Patients with low blood pressure before an operation are at an increased risk of death during or after the surgery than those with preoperative high blood pressure, say researchers, including Indian-origin scientists.
"While high blood pressure control is important for long-term health, high blood pressure itself does not impose a significant risk of postoperative death," said the study by Puja Myles and Sudhir Venkatesan from the University of Nottingham in Britain and colleagues.
They used data from 252,278 patients from the United Kingdom Clinical Practice Research Datalink to perform their analysis.
A number of models of varying complexities were used to account for 29 perioperative risk factors including age, gender, race, comorbidities, medications, and surgical risk score.
Perioperative generally refers to the three phases of surgery: preoperative, intraoperative, and postoperative.
After risk factor adjustment, the effect of high blood pressure was not found to be associated with increased odds of post-surgery mortality.
However, preoperative low blood pressure was associated with statistically significant increases in the odds of perioperative mortality.
For patients with a systolic (the top number) blood pressure of below 100 mmHg, the likelihood of death increased by 40 percent.
For those with a diastolic (the bottom number) BP of under 40 mmHg, the likelihood of death increased by 2.5 times.
While the risk from low blood pressure was present in patients with low systolic or low diastolic pressure, values below 100/40 were of greatest risk.
Hence the likelihood of death further increased as either or both systolic or diastolic blood pressure decreased further.
"Preoperative low blood pressure is under-recognised as a risk factor for perioperative mortality. Future studies will need to identify how this risk can be modified to improve patient outcomes," the researchers noted.
The study was presented at Euroanaesthesia 2015, the European Anaesthesiology Congress, in Berlin, Germany.
