Anti-factor Xa monitoring of anticoagulation during cardiopulmonary bypass in a patient with antiphospholipid syndrome.

The activated clotting time (ACT) may be an unreliable monitor of coagulation for patients with the antiphospholipid syndrome. We describe a patient with antiphospholipid syndrome in whom adequate anticoagulation during cardiopulmonary bypass was confirmed by monitoring both the ACT and anti-factor Xa levels. The cardiopulmonary bypass was uneventful, and there were no thrombotic or bleeding complications. The use of anti-factor Xa levels provided confirmation of adequate anticoagulation (and reversal of anticoagulation) that was not possible using the ACT alone.

The effects of recent aspirin ingestion on platelet function in cardiac surgical patients.

OBJECTIVE: To examine the effects of the preoperative aspirin-free interval on platelet function in cardiac surgical patients. DESIGN: Prospective clinical investigation. SETTING: University-affiliated teaching hospital. PARTICIPANTS: Patients undergoing elective coronary artery bypass graft surgery (n = 100). INTERVENTIONS: The patients were divided into 3 groups based on the number of days since they last ingested aspirin: < or =2 days, 3 to 7 days, and >7 days. Preoperative platelet function was assessed in all patients using platelet aggregation responses to arachidonic acid, 5 microg/mL, and Platelet Function Analyser (PFA100) collagen/epinephrine closure times. MEASUREMENTS AND MAIN RESULTS: Patients who ceased aspirin < or =2 days preoperatively had weaker platelet aggregation responses (18.5% +/- 7% maximum aggregation, mean +/- SD, n = 36) than patients who ceased aspirin 3 to 7 days preoperatively (68.8% +/- 29%, n = 48, p < 0.001) or >7 days preoperatively (68.3% +/- 28%, n = 16, p < 0.001). Similarly, patients who ceased aspirin < or =2 days preoperatively had longer PFA100 closure times (168 +/- 52 sec) than patients who ceased aspirin 3 to 7 days preoperatively (122 +/- 43 sec, p < 0.001) or >7 days preoperatively (128 +/- 42 sec, p < 0.01). The percentage of abnormal responses was also greatest in the aspirin < or =2 days group. CONCLUSION: Cardiac surgical patients who ingest aspirin < or =2 days preoperatively have greater impairment of platelet function than patients who have a longer preoperative aspirin-free interval.

Reduction of preoperative investigations with the introduction of an anaesthetist-led preoperative assessment clinic.

Preoperative investigations, when used to screen for disease not clinically evident, have been shown to be unnecessary. The aim of this study was to rationalize the ordering of preoperative investigations by introducing guidelines and screening all investigations ordered at a new Day of Surgery Admissions clinic. Two hundred and one elective general and ear, nose and throat (ENT) patients attending this clinic at Sir Charles Gairdner Hospital from July to September 1997 were induced in a prospective study group. These were compared to a retrospective control group of 168 elective general and ENT surgical patients who had been admitted for surgery during May to July 1996. Patient demographics were similar for both groups. There were also similar proportions of each surgical subtype and degrees of surgical complexity in each group. There were significant reductions in most types of investigations (electrocardiogram, chest X-ray, liver function tests, urea and electrolytes, full blood examination, coagulation profile) ordered with the Day of Surgery Admissions clinic intervention. This resulted in an estimated reduction of preoperative investigation costs by 38%. It was concluded that the clinic intervention was associated with a reduction in indiscriminate preoperative investigation ordering patterns.

Evaluation of the TAS coagulation analyzer for monitoring heparin effect in cardiac surgical patients.

OBJECTIVE: To assess the relationship between the Thrombolytic Assessment System (TAS); (Cardiovascular Diagnostics, Inc, Raleigh, NC) measurements and heparin levels in cardiac surgical patients. DESIGN: Equipment evaluation in vitro and in vivo. SETTING: A university teaching hospital. PARTICIPANTS: Sixty adult patients undergoing elective cardiac surgery requiring cardiopulmonary bypass (CPB). INTERVENTIONS: Part 1: Simultaneous heparin management tests (HMTs) and activated coagulation times (ACTs) were measured in 20 patients pre-CPB, during CPB, and post-CPB. In the same patients, the effect of heparin, 1 to 5 IU/mL, on the HMT was assessed in vitro. The effect of aprotinin, 50 to 200 KIU/mL, on the HMT, was assessed in vitro in a further 10 patients. Part II: Simultaneous TAS and laboratory (LAB) activated partial thromboplastin times (APTTs) were measured pre-CPB and post-CPB in 20 patients. In the same patients, the effect of heparin, 0.1 to 0.5 IU/mL, on the TAS APTT was assessed in vitro. The effect of aprotinin on the TAS APTT was assessed in vitro in a further 10 patients. MAIN RESULTS: Part I: Heparin, 0, 1, 2, and 5 IU/mL in vitro resulted in HMTs of 164 +/- 12, 281 +/- 19, 338 +/- 16, and 436 +/- 33 seconds (mean +/- standard deviation [SD]), respectively. The HMT had less variability than the ACT in vivo. Part II: Heparin, 0, 0.1, 0.2, and 0.5 IU/mL in vitro, resulted in TAS APTTs of 34.9 +/- 4.7, 61.2 +/- 2.5, 97.4 +/- 34.7, and 197.1 +/- 64.3 seconds, respectively. The correlation (r) between the TAS and LAB APTT was 0.726 pre-CPB and 0.794 post-CPB. Aprotinin increased both the HMT and TAS APTT in a dose-related manner. CONCLUSION: The TAS may be a useful monitor of heparin effect in cardiac surgical patients.

Risk prediction in coronary artery surgery: a comparison of four risk scores.

OBJECTIVE: To determine which of four proposed risk scores best predicts immediate outcome of cardiac surgery. DESIGN: Observational cohort study. SETTING: Sir Charles Gairdner Hospital (a university teaching hospital), Perth, Western Australia, 18 March 1993 to 5 March 1996. SUBJECTS: 927 consecutive patients undergoing surgery for coronary artery disease. OUTCOME MEASURES: Patient risk scores (by methods of Parsonnet et al., Higgins et al., Tremblay et al. and Tu et al.); in-hospital mortality; postoperative hospital stay > 14 days; receiver operating characteristic (ROC) curves comparing sensitivity and specificity in predicting adverse outcomes for each risk score. RESULTS: In-hospital mortality rate was 3.5% and mean postoperative hospital stay was 10.7 days. The four scores had similar predictive abilities, with mean areas under the ROC curves (95% confidence intervals) for mortality and postoperative stay > 14 days, respectively: 0.70 (0.62-0.78) and 0.70 (0.65-0.75) for the Parsonnet score; 0.68 (0.59-0.77) and 0.70 (0.64-0.75) for the Higgins score; 0.68 (0.59-0.77) and 0.67 (0.62-0.73) for the Tremblay score; and 0.68 (0.60-0.76) and 0.69 (0.64-0.75) for the Tu score. CONCLUSION: Any of the scores may be used to estimate perioperative risk and to compare outcome between coronary surgery units, but none has sufficient specificity and sensitivity to identify specific individuals who will experience an adverse outcome. Further development of risk assessment is needed before adverse outcome can be accurately predicted in cardiac surgical patients.

Phenytoin-induced resistance to vecuronium.

Chronic phenytoin therapy causes resistance to some nondepolarising muscle relaxants. We have confirmed that this resistance is seen with vecuronium and suggest that at least a week of phenytoin therapy is required for a significant effect to develop. The mechanism of this resistance is not known. We have shown that an exaggerated rise in serum potassium after succinylcholine does not occur in patients with demonstrated resistance to vecuronium from chronic phenytoin therapy. This would suggest that significant extrajunctional acetylcholine receptor proliferation is an unlikely mechanism.