Intraoperative monitoring of pHi as a predictor of successful extubation at the end of major abdominal operations

Introduction

Reintubation following failed extubation is an independent predictor of prolonged ICU stay, morbidity and mortality. Extubation criteria at the end of surgical procedures are similar to those applied to critically ill patients in mechanical ventilation.

Patients and methods

This prospective, observational, non-interventional study was conducted in a teaching University Surgical Clinic. Data from all consecutive patients that underwent elective major abdominal operations by a single surgeon in a 6-month period were recorded and examined. In all patients, 30 min prior to the induction of anesthesia, a nasogastric tonometry catheter was inserted and measurements were obtained by a tonometer. At the end of the operation, the optimal goal was successful extubation unless prevented by the patient's general condition. Patients were extubated when they complied with the following criteria: patient alert and rested, arterial pH > 7.25, PO₂ > 60 mmHg with FiO₂ < 50% and positive end expiratory pressure (PEEP) < 5 cmH₂O, PCO₂ < 50 mmHg, tidal volume > 5 ml/kg, respiratory rate < 24/min, negative inspiratory force more than -20 cmH₂O, minute ventilation <10 l/min, stable hemodynamic status, hemoglobin >10 mg/dl, presence of cough and no excessive or thick secretions. Extubation failure was defined as the need for reintubation within 24 hours.

Results

Twenty-four consecutive patients (11 males, 13 females) of mean age of 66.79 years (range: 27–85), who underwent elective major abdominal operations, were included in the study. Mean operative time was 3.16 hours (range: 1.8–4.5). Patients were divided into two groups based on extubation outcome. Twenty-two of the patients met the extubation criteria at the end of the procedure and were therefore extubated. Three of these patients required reintubation within the next hour due to acute respiratory failure. One patient was not extubated due to acidosis (arterial pH < 7.25, hypothermia: 35.5°C) and one other patient was not extubated as his hemoglobin level had dropped to 8 mg/dl. Consequently, 19 patients that were successfully extubated were included in group I and five patients were included in group II.

Mean values of baseline measurements for pHi in the two groups were similar (P = 0.773). In all patients, the mean pHi value at induction of anesthesia compared with the means of 30-min and 60-min measurements differed significantly (P < 0.001). pHi values decreased for the first 2 hours of operating time in a linear pattern. Thereafter, pHi values appeared stable. No further decrease was observed until the end of the operation. The mean pHi values at the end of the operation between the two groups differed significantly (P = 0.027, confidence interval: -6.175 to -0.408).

Conclusion

Early detection of extubation failure in the operative room will save time and will orient resuscitation efforts towards more beneficial actions for the patient (hypothermia prevention, volume depletion, hemodynamic stability).