Nasogastric Tube Insertion Using Different Techniques in Anesthetized Patients

Abstract

P ulse oximeters can be reusable or disposable. The design of the reusable probe enhances proper alignment of the lightemitting diode (LED) with the photodetector. With the disposable probes, the alignment of the LED and photodetector depends entirely on how carefully the operator places the probe on the patient's finger. This report discusses 3 cases in which misaligned disposable adhesive pulse oximeter probes gave false intraoperative saturation readings that led to unnecessary invasive interventions or changes in anesthesia management.Case 1: A woman, aged 39 years, was undergoing total knee replacement. The disposable probe gave a preoperative oxygen saturation reading of 99% while she was on 100% oxygen. During anesthesia maintenance, the fraction of inspired oxygen (FIO 2 ) was kept at 30%. During surgery, the oximeter reading gradually decreased to 88%, although the plethysmographic tracing quality indicated good signal quality. The endotracheal tube was correctly placed and the tracheobronchial tree was clear. Nitrous oxide was reduced to increase the FIO 2 from 97% to 99%. The anesthesia team checked the probe and found that the light source and detector were misaligned axially along the finger by approximately 15 mm. A new probe was placed, with a misalignment distance of 2 mm. The reading was 100% with an FIO 2 of 95%, which was gradually reduced to 30%. Her saturation reading was 97% or higher during the rest of the surgery.Case 2: A woman, aged 37 years, was to undergo thoracoscopic surgery to remove a left upper lobe lung mass. The disposable probe was placed, and the initial reading was 99% while she was breathing 100% oxygen. During fiber-optic bronchoscopy, the reading was 96% to 98% with an FIO 2 of 97%. The FIO 2 was 99% during right-sided 1-lung ventilation but gradually declined to 94%. The double-lumen tube was correctly placed, and the tracheobronchial tree was clear. When the probe was checked, the misalignment distance, axially along the finger, was 10 mm. A new probe was placed, and it gave a reading of 100%, which remained at 100% with an FIO 2 of 99% during 1-lung ventilation throughout the rest of the surgery.Case 3: A man, aged 71 years, was to have a right common femoral endarterectomy. A disposable probe was placed and showed a preoperative saturation of 98% to 99% with 100% oxygen. The FIO 2 was kept at 30% during maintenance of anesthesia when the reading was 96% to 97%. It gradually decreased to 93%; the patient's arterial blood pressure and heart rate were stable. When the FIO 2 was initially increased to 52%, the saturation increased to 95% but then decreased to 93%, although the FIO 2 was increased to 95%. An arterial blood gas determination was inconsistent with the measured saturation of 91% to 92%. A new probe was placed and immediately registered a reading of 99% to 100%, with the patient receiving an FIO 2 of 29%. The first probe, on the patient's left middle finger, had a misalignment distance of greater than 20 mm. When it was removed and reapplied to the patient's fi...