5 days ago
How Much Does Maintaining BP During Surgery Matter?
Efforts to avoid either high or low blood pressure during noncardiac surgery do not appear to make a difference in the cognitive outcomes of patients after the procedures, a new study found.
More than 300 million adults worldwide undergo noncardiac surgery each year, and most are taking medications to control their blood pressure, said Maura Marcucci, MD, a specialist in perioperative medicine at McMaster University in Hamilton, Ontario, Canada, and lead author of the study, which her group published last month in Annals of Internal Medicine .
'Blood pressure abnormalities are common during and after noncardiac surgery, and observational evidence have suggested that they are related to possible organ damage, including brain insult, especially in older patients and those whose mechanisms of brain protection might be affected by chronic vascular disease,' Marcucci said. 'On a daily basis, physicians taking care of these patients are confronted with questions around what blood pressure to target intraoperatively and what to do with the patient's blood pressure medications, with the assumption that these choices would affect the patient's risk of complications.'
The new study evaluated 2603 surgery patients (mean age, 70 years) with a history of vascular disease or multiple risk factors for vascular events and who were taking antihypertensive medications chronically.
The researchers compared outcomes associated with two approaches to regulating blood pressure during the procedures: One aimed to prevent hypotension, the other to avoid hypertension. The primary outcome was delirium in the hospital in the first 3 days after surgery.
In the hypotension-avoidance group, patients taking angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, or direct renin inhibitors have those medications withheld before surgery and for the first 2 days afterward. For other types of blood pressure medications, decisions on whether to continue or discontinue the drugs were based on the patient's systolic blood pressure following surgery (≥ 130 mm Hg following an algorithm). Anesthesiologists were asked to maintain patients' mean arterial pressure (MAP) ≥ 80 mm Hg throughout surgery.
In the hypertension-avoidance group, patients took all of their usual blood pressure medications at the hospital before their operation. The anesthesiologists in these cases were asked to aim to keep MAPs ≥ 60 mm Hg throughout surgery using strategies at their discretion. After surgery, the patients in this group continued taking all of their blood pressure medications as they normally would.
All the patients remained on their assigned blood pressure management strategy for 2 days after surgery or until they were discharged from the hospital, whichever came first. In the hypotension-avoidance group, on day 3 after surgery or at discharge, patients were allowed to resume taking all of their blood pressure medications.
Marcucci and her colleagues found no difference in neurocognitive outcomes between the two strategies in either the short or the long term.
The analysis showed 95 of 1310 patients (7.3%) in the hypotension-avoidance group and 90 of 1293 patients (7%) in the hypertension-avoidance group had delirium (relative risk [RR], 1.04; 95% CI, 0.79-1.38). Of the 701 patients who completed the cognitive assessment at the 1-year mark, 129 of 347 (37.2%) in the hypotension-avoidance group and 117 of 354 (33.1%) in the hypertension-avoidance group had a decline of two or more points on the test (RR, 1.13; 95% CI, 0.92-1.38). By the end of the trial, 19% in the hypotension-avoidance strategy and 27% in the hypertension-avoidance strategy had hypotension requiring some form of intervention (RR, 0.63; 95% CI, 0.52-0.76).
Marcucci said the study helps answer two important questions confronting anesthesiologists, cardiologists, and internists:
'It taught us that ensuring that patients' MAP remains above 60 throughout the surgery is safe and that targeting a higher MAP does not make a difference,' she said. 'Also, whether or not patients continued to take all their chronic blood pressure medications throughout the perioperative period did not make any real difference to their blood pressure and heart rate, and hence any difference in patient-centered outcomes.'
That the findings held across different subgroups of patients — from young to old, and those on single or multiple drugs for hypertension — 'are reassuring regarding the fact that patients are stable on their chronic medications and that it does not seem that their continuation or discontinuation perioperatively will affect major outcomes, at least not on average. They also leave discretion to physicians to individualize care based on specific situations and following patients' preferences.'
In an editorial accompanying the journal article, Idalid Franco, MD, MPH, and Alexander Arriaga, MD, MPH, ScD, of Brigham and Women's Hospital in Boston, wrote the study 'adds to a growing list of publications from high-impact journals, including Annals of Internal Medicine , that have used original research and multidisciplinary guidelines to challenge and update long-standing beliefs about the perioperative management of older adults' and renin-angiotensin-aldosterone system inhibitors (RAASIs).
'At a time when substantial resources are being devoted to improving the quality of perioperative care for an increasingly aging population, Marcucci and colleagues provide us timely and relevant reassurance that the key to improving outcomes may not rely on whether a few doses of RAASIs are held perioperatively or whether intraoperative MAP targets are scripted beyond clinical judgment,' they added.
