.8 +/- 0.8 L/min, which, because of a 22% increase in systemic vascular resistance, far exceeded the reduction in mean arterial pressure. Systemic vascular resistance increased despite a 32% decrease in plasma renin activity. In contrast, with sodium nitroprusside or isoflurane, the decrease in mean arterial pressure was associated with decreases in systemic vascular resistance of similar magnitude, with no change in cardiac output. Plasma renin activity levels increased 48% with sodium nitroprusside and 126% with isoflurane. Heart rate increased 13% with sodium nitroprusside, remained unchanged with isoflurane, and decreased 23% with esmolol. Although esmolol may be used as a primary hypotensive agent, the potential for marked myocardial depression must be recognized. The differences in pharmacologic properties for the different hypotensive agents suggest that combinations of these agents may provide a pharmacologic profile superior to either agent alone.

Adrenergic beta-Antagonists↗
PubMed1991

Distribution, elimination, and action of vecuronium in the elderly.

The effects of age on the pharmacokinetics and pharmacodynamics of vecuronium in eight elderly patients aged 72-86 yr and eight younger adults aged 26-48 yr undergoing elective surgical procedures under nitrous oxide-fentanyl anesthesia were studied. Vecuronium (0.1 mg/kg) was given as an intravenous bolus, and the ulnar nerve was stimulated with a square-wave impulse of 0.2-ms duration. The response to stimulation at a frequency of 0.1 Hz was measured and recorded with a force displacement transducer applied to the thumb. Spontaneous recovery was significantly longer in elderly patients than in younger patients (50% recovery time, 97.1 +/- 29 vs 39.8 +/- 14 min, mean +/- SD; recovery index [25%-75%], 49.4 +/- 11 vs 15.0 +/- 8 min). In addition, in elderly patients elimination half-life of vecuronium was significantly prolonged (125 +/- 55 vs 78 +/- 21 min, P = 0.04) and plasma clearance reduced (2.6 +/- 0.6 vs 5.6 +/- 3.2 mL.kg-1.min-1, P = 0.049). The prolonged duration of action of vecuronium in the elderly surgical patients thus appears to be secondary to altered pharmacokinetics consistent with an age-related decrease in renal and hepatic functions.

Adult↗
PubMed1991

Pharmacokinetics of sufentanil in obese patients.

The pharmacokinetics of sufentanil were determined in eight obese (94.1 +/- 14 kg, mean +/- SD) and eight control patients (70.1 +/- 13 kg) anesthetized for neurosurgery. After induction of anesthesia, 4 micrograms/kg of sufentanil was administered in a single intravenous bolus. Multiple arterial samples were obtained at timed intervals over 6 h, and plasma concentrations of sufentanil were measured by radioimmunoassay. Calculation of pharmacokinetic variables from the derived compartmental models demonstrated an increased volume of distribution of sufentanil in the obese (9098 +/- 2793 mL/kg ideal body weight, mean +/- SD) when compared with a control group (5073 +/- 1673 mL/kg ideal body weight) (P less than 0.01) and a prolonged elimination half-life (208 +/- 82 min vs 135 +/- 42 min, P less than 0.05). The total volume of distribution correlated linearly with the degree of obesity, as expressed in percent ideal body weight (r = 0.67). In contrast, plasma clearance was similar in both obese and control groups (32.9 +/- 12.5 vs 26.4 +/- 5.7 mL/kg ideal body weight). The high lipid solubility of sufentanil probably explains the altered pharmacokinetics of this opioid in obese patients.

Adult↗