Systematic review of the association of venous oxygenation and outcome in adult hospitalized patients

The effects of general anaesthesia on oxygen consumption: A meta-analysis guiding future studies on perioperative oxygen transport

BACKGROUND

Increased oxygen extraction, the ratio of consumption to delivery, has been associated with poor outcome after surgery. Oxygen consumption (VO2) can change in several ways in the perioperative period, but is seldom monitored directly in routine care. This study investigates the effects of general anaesthesia on VO2.

METHODS

We searched PubMed, EMBASE, and Cochrane Library 1946-2018 for studies including VO2 measurements before and after anaesthesia induction. Quality was assessed by Cochrane risk of bias tool and NIH Quality Assessment tool for before-and-after studies. Changes in VO2 after anaesthesia induction were pooled in a random effects model meta-analysis with standardized mean differences transformed to absolute changes of VO2. Changes in VO2 after surgical incision and after recovery from anaesthesia were analysed as secondary outcomes in the included studies.

RESULTS

Twenty-four studies including 453 patients were analysed for VO2 changes induced by anaesthesia. Studies were published during 1969-2000 and mean age of patients ranged 28-70 years. VO2 decreased after anaesthesia induction by -65 (-75; -55, 95% CI) mL min^-1 and indexed VO2 (VO2I) by -33 (-38; -28, 95% CI) mL min^-1  m^-2 . After surgical incision and in the post-operative period VO2 increased again. Heterogeneity was considerable among the studies and the overall quality of evidence was very low.

CONCLUSIONS

General anaesthesia probably reduces oxygen consumption but the effect estimate is uncertain. Given the limited generalizability and low quality of the available evidence, new studies in modern perioperative settings and in today's older high-risk surgical patient populations are needed.

Peripheral measurements of venous oxygen saturation and lactate as a less invasive alternative for hemodynamic monitoring

Background

Peripheral measurement of venous oxygen saturation and lactate is a less invasive alternative to monitor tissue oxygenation as compared to measurements from a central venous catheter. However, there is a lack of evidence to support the use of peripheral measurements. In this study, we investigated the agreement between central and peripheral venous oxygen saturation and lactate.

Methods

We conducted a prospective observational study including 115 patients who underwent elective cardiac surgery between April and May 2015 at Rigshospitalet, Copenhagen, Denmark. Measurements were obtained simultaneously at induction of anaesthesia, upon arrival in the ICU and 3–4 h postoperatively. Bias and trending ability was identified using Bland-Altman analysis and a four-quadrant plot.

Results

Bias was 13.37% for venous oxygen saturation preoperatively (95% CI: 11.52–15.22, LoA: ±19.10, PE: 22.08%), 11.29% at arrival to the ICU (95% CI: 8.81–13.77, LoA: ±25.10, PE: 32.39%) and 16.49% at 3–4 h postoperatively (95% CI: 14.16–18.82, LoA: ±21.20, PE: 26.82%). A four-quadrant plot demonstrated an 89% concordance. Central and peripheral lactate showed a bias of 0.14 mmol/L preoperatively (95% CI: 0.11–0.17, LoA: ±0.30, PE: 32.08%), 0.16 mmol/L at arrival to ICU (95% CI: 0.09–0.23, LoA: ±0.70, PE: 38.88%) and 0.23 mmol/L at 3–4 h postoperatively (95% CI: 0.11–0.35, LoA: ±0.50, 25.18%).

Discussion

Measurements of peripheral oxygen saturation and lactate may be valuable in an emergency setting, avoiding unnecessary and time consuming application of a CVC.

Conclusion

We found a high bias but an acceptable trending ability between central and peripheral venous oxygenation. Central and peripheral lactate had excellent agreement. Further studies are necessary to validate the use of peripheral venous samples to identify patients at risk of impaired tissue oxygenation.