Showing papers in "Anesthesiology in 1978"

ASA Physical Status Classifications: A Study of Consistency of Ratings

Abstract: The American Society of Anesthesiologists' (ASA) Physical Status Classification was tested for consistency of use by a questionnaire sent to 304 anesthesiologists. They were requested to classify ten hypothetical patients. Two hundred fifty-five (77.3 percent) responded to two mailings. The mean number of patients rated consistently was 5.9. Four patients elicited wide ranges of responses. Age, obesity, previous myocardial infarction, and anemia provoked controversy. There was no significant difference in responses from different regions of the country. Academic anesthesiologists rated a greater number identical than did those in private practice (P less than 0.01). There was no difference in ratings between those who used the classification for billing purposes and those who did not. The ASA Physical Status Classification is useful but suffers from a lack of scientific precision.

Preventable Anesthesia Mishaps: A Study of Human Factors

Abstract: A modified critical-incident analysis technique was used in a retrospective examination of the characteristics of human error and equipment failure in anesthetic practice. The objective was to uncover patterns of frequently occurring incidents that are in need of careful prospective investigation. Forty-seven interviews were conducted with staff and resident anesthesiologists at one urban teaching institution, and descriptions of 359 preventable incidents were obtained. Twenty-three categories of details from these descriptions were subjected to computer-aided analysis for trends and patterns. Most of the preventable incidents involved human error (82 per cent), with breathing-circuit disconnections, inadvertent changes in gas flow, and drug-syringe errors being frequent problems. Overt equipment failures constituted only 14 per cent of the total number of preventable incidents, but equipment design was indictable in many categories of human error, as were inadequate experience and insufficient familiarity with equipment or with the specific surgical procedure. Other factors frequently associated with incidents were inadequate communication among personnel, haste or lack of precaution, and distraction. Results from multi-hospital studies based on the methodology developed could be used for more objective determination of priorities and planning of specific investments for decreasing the risk associated with anesthesia.

Ventilatory responses to hypoxia and hypercapnia during halothane sedation and anesthesia in man.

Abstract: To elucidate the effects of halothane on chemical regulation of ventilation in man, the authors studied the ventilatory responses to isocapnic hypoxia and hyperoxic hypercapnia in 33 human subjects while fully conscious and during sedation or anesthesia with halothane, .1, 1.1, or 2 MAC. In each group, the ventilatory effect of intravenous administration of doxapram, .4 mg/kg, was also measured. Halothane, 1.1 and 2 MAC, totally abolished the hypoxic response and nearly abolished the response to doxapram, while leaving the response to CO2 relatively brisk. Halothane, .1 MAC, decreased the responses to hypoxia and doxapram to less than a third of control, but did not alter the response to C02. It is concluded that halothane selectively impairs two ventilatory responses mediated by peripheral chemoreceptors in man.

Pathophysiology of Intravenous Air Embolism in Dogs

Abstract: Despite increasing awareness of the clinical incidence of venous air embolism, the pathophysiology of the resultant cardiovascular collapse is still obscure. Since venous air emboli frequently result from gradual aspiration of air into a vein opened surgically, slow infusion (0.01 to 2.00 mg/kg/min)

Thiopental amelioration of brain damage after global ischemia in monkeys.

Abstract: The authors studied the effect of thiopental in ameliorating permanent brain damage in monkeys after 16 min of global ischemia of the brain produced by a high-pressure neck tourniquet and systemic arterial hypotension. Intensive care and life support, including monitoring of physiologic variables, w

Hypotensive anesthesia for total hip arthroplasty: a study of blood loss and organ function (brain, heart, liver, and kidney)

Abstract: The authors attempted to determine whether hypotensive anesthesia or the method of inducing hypotension has any effect on postoperative brain, liver, or kidney function and myocardial status following total hip arthroplasty. Thirty patients were anesthestized with halothane-nitrous oxide for total hip arthroplasty and randomly assigned to one of three groups. In two groups mean arterial blood pressure was decreased to 50 torr by high inspired concentrations of halothane (n = 90) or sodium nitroprusside (n = 12). In the third group (n = 9) mean blood pressure was maintained within 20% of control. Intraoperative blood losses decreased from 1,183 +/- 172 ml in the normotensive group to 406 +/- 102 ml and 326 +/- 41 ml in the halothane and nitroprusside hypotensive groups, respectively. Neither method of inducing hypotension nor hypertensive technique affected the results of postoperative tests of cerebral, hepatic, or renal function and myocardial status. These tests were performed before anesthesia and operation and at intervals in the postoperative course. In this small group of patients, deliberate hypotension for total hip arthroplasty added no morbidity and significantly shortened operating time, decreased blood loss, and decreased the number of blood transfusions needed.

Pharmacokinetics of etomidate, a new intravenous anesthetic.

Abstract: Etomidate sulfate, 0.3 mg/kg, was administered intravenously to eight patients and venous blood samples were drawn at intervals for the subsequent 10 hours. Plasma etomidate was determined by mass fragmentography. Plasma concentrations were fitted to a triexponential equation consistent with a three-compartment open pharmacokinetic model. Mean (+/-SD) variables were: initial t1/2, 2.6 +/- 1.3 min; intermediate t1/2, 28.7 +/- 14.0 min; apparent elimination t1/2, 4.6 +/- 2.6 hours; volume of the central compartment, 23.2 +/- 11.41; total apparent volume of distribution, 4.5 +/- 2.21/kg; fraction of drug in the central compartment, 7 per cent; total plasma clearance, 860 +/- 230 ml/min. Total blood clearance was estimated to be 754 ml/min and hepatic clearance, 739 ml/min. The large apparent volume of distribution indicates considerable tissue uptake. The hepatic clearance, being about 50 per cent of hepatic blood flow, indicates that changes in hepatic blood flow or hepatic metabolism will have only moderate effects on etomidate disposition.

Time vs. success rate for epidural blood patch.

Abstract: Headache is a frequent complication of dural puncture, particularly with a large-bore needle.1'2 Epidural blood patching is a well-accepted therapeutic modality for dural puncture headache3; it seemed reasonable that the sooner done, the shorter would be the duration of the headache. We had noticed

Hemodynamics of Increased Intra-abdominal Pressure: Interaction with Hypovolemia and Halothane Anesthesia

Abstract: The hemodynamic interaction of acute hypovolemia and halothane anesthesia in dogs with increased intra-abdominal pressure caused by intraperitoneal instillation of N2, N2O and CO2 was studied. During normovolemia and just basal pentobarbital anesthesia, the response to increase of intra-abdominal pressure to 40 torr consisted of a 35 per cent decrease in cardiac output, which was equal to the decrease in magnitude of inferior vena caval blood flow. During basal pentobarbital anesthesia, the addition of halothane anesthesia (1 MAC) in combination with hypovolemia (15 per cent blood volume loss) depressed the pre-inflation cardiac output more than addition of halothane anesthesia alone or induction of hypovolemia alone. During each of these conditions, superimposition of increased intra-abdominal pressure to 40 torr caused a further 26-43 per cent decrease in cardiac output compared with the pre-inflation value. Therefore, the greatest cardiovascular depression occurred when the animals were both hypovolemic and anesthetized with halothane. There was no difference in the responses to increased intra-abdominal pressure with the different inflating gases at any time. These findings indicate that in the presence of halothane anesthesia or hypovolemia, induction of pneumoperitoneum may cause severe cardiovascular depression.

A Water-soluble Benzodiazepine, RO 21–3981, for Induction of Anesthesia

Abstract: Diazepam, a benzodiazepine, is widely used to produce basal narcosis prior to anesthesia because of its effectiveness and lack of cardiorespiratory side effects. The venous irritation or occasional phlebitis related to its insolubility in water is a distinct drawback.1–3 Dilution of diazepam and pri

Comparative Penetration of Glycopyrrolate and Atropine across the Blood—Brain and Placental Barriers in Anesthetized Dogs

Abstract: The levels of 14C-glycopyrroIate, a quaternary ammonium anticholinergic agent, appearing in cerebrospinal fluid (CSF) and serum (S) following a single intravenous dose of 0.1 mg/kg were determined in mongrel dogs during barbiturate anesthesia and compared with levels reached in dogs treated with sim

Nitroglycerin as a Hypotensive Drug during General Anesthesia

Abstract: Circulatory variables and arterial partial pressure for oxygen (PaO2) were compared in 91 anesthetized patients who received infusions of either nitroglycerin (TNG) or nitroprusside (SNP) to induce hypotension for the purpose of decreasing intraoperative blood loss. At comparable systolic arterial blood pressures, the mean and diastolic arterial blood pressures were significantly higher with TNG. Electrocardiographic changes suggestive of ischemia occurred in 18 patients who received SNP, whereas none were detected in patients given TNG. Both drugs significantly decreased PaO2 and rate-pressure product, an indirect index of myocardial oxygen consumption. No untoward response to TNG occurred. No clinical evidence of myocardial infarction, renal damage, or cerebral vascular complication was encountered in the postoperative period in any patient. Thus, TNG is an effective hypotensive drug that may prove superior to currently available agents.

Fetotoxicity in Rats Following Chronic Exposure to Halothane, Nitrous Oxide, or Methoxyflurane

Abstract: An animal model was used to investigate the comparative fetal toxicities of three inhalational anesthetics. Pregnant Sprague-Dawley rats were exposed for eight hours a day throughout the 21 days of gestation to graded concentrations of halothane (0.16-0.32 per cent), or nitrous oxide (1-50 per cent), or a nitrous oxide (10 per cent) and halothane (0.16 per cent) mixture, or methoxyflurane (0.01-0.08 per cent). High subanesthetic concentrations of all the inhalational anesthetics could cause fetal growth retardation (e.g., 3-21 per cent decreases in normal fetal weights), but this was unaccompanied by significant fetal loss (overall rate: 4.8 +/- 1.2 per cent, mean +/- SE, in anesthetic groups) or any evidence of skeletal or gross abnormalities related to treatment. It is concluded that these rodent studies do not implicate any specific inhalational anesthetic agent in fetal toxicity, and that the effects of additional factors, such as stress, must be considered.

Antibiotic-induced Paralysis of the Mouse Phrenic Nerve–Hemidiaphragm Preparation, and Reversibility by Calcium and by Neostigmine

Abstract: Certain antibiotics can induce neuromuscular paralysis, but the mechanism of this action is largely unknown. The purpose of this study was to compare the neuromuscular blocking potencies and reversibilities of 16 antibiotics in the isolated mouse phrenic nerve-hemidiaphragm preparation. The antibiotics tested were five aminoglycosides (neomycin, gentamicin, streptomycin, dihydrostreptomycin and kanamycin), tetracycline and oxytetracycline, polymyxins B and E, penicillins G and V, cephradine, cephaloridine, crythromycin, lincomycin, and clindamycin. Reversibility of the muscle paralysis by calcium and neostigmine was assessed. All the aminoglycosidcs resembled magnesium in blocking neuromuscular transmission, the neuromuscular blockade being almost completely reversed (to 64–77 per cent of control) by calcium but only poorly reversed by neostigmine (to 20-67 per cent of control). Neuromuscular blockade produced by the tctracyclines was also reversed by calcium (44-104 per cent) but not by neostigmine (0-15 per cent). Neuromuscular blockade produced by the polymyxins or by lincomycin was only partially reversed by calcium (0–34 per cent). Penicillin V, erythromycin, clindamycin, polymyxin B and the tetracyclines could also produce muscle paralysis by decreasing muscle contractility. This effect on contractility was irreversible by pharmacologic means. Penicillin G, cephradine and cephaloridine possessed negligible paralyzing effects on the nerve-muscle preparation. It is concluded that the different groups of antibiotics tested act by different mechanisms and that only the calcium-induced reversal of aminoglycoside block is predictable.

Plasma levels of thiopental necessary for anesthesia.

Abstract: This study determined the plasma levels of thiopental necessary for anesthesia in human patients. In Group I, corneal reflex (CR) and trapezius muscle response (TMR) showed highly significant correlations (P For CR loss, thiopental requirements were 39.4 ± 2.5 μg/ml (mean ± SE) for total plasma thiopental and 5.9 ± 0.4 μg/ml for free plasma thiopental. For TMR loss, thiopental requirements were 42.4 ± 2.8 μg/ml for total plasma thiopental and 6.3 ± 0.6 μg/ml for free plasma thiopental. Nitrous oxide, 67 per cent, decreased these requirements 67–71 per cent. Age, sex, and weight of the patient and serum albumin level had little effect on thiopental requirements. Mean percentage of free thiopental was 14.4 ± 0.3 per cent of total. It is concluded that: 1) losses of corneal reflex, trapezius muscle response, and response to surgical stimulation all define essentially the same depth of thiopental anesthesia; 2) total plasma thiopental levels of 39–42 μg/ml and free plasma thiopental levels of 5.9–6.3 μg/ml produce surgical anesthesia in human subjects.

Tracheal Constriction by Morphine and by Fentanyl in Man

Abstract: The effects of morphine and fentanyl on tracheal smooth muscle tone were studied in 38 patients during induction of anesthesia. Endotracheal tube cuff pressure was used to measure tracheal tone. Anesthesia was maintained with nitrous oxide, 70 per cent in oxygen, and pancuronium and ventilation was controlled with a respirator. Morphine, 0.5 mg/kg, produced a biphasic response, initially causing tracheal dilatation and then tracheal constriction. Ten minutes after morphine injection, cuff pressure increased to significantly (21 +/- 8 per cent) above control. Morphine-induced tracheal constriction could be completely blocked by the prior administration of atropine, 0.5 mg. Fentanyl, 0.006 mg/kg, also produced significant tracheal constriction, cuff pressures increasing to 44 +/- 11 per cent above control at 10 min. Fentanyl-induced tracheal constriction could be blocked by pretreatment with droperidol, 0.25 mg/kg. At equianalgesic doses, morphine and fentanyl produced similar tracheal constriction.

Ventricular function in children during halothane anesthesia: an echocardiographic evaluation

Abstract: The effect of halothane on ventricular function in normal children was studied with the aid of echocardiography, which offers a noninvasive method to obtain these measurements safely. Thirteen healthy children ranging in age from 19 months to 12 years (mean=6 years), undergoing elective non-cardiac surgical procedures, were studied. Secobarbital, 4 mg/kg, and morphine, 0.1 mg/ kg, were administered intramuscularly an hour prior to induction of general anesthesia. Echocardiographic measurements were obtained while the patients breathed room air (control) and following nitrous oxide, 60 per cent, and concentrations of halothane ranging from 0.5 to 2 per cent. Increasing inspired concentrations of halothane significantly altered ventricular function in a dosedependent fashion. At halothane, 2 per cent, systolic blood pressure, pulse rate, and cardiac output decreased to 82, 94, and 72 per cent of control values, respectively. Measurements of ventricular performance, ejection fraction (EF), left ventricular enddiaslolic volume (LVEDV), and mean normalized rate of circumferential fiber shortening (Vuf) showed parallel decreases. Following atropine, 0.02 mg/kg, intravenously, improvement in cardiac output and all rate-dependent variables was observed. Although V,.r improved by 18 per cent, other indices of myocardial performance (EF, LVEDV, PEP/LVET) still showed depression. It is concluded that halothane can significantly decrease ventricular function in children undergoing surgical procedures. The accompanying decrease in cardiac output was completely offset by the administration of atropine.

Plasma antidiuretic hormone levels in cardiac surgical patients during morphine and halothane anesthesia.

Abstract: The effects of halothane and morphine anesthesia on plasma antidiuretic hormone (ADH) levels and urinary flow were determined in 18 patients undergoing elective open-heart operations. Patients were divided into three groups of six each: Group I, halothane, 0.5 per cent; Group II, morphine, 1 mg/ kg;

Placental transfer of lidocaine: effects of fetal acidosis.

Abstract: To investigate whether fetal acidosis increases the placental transfer of lidocaine, resulting in higher fetal blood levels of the drug, lidocaine was infused intravenously into ten pregnant ewes to maintain plasma levels of 2-4 microgram/ml. After maternal-fetal equilibrium was reached, the fetus was made acidotic by infusing lactic acid intravenously. Fetal blood pH decreased from 7.35 to 7.10. With fetal acidemia, fetal blood lidocaine levels increased significantly from 1.60 +/- 0.11 microgram/ml to 2.72 +/- 0.26 microgram/ml. The fetal-maternal lidocaine ratio increased from 0.76 to 1.21. Correction of the acidosis by bicarbonate infusion returned the fetal-maternal ratios to control values. It is concluded that acidosis in the fetus may result in trapping of ionized lidocaine in the fetal circulation and increase the transfer of lidocaine across the placenta.

Behavioral Effects of Trace and Subanesthetic Halothane and Nitrous Oxide in Man

Abstract: Using tests of complex reaction time and of immediate recall (digit span), the authors could not demonstrate that trace concentrations of halothane (to 0.02 per cent, or 200 parts per million) or halothane plus nitrous oxide (0.002 per cent plus 0.05 per cent, respectively) or nitrous oxide alone (0.4 per cent) affected mental function of male volunteers. However, subanesthetic concentrations of both nitrous oxide (20 to 30 per cent) and halothane (0.2 per cent) did impair mental function.

Naloxone does not antagonize general anesthesia in the rat.

Abstract: The administration of naloxone 2, 10, 50, or 250 mg/kg intravenously did not alter halothane requirement (MAC) in Sprague-Dawley rats (12 rats per group). Two rats convulsed when given 50 mg/kg while anesthetized with halothane. In a separate group of awake rats, seven of nine animals convulsed when

Neurologic activity of infants following anesthesia for cesarean section.

Abstract: Elective cesarean section was performed in a consecutive series of 30 patients with full-term pregnancies who were not in labor. Epidural (lidocaine, 1.5 per cent, with epinephrine, 1:200,000) and general anesthesia (thiopental, nitrous oxide-oxygen, succinylcholine infusion) was used alternately. Neonatal acid-base values and Apgar scores showed no significant difference between the two anesthetic groups, and most infants were vigorous at birth. The neurologic recoveries of the infants showed no significant difference between the two groups. In the group receiving epidural anesthesia, there was a significant correlation between maternal hypotension and weak rooting and sucking reflexes of the infants during the first two days. All infants of high-risk obstetric patients in the series, independent of anesthetic technique used, had abnormal neurologic activity, as evidenced by either depression of muscle tone and the reflexes or all the tested variables. Neurologic assessment as followed in this series is a sensitive indicator of the effects of fetal stress factors acting during cesarean section.

Physical Characteristics of and Rates of Nitrous Oxide Diffusion into Tracheal Tube Cuffs

Abstract: Physical characteristics and time-related volume changes in air-inflated tracheal tube cuffs exposed to nitrous oxide were measured in an environmental chamber. Cuff wall diameter, thickness, residual volume, and length were also measured. Gas volumes in most air-inflated tracheal tube cuffs increased 1.7 to 7 ml within 30 min of exposure to pure nitrous oxide. Diffusion rates into most cuffs varied inversely with cuff thickness and directly with the partial pressure of nitrous oxide. There were significant differences in diffusion rates among cuffs of the same composition with different densities or porosities as well as among cuffs of different compositions. Cuff diameters ranged from 13.8 to 32 mm; thicknesses from .033 to .55 mm; residual volumes from .22 to 19.4 ml; lengths from 23.1 to 49.1 mm. Intracuff volume and pressure increase related to gas diffusion into air-inflated cuffs should be periodically adjusted or pressure automatically controlled during nitrous oxide anesthesia. Large-diameter, thin-walled cuffs are recommended.

Platelet aggregation following heparin and protamine administration.

Abstract: The effects of heparin, protamine, and the heparin-protamine complex on the abilities of platelets to aggregate in vitro in response to adenosine diphosphate (ADP) and epinephrine were determined. Citrated blood was obtained from normal volunteers and portions were treated with heparin, protamine, and three different ratios of heparin and protamine. The threshold concentrations of ADP and epinephrine required to produce complete platelet aggregation were then determined. Compared with control citrated plasma, the geometric mean of the threshold concentration for ADP in the heparinized sample was decreased twofold, from 1.88 to 0.94 micrometer; and that for epinephrine more than threefold, from 0.5 to 0.14 micrometer. In contrast, the threshold concentration for ADP was increased to 3.68 micrometer in the neutralized and to 2.78 micrometer in the overneutralized samples and that for epinephrine to 1.62 micrometer in the neutralized and 1.82 micrometer in the overneutralized samples. These data indicate that heparin increases the sensitivity of platelets to ADP and epinephrine as determined by platelet aggregation, and protamine added to heparinized blood not only reverses this effect, but decreases platelet sensitivity when it is added in concentration that neutralize heparin. Additional protamine has no further effect, and protamine alone has no effect on platelet aggregation.

Cerebral Hypometabolism Obtained with Deep Pentobarbital Anesthesia and Hypothermia (30 C)

Abstract: Cerebral metabolic and vascular effects of hypothermia (30 C) and deep pentobarbital anesthesia, separately and combined, were evaluated in 15 mongrel dogs. External cardiovascular support was not used, and mean arterial blood pressures remained greater than 60 torr. Normothermic deep pentobarbital anesthesia, characterized by an electroencephalographic (EEG) frequency of less than 1 Hz, was associated with 30% decreases in cerebral metabolic rates for oxygen (CMRO2) and glucose (CMRG) from lightly anesthetized control values. Hypothermia (30 C) alone caused similar decreases in CMRO2 and CMRG in the presence of an active EEG. The use of pentobarbital anesthesia and hypothermia combined achieved significantly greater (P less than 0.05) decreases in CMRO2 (70%) and CMRG (72%) from the control state. Cerebral vascular resistance (CVR) increased by 70% (P less than 0.05) during hypothermia and about 20% when pentobarbital was administered to normothermic dogs. In hypothermic animals the addition of pentobarbital had a minimal effect on CVR. No alteration in the oxygen-glucose or lactate-glucose index indicative of cerebral hypoxia occurred in any experimental group. This study indicates that barbiturates combined with hypothermia decrease cerebral metabolism to a greater extent than hypothermia or barbiturate alone. When cerebral hypometabolism is therapeutically necessary, barbiturates may be indicated as an adjunct to moderate hypothermia.