Debra L. Caldera

Multifactorial Index of Cardiac Risk in Noncardiac Surgical Procedures

To determine which preoperative factors might affect the development of cardiac complications after major noncardiac operations, we prospectively studied 1001 patients over 40 years of age. By multivariate discriminant analysis, we identified nine independent significant correlates of life-threatening and fatal cardiac complications: preoperative third heart sound or jugular venous distention; myocardial infarction in the preceding six months; more than five premature ventricular contractions per minute documented at any time before operation; rhythm other than sinus or presence of premature atrial contractions on preoperative electrocardiogram; age over 70 years; intraperitoneal, intrathoracic or aortic operation; emergency operation; important valvular aortic stenosis; and poor general medical condition. Patients could be separated into four classes of significantly different risk. Ten of the 19 postoperative cardiac fatalities occurred in the 18 patients at highest risk. If validated by prospective application, the multifactorial index may allow preoperative estimation of cardiac risk independent of direct surgical risk.

Risks of general anesthesia and elective operation in the hypertensive patient.

To determine the risks of general anesthesia and elective surgical procedures in patients who have histories of hypertension, the authors prospectively studied 676 consecutive operations in a series of patients more than 40 years old. All patients were examined preoperatively, monitored intraoperatively, and closely followed postoperatively. Although patients with higher preoperative blood pressure values had larger absolute intnoperative blood pressure decreases, the mean intraoperative systolic pressure nadirs in patients with tightly-controlled hypertension (100 ± 2 torr) did not differ from those in patients with persistent treated (97 ± 3 torr) or untreated (98 ± 2 torr) mild to moderate hypertension. Similarly, among these three groups of patients, the needs for intraoperative adrenergic agents or fluid challenges (20, 33, and 27 per cent, respectively) and the incidences of perioperative hypertensive events (27, 25, and 20 per cent, respectively) were not significantly different. Multivariate analysis of data for the patients with histories of hypertension showed that neither the preoperative in-hospital diastolic nor preoperative in-hospital systolic blood pressure values independently correlated with any of these three indices of perioperative blood pressure lability, with the development of cardiac arrhythmias, ischemia, or failure, or with postoperative renal failure. Effective intraoperative management may be more important than preoperative hypertensive control in terms of decreasing clinically significant blood pressure lability and cardiovascular complications in patients who have mild to moderate hypertension.

Cardiac risk factors and complications in non-cardiac surgery.

In an attempt to assess cardiac risk in non-cardiac surgery, 1001 patients over 40 years of age who underwent major operative procedures were examined preoperatively, observed through surgery, studied with at least one postoperative electrocardiogram, and followed until hospital discharge or death. Documented postoperative myocardial infarction occurred in only 18 patients; though most of these patients had some pre-existing heart disease, there were few preoperative factors which were statistically correlated with postoperative infarction. Postoperative pulmonary edema was strongly correlated with preoperative heart failure, but 21 of the 36 patients who developed pulmonary edema did not have any prior history of heart failure. Nearly all of these 21 patients were elderly, had abnormal preoperative electrocardiograms, and had intraabdominal or intrathoracic surgery. In the absence of an acute infarction, bifascicular conduction defects, with or without PR interval prolongation, never progressed to complete heart block. Spinal anesthesia protected against postoperative heart failure but not against other cardiac complication. By multivariate regression analysis, postoperative cardiac death was significantly correlated with (a) myocardial infarction in the previous 6 months; (b) third heart sound or jugular venous distention immediately preoperatively; (c) more than five premature ventricular contractions per minute documented at any time preoperatively; (d) rhythm other than sinus, or premature atrial contractions on preoperative electrocardiogram; (e) age over 70 years; (f) significant valvular aortic stenosis; (g) emergency operation; (h) a 33% or greater fall in systolic blood pressure for more than 10 minutes intraoperatively. Notably unimportant factors included smoking, glucose intolerance, hyperlipidemia, hypertension, peripheral atherosclerotic vascular disease, angina, and distant myocardial infarction.

Benefit of Elective Intensive Care Admission After Certain Operations

To determine if patients who have undergone uneventful vascular surgery (VS), nonvascular intracranial surgery (ICS), or anterior cervical laminectomies (ACL) have enough serious postoperative problems to justify routine overnight observation in an intensive care unit (ICu), we recorded every problem and associated therapy administered to 263 such patients within 36 h of ICu admission. The severity of each treated problem was graded from 1 (safe to delay treatment for at least 2 h) to 4 (life-threatening, immediate treatment required). Defining patient benefit from the ICu as treatment for one grade 4 problem or more than one grade 3 problem, 44% of VS patients (N = 177), 14% of ICS patients (N = 73), and none of the ACL patients (N = 13) benefited. We conclude that these percentages justify an overnight ICu stay for all VS patients, especially as the occurrence of serious problems was unpredictable and most serious problems were still being treated 4 h postoperatively. Furthermore, routine ICu admission of all patients in the groups studied would reduce patient costs if only 13 of the 88 patients who benefited were prevented from becoming critically ill.

Comparative evaluation of new fine-screen filters: effects on blood flow rate and microaggregate removal.

Fine-screen filters were studied in a simulated clinical situation wherein ten units of outdated concentrated erythrocytes were rapidly transfused per filter to determine flow rates and effectivenesses of debris removal. Preliminary studies to evaluate flow rates with outdated whole blood indicated that the Bentley PFF-100®, Fenwal 4C9003®, and Biotest MF-10® fine-screen filters allowed flow rates sufficient to justify further detailed testing. For comparative purposes, the filter the authors have used clinically, the Pall Ultipor® 40-µm filter, was studied again. As many as ten units of outdated, concentrated erythrocytes (hematocrits 75–85 per cent) were infused through each of the fine-screen filters at 300 torr pressure. All filters (except one of five Pall filters) accepted all ten units. The Bentley PFF-100 filter allowed the highest flow rates, such that the tenth unit of erythrocytes required 5 ± 3 min (1 SD) to pass the filter. The Biotest MF-10, Bentley PFF-100 and Fenwal 4C9003 filters retained more debris/g erythrocytes, decreased screen filtration pressure, and eliminated more particulate matter (as determined by Coulter® counter testing) than did the Pall Ultipor filter. When three or more units of blood are transfused, any of the four filters tested is cost-effective when compared with the current 170-µm standard transfusion filter.