Influence of central venous oxygen saturation on in-hospital mortality of surgical patients

[Perioperative central venous oxygen saturation and its correlation with mortality during cardiac surgery: an observational prospective study]

BACKGROUND

Cardiac surgery can produce persistent deficit in the ratio of Oxygen Delivery (DO₂) to Oxygen Consumption (VO₂). Central venous oxygen Saturation (ScvO₂) is an accessible and indirect measure of DO₂/VO₂ ratio.

OBJECTIVE

To monitor perioperative ScvO₂ and assess its correlation with mortality during cardiac surgery.

METHODS

This prospective observational study evaluated 273 patients undergoing cardiac surgery. Blood gas samples were collected to measure ScvO₂ at three time points: T0 (after anesthetic induction), T1 (end of surgery), and T2 (24hours after surgery). The patients were divided into two groups (survivors and nonsurvivors). The following outcomes were analyzed: intrahospital mortality, length of Intensive Care Unit (ICU) and hospital stay (LOS), and variation in ScvO₂.

RESULTS

Of the 273 patients, 251 (92%) survived and 22 (8%) did not. There was a significant perioperative reduction of ScvO₂ in both survivors (T0=78%± 8.1%, T1=75.4%±7.5%, and T2=68.5%±9%; p<0.001) and nonsurvivors (T0=74.4%±8.7%, T1=75.4%±7.7%, and T2=66.7%±13.1%; p <0.001). At T0, the percentage of patients with ScvO₂ <70% was greater in the nonsurvivor group (31.8% vs. 13.1%; p=0.046) and the multiple logistic regression showed that ScvO₂ is an independent risk factor associated with death, OR=2.94 (95% CI 1.10-7.89) (p=0.032). The length of ICU and LOS were 3.6±3.1 and 7.4±6.0 days respectively and was not significantly associated with ScvO₂.

CONCLUSIONS

Early intraoperative ScvO₂ <70% indicated a higher risk of death. A perioperative reduction of ScvO₂ was observed in patients undergoing cardiac surgery, with high intraoperative and lower postoperative levels.

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.

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

BACKGROUND

Adequate tissue oxygenation is necessary to maintain organ function. Low venous oxygen saturation may reflect impaired tissue oxygenation, and may be used as a predictive tool and a therapeutic target to improve the care of critically ill patients. We therefore conducted a systematic review of the existing literature reflecting these aspects.

METHODS

We searched electronic databases in January 2016 for relevant studies on venous oxygen saturation for treatment guidance and patient outcome. We sub-grouped results based on patient groups and setting.

RESULTS

The search resulted in 5590 papers of which 42 studies were deemed relevant. The majority of the studies in cardiac and abdominal surgery patients showed associations between low venous oxygen saturation and increased mortality and morbidity, in particular increased length of intensive care. However, the cut-off level for low venous oxygen saturation varied between < 55 and 70% and all studies had high risk of bias. In patients with septic shock, recent randomized trials showed no benefit of early resuscitation guided by venous oxygen saturation.

CONCLUSION

Low venous oxygen saturation may be associated with increased mortality, morbidity and length of intensive care in patients following cardiac or abdominal surgery. However, the wide range of cut-off levels and low quality of evidence hampers the clinical application. In patients with septic shock, the present evidence does not support goal-directed therapy using venous oxygen saturation during early resuscitation.

Continuous central venous oxygen saturation assisted intraoperative hemodynamic management during major abdominal surgery: a randomized, controlled trial

Background

Major abdominal surgery is associated with significant risk of morbidity and mortality in the perioperative period. Optimising intraoperative fluid administration may result in improved outcomes. Our aim was to compare the effects of central venous pressure (CVP), and central venous oxygen saturation (ScvO₂)-assisted fluid therapy on postoperative complications in patients undergoing high risk surgery.

Methods

Patients undergoing elective major abdominal surgery were randomised into control and ScvO₂ groups. The target level of mean arterial pressure (MAP) was ≥ 60 mmHg in both groups. In cases of MAP < 60 mmHg patients received either a fluid or vasopressor bolus according to the CVP < 8 mmHg in the control group. In the ScvO₂ group, in addition to the MAP, an ScvO₂ of <75 % or a >3 % decrease indicated need for intervention, regardless of the actual MAP. Data are presented as mean ± standard deviation or median (interquartile range).

Results

We observed a lower number of patients with complications in the ScvO₂ group compared to the control group, however it did not reach statistical significance (ScvO₂ group: 10 vs. control group: 19; p = 0.07). Patients in the ScvO₂ group (n = 38) received more colloids compared to the control group (n = 41) [279(161) vs. 107(250) ml/h; p < 0.001]. Both groups received similar amounts of crystalloid (1126 ± 471 vs. 1049 ± 431 ml/h; p = 0.46) and norepinephrine [37(107) vs. 18(73) mcg/h; p = 0.84]. Despite similar blood loss in both groups, the ScvO₂ group received more blood transfusions (63 % vs. 37 %; p = 0.018). More patients in the control group had a postoperative PaO₂/FiO₂ < 200 mmHg (23 vs. 10, p < 0.01). Twenty eight day survival was significantly higher in the ScvO₂ group (37/38 vs. 33/41 p = 0.018).

Conclusion

ScvO₂-assisted intraoperative haemodynamic support provided some benefits, including significantly better postoperative oxygenation and 28 day survival rate, compared to CVP-assisted therapy without a significant effect on postoperative complications during major abdominal surgery.

Trial registration

ClinicalTrials.gov NCT02337010.

Can we Improve Outcome in High Risk Surgery?

Despite the small number of high-risk surgical patients in comparison to all surgical patients, they account for the largest proportion of overall perioperative mortality. Goal directed hemodynamic support may result in a lower incidence of complications and reduced length of hospital stay in these patients. Beyond the standard monitoring of circulation, such as blood pressure and heart rate, further parameters and procedures such as pulse pressure/stroke volume variation-, stroke volume/cardiac index-, and central venous oxygen saturation-guided resuscitation may improve the outcome of high-risk surgical patients. The aim of this review is to focus on the results of animal and clinical studies investigating the usefulness of these indices in the context of goal-directed perioperative support.