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PERIOPERATIVE RISK & HYPERTENSION
A New Look at an Old QuestionSolomon Aronson, M.D., F.A.C.C., F.A.C.C.P.
University of Chicago
Isolated systolic blood pressure has not been sufficiently studied in the perioperative setting and may contribute to morbidity and mortality after coronary artery bypass grafting (CABG) surgery. Our objective was to determine the prevalence of isolated systolic hypertension among patients who had CABG surgery and to assess whether isolated systolic hypertension is associated with perioperative and postoperative in-hospital morbidity or mortality. Patients who underwent CABG were selected from a prospective epidemiological study involving 2417 patients in 24 medical centers. Patients were classified as having normal preoperative blood pressure, isolated systolic hypertension (systolic blood pressure>140 mmHg), diastolic hypertension (diastolic blood pressure>90 mmHg), or a combination of these. Demographic risk factors (age, sex, and ethnicity), clinical risk factors (diabetes mellitus, increased cholesterol, antihypertensive medications, history of congestive heart failure, myocardial infarction, hypertension, and neurological deficits), and behavioral risk factors (smoking and heavy drinking) were controlled for statistically. Adverse outcomes included left ventricular dysfunction, cerebral vascular dysfunction or events, renal insufficiency or failure, and all-cause mortality. Isolated systolic hypertension was found in 29.6% of patients. Unadjusted isolated systolic hypertension was associated with a 40% increased risk of adverse outcomes (odds ratio, 1.4; confidence interval, 1.1-1.7). After adjusting for other potential risk factors, the increased risk of adverse outcomes with isolated systolic hypertension was 30%. We conclude that isolated systolic hypertension is associated with a 40% increase in the likelihood of cardiovascular morbidity perioperatively in CABG patients. This increase remains present regardless of antihypertensive medications, anesthetic techniques, and other perioperative cardiovascular risk factors (e.g., age older than 60 yr or history of congestive heart failure, myocardial infarction, or diabetes).
(Aronson S, et al: Isolated systolic hypertension is associated with adverse outcomes from coronary artery bypass grafting surgery. Anesth Analg 2002; 94:1079-84)The inidence of isolated systolic hypertension (ISH) and increased pulse pressure (PP) increases with age as the aorta becomes less distensible. Further, both pathologic conditions add to the risk of cardiovascular morbidity and mortality. Whether the presence of ISH and increased PP also raises the risk of cardiac death in patients undergoing CSBG surgery is unknown.
Method: After institution review board approval, 5065 patients undergoing elective CABG and combined CABG valve surgery were prospectively enrolled in the McSPI Research Group. The present study is to determine which component of preoperative blood pressure is predictive of cardiovascular mortality. Comprehensive data were recorded for past medical history, intraoperative and postoperative hemodynamic, laboratory values, and clinical events. Four groups of hypertensive patients were identified preoperatively using standard definitions: isolated systolic hypertension-ISH=SBP>160 mmHg with DBP <90 mmHg; combined systolic-diastolic hypertension-CSDH=SBP>160 mmHg with DBP >90 mmHg; pulse pressure hypertension-PPH=preoperative pulse pressure >80 mmHg; and isolated diastolic hypertension (IDH=SBP<160 mmHg with DBP >90 mmHg). Cardiac death was the main outcome variable. Univariate and multiple logistic regression analysis were used. P-values<0.05 were considered significant.
Results: The final analysis included 4801 patients (256 did not undergo cardiopulmonary bypass and 8 had incomplete preoperative blood pressure recordings). Two hundred and forty patients (5%) had ISH, 382 (8%) had PPH, 101 (2%) had CSDH; and 144 had IDH (3%). There were 147 fatalities (3%) of which 95 (2%) represented cardiac death. Of the four types of preoperative hypertension, PPH significantly increased the risk cardiac death-Odds Ratio 2.22 (1.26-3.89) p=0.005.
Summary: Increase in preoperative PP significantly raises of perioperative cardiac death. While the potential mechanism for this association is uncertain, our finding is consistent with those of longitudinal studies on ambulatory subjects and calls for additional investigation on both mechanistic relationship between PPH and adverse outcome as well as therapeutic interventions aimed at mitigating the deleterious effects of PPH.
(Fontes ML, Aronson S and McSPI Investigators: Preoperative pulse pressure increases the risk of cardiac death in patients undergoing CABG surgery. Abstract of Symposium at ASA 2002 Annual Meeting)