Near Infrared Spectroscopy in Cyanotic Congenital Heart Disease

Overview

We are conducting a prospective cohort study of 20 children with cyanotic congenital heart disease who are admitted for cardiac surgery. We will record cerebral and somatic near infrared spectroscopy (NIRS) at two sites - forehead and flank regions using the Covidien INVOS™ 5100C Cerebral / Somatic Oximeter. The monitoring will begin one hour pre-operatively (baseline) and continue until 48hours post-operatively. We will also take measurements prior to discharge from hospital. Baseline demographics, physiological and laboratory variables will be recorded. Clinical outcome variables including mortality, duration of intensive care unit (ICU) stay, duration of mechanical ventilation, inotropic support and feed tolerance will also be recorded.

NIRS has been used to predict short term clinical outcomes (low cardiac output states, prolonged ventilation, and prolonged hospital stay) and long term clinical outcomes (reduced neurodevelopmental scores at 1year, radiological changes on magnetic resonance imaging). NIRS has also been tested against traditional markers of global tissue perfusion like mixed venous saturation and serum lactate, however, results from these studies are mixed. There is insufficient prospective data evaluating NIRs with direct clinical outcomes and uncertainty about the threshold value or the duration below a threshold value that leads to tissue injury. Because of this lack of data, the benefit and risk of management strategies targeted to improve NIRS values remains unknown. We will characterize the time series of cerebral and somatic oximetry, pulse oximetry and partial pressure of arterial oxygen in the cyanotic child undergoing surgical repair of a congenital heart defect. We will then determine the correlation between the time series if any. This new information will advance our understanding of the hemodynamic changes that occur in the perioperative period and may lead to new therapeutic targets. The primary hypothesis is that there is a delayed increase in cerebral and somatic oximetry post-operation as compared pulse oximetry (SpO2) and partial pressure of arterial oxygen (PaO2) which occur immediately. The secondary hypothesis is to establish the applicability of a desaturation score (decrease of 20% in area under the curve \[AUC\] over an hour) in the early prediction of adverse outcomes. The oximetry probes will be placed pre-induction of anesthesia (to determine baseline) and recordings will be continuous throughout the operation and 48hours post-operatively. Children undergoing cardiac surgery generally stay in the hospital for 1-2weeks. We will also take oximetry measurements prior to discharge from hospital (to determine the new steady state). Sites measured are cerebral (forehead) and somatic (left flank).