Investigating the Peripheral Perfusion Index; Correlations Between Peripheral and Mesenteric Perfusion in Elective Surgical Patients

An important goal of haemodynamic monitoring and resuscitation is early detection of insufficient tissue perfusion and oxygenation, but in clinical practice, monitoring and resuscitation is routinely based on measuring of blood pressure and heart rate, which might be inadequate endpoints for optimal resuscitation. Haemodynamic management targeting cardiac output and stroke volume (SV), and to some extent, flow and tissue perfusion is feasible when applying minimally-invasive or non-invasive methods, but has been limited to a narrow number of critically ill patients and to the intraoperative setting. Another approach to resuscitation is aimed at flow and perfusion of vital organs. Ideally, measurements would be done directly on these organs, but no feasible methods exist. Assuming blood flow is diverted from the peripheral tissue and the gastrointestinal tract to vital organs, during circulatory shock, an objective, simple and non-invasive method of detecting peripheral tissue perfusion impairment might detect this at an early stage. The peripheral perfusion index (PPI) is derived from the photoelectric plethysmographic pulse oximetry signal, which all patients are monitored by perioperatively to assess arterial oxygen saturation. The PPI is a numerical non-invasive measure representing the ratio between the pulsatile (arterial) and non-pulsatile component of the light reaching the pulse oximeter, and PPI decreases in states of hypoperfusion. PPI reflects changes in peripheral perfusion and blood volume and decreased peripheral perfusion determined by PPI predicts surgical complications and morbidity in acute surgical and septic shock patients.

The mesenteric haemodynamic response to circulatory shock is complex, and diagnosis of bowel ischaemia poses significant difficulty for the clinicians due to its non specific presentations and lack of a simple diagnostic test. In patients undergoing colorectal surgery for malignancy, laser doppler flowmetry allows measurement of bowel tissue perfusion.

The aim of this study is to explore the association between changes in peripheral and intestinal perfusion in patients undergoing elective colorectal surgery exposed to intraoperative haemodynamic challenges.