Heparin dosing and monitoring for cardiopulmonary bypass. A comparison of techniques with measurement of subclinical plasma coagulation.

Subclinical plasma coagulation during cardiopulmonary bypass has been associated with marked platelet and clotting factor consumption in monkeys. To better define subclinical coagulation in man, we measured plasma fibrinopeptide A concentrations before, during, and after cardiopulmonary bypass. Patients were assigned to one of three groups of heparin management: group 1 (n = 10)--initial heparin dose 300 IU/kg, with supplemental heparin if the activated coagulation time fell below 400 seconds; group 2 (n = 6)--initial heparin dose 250 IU/kg, with supplemental heparin if activated coagulation time was less than 400 seconds; and group 3 (n = 5)--initial heparin dose 350 to 400 IU/kg, with supplemental heparin if whole blood heparin concentration was less than or equal to 4.1 IU/ml. Activated coagulation time and heparin concentration were measured every 30 minutes during cardiopulmonary bypass, and fibrinopeptide A was measured at hypothermia, normothermia, and whenever activated coagulation time was less than 400 seconds. Quantitative and qualitative blood clotting competence was assessed after cardiopulmonary bypass, including mediastinal drainage for the first 24 hours. Fibrinopeptide A values were markedly elevated during cardiopulmonary bypass but were well below the levels present before and after cardiopulmonary bypass. Fibrinopeptide A correlated inversely with heparin concentration during cardiopulmonary bypass (r = -0.46, p = 0.03), but higher fibrinopeptide A levels during cardiopulmonary bypass did not correlate with post-cardiopulmonary bypass coagulopathy. Group 3 patients received the highest heparin doses (p less than 0.05) and had the greatest postoperative blood loss (p less than 0.05). Protamine dose and heparin concentration during cardiopulmonary bypass correlated best with postoperative mediastinal drainage. Our findings support the following conclusions: (1) compensated subclinical plasma coagulation activity occurs during cardiopulmonary bypass despite activated coagulation time greater than 400 seconds or heparin concentration greater than or equal to 4.1 IU/ml; (2) post-cardiopulmonary bypass mediastinal drainage correlates strongly with increased heparin concentration during cardiopulmonary bypass (p less than 0.05) and protamine dose (p less than 0.05); and (3) during cardiopulmonary bypass at both normothermia and hypothermia, activated coagulation times greater than 350 seconds result in acceptable fibrinopeptide A levels and post-cardiopulmonary bypass blood clotting.

The Reduction of Uncertainties for Absolute Piston Gage Pressure Measurements in the Atmospheric Pressure Range.

NIST pressure calibration services with nitrogen are now based on two transfer standard piston gages for which the effective areas have been determined by calibration with the manometer developed at NIST for gas thermometry. Root-sum-squared three sigma uncertainties for the areas for the two gages are 3.05 ppm and 4.18 ppm.

Sufentanil is preferable to etomidate during rapid-sequence anesthesia induction for aortocoronary bypass surgery.

To evaluate rapid-sequence anesthetic induction techniques for aortocoronary bypass grafting, 20 patients scheduled for elective surgery were randomly assigned to receive bolus injections of either etomidate, 0.4 mg/kg, intravenously (IV), or sufentanil, 5 micrograms/kg, IV, with succinylcholine, 1 mg/kg, IV. Patients in the two groups had similar demographic characteristics and baseline (preinduction) hemodynamic values. Following induction and intubation, 8 of 9 etomidate patients required a pharmacologic intervention to treat hypertension and tachycardia, whereas only 1 of 11 sufentanil patients required additional treatment (P less than 0.001). Three of 9 etomidate patients had ST segment changes of new myocardial ischemia following induction and intubation; two other etomidate patients developed Q waves on their postoperative electrocardiograms, indicative of a perioperative myocardial infarction. No sufentanil patient demonstrated either ischemia or infarction. It is concluded that sufentanil-succinylcholine provides more stable hemodynamics and fewer ischemic myocardial events than etomidate-succinylcholine in patients undergoing myocardial revascularization surgery.

Premedication determines the circulatory responses to rapid sequence induction with sufentanil for cardiac surgery.

Thirty-three patients undergoing elective aortocoronary bypass were allocated randomly to receive morphine 0.1 mg kg-1 i.m. and either lorazepam 50 micrograms kg-1 by mouth or hyoscine 6 micrograms kg-1 i.m. before rapid sequence induction of anaesthesia with sufentanil 5 micrograms kg-1 i.v.and suxamethonium 1 mg kg-1 i.v. Following induction and tracheal intubation, patients premedicated with hyoscine had a significantly higher mean heart rate, mean arterial pressure, cardiac index and left ventricular stroke-work index than patients premedicated with lorazepam. The incidence of new myocardial ischaemia was low in both groups.