Postoperative hypotension is common, life-threatening and poorly understood. It is associated with an increased risk of perioperative myocardial infarction, stroke, acute kidney injury and mortality. The physiological basis of postoperative hypotension after non-cardiac surgery has not been extensively investigated. As the Australian surgical population ages and acquires risk factors for postoperative hypotension, there is an urgent need to identify the common causes of postoperative hypotension so that appropriate treatments can be delivered.
This project uses point of care cardiac ultrasound and side-stream dark-field microscopy, which images the capillary circulation under the oral mucosa to identify the major physiological disturbance driving hypotension. Both techniques have been extensively used in intensive care, but few studies have used them after major non-cardiac surgery.
This project aims to illuminate the common physiological basis for postoperative hypotension and define the relative contribution of vasodilation compared to other causes of hypotension in patients having major vascular surgery. The investigators hypothesise that a majority of patients who are hypotensive postoperatively will have evidence of vasodilation. Fully understanding the causative mechanisms behind the syndrome of postoperative hypotension will allow perioperative clinicians to design appropriate treatment plans to reduce morbidity and mortality after major surgery.
This project forms part of Dr Douglas' PhD program at the University of Melbourne with the research to be undertaken at the Royal Melbourne Hospital.
Dr Ned Douglas
Associate Professor Jai Darvall
Professor Kate Leslie
The Royal Melbourne Hospital, Victoria and Department of Critical Care, University of Melbourne.
The project was awarded $A83,685 funding through the ANZCA research grants program for 2023.
We aimed to determine why patients who have had surgery develop low blood pressure by looking for changes to the circulation at the end of surgery. Low blood pressure after surgery is an important problem because it can cause damage to organs such as the heart, kidneys and brain. There are a wide variety of ways to treat low blood pressure, but which one will work is determined by what the cause of the low blood pressure might be. Given we did not know which of these causes was most common, we set out to find out using techniques that looked at the heart and blood vessels directly to help us understand what was going on.
We identified the most common change to the circulation that was associated with developing low blood pressure on the ward.
Now that we understand which problem is driving low blood pressure on the ward, we can design studies to prevent or treat this problem, which may in turn reduce the impact that low blood pressure after surgery has on patients during their recovery.
The study is currently undergoing review at the Canadian Journal of Anaesthesia.
We presented the study at the 2025 ANZCA Annual Scientific Meeting where it was selected for the Gilbert Brown Prize session.