Glenn P. Gravlee

Response of cerebral blood flow to changes in carbon dioxide tension during hypothermic cardiopulmonary bypass

Changes in cerebral blood flow (CBF) in response to changes in Pa were measured by intraaortic injection of133Xe in 12 patients during hypothermic (23–30°C) cardiopulmonary bypass. In each patient, CBF was determined at two randomly ordered levels of Paco2 obtained by varying the rate of gas inflow into the pump oxygenator (Group I, n = 6) or by varying the percentage of CO2 added to the gas inflow (Group II, n = 6). Nasopharyngeal temperature, mean arterial pressure, pump-oxygenator flow, and hematocrit were maintained within a narrow range. In group I, a Paco2 (uncorrected for body temperature) of 36± 4 mmHg (mean ± SD) was associated with a CBF of 13 ± 5 ml.100 g−1·min−1, while a Paco2 of 42 ± 4 mmHg was associated with a CBF of 19± 10 ml · 100 g−1·min−1. In group II, a Paco2 of 47 ± 3 mmHg was associated with a CBF of 20± 8 ml. 100 g−1·min−1, and a Paco2 of 53± 3 mmHg was associated with a CBF of 26 ± 9 ml. 100 g−1·min−1. Within group I, the difference in CBF was significant (p < 0.05); within group II, the difference in CBF was significant at the P < 0.002 level. All CBF measurements were lower than those reported for normothermic, unanesthetized subjects of similar age. The response of the cerebral circulation to changes in CO2 tension was well-maintained during hypothermic cardiopulmonary bypass. CBF increased by an average of 1.07 ± 1.19 (SD) ml. 100 g−1·min−1·mmHg−1increase in temperature-uncorrected Paco2 in Group I, and by 1.05 ± 0.54 ml · 100 g−1·min−1· mmHg−1increase in group II.

Predictive Value of Blood Clotting Tests in Cardiac Surgical Patients

Abstract This study ptospectively evaluated numerous tests of clolting function in 897 consecutive adult cardiac surgical patients over 18 months. This included coronary operation, valve replacement, and reoperative patients. The tests included activated clotting time, activated partial thromboplastin time, prothrombin time, thiombin time, fibrinogen, fibrin/fibrinogen degradation products, platelet count, and Dukes earlobe bleeding time. Other variables such as age, sex, and cardiopulmonary bypass duration were included in the multivariate analysis. Statistically significant correlations were found between 16-hour mediastinal drainage and activated partial thromboplastin time, fibrinogen, activated clotting time, fibrin/fibrinogen degradation products, platelet count, and prothrombin time. Scatter plots indicate that these relationships, although statistically significant, had little predictive value and were largely significant is a result of the large number of patients in each group, which permitted weak correlations to reach statistical significance. The best multivariate model constructed could explain only 12% of the observed variation in postoperative blood loss. Because the predictive values of the tests are so low, it does not appear sensible to screen patients routinely using these clotting tests shortly after cardiopulmonary bypass.

Rapid administration of a narcotic and neuromuscular blocker: a hemodynamic comparison of fentanyl, sufentanil, pancuronium, and vecuronium

High-dose narcotic anesthetic inductions usually avoid circulatory depression bettrthan do other techniques; however, the selection of a narcotic and neuromuscular blocker influences subsequent hemodynamic responses. One hundred-one patients having aortocoronary bypass graft (CABG) surgery were investigated using four combinations of a narcotic and neuromuscular blocker: group FP (fentanyl 50 μg/kg, pancuronium 100 μg/kg); group FV (fentanyl 50 μg/kg, vecuronium 80 μg/kg); group SP (sufentanil 10 μg/kg, pancuronium 100 μg/kg); and group SV (sufentanil 10 μg/kg, vecuronium 80 μg/kg), each combination being administered over 2 minutes. Hemodynamic functions were then monitored for 10 minutes before tracheal intubation. Significant changes included increases in heart rate in the groups receiving pancuronium and decreases in those receiving vecuronium. In all groups mean arterial pressure initially decreased; systemic vascular resistance index decreased significantly in all groups except SV. Cardiac index decreased significantly only in group SV. Circulatory depression requiring treatment with vasopressor or anticholinergic drugs was more common in patients given vecuronium. Cardiac arrhythmia occurred most often in group SP; only in group FP were there no arrhythmias, ischemic changes, or hemodynamic disturbances requiring intervention. Time to onset of neuromuscular blockade did not differ among the four groups, but transient chest wall rigidity occurred significantly more often with sufentanil than with fentanyl. Overall, the fentanyl/pancuronium combination afforded the greatest hemodynamic stability, whereas the sufentanil/vecuronium combination proved least satisfactory because of bradycardia and hypotension, requiring treatment in 35% of group SV patients. Differences in anesthetic premedication, social habits, preoperative medications, narcotic and muscle relaxant doses, and speed of anesthetic drug administration may also influence hemodynamicresponses and may explain differing results reported by others using the same drug combinations.

Predicting Success on the Certification Examinations of the American Board of Anesthesiology

Background:Currently, residency programs lack objective predictors for passing the sequenced American Board of Anesthesiology (ABA) certification examinations on the first attempt. Our hypothesis was that performance on the ABA/American Society of Anesthesiologists In-Training Examination (ITE) and other variables can predict combined success on the ABA Part 1 and Part 2 examinations. Method:The authors studied 2,458 subjects who took the ITE immediately after completing the first year of clinical anesthesia training and took the ABA Part 1 examination for primary certification immediately after completing residency training 2 yr later. ITE scores and other variables were used to predict which residents would complete the certification process (passing the ABA Part 1 and Part 2 exam- inations) in the shortest possible time after graduation. Results:ITE scores alone accounted for most of the explained variation in the desired outcome of certification in the shortest possible time. In addition, almost half of the observed variation and most of the explained variance in ABA Part 1 scores was accounted for by ITE scores. A combined model using ITE scores, residency program accreditation cycle length, country of medical school, and gender best predicted which residents would complete the certification examinations in the shortest possible time. Conclusions:The principal implication of this study is that higher ABA/ American Society of Anesthesiologists ITE scores taken at the end of the first clinical anesthesia year serve as a significant and moderately strong predictor of high performance on the ABA Part 1 (written) examination, and a significant predictor of success in completing both the Part 1 and Part 2 examinations within the calendar year after the year of graduation from residency. Future studies may identify other predictors, and it would be helpful to identify factors that predict clinical performance as well.

Hemodynamic and pharmacodynamic comparison of doxacurium and pipecuronium with pancuronium during induction of cardiac anesthesia: does the benefit justify the cost?

We compared the pharmacodynamic effects and hospital costs of three long-acting neuromuscular blocking drugs in a prospective, randomized, double-blind manner. Each neuromuscular blocking drug was administered with fentanyl (50 micrograms/kg) for intravenous induction of anesthesia for coronary artery bypass surgery. Each patient received twice the 95% effective dose (ED95) of either pancuronium (0.14 mg/kg, n = 10), pipecuronium (0.10 mg/kg, n = 10), or doxacurium (0.05 mg/kg, n = 10). Hemodynamic measurements were recorded at baseline, 5 min after completion of anesthetic induction, immediately after endotracheal intubation, and 5 min after intubation. Only small hemodynamic differences between neuromuscular blocking drugs were observed. Doxacurium (but not pancuronium or pipecuronium) significantly decreased mean arterial blood pressure (from 94 +/- 4 mm Hg before induction to 83 +/- 3 mm Hg 5 min after intubation); nevertheless, there were no significant between-group differences at any time. Pancuronium increased heart rate (from 68 +/- 4 beats/min before induction to 76 +/- 5 beats/min 5 min after intubation); however, pancuronium differed significantly from doxacurium and pipecuronium only 5 min after induction and 5 min after intubation. Central venous pressure, pulmonary artery occlusion pressure, cardiac index, and systemic and pulmonary vascular resistance indices did not change. Electrocardiographic abnormalities were observed in two pipecuronium patients: ST segment depression in one and premature ventricular contractions in another. No other electrocardiographic changes were observed. There were no significant between-group differences in the need for hemodynamic interventions.(ABSTRACT TRUNCATED AT 250 WORDS)

A dose-determining trial of heparinase-I (Neutralase) for heparin neutralization in coronary artery surgery

Heparinase-I, a specific heparin-degrading enzyme, may represent an alternative to protamine. We explored the dose of heparinase-I for efficacy and safety in patients undergoing coronary artery surgery. At the conclusion of cardiopulmonary bypass, subjects received 5, 7, or 10 &mgr;g/kg of open-label heparinase-I instead of protamine. Activated clotting time (ACT) and its difference from a contemporaneous heparin-free sample (&Dgr;ACT) at 3 min before and 3, 6, and 9 min after heparinase-I determined reversal efficacy. After surgery, we recorded hourly chest tube drainage. Systemic and pulmonary arterial blood pressure and cardiac output measurements before and immediately after heparinase-I were used to evaluate hemodynamic safety. Coagulation measurements included anti-factor Xa and anti-factor IIa activities. Forty-nine patients from seven institutions participated: 12 received 5 &mgr;g/kg, 21 received 7 &mgr;g/kg, 4 received two doses of 7 &mgr;g/kg, 8 received 10 &mgr;g/kg, and 4 received two doses of 10 &mgr;g/kg. Treatment groups did not differ demographically. Median &Dgr;ACT 9 min later was 11, 7, and 4 s for the 5, 7, and 10 &mgr;g/kg groups, respectively. No adverse hemodynamic changes occurred with heparinase-I administration. The authors conclude that heparinase-I effectively restored the ACT after cardiopulmonary bypass. This effect appeared to be dose dependent.

Succinylcholine-induced hyperkalemia in a patient with Parkinson's disease.

A critically ill 64-year-old 72 kg white man was transferred from an outlying hospital for further evaluation and consideration for coronary artery bypass surgery. He had been reasonably well until 6 days previously when he suffered an extensive anterior myocardial infarction complicated by persistent chest pain and pulmonary edema responding poorly to aggressive therapy with digoxin, furosemide, and nitrates. Past history included Parkinson’s disease diagnosed in 1973 and well controlled with carbidopa/levodopa (Sinemet), 25/250 mg orally twice a day. Lumbar laminectomies had been performed in 1967 and 1972 under general anesthesia without known untoward incident. No residual neurologic deficit was reported after either operation. Shortly after arrival at this institution an intra-aortic balloon pump was inserted for counterpulsation because of continued episodic chest pain, increasing ST segment elevation in the anterior leads, and rising pulmonary capillary wedge (PCW) pressures responding only to high-dose intravenous nitroglycerin. These changes were attenuated or eliminated by counterpulsation so that the nitroglycerin infusion could be discontinued. Medications then included digoxin, quinidine gluconate, isosorbide dinitrate, furosemide, diazepam, carbidopa/levodopa, trihexyphenidyl, morphine sulfate, and acetaminophen. A neurologic consultant’s evaluation on the day of transfer revealed no sensory or motor deficit and mild signs of Parkinson’s disease consisting of masking and a decreased blink rate. The carbidopa/Ievodopa and the trihexypheni-

Arrhythmias during Venous Cannulation prior to Pulmonary Artery Catheter Insertino

Previous reports of arrhythmias during pulmonary artery (PA) catheter insertion have not directly assessed the incidence of arrhythmias occurring during the cannulation of the venous system using a flexible guidewire, vessel dilator, and catheter sheath introducer system (1,2). We report a case of a life-threatening ventricular arrhythmia occurring during insertion of a guidewire through the right inteRNal jugular vein, and a prospective clinical study prompted by that case to determine the incidence of arrhythmias during right inteRNal jugular vein cannulation prior to pulmonary artery catheterization.

The clinical onset of heparin is rapid.

This study used the activated clotting time (ACT) to determine the clinical onset of four different doses of heparin after bolus injection into the central circulation. Ten consenting adults (Group A) undergoing coronary artery bypass grafting were given 350 U/kg of bovine lung heparin and had simultaneous duplicate arterial and venous ACT determinations at baseline and at 30, 60, 90, 120, 180, and 600 s after heparin injection. Twenty additional coronary artery bypass grafting patients were alternately assigned to one of two 10-patient groups (B and C), which were given 200 and 300 U/kg of bovine lung heparin, respectively. Group D consisted of 10 abdominal aortic aneurysmectomy patients who received 70 U/kg of bovine lung heparin. In Groups B, C, and D, duplicate ACT measurements were taken from an indwelling arterial catheter at baseline and at 30, 60, 90, 120, 180, and 300 s after completion of a bolus injection of heparin into the central circulation. After a 70 U/kg heparin dose, all patients had significant ACT prolongation within 30 s, and 8 of 10 had effectively achieved their peak anticoagulation response by that time. In all patients receiving 200, 300, and 350 U/kg of heparin, arterial anticoagulation (ACT > 300 s) occurred and in most patients peaked within 30 s after heparin administration (P < 0.05). Arterial and venous ACTs did not differ significantly from each other at any measurement period, but venous ACTs peaked slightly later than arterial ACTs (within 60 s in 9 of 10 patients). When 200 U/kg or more of heparin is administered into the central venous circulation in hemodynamically stable anesthetized patients, peak arterial ACT prolongation occurs within 30 s and peak venous ACT prolongation within 60 s.

The Relationship Between the American Board of Anesthesiology Part 1 Certification Examination and the United States Medical Licensing Examination

BACKGROUNDnThe graduate medical education community uses results from the United States Medical Licensing Examination (USMLE) to inform decisions about individuals readiness for postgraduate training.nnnOBJECTIVEnWe sought to determine the relationship between performance on the USMLE and the American Board of Anesthesiology (ABA) Part 1 Certification Examination using a national sample of examinees, and we considered the relationship in the context of undergraduate medical education location and examination content.nnnMETHODSnApproximately 7800 individuals met inclusion criteria. The relationships between USMLE scores and ABA Part 1 pass rates were examined, and predictions for the strength of the relationship between USMLE content areas and ABA performance were compared with observed relationships.nnnRESULTSnPearson correlations between ABA Part 1 scores and USMLE Steps 1, 2 (clinical knowledge), and 3 scores for first-taker US/Canadian graduates were .59, .56, and .53, respectively. A clear relationship was demonstrated between USMLE scores and pass rates on ABA Part 1, and content experts were able to successfully predict the USMLE content categories that would least or most likely relate to ABA Part 1 scores.nnnCONCLUSIONSnThe analysis provided evidence on a national scale that results from the USMLE and the ABA Part 1 were correlated and that success on the latter examination was associated with level of USMLE performance. Both testing programs have been successful in conceptualizing many of the knowledge areas of interest and in developing test content to reflect those areas.