Review question
What effect does a high blood pressure target compared with a low blood pressure target have in people undergoing heart surgery while on cardiopulmonary bypass (CPB).
Key messages
A high blood pressure target compared with a lower target may result in little to no difference in kidney injury, cognition (ability to learn and understand) damage, or survival.
A high blood pressure target may increase the length of hospital stay slightly.
What is heart surgery?
Heart surgery is a common type of surgery throughout the world. Most types of heart surgery are performed with CPB. CPB is a medical device that replaces the work of the heart and lungs by pumping the blood, and taking oxygen into and removing carbon dioxide from the blood. People undergoing heart surgery usually have high blood pressure (called hypertension). People with hypertension need a higher blood pressure to keep the blood flow to important organs such as the brain and kidneys. However, the evidence about the best blood pressure targets to use during heart surgery is scarce.
What did we want to find out?
We wanted to assess the effects of a higher blood pressure target compared with a lower blood pressure target on the kidneys, brain, quality of life, and complications occurring while in hospital.
What did we do?
We searched medical databases for clinical trials comparing high versus low blood pressure targets during heart surgery while on CPB.
What did we find?
We found three studies including 737 people undergoing heart surgery. The duration of the studies varied from two to three years. The average age of included participants ranged between 65.8 and 76 years and about 72% were men.
There was little to no difference between a high and low blood pressure target in injury to the kidneys, cognition damage, or deaths. Although a high blood pressure target may increase the length of hospital stay slightly, there may be little to no differences in quality of life or complications during hospitalisation.
What are the limitations of the evidence
Our confidence in the evidence for kidney injury and death was very limited as the studies were small, did not provide data about everything that we were interested in, and included different types of people. We are also less confident in the evidence for cognition damage as the studies were small and did not provide data about everything that we were interested in.
How up to date is this evidence?
The evidence is current to November 2021.
A high blood pressure target may result in little to no difference in patient outcomes including acute kidney injury and mortality. Given the wide CIs, further studies are needed to confirm the efficacy of a higher blood pressure target among those who undergo cardiac surgery with CPB.
Cardiac surgery is performed worldwide. Most types of cardiac surgery are performed using cardiopulmonary bypass (CPB). Cardiac surgery performed with CPB is associated with morbidities. CPB needs an extracorporeal circulation that replaces the heart and lungs, and performs circulation, ventilation, and oxygenation of the blood. The lower limit of mean blood pressure to maintain blood flow to vital organs increases in people with chronic hypertension. Because people undergoing cardiac surgery commonly have chronic hypertension, we hypothesised that maintaining a relatively high blood pressure improves desirable outcomes among the people undergoing cardiac surgery with CPB.
To evaluate the benefits and harms of higher versus lower blood pressure targets during cardiac surgery with CPB.
We used standard, extensive Cochrane search methods. The latest search of databases was November 2021 and trials registries in January 2020.
We included randomised controlled trials (RCTs) comparing a higher blood pressure target (mean arterial pressure 65 mmHg or greater) with a lower blood pressure target (mean arterial pressure less than 65 mmHg) in adults undergoing cardiac surgery with CPB.
We used standard Cochrane methods. Primary outcomes were 1. acute kidney injury, 2. cognitive deterioration, and 3. all-cause mortality. Secondary outcomes were 4. quality of life, 5. acute ischaemic stroke, 6. haemorrhagic stroke, 7. length of hospital stay, 8. renal replacement therapy, 9. delirium, 10. perioperative transfusion of blood products, and 11. perioperative myocardial infarction. We used GRADE to assess certainty of evidence.
We included three RCTs with 737 people compared a higher blood pressure target with a lower blood pressure target during cardiac surgery with CPB. A high blood pressure target may result in little to no difference in acute kidney injury (risk ratio (RR) 1.30, 95% confidence interval (CI) 0.81 to 2.08; I² = 72%; 2 studies, 487 participants; low-certainty evidence), cognitive deterioration (RR 0.82, 95% CI 0.45 to 1.50; I² = 0%; 2 studies, 389 participants; low-certainty evidence), and all-cause mortality (RR 1.33, 95% CI 0.30 to 5.90; I² = 49%; 3 studies, 737 participants; low-certainty evidence). No study reported haemorrhagic stroke. Although a high blood pressure target may increase the length of hospital stay slightly, we found no differences between a higher and a lower blood pressure target for the other secondary outcomes.
We also identified one ongoing RCT which is comparing a higher versus a lower blood pressure target among the people who undergo cardiac surgery with CPB.