Background Hypoxic events require convenient information about cerebral perfusion and oxygenation. Near infrared spectroscopy (NIRS) is a non invasive technique that measures continuously changes in tissue haemoglobin but it has not been fully validated.

Objective To compare NIRS parameters with carotid blood flow and blood oxygen saturation in hypoxic piglets.

Methods Six anesthetized and mechanically ventilated neonatal piglets (<3d) were used (RD1201/2005). An ultrasonic flow probe was placed around carotid artery to measure carotid blood flow. Femoral artery and jugular vein catheters were placed to obtain blood samples and to monitor systemic arterial pressure (SAP). The concentration changes in oxygenated haemoglobin (HbO2) and deoxygenated haemoglobin (HHb), their sum (cHb) and difference (HbD) and the brain tissue oxygenation index (TOI) were continuously measured by NIRS. Hypoxia was induced by reduction of FiO2 at 8% during 20 min. Different measurements were registered during hypoxia and resuscitation intervals. One-factor ANOVA was performed (p<0.05).

Results Hypoxic event induced hypotension (MAP: 40±15 mmHg), acidosis (pH: 7.01±0.06) and hypoxia (PaO2: 39±11 mmHg). During hypoxia and resuscitation intervals a significant correlation between changes in the carotid blood flow and changes in HbD measured by NIRS was observed (r = 0.76, p<0.0001). Besides there was a strong correlation between TOI measured by NIRS and blood oxygen saturation (r = 0.85, p<0.0001).

Conclusion In this hypoxic model NIRS reliably reflects changes in cerebral oxygenation and perfusion, so the continuous and non-invasive NIRS measurements could facilitate decisions concerning therapeutic interventions.

Grants: GV2006111020 and FIS06/0839.