A large, international study in patients undergoing non-cardiac surgery found that a strategy aimed at preventing hypotension (i.e., low blood pressure) by withholding some or all chronic antihypertensive medications before and after surgery, and by targeting higher blood pressures during surgery, did not affect the risk of major vascular complications.
The study was published today in Annals of Internal Medicine.
In the study, half of 7,490 patients in 22 countries were randomly assigned to a hypotension-avoidance strategy, half to a hypertension-avoidance strategy.
In the hypotension-avoidance strategy, patients did not take angiotensin-converting enzyme inhibitors (ACEIs) or angiotensin-receptor blockers (ARBs) from the night before surgery through day 2 after surgery; other chronic antihypertensive medications were administered based on patient’s blood pressure, in a stepwise manner, and prioritizing agents that control heart rate like beta-blockers.
In the hypertension-avoidance strategy (which reflected usual practice in most centres), patients received all their usual anti-hypertensives on the morning of surgery, and after surgery.
The two strategies differed also in the blood pressure target that anesthesiologists were to target in the operating room (expressed as mean arterial blood pressure), i.e., 80 mm Hg or higher in the hypotension-avoidance strategy and 60 mm Hg or higher in the hypertension-avoidance strategy.
Patients in the trial were 45 years or older (average age 69 years); 44% of them were female; they were all receiving chronically at least one antihypertensive medication.
“Hypotension during and after non-cardiac surgery is a common problem in patients undergoing noncardiac surgery and it has been linked to death and major organ injury. We designed the study based on preliminary data suggesting that withholding patient’s ACEIs or ARBs may reduce hypotension around the time of surgery, and that continuing beta-blockers may protect from vascular complications. A large study was required to test and confirm these hypotheses,” said PJ Devereaux, a senior scientist at the Population Health Research Institute of McMaster University and Hamilton Health Sciences (HHS).
“Compared to the hypertension-avoidance strategy, our hypotension-avoidance strategy reduced hypotension only during surgery when blood pressure abnormalities are very short in duration due to close monitoring and prompt intervention. It did not affect blood pressure or heart rate outside the operating room, which is likely the explanation why we did not see a difference in vascular complications,” added Devereaux, who is also a professor of medicine and of health research methods, evidence and impact at McMaster, and a cardiologist and perioperative care physician at HHS.
“Some 300 million of patients have non-cardiac surgery annually around the world, and the majority of these patients take antihypertensive medications. On a daily base, 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,” said Maura Marcucci, a PHRI scientist and an assistant professor of health research methods, evidence and impact and of medicine at McMaster, and an internal medicine and perioperative care physician at HHS.
“Our trial provided answers to those questions. Our results demonstrate that intraoperative targets of 60 or 80 mm Hg appear safe and that overall holding or continuing chronic antihypertensive medications perioperatively have minimal to no effect on blood pressure or heart rate and on major vascular complications.”
“Our group is committed to identify and evaluate other possible interventions that will decrease hypotension intraoperatively but also postoperatively, and have a favourable impact on major vascular complications,” says Marcucci.
POISE-3 was funded by the Canadian Institutes of Health Research (CIHR) Foundation Grant; National Health and Medical Research Council Funding Schemes (Australia); General Research Fund, Research Grant Council, Hong Kong, China; and the PHRI.