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Biomedical subjects

C A Shanks

Publications and source records attributed to C A Shanks.

At least 55 records · Page 3Linked to original sources
PubMed1985

The pharmacokinetics of d-tubocurarine with surgery involving salvaged autologous blood.

The disposition of d-tubocurarine (dTc) was assessed when a bolus and infusion dosage regimen was used to obtain relaxation during major orthopedic surgery on the spine. Renal clearance of dTc was 0.63 +/- 0.23 ml X min-1 X kg-1 and was correlated with creatinine clearance. Total plasma clearance of 1.21 +/- 0.40 ml X min X -1 X kg-1 was lower than that found in many previous studies, and the predetermined continuous dTc infusion produced an apparent plateau in plasma concentrations of 1.8 +/- 0.3 micrograms X ml-1. Despite the operative blood loss, these concentrations were greater than anticipated and were associated with a more intense neuromuscular blockade than the infusion was designed to produce. Autologous blood transfusion was used to reduce the reliance on homologous donor blood, and the erythrocytes from the 2.2 +/- 1.2 1 of blood loss during the procedure were reinfused after intraoperative salvage, washing, and centrifugation. With 80 +/- 23 mg dTc administered, 1.4 +/- 0.8% was recovered from the fluid discarded after centrifugation. These results indicate that even massive intraoperative blood loss will not entail a significant reduction in the amount of dTc present in the body.

Adult↗
PubMed1985

Changes of body temperature and heat in cardiac surgical patients.

Changes in body temperature were assessed in ten adult patients undergoing surgery involving cardiopulmonary bypass (CPB) and induced hypothermia. Intraoperatively, in comparable time intervals before CPB and after rewarming, the patients lost body heat. Between the time of induction of anaesthesia and CPB, the temperature of blood in the pulmonary artery fell 1.46 (SD 0.28 degrees C); between CPB and the end of surgery the fall was 1.55 (SD 0.86 degrees C). The extent of spontaneous hypothermia did not correlate with the amount of subcutaneous fat. Hypothermia was induced to obtain a stable deep body temperature of 27.2 (SD 1.3) degrees C, when mean skin temperature averaged 2 degrees C higher. The CPB machine returned approximately 2000 kJ of heat in the rewarming period, to produce pulmonary artery and mean skin temperatures of 37.1 (SD 0.7) degrees C and 31.4 (SD 2.1) degrees C respectively. Intraoperative deep body temperatures demonstrated the expected exponential relationship with metabolic rate. Postoperatively, increase in metabolic rate was associated with rising deep body and skin temperatures. Low resistance to the flow of heat toward the skin surface was demonstrated by low postoperative values for thermal insulation, which may indicate good peripheral perfusion seen during continuing vasodilator therapy.

Body Temperature↗
PubMed1985

Statistical methods in anesthesia articles: an evaluation of two American journals during two six-month periods.

Simple criteria were used to evaluate the statistical analyses in 243 articles from two American anesthesia journals published in the latter six months of 1981 and 1983. Eighty-two percent of the articles reported the use of control measures and 37% reported randomization of treatment, where they were possible. Data were classified as nominal, ordinal, or interval; as independent or related samples; as two-sample or more-than-two-sample cases. The descriptive, inferential, and correlative tests used were evaluated for appropriate application and primary errors were identified. Nine percent of the 722 descriptive statistics had major errors, most of which were a description of ordinal data as though they were interval. The incidence of erroneous applications of 394 inferential statistical tests was 78%. Nearly three-quarters of the 308 primary inferential statistical errors involved either use of a test for independent samples on related data (and vice versa) or multiple applications of an uncorrected test to the same data. Only 4% of the 113 statistics of association were considered erroneous, most because the method was not identified. No differences were detected in the incidence of errors in either experimental design or statistical analysis across time or across the two anesthesia journals. Fifteen percent of the 243 articles in both journals at both times were without major errors in statistical analysis. Recognition of potential sources of error should make it easier for investigators to use experimental designs and statistical analyses appropriate to their needs.

Anesthesia↗
PubMed1984

Pharmacokinetic and pharmacodynamic modelling with pancuronium.

The pharmacokinetics and pharmacodynamics of pancuronium were studied following intravenous infusion in eleven patients undergoing surgical anaesthesia. Measurement of the plasma concentrations (Cp) of the neuromuscular blocking agent ( NMBA ) and the concomitant intensities of paralysis allowed their simultaneous modelling. The pharmacokinetic parameters derived for pancuronium were in the range of previously reported values, except that the mean total systemic plasma clearance (0.79 +/- 0.28 ml X min-1 X kg-1) was reduced and the mean terminal phase half-life (169 min) was longer in these patients. Plasma concentration and % paralysis data were successfully fitted to a previously proposed pharmacodynamic model. This model assumes a separate effect compartment which exchanges drug directly with the central kinetic compartment (integrated effect model). The 'steady-state' Cp necessary to produce 50% paralysis ( ECpss (50] was estimated to be 0.21 +/- 0.08 micrograms X ml-1 (mechanical response) and 0.18 +/- 0.05 micrograms X ml-1 (EMG response). An analysis using the Hill equation of the Cp-response relationship, during and after the constant-rate infusion of pancuronium bromide, resulted in effective plasma concentrations for 50% paralysis ( ECp50 ) of 0.35 +/- 0.06 micrograms X ml-1 and 0.20 +/- 0.09 micrograms X ml-1, respectively, for mechanical twitch response. The corresponding values for EMG response were 0.32 +/- 0.06 micrograms X ml-1 and 0.17 +/- 0.06 micrograms X ml-1. Using this latter approach, the ECp50 estimated during onset of paralysis was significantly higher than that estimated during offset of paralysis (p less than 0.05); no such difference was apparent between this latter parameter and the ECpss (50) of the integrated effect model (p greater than 0.05). No significant differences were observed between any of the pharmacodynamic parameter estimates generated from the data obtained from the two methods of assessment of neuromuscular function (mechanical vs. EMG response) (p greater than 0.05).

Adult↗
PubMed1984

Altered d-tubocurarine disposition during cardiopulmonary bypass surgery.

Kinetics of the neuromuscular blocker d-tubocurarine (dTc) were investigated in 13 adult patients undergoing surgery involving cardiopulmonary bypass (CPB). Approximately 1 hr before CPB surgery, each received dTc as an intravenous bolus of 0.6 mg/kg and a maintenance infusion of 3 micrograms/kg/min. dTc plasma concentration-time data before CPB did not differ from those reported in normal surgical patients. There was an abrupt discontinuity in the plasma concentration-time profile with the onset of CPB, and both total and free plasma concentrations increased 400% during the period of CPB. Although computer simulations suggest that these rises in dTc plasma concentrations can be attributed to contraction in central compartment volume, there also was decreased renal and total plasma clearance of dTc together with a prolonged elimination 1 1/2, which suggests that clearance processes of dTc are also altered as a result of CPB. A 27% rise in dTc free fraction in plasma during CPB could be attributed to hemodilution associated with the CPB procedure itself. Lower doses of dTc will need to be used in patients undergoing surgery that involves CPB unless the concentration-effect relationship for dTc is so altered that higher concentrations are needed to elicit the same response as in normal patients.

Adult↗
PubMed1984

Effects of etomidate on hormonal responses to surgical stress.

The hormonal responses to surgical stress were examined in 10 patients scheduled for elective gynecologic laparotomy. Anesthesia was induced with either thiopental, 4 mg/kg, or etomidate, 0.35 mg/kg, and maintained with nitrous oxide and enflurane. Plasma cortisol, aldosterone, ACTH, and catecholamines were measured during the 24 h after the induction of anesthesia. The catecholamine responses of the patients whose anesthesia was induced with either drug were similar. The plasma ACTH concentrations for the etomidate group were greater than baseline values and the concentrations in the thiopental group (P less than 0.05) in the fourth and fifth hours. In the patients receiving thiopental, both cortisol and aldosterone concentrations were greater than the baseline value (P less than 0.05) in the second to fourth hours after induction. In the etomidate group, the plasma concentrations of cortisol were less than baseline values (P less than 0.05) in the first and second hours after induction of anesthesia and both cortisol and aldosterone were lower than those in the thiopental group (P less than 0.05) in the half to fourth hours after induction. These results confirm an earlier report of the suppression of cortisol after etomidate administration and, because aldosterone also was suppressed, suggests that etomidate exerts its effect by inhibiting early stages of steroidogenesis in the adrenal cortex.

Adrenocorticotropic Hormone↗
PubMed1984

Relationship between past academic performance and results of specialty in-training examinations.

In this study, the authors review the records of 63 graduates of Northwestern University Medical School who were residents in its graduate medical education programs of anesthesia and orthopedic surgery. They examine the relationship among college grades, medical school performance, and the results of assessment by annual, nationwide, medical specialty in-training examinations. For the anesthesia group, the best predictors of in-training examination performance were the Medical College Admission Test (MCAT) Verbal Ability score, the college grade-point average for nonscience subjects, and the MCAT Science, General Information, and Quantitative Ability scores. For the orthopedic group, the best predictors were the MCAT Verbal Ability score, the college grade-point average in nonscience subjects, the MCAT Science score, and the National Board of Medical Examiners Part I and Part II examination scores. The previous academic records for the 63 residents contained little to presage results in the in-training examination. The correlation obtained between nonscience college subjects and the in-training examination results was negative.

Achievement↗
PubMed1984

Neuromuscular recovery after laparoscopy.

Vecuronium bromide, 0.045 mg X kg-1, was compared with pancuronium, 0.07 mg X kg-1, when used to provide muscle relaxation for tracheal intubation and abdominal relaxation for outpatient gynecologic laparoscopy. Both drugs provided adequate intubating conditions within 5 min and satisfactory abdominal relaxation. Because spontaneous recovery from vecuronium was more rapid, either with inhalational or nitrous oxide-narcotic techniques, pharmacological reversal with edrophonium and atropine was either not necessary or more easily accomplished after vecuronium, as shown by the train-of-four. All patients receiving pancuronium required reversal of the blockade, and in a few patients reversal was difficult. Tests of muscle power and coordination performed 30 and 60 min postoperatively showed no difference between the drugs. There were no postoperative complications related to muscle relaxants and all patients met our discharge criteria the day of surgery. Given the conditions observed at the end of the procedure, we would choose vecuronium for muscular relaxation in laparoscopic surgery.

Ambulatory Surgical Procedures↗
PubMed1983

Gallamine disposition in open-heart surgery involving cardiopulmonary bypass.

Kinetics of gallamine, a neuromuscular blocker, were investigated in 22 adult patients undergoing surgery involving cardiopulmonary bypass (CPB). Approximately 60 min before CPB, 11 patients received 480 mg gallamine IV; the other 11 patients received an initial dose of 240 mg IV, followed by another 240 mg through the pump priming fluid at the start of CPB. In 14 of our patients, the time course of gallamine concentrations in the plasma before, during, and after CPB was similar to that in normal surgical patients, indicating little or no effect of cardiac disease or CPB. In the remaining patients, perturbations were not observed before CPB, but with its onset there were varying changes, typically, rises in gallamine concentration ranging from an alteration during the period of CPB only or during the elimination phase, to an alteration at all times after starting CPB. Although the mechanism for this rise in gallamine plasma concentrations during and after CPB is not known, computer simulations suggest that it is due to a contraction in blood volume or decreased tissue perfusion during the period of extracorporeal circulation. Gallamine disposition differed only moderately in our patients from that in control patients. Therefore, from a kinetic viewpoint, provided that renal function is not impaired, gallamine is not contraindicated in CPB surgery.

Adult↗
PubMed1983

Alcuronium kinetics in patients undergoing cardiopulmonary bypass surgery.

1 The disposition of alcuronium was investigated in 10 patients undergoing surgery involving cardiopulmonary bypass (CPB) and compared with results from a group of non-cardiac patients studied previously. 2 After intravenous administration of a combined bolus and infusion dosage regimen, plasma concentrations fell in a bi-exponential fashion to a mean value of 0.55 micrograms/ml immediately before the start of extracorporeal circulation. 3 During CPB an apparent steady-state of alcuronium was reached immediately after commencement of CPB, however plasma concentrations were some 50% higher than those noted prior to commencement of CPB and those predicted using previous pharmacokinetic data from normal surgical patients. 4 Once CPB was completed and the alcuronium infusion terminated, post-infusion alcuronium plasma concentrations again appeared to decline bi-exponentially with time. 5 Of the pharmacokinetic parameters which were calculated model-independently, the apparent volume of distribution (Vss) was unchanged (329 vs 313 ml/kg) and the elimination half-life (t1/2,z) (532 vs 199 min) was prolonged and the plasma clearance (CL) (0.8 vs 1.34 ml min-1kg-1) markedly reduced in these patients compared to non-cardiac surgical patients. 6 As a result of these changes in alcuronium concentration during CPB and the diminished elimination of alcuronium following CPB, a closer monitoring of neuromuscular function may be necessary in cardiac patients undergoing CPB.

Adult↗
PubMed1983

The making of an anesthesiologist: a review of the American scene.

Many anaesthetists practising in Australia and New Zealand realise that differences exist in the training of their counterparts in the United States. This review attempts to highlight the differences observed by two anaesthetists who have been involved in both systems. Aspects of the American Board of Anesthesiology examination are discussed from this viewpoint.

Anesthesiology↗
PubMed1983

Determinants of d-tubocurarine plasma protein binding in health and disease.

d-Tubocurarine protein binding was determined in plasma from normal surgical patients; patients with renal dysfunction; patients with alcoholic cirrhosis; and patients scheduled for coronary artery surgery and was compared with binding determined in solutions of isolated human serum albumin (HSA). The free fraction of d-tubocurarine was independent of plasma drug concentration throughout the range 0.1-3.0 micrograms/ml. The free fraction of d-tubocurarine in renal disease (0.44 +/- 0.05), liver disease (0.53 +/- 0.05), and cardiac disease (0.49 +/- 0.05) was not significantly different from that in normal patients (0.50 +/- 0.04). Furthermore, the free fraction of d-tubocurarine was unrelated to plasma concentrations of total protein, total globulin, albumin, total lipids, or alpha 1-acid glycoprotein in the four patient groups. The free fraction of d-tubocurarine (0.55 +/- 0.02, n = 7) in solutions of HSA (0.58 mM) was similar to that observed in plasma. Albumin, therefore, appears to be the major plasma binding protein for d-tubocurarine.

Adolescent↗
PubMed1982

Dose-response curves for alcuronium and pancuronium alone and in combination.

Simultaneous administration of pancuronium and alcuronium was used in surgical patients during nitrous oxide-narcotic-barbiturate anaesthesia in order to determine the intensity of neuromuscular blockade. When compared with the results obtained when each of the drugs was given alone, the effect was not greater than the additive. The mean effective dose of pancuronium to produce 95% paralysis was 76 micrograms per kg for the mechanical twitch response and 70 micrograms per kg for the electrical response. The respective mean doses of alcuronium producing that degree of paralysis were 285 and 244 micrograms per kg. Usually the curve derived for the mechanical twitch response was to the right of, and roughly parallel to, that for the electrical response.

Adult↗