Current Ventilator and Oxygen Management during General Anesthesia: A Multicenter, Cross-sectional Observational Study.

BACKGROUND: Intraoperative oxygen management is poorly understood. It was hypothesized that potentially preventable hyperoxemia and substantial oxygen exposure would be common during general anesthesia. METHODS: A multicenter, cross-sectional study was conducted to describe current ventilator management, particularly oxygen management, during general anesthesia in Japan. All adult patients (16 yr old or older) who received general anesthesia over 5 consecutive days in 2015 at 43 participating hospitals were identified. Ventilator settings and vital signs were collected 1 h after the induction of general anesthesia. We determined the prevalence of potentially preventable hyperoxemia (oxygen saturation measured by pulse oximetry of more than 98%, despite fractional inspired oxygen tension of more than 0.21) and the risk factors for potentially substantial oxygen exposure (fractional inspired oxygen tension of more than 0.5, despite oxygen saturation measured by pulse oximetry of more than 92%). RESULTS: A total of 1,786 patients were found eligible, and 1,498 completed the study. Fractional inspired oxygen tension was between 0.31 and 0.6 in 1,385 patients (92%), whereas it was less than or equal to 0.3 in very few patients (1%). Most patients (83%) were exposed to potentially preventable hyperoxemia, and 32% had potentially substantial oxygen exposure. In multivariable analysis, old age, emergency surgery, and one-lung ventilation were independently associated with increased potentially substantial oxygen exposure, whereas use of volume control ventilation and high positive end-expiratory pressure levels were associated with decreased potentially substantial oxygen exposure. One-lung ventilation was particularly a strong risk factor for potentially substantial oxygen exposure (adjusted odds ratio, 13.35; 95% CI, 7.24 to 24.60). CONCLUSIONS: Potentially preventable hyperoxemia and substantial oxygen exposure are common during general anesthesia, especially during one-lung ventilation. Future research should explore the safety and feasibility of a more conservative approach for intraoperative oxygen therapy.

Blood flow-dependent changes in intrarenal nitric oxide levels during anesthesia with halothane or sevoflurane.

We previously demonstrated that intrarenal nitric oxide (NO) levels and renal blood flow are reduced during halothane anesthesia. Studies were performed to determine if volatile anesthetics-induced reductions in renal NO levels are associated with blood flow changes. Halothane and sevoflurane at 0.8 and 2.4 Mac were administered by inhalation to dogs, and cGMP and NOx concentrations in the renal interstitial fluid were measured by a microdialysis method. Neither halothane nor sevoflurane at 0.8 Mac altered renal blood flow and renal interstitial cyclic guanosine monophosphate (cGMP) and NOx levels, but both anesthetics significantly decreased these values at 2.4 Mac. Using an adjustable aortic clamp, renal perfusion pressure was reduced in 2 steps without halothane and sevoflurane anesthesia. Renal blood flow as well as cGMP and NOx concentrations in the renal interstitial fluid were unchanged within the autoregulatory range, but significantly decreased below the autoregulatory range. Changes in cGMP and NOx concentrations in the renal interstitial fluid were highly correlated with renal blood flow changes during halothane or sevoflurane anesthesia, and during stepwise reductions in renal perfusion pressure. The results suggested that halothane- and sevoflurane-induced decreases in intrarenal NO levels result from reductions in blood flow.