Showing papers in "Anesthesiology in 1983"

The Premenstrual Syndrome

Abstract: In a crossover study conducted over a six-month period in eight patients with well-characterized premenstrual syndrome, physical and behavioral symptoms were relieved by daily administration of an agonist of gonadotropin-releasing hormone. The reversible "medical ovariectomy" attained with this agonist suggests that it may be an effective and rational treatment for this distressing syndrome in the short term. Whether prolonged therapy would be safe and effective, or even necessary, remains to be determined. (N Engl J Med 1984; 311:1345–9.)

Reinfarction following anesthesia in patients with myocardial infarction.

Abstract: The authors studied the incidence of and factors related to recurrent perioperative myocardial infarction retrospectively during 1973–1976 (Group 1) and prospectively during 1977–1982 (Group 2). Reinfarction occurred in 28 of 364 (7.7%) patients in Group 1 and 14 of 733 (1.9%) in Group 2 (P < 0.005)

On the Safety of Radial Artery Cannulation

Abstract: The frequency of complications following radial artery cannulation for monitoring purposes was determined in 1,699 cardiovascular surgical patients and in 83 patients in whom cannulation was performed in another artery after failure at the radial site. Patients were examined and radial artery flow d

Functional Anatomy of the Brachial Plexus Sheaths

Abstract: The brachial plexus sheath was examined in cadavers by using a combination of anatomic dissection, histologic preparations, and x-rays made after injection of x-ray contrast media, and in surgical patients by using computed tomography (CT) dye studies. The connective tissue forming the sheath was organized more densely proximally near its origin and became loosely organized distally as it ended by joining the medial intermuscular septum of the arm. The connective tissue forming the sheath extends inward, forming septa between components of the plexus. Thus, the sheath is a multicompartmented structure, formed by the thin connective tissue sheath surrounding the plexus and by the septa which extend inward from the sheath. A fascial compartment is created for each nerve, and this compartment serves to define the anatomic limits of that nerve. These compartments have potential clinical importance and implication in the techniques for brachial plexus block. They serve functionally to limit the circumferential spread of injected solutions of local anesthetics. These studies also indicate that injected anesthetic solutions spread easily in a longitudinal manner up and down the nerve and remain compartmentalized. The data presented here provide a rational explanation for the not uncommon occurrence of a profound block of rapid onset in one nerve, yet partial or absent block in other nerves, following any of the techniques of brachial plexus anesthesia.

Isoflurane—A Powerful Coronary Vasodilator in Patients with Coronary Artery Disease

Abstract: The coronary hemodynamic effects of 1% end-tidal isoflurane administered in oxygen-nitrogen by intermittent positive-pressure ventilation (IPPV) were investigated in 21 patients with stable coronary artery disease. Besides standard central hemodynamic measurements, coronary sinus blood flow was meas

Intraoperative Monitoring of Sensory Evoked Potentials

Abstract: Sensory evoked potentials (EP), the electrophysiologic responses of the nervous system to sensory stimulation, can be used to assess the functional integrity of specific sensory pathways in anesthetized patients (1, 2). Thus, neurologic function can be partially assessed when clinical examination is severely limited by the effects of anesthetic agents and adjuvant drugs.

The cerebral metabolic effects of isoflurane at and above concentrations that suppress cortical electrical activity.

Abstract: The effects of 1.4-6.0% end-expired isoflurane on cerebral metabolism and hemodynamics were examined in dogs. A dose-related decrease in cerebral oxygen consumption (CMRO2) occurred until there was suppression of cortical electrical activity as reflected by the onset of an isoelectric electroencephalogram. This occurred at an end-expired concentration of 3% isoflurane when the mean CMRO2 was 2.02 ml X 100 g-1 X min-1. Thereafter, increasing concentrations of isoflurane to 6% had no further effect on the CMRO2. Brain biopsies taken at the end of the study revealed normal concentrations of ATP and phosphocreatine and a normal energy charge. Despite a normal cerebral energy state, there was a mild, dose-related, cerebral lactic acidosis (up to 2.84 mumol/g) that accompanied a mild systemic acidosis. It is concluded that the cerebral metabolic changes produced by isoflurane are secondary to an effect on cortical electrical activity, that abolition of this activity can be produced in dogs by a clinically relevant concentration of isoflurane (3%) without marked systemic hemodynamic effects, and that concentrations of isoflurane necessary to abolish cortical activity have no direct toxic effect on cerebral metabolic pathways.

Hypothermia and barbiturates: individual and combined effects on canine cerebral oxygen consumption.

Abstract: Following establishment of total spinal anesthesia, the cerebral metabolic effects of progressive hypothermia (37, 28, 18, and 14 degrees C) were studied initially in six awake dogs. The EEG became isoelectric at temperatures below 18 degrees C. At 14 degrees C, CMRO2 was reduced to 7% of control. Thereafter, 40 mg/kg thiopental, iv, was given and the dogs were rewarmed while an isoelectric EEG was maintained by a continuous thiopental infusion. The CMRO2 was then compared at the different temperatures with and without thiopental. The CMRO2 was unaffected by the barbiturate at 14 and 18 degrees C. At 28 and 37 degrees C the CMRO2 was significantly reduced by the barbiturate (at 37 degrees C to 55% of the 37 degrees C value without thiopental). The change in CMRO2 with temperature in the absence of EEG activity (due to barbiturates) closely approximated an Arrhenius curve (relating log CMRO2 to the reciprocal of absolute temperature). In the presence of EEG activity (no barbiturates) such a simple relationship was less apparent. The results support the following conclusions: barbiturates only affect CMRO2 in the presence of neuronal electrical activity; the combined effect of hypothermia and barbiturates on CMRO2 cannot be expressed as a simple additive relationship; and in the presence of electrical activity, the relationship between temperature and CMRO2 cannot be defined by any simple mathematical function.

Life-threatening apnea in infants recovering from anesthesia.

Abstract: To determine whether prematurely born infants with a history of idiopathic apneic episodes are more prone than other infants to life-threatening apnea during recovery from anesthesia, the authors prospectively studied 214 infants (173 full term, 41 premature) who received anesthesia. Fifteen premature infants had a preanesthetic history of idiopathic apnea. Six of these required mechanical ventilation because of idiopathic apneic episodes during emergence from anesthesia. Two were ventilated for other reasons, and seven recovered normally. Infants ventilated for apnea were younger (postnatal age 1.6 +/- 1.2 months, mean +/- SD; conceptual age 38.6 +/- 3.0 weeks) than those who recovered normally (postnatal age 5.6 +/- 2.7 months; conceptual age 55.1 +/- 11.3 weeks) (P less than 0.01). No other premature or full-term infant was ventilated because of postoperative apneic episodes. The authors conclude that anesthetics may unmask a defect in ventilatory control of prematurely born infants younger than 41-46 weeks conceptual age who have a preanesthetic history of idiopathic apnea.

A model for studying depth of anesthesia and acute tolerance to thiopental.

Abstract: Using power spectral analysis of the electroencephalogram (EEG) to measure the effect of thiopental on the brain, the authors investigated the phenomenon of acute tolerance. Three sequential infusions of thiopental, 20–25 min apart, were given to eight healthy volunteers. The infusions were stopped when moderately deep anesthesia, indicated by burst-suppression on the EEG, was reached. The mean (±SD) doses of thiopental for the first, second, and third infusions were 9.6 ± 2.0, 5.6 ± 0.9, and 5.2 ± 1.2 mg·kg-1, respectively. The spectral edge (Hz), defined as the frequency below which 95% of the total EEG power is located, was used to measure thiopental effect. A pharmacodynamic model was used to quantify the relationship of the plasma concentration of thiopental to its effect on the spectral edge. The model estimates the baseline spectral edge, Emax (Hz), the maximal decrease of the spectral edge due to thiopental, Emax (Hz), and the thiopental serum concentration required to produce 50% of the maximal shift of the spectral edge, the IC50 (μg·ml-1). The IC50 is an index of brain sensitivity to thiopental. If acute tolerance to thiopental had developed, the IC50 of the second and third infusions would have been greater than the IC50 of the first infusion. However, there were no significant differences between the values of the IC50 of each infusion (15.9 ± 5.1, 13.9 ± 3.4, and 16.0 ± 4.4 μg·ml-1 respectively), indicating that acute tolerance did not develop during repeated infusions of thiopental. The values for Emax and Emax also did not change significantly, providing additional evidence that the concentration-effect relationship remained constant. The combination of power spectral analysis of the EEG with pharmacodynamic modeling may prove to be a powerful tool for studying the clinical pharmacology of intravenous anesthetics.

Anesthetic requirements for halothane in young children 0-1 month and 1-6 months of age.

Abstract: In a previous study, the authors found that infants, in the first 6 months of life, required the highest minimum alveolar concentration (MAC) of any age group (1.09% halothane). Because only two neonates (0-31 days of age) were included in the original study and because profound depression of blood pressure and heart rate have been reported in neonates, the authors determined 1) whether the MAC of halothane in neonates (n = 12) differs from that in infants (1-6 months of age) (n = 12) and 2) whether the blood pressure and heart rate responses in neonates differ from those in infants at approximately 1 MAC. The authors found that the MAC of halothane in neonates, 0.87% +/- 0.03 SEM, was significantly lower (P less than 0.01) than that in infants, 1.20% +/- 0.06 SEM. With induction of anesthesia, the systolic blood pressure decreased 23% in neonates (P less than 0.05) and 34% in infants (P less than 0.005) from awake values. Similarly, the heart rate decreased 12% in neonates and 22% in infants (P less than 0.05). The incidence of hypotension (greater than 30% decrease in systolic blood pressure from awake) in neonates, 33%, was not significantly different from that in infants, 44%. The authors conclude that the MAC of halothane in neonates is 25% less than that in infants and significantly less than was thought previously. The MAC in infants is the highest of any age group. The decrease in blood pressure and the incidence of hypotension in neonates are similar to those in infants at approximately 1 MAC of halothane.

Effect of PEEP ventilation on renal function, plasma renin, aldosterone, neurophysins and urinary ADH, and prostaglandins.

Abstract: To explore the main factors which could be involved in the fluid retention induced by continuous positive pressure ventilation (CPPV), hemodynamics, renal, and hormonal parameters were measured in seven intensive care patients during three consecutive 60-min periods; one of intermittent positive pressure ventilation (IPPV), one of CPPV (PEEP 10 cmH2O), and finally one of IPPV During CPPV, a 15% decrease in cardiac output was observed, without alteration in arterial pressure or right atrial transmural pressure In addition, decreases were observed in urinary output by 34%, glomerular filtration rate by 19%, renal blood flow by 32%, sodium excretion by 33%, and potassium excretion by 26% There was no change in the fractional excretion of sodium and free water Institution of PEEP also led to a significant increase in plasma renin activity, plasma aldosterone, and urinary antidiuretic hormone, without significant variation in plasma neurophysins and urinary prostaglandins E and F alpha All of the changes that occurred during CPPV were reversed when PEEP was withdrawn It is concluded that the short-term antidiuretic effect of PEEP is mainly due to a hemodynamic impairment of renal function The water- and sodium-retaining hormonal systems also are stimulated and could participate in the fluid retention during more prolonged respiratory support with PEEP

The pharmacokinetics of midazolam in chronic renal failure patients.

Abstract: Fifteen patients with chronic renal failure (CRF) were given midazolam 02 mg/kg iv over 15 s All but one lost consciousness in a time ranging from 22-100 s (mean +/- SD was 55 +/- 26 s) after drug administration Patients regained consciousness from 6-105 min (mean 53 +/- 32) after drug administration The calculated mean plasma level of midazolam at arousal was 81 +/- 47 ng/ml Pharmacokinetics parameters were determined from midazolam plasma levels measured in 16 consecutive venous blood samples The pharmacokinetic parameters in CRF patients were compared with those of healthy volunteers matched for age, sex, and body size with the CRF patients Protein binding was determined by equilibrium dialysis CRF patients had a significantly higher (P less than 0005) plasma-free drug fraction (65% +/- 07) compared with the control patients (39% +/- 01) Total (bound plus unbound) kinetics differed in the two groups: volume of distribution 38 +/- 3 1/kg in CRF patients versus 22 +/- 2 1/kg in controls (P less than 0001), and clearance 114 +/- 16 ml X min-1 X kg-1 in CRF patients versus 67 +/- 09 ml X min-1 X kg-1 in controls (P less than 002) When kinetic parameters were corrected for protein binding, CRF patients unbound volume of distribution (635 +/- 68 1/kg) and free drug clearance (189 +/- 29 ml X min-1 X kg-1) were not different from the control group's volume of distribution (556 +/- 57 1/kg) and free drug clearance (176 +/- 24 ml X min-1 X kg-1)(ABSTRACT TRUNCATED AT 250 WORDS)

Dantrolene dose response in awake man: implications for management of malignant hyperthermia.

Abstract: Dantrolene sodium was administered intravenously to 12 adult volunteers to assess muscular and cardiopulmonary response. Pharmacokinetic results were obtained from whole blood drug concentration. Indirectly evoked thumb adduction was quantitated. Handgrip strength and subjective weakness score (10 e

Effects of Isoflurane on the Baroreceptor Reflex

Abstract: The baroreceptor reflex has been found to be attenuated during anesthesia, but the effects of the relatively new anesthetic, isoflurane, on baroreflex function have not been examined thoroughly. This study was performed to determine the effects of isoflurane on each component of the baroreceptor reflex arc, including the receptors, afferent and efferent nerve pathways, central integratory centers, peripheral ganglia, and the heart. Baroreflex effects on heart rate initiated by systemic pressure changes were examined in conscious and anesthetized dogs (1.3% and 2.6% isoflurane). The effects on individual components of the reflex arc were determined by examining carotid sinus baroreceptor afferent activity, sympathetic efferent nerve activity, and heart rate response to direct sympathetic and parasympathetic efferent nerve stimulation in anesthetized dogs. Preganglionic and postganglionic nerve activities were recorded simultaneously during baroreflex activation to determine ganglionic effects of isoflurane. Baroreflex-induced changes in heart rate were not depressed significantly until 2.6% isoflurane if blood pressure changes due to anesthetic administration were prevented. Significant decreases in baseline sympathetic efferent nerve activity were found at 1.3% and 2.6% isoflurane, with depression of postganglionic activity significantly greater than preganglionic activity at 2.6% isoflurane, indicating a ganglionic effect of isoflurane. Cardiac chronotropic responses to direct stimulation of sympathetic and vagal fibers were attenuated significantly by isoflurane, with sympathetic stimulation showing the greater sensitivity to the anesthetic. Carotid baroreceptor afferent activity was increased by isoflurane, and this sensitization of the baroreceptors appeared to contribute to the decreased levels of sympathetic tone. Therefore, although isoflurane was found to alter the baroreceptor reflex through its effects at multiple sites of the baroreflex arc, significant depression of the cardiac chronotropic component of the reflex was seen only at 2.6% isoflurane.

Effects of halothane, enflurane, and isoflurane on the SA node.

Abstract: The present experiments were carried out to study the influence of halothane, enflurane, and isoflurane on the electrophysiologic properties of single sinoatrial (SA) node cells of the guinea pig. The authors used the isolated, spontaneously beating guinea pig SA node superfused with modified Krebs'

The antiemetic effect of droperidol following outpatient strabismus surgery in children.

Abstract: The Antiemetic Effect of Droperidol Following Outpatient Strabismus Surgery in Children Michael Abramowitz;Tae Oh;Burton Epstein;Urs Ruttimann;David Friendly; Anesthesiology

The Cardiovascular Effects of Vecuronium (ORG NC45) and Pancuronium in Patients Undergoing Coronary Artery Bypass Grafting

Abstract: Vecuronium is a new nondepolarizing muscle relaxant which has been shown to cause no significant cardiovascular effects. Utilizing invasive monitoring in patients undergoing coronary artery bypass grafting, the authors compared the cardiovascular effects of vecuronium (0.28 mg/kg) in seven anesthetized patients with those of pancuronium (0.1 mg/kg) in five anesthetized patients. This dose of pancuronium represents three times its ED90 (dose producing a 90% depression of evoked twitch tension), while the vecuronium dose represents twelve times its ED90. This relatively large dose of vecuronium was chosen deliberately in an attempt to manifest any possible cardiovascular effects. Following administration of vecuronium, cardiac output increased 9% and systemic vascular resistance decreased 12%, while pancuronium produced a significantly greater 17% increase in cardiac output without change in systemic vascular resistance. Heart rate and systemic mean arterial pressure did not change following vecuronium, while increasing 22% and 24%, respectively, following pancuronium. The authors conclude that large doses of vecuronium have minimal cardiovascular effects and thus offer an advantage over pancuronium in patients anesthetized for coronary artery surgery.

Detection of air embolism by transesophageal echocardiography

Abstract: In this study transesophageal echocardiography was utilized for detecting air embolism in dogs in the supine position and in patients undergoing neurosurgery in the sitting position. In dogs, the threshold dose of venous air for detection was determined using either a bolus injection or continuous infusion of air via the jugular vein for up to three minutes. The ability to detect air in the aorta also was determined by a bolus injection into the left ventricular via an arterial catheter. For venous injection of air, the threshold dose by bolus was 0.02 ml/kg. When given by infusion, air could be detected in all cases by both contrast echocardiogram and Doppler sound changes at the rate of 0.05 ml . kg-1 . min-1. When air was injected into the left ventricle, the threshold dose was 0.001 ml/kg using contrast echocardiogram. In the clinical evaluation, air was clearly demonstrated in five of six patients by transesophageal echocardiogram along with appropriate changes in Doppler sounds, pulmonary artery pressure, and end-tidal carbon dioxide concentration. Our results suggest that transesophageal echocardiography may be a more sensitive and accurate method for detecting venous air embolism than other commonly used monitors for patients undergoing neurosurgical procedures in the sitting position. This device may also be able to detect air in the aorta in patients experiencing paradoxical air embolism during surgery due to intracardiac or pulmonary shunts.

Measurement of pleural pressure with esophageal balloon in anesthetized humans.

Abstract: Simultaneous measurement of tracheal and esophageal pressures during occluded inspiratory efforts (occlusion test) was used to assess the validity of the esophageal balloon technique in anesthetized supine subjects. Ten ASA 1 patients undergoing general anesthesia (halothane 1 MAC, nitrous oxide 70%, and oxygen) for minor surgery were studied. Esophageal pressure (Pes) was measured using a 5-cm-long balloon and was plotted against tracheal pressure (Pt). Occlusion tests were performed at end expiration with the balloon top positioned 5, 10, 15, and 20 cm above the cardia. The results show that with the balloon positioned at the classical level of 10 cm above the cardia, the difference between delta Pes and delta Pt did not exceed 8% in seven of 10 subjects. In the remaining three, however, the difference between delta Pes and delta Pt ranged between +20% and -40%. By repositioning the balloon to 5 or 15 cm above the cardia, a locus was found in all subjects where the difference is less than 10%. We conclude that the esophageal balloon technique can be used in anesthetized supine subjects to give reliable measurements of changes in pleural pressure, provided that it is validated with the occlusion test.

Influence of mixed venous oxygen tension (PVO2) on blood flow to atelectatic lung.

Abstract: The influence of mixed venous oxygen tension (PVO2) on blood flow to the atelectatic left lung was studied at normal and reduced cardiac outputs (CO) using extracorporeal veno-venous bypass in six pentobarbital anesthetized, mechanically ventilated dogs. Aortic and left pulmonary artery flows; airwa

Pharmacokinetic aspects of epidural morphine analgesia.

Abstract: Twenty patients undergoing thoracotomy were given 2, 4, or 6 mg morphine epidurally in a double-blind, randomized study for postoperative analgesia. Administration at T12-L1 or L1-L2 resulted in a dose-related analgetic duration (514 +/- 118 min, 778 +/- 207 min, and 938 +/- 155 min; means +/- SEM, respectively, for the groups). For the three groups, peak plasma morphine concentrations (range 19-34 ng/ml) were reached within 15 min. The plasma curves had a similar appearance as after an intramuscular injection and pharmacokinetic calculations showed an elimination half-life (mean +/- SEM) of 173 +/- 24 min, 200 +/- 60 min, and 213 +/- 57 min for the groups, respectively. The morphine concentrations in the CSF were considerably higher compared with plasma (45-100 times the plasma concentration at 1 h, 100-250 times at 3 h, and 125-175 times at 5 h) but the elimination half-life of morphine in the cerebrospinal fluid (CSF) was similar to that in plasma. The lumbar approach was used with similar efficacy as reported for thoracic administration. Side effects were few and nonsignificant. The authors conclude that epidural morphine administration results in a dose-dependent analgesia, as well as concentrations in the CSF that are considerably higher than in plasma. With similar elimination half-lives for morphine in CSF and plasma, the long analgetic duration probably depends on the locally high morphine concentrations achieved. For safety purposes, one may use the lumbar approach to the epidural space even for thoracic pain without reducing the efficacy.

The Role of Metabolism and Protein Binding in Thiopental Anesthesia

Abstract: The role of metabolism, relative to redistribution, in the termination of anesthesia was examined in patients receiving a single bolus iv injection of thiopental. Additionally, it was determined if nonlinear protein binding occurs immediately after the bolus iv injection of thiopental, possibly enhancing thiopental effect. Thiopental pharmacokinetics and protein binding were determined in 12 surgical patients with normal hepatic function. Using the pharmacokinetic equations listed in the appendix, plasma concentration over time data were used to quantitate the contribution of metabolism to the early decline of thiopental plasma concentrations after a single iv bolus administration. The fraction of thiopental loss from the central compartment due to metabolism was calculated to be 0.14 +/- 0.06 (mean +/- SD) at 1 min and 0.18 +/) 0.04 at 15 min. These data confirm that metabolism is far less important than distribution in the initial decline of blood and brain concentrations of thiopental, and, therefore, termination of thiopental anesthetic effect. The protein binding of thiopental from 0.5 to 15 min was found to be linear over a concentration range of 93 +/- 60 micrograms/ml to 6.9 +/- 0.62 micrograms/ml. Thus, concentration-dependent or nonlinear protein binding of thiopental after a single iv bolus administration could not be demonstrated and does not enhance thiopental anesthetic effect.