Original Article

Transient Hypoxemia Upon Initiation of Cardiopulmonary Bypass

From the Perfusion Service, Baystate Medical Center, Springfield, Massachusetts

^* Address for reprints: Charlene H. Rohrer, Cardiac Surgery, Baystate Medical Center, 759 Chestnut Street, Springfield, Massachusetts 01107

Abstract

A review of 38 consecutive coronary artery bypass perfusions was undertaken with the goal to determine the efficiency of oxygenation with the BOS-10 oxygenator. In reviewing these 38 cases, six (16%) showed surprisingly low initial arterial oxygen tension (PaO₂ 56–70 torr). These six patients required active remedial measures to correct this deficit which was corrected within 10 minutes of continued perfusion. In addition, there were five more patients (13%) with initial PaO₂ 70–100 torr, or a total of eleven (29%) of the 38 cases with less than optimal PaO₂. All of the initial blood gases were drawn after stabilization of perfusion flows and pressures, discontinuation of patient ventilation, and the initiation of moderate hypothermia (30°C). No explanation could be found for this transient hypoxemia which appeared to correlate only with a higher hematocrit in patients with the lowest oxygen tensions.

It has been observed that, on occasion, an unacceptably low arterial oxygen tension (PaO₂) develops during the initial phase of routine perfusion. This observation prompted a review of the last 38 consecutive coronary artery bypass perfusions done in this institution. The review has shown that eleven (28.9%) of the cases done with the BOS-1 0* oxygenator had PaO₂’s less than 100 torr. An attempt was therefore made to delineate the factors involved and to try to isolate the problem. Realizing fully that at a PaO₂ of 70 torr, the hemoglobin is still well saturated, and probably is not detrimental to the anesthetized patient, six patients (16%) had truly depressed oxygenation with PaO₂ 56–0 torr and in these six patients, arterial desaturation could become a factor in successful perfusion.