MedWire News: Two studies published in Anesthesia and Analgesia have muddied the water regarding the effect of preoperative pulse pressure (PP) on perioperative outcomes.
The findings show no apparent effect of high PP in patients undergoing lower extremity vascular bypass surgery, contrasting with the recognized adverse impact in cardiac surgery patients.
In an editorial accompanying the papers, Manuel Fontes and Solomon Aronson (Duke University Medical Center, Durham, North Carolina, USA) highlight several limitations of the studies, for the most part related to the retrospective, descriptive designs. But despite this, they say it "may be that these studies have revealed an important, although not yet fully understood, difference in the relationship between hypertensive subtypes and perioperative outcome."
The first study, by Michael Mazzeffi (Mount Sinai School of Medicine, New York, USA) and team, found that 44.9% of 556 patients undergoing infrainguinal arterial bypass surgery had elevated PP (≥80 mmHg). But these patients were no more likely to die within 30 days of surgery than those with lower PP, after accounting for confounders.
In fact, although not significant, the researchers found a U-shaped association, with mortality rates of 3.7% and 3.3% among patients with low (≤40 mmHg) and high (>80 mmHg) PP, respectively, compared with 6.5-7.0% among those with intermediate PP.
In the second study, Balachundhar Subramaniam (Beth Israel Deaconess Medical Center, Boston, Massachusetts, USA) and co-workers found that high PP was present in 35.9% of 412 patients undergoing lower extremity bypass surgery. Major adverse cardiovascular events (myocardial infarction, congestive heart failure, stroke, in-hospital mortality) occurred in 8.8% of the high PP group and 5.7% of other patients, which was not a significant difference after accounting for confounders.
Fontes and Aronson note that pinning down the relationship between PP and surgical outcomes is "critically important" for guiding risk stratification, and possibly for improving perioperative outcomes.
"In terms of therapeutic approaches, the limitations are many and the stakes are high," they say, observing that it is not currently possible to control individual blood pressure components. Yet a large number of elderly surgical patients have isolated systolic hypertension and high PP.
"Whereas awareness of [hypertension] may be increasing, achieving an understanding of what constitutes 'adequate control' of [blood pressure] remains a major challenge," say the editorialists. "This challenge is amplified in the acute-care perioperative arena, in which more mystery than evidence exists about best practice in a given patient in a given situation with a given condition."
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Free abstract (Mazzeffi)
Free abstract (Subramaniam)