Recently I had a conversation with one of my colleagues regarding tight blood pressure control intraoperatively. I was told that the blood pressure should be strictly controlled within 10% of resting pressure based on this study from JAMA in 2017. As you all know me, I don’t take other people’s word for it. I like to assess it myself. A paper published in JAMA or New England Journal doesn’t mean that it is 100% true.
Lets take a look at the paper together. First of all, the quality of the paper is not that strong. It was a randomized prospective trial. However, the sample size was rather small in the high risk patients undergoing major surgery. : roughly 149 patients in the individualized blood control group (within 10% of resting BP) vs. 149 patients in standard blood pressure control group (treat SBP<80 or 40% of resting BP). 60% of the subjects are ASA 3, and all of them are acute injury index 3 or above. If you delve into table 3, the authors didn’t find any difference in acute kidney injury or other organ injuries in the treatment group compared to control. However, they did find altered mental status and infection rate in less aggressive blood pressure control group. Do we usually wait till SBP<80 to intervene in ASA 3 patients undergoing high risk surgeries? The answer is NO. We can see this flaw in this study design. In addition, the altered mental status is considered one of the end organ failure. Hence, they drew the final conclusion that standard blood pressure treatment (within 10% resting BP) is better. Based on the results, it doesn’t fully support their statement that it reduces end organ injury.
We need to ask ourselves the question what caused the difference in mental status in these two groups? Maybe patients were more burst suppressed intraoperatively based on the low blood pressure. It may imply that lower BP may associate with more alter cognitive function in the elderly patients. They only found marginal difference in infection rate. It could be due to the fact that patients were confused and hence less care was given to the wound.
Overall, I would say I would agree the practice in vascular patients, cardiac patients or patients undergoing high risk surgeries involving significant blood loss. I hope you can see from this post that sometimes we have to examine the evidence before we can utilize it in our practice.