EVALUATION OF PULSE OXIMETRY IN HORSES SURGICALLY TREATED FOR COLIC

All 43 horses anaesthetised for colic surgery were premedicated with x ylazine or diazepam. Anaesthesia was induced with guaifenesin and keta mine, horses were placed in dorsal recumbency and anaesthesia was main tained with isoflurane in oxygen and mechanical ventilation. Haemoglob in saturation readings (SpO2) were taken with a pulse oximeter and com pared with computed haemoglobin saturation (SaO2) from arterial blood samples. Readings were taken over a range of SaO2 of 78-100%, mean art erial blood pressure ranged from 24 to 108 mmHg and PaO2 ranged from 5 3 to 490 mmHg. Analysis of 107 readings showed that SpO2 values predic ted SaO2 but time, blood pressure and individual horse did not. Correl ation coefficients between SpO2 and SaO2 were 0.85 for all values and 0.88 for values at 30 min. Values for bias and precision were calculat ed for all SpO2 values and for readings separated into 3 saturation gr oups: normal, low normal, and abnormal. The pulse oximeter tended to u nderestimate SaO2 at all times, and was less precise as the saturation decreased.