Peripheral Perfusion Index in Acute Surgical Patients
Peripheral Perfusion Index in Acute Surgical Patients
Introduction Perioperative haemodynamic instability is associated with postoperative
 morbidity and mortality. Macrocirculatory parameters, such as the conventionally obtained
 mean arterial blood pressure and cardiac output, may be uncoupled from the microcirculation
 during sepsis and severe blood loss and may not necessarily be optimal resuscitation
 parameters. The peripheral perfusion index (PPI) is derived from the pulse oximetry signal
 and reflects perfusion. Reduced peripheral perfusion is associated with morbidity in
 critically ill patients and in patients following acute surgery. We hypothesize that patients
 with low intraoperative PPI demonstrate high frequency of postoperative complications and
 mortality regardless of blood pressure.

 Methods and analysis We plan to conduct a prospective observational cohort study in patients
 undergoing acute non-cardiac surgery (November 1st, 2017 to October 31st, 2018) at two
 University Hospitals. Data will be collected prospectively from patient records including
 patient demographics, comorbidity and intraoperative hemodynamic values, with PPI as the
 primary exposure variable, and postoperative complications and mortality within 30 and 90
 days as outcome variables. We primarily assess association between PPI and outcome in
 multivariate regression models. Secondly, the predictive value of PPI for outcome, using area
 under the receiver operating characteristics curve is assessed.

 Ethics and dissemination Data will be reported according to The Strengthening the Reporting
 of Observational Studies in Epidemiology (STROBE). Results will be published in a peer
 reviewed journal. The study is approved by the regional research ethics committee, storage
 and management of data has been approved by the Regional Data Protection Agency, and access
 to medical records is approved by the hospital board of directors at the involved hospitals
 and departments.
Background Perioperative haemodynamic instability is associated with postoperative morbidity
 and mortality. Patients undergoing acute major abdominal or hip fracture surgery have high
 complication rates and account for a major part of overall postoperative mortality in
 developed countries. These patients are often frail, with multiple comorbidities making them
 vulnerable to anaesthesia and surgery. Despite the benefit of a multidisciplinary effort to
 improve perioperative care, such patients demonstrate a high risk of complications and death.
 Conventional perioperative haemodynamic monitoring is often based only on heart rate (HR) and
 mean blood pressure (MAP). Although perioperative hypotension is associated with
 complications in major surgery, blood pressure is often an inadequate marker of perioperative
 organ perfusion, consequently leading to little precision in administration of fluid and
 vasoactive medication. Minimally-invasive haemodynamic monitoring of cardiac output (CO), and
 goal directed therapy based on stroke volume optimization, has been associated with improved
 outcome in major elective surgery, but high quality evidence for the advantage of such
 monitoring in emergency surgery is sparse.

 Macrocirculatory parameters such as MAP and CO may be uncoupled from the microcirculation
 during sepsis and severe blood loss due to sympathetic or medically induced vasoconstriction,
 and as such, these parameters are not necessarily optimal for resuscitation.

 Assuming that blood flow is directed from peripheral tissue to vital organs during
 progressive stages of circulatory impairment and shock, a non-invasive method to detect
 impaired peripheral perfusion could be a relevant endpoint.

 The peripheral perfusion index (PPI) has the advantage that is derived from the photoelectric
 plethysmographic pulse oximetry signal most likely obtained in all patients for evaluation of
 arterial oxygen saturation (SAT) already in the emergency room and continued during and after
 surgery as in wards and in the ICU. The PPI reflects the ratio between the pulsatile and
 non-pulsatile component of the arterial waveform as assessed by light traversing the tissue
 addressed, most often the finger, and it decreases in response to hypoperfusion.Thus, PPI
 reflects changes in peripheral perfusion and blood volume and reduced peripheral perfusion is
 associated with morbidity following acute surgery, in critically ill patients, and patients
 presenting septic shock. However, it remains uncertain which threshold for PPI should trigger
 intervention in patients undergoing acute surgery reflecting that evaluation is made only in
 relatively small populations of mixed medical and surgical patients.

 Hypothesis We hypothesize that PPI reflects impaired peripheral circulation and that patients
 with low intraoperative PPI, independent of MAP, have higher risk of postoperative
 complications and mortality than patients with normal or high PPI.

 Objectives The main objective of this study is to evaluate the association between
 intraoperative PPI and outcome defined as severe postoperative complications and 30- and
 90-days mortality. Secondly, we assess the predictive value of intraoperative PPI in relation
 to outcome and evaluate whether PPI has better prediction of adverse outcome than the
 commonly used MAP thresholds and try to establish intervention thresholds for PPI that in
 acute non-cardiac surgical patients.
Inclusion Criteria:

 Orthopedic surgery patients with fracture of the hip booked for or having performed
 procedures with the following procedural codes: KNFB02, KNFJ81, KNFJ51, KNFJ52, KNFJ70
 representing arthroplasty, intra-medullar nailing, and screws respectively.

 For abdominal surgery patients we include patients booked for acute laparoscopy for
 diagnostic purposes (KJAH01) and explorative laparotomy (KJAH00). To identify all patients
 having performed acute abdominal surgery, we also include surgery related to ileus: KJFK00,
 KJFK01, KJFK10, KJAP00, KJAP01, KJFK96, KJFK97, any perforation of vicera: KJDA60, KJDA70,
 KJDA80, and any ischemic condition of the gut: KJFB00, KJFB01, KJFB33, KJFB34, KJFB96,
 KJFB97.

 Exclusion Criteria:

 -  No sampling of PPI registered

 -  Foreign/temporary civil registration number that prevents follow up

 -  Earlier enrollment in cohort