Accuracy of pulse oximetry in hypothermic neonates and infants undergoing cardiac surgery
Iyer, P.; McDougall, P.; Loughnan, P.; Mee, R.B.; Al-Tawil, K.; Carlin, J.
Critical Care Medicine 24(3): 507-511
1996
ISSN/ISBN: 0090-3493 PMID: 8625642 Document Number: 465856
Objectives: To assess the accuracy of pulse oximetry under hypothermic conditions in neonates and infants undergoing cardiac surgery, and to assess the effect of probe site as well as probe site skin temperature on the reliability of pulse oximetry. Design: Prospective study. Setting: Cardiac operating room and intensive care unit of a children's hospital. Patients: Twenty-five infants lt 3 months of age undergoing cardiac surgery with cardiopulmonary bypass. Interventions: Pulse oximeter readings (Spo-2) from probes placed on the hand and foot were recorded at various skin temperatures and compared with hemoximeter oxygen saturations (Sao-2) obtained on simultaneously drawn arterial blood samples. Core temperature, arterial pressure and vasodilator use were recorded simultaneously. Measurements and Main Results: Pulse oximetry bias (Spo-2-Sao-2) increased to an unacceptable range ( gt +3% or lt -3%) in 45.5% of the readings at foot probe site temperatures of ltoreq 27 degree C. Pulse oximetry bias was within an acceptable range in 94.7% of the readings at temperatures gt 29 degree C. There was no significant difference between oximeter readings obtained from two probe sites (hand and foot). Administration of phenoxybenzamine improved the accuracy of pulse oximetry in ten infants at skin temperature of lt 27 degree C. Conclusions: Pulse oximetry readings in small infants are likely to be unreliable at skin temperatures of lt 27 degree C, irrespective of probe site. Intravenous phenoxybenzamine appeared to improve the accuracy of pulse oximetry at low temperatures.