USE OF PaO2 IN HEMOGLOBINOPATHIESINTRODUCTION Hemoglobinopathiesare the group of disorders in which pulseoximetrymay be useful for diagnosis, but not for the effective intra-operative management. Hemoglobin MIWATE is one such abnormal hemoglobin which is unable to carry oxygen to peripheral tissues.

One yearchild with no comorbidities was admitted for cleft palate repair. Pulseoximeter showed a saturation of 87%.An arterial blood gas analysis showed the PaO2 of 287 and calculated SaO2 of 99.1% on supplemental oxygen. Surgery was postponed for further evaluation. Detailed evaluation includingHbelectrophoresis found an unknown fast moving band (13.2%) with retention timing of 4.77 minutes. DNA analysis confirmed the abnormal variant to be Hemoglobin MIWATE. Elective surgery was planned after diagnosis was established whereinmonitoring of ventilation remained our utmost priority in addition to intermittent arterial blood gas analysis to monitor oxygenation. After the surgery, the child had an uneventful recovery

Hemoglobin MIWATE has completely different absorption spectra from that of methemoglobinruling out co-oximetry as an option for intraoperative monitoring1.Devices that monitor peripheral oxygen content (Masimo Radical 7) was considered, but not found useful as it calculates the oxygen content based on normograms derived from normal haemoglobin. Continuous intra-arterial blood gas analysis may be worth considering, but the availability and cost-effectiveness remains a question. Considering these limitations, monitoring PaO2 and end tidal gas concentration are simple and cost-effective methods to ensure peripheral tissue oxygenation.

1.Kikuchi G,HayashiN,Tamura A.Oxygen equilibrium of hemoglobin MIwate.BiochimBiophysActa 1964;90:199–201.