Ventilation strategies with different inhaled Oxygen conceNTration during CardioPulmonary Bypass in cardiac surgery (VONTCPB): study protocol for a randomized controlled trial

Effect of static lung expansion on pulmonary function following cardiopulmonary bypass in children

Objective

To observe the effect of the lung-protective ventilation strategy, static lung expansion, during cardiopulmonary bypass (CPB) on pulmonary function and tracheal intubation time following cardiac surgery in children.

Methods

A total of 48 child patients (aged 1-3) with ventricular septal defect (VSD) were enrolled, and all underwent CPB cardiac surgery for the first time. The patients were divided into two groups using the random number table method: the experimental group (Group A, n = 30) and the control group (Group B, n = 18). After terminating the mechanical ventilation during CPB, the adjustable pressure limiting valve of the anesthesia machine was adjusted in the experimental group to maintain the pressure of the breathing circuit at 5 cmH2O, such that both lungs remained in a static expansion state. In the control group, routine mechanical ventilation was terminated as usual.

Results

When static lung expansion with a continuous positive airway pressure of 5 cmH2O was employed in the VSD children during CPB, compared with termination of mechanical ventilation, the partial pressure of oxygen in the arterial blood increased, while the respiratory index decreased and the oxygenation index increased following the surgery.

Conclusion

In child patients undergoing VSD reparation under CPB, lung injury occurs following the procedure, and the pulmonary oxygenation function and pulmonary oxygen diffusion function decrease. When static lung expansion of 5 cmH2O is performed during CPB, the improvement in lung function is better than that of apnea without lung expansion pressure.

Hyperoxemia During Cardiac Surgery Is Associated With Postoperative Pulmonary Complications

The use of hyperoxemia during cardiac surgery remains controversial. We hypothesized that intraoperative hyperoxemia during cardiac surgery is associated with an increased risk of postoperative pulmonary complications.

DESIGN

Retrospective cohort study.

SETTING

We analyzed intraoperative data from five hospitals within the Multicenter Perioperative Outcomes Group between January 1, 2014, and December 31, 2019. We assessed intraoperative oxygenation of adult patients undergoing cardiac surgery with cardiopulmonary bypass (CPB). Hyperoxemia pre and post CPB was quantified as the area under the curve (AUC) of Fio₂ above 0.21 in minutes when the corresponding peripheral oxygen saturation was greater than 92% measured by pulse oximetry. We quantified hyperoxemia during CPB as the AUC of Pao₂ greater than 200 mm Hg measured by arterial blood gas. We analyzed the association of hyperoxemia during all phases of cardiac surgery with the frequency of postoperative pulmonary complications within 30 days, including acute respiratory insufficiency or failure, acute respiratory distress syndrome, need for reintubation, and pneumonia.

PATIENTS

Twenty-one thousand six hundred thirty-two cardiac surgical patients.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

During 21,632 distinct cardiac surgery cases, 96.4% of patients spent at least 1 minute in hyperoxemia (99.1% pre-CPB, 98.5% intra-CPB, and 96.4% post-CPB). Increasing exposure to hyperoxemia was associated with an increased risk of postoperative pulmonary complications throughout three distinct surgical periods. During CPB, increasing exposure to hyperoxemia was associated with an increased odds of developing postoperative pulmonary complications (p < 0.001) in a linear manner. Hyperoxemia before CPB (p < 0.001) and after CPB (p = 0.02) were associated with increased odds of developing postoperative pulmonary complications in a U-shaped relationship.

CONCLUSIONS

Hyperoxemia occurs almost universally during cardiac surgery. Exposure to hyperoxemia assessed continuously as an AUC during the intraoperative period, but particularly during CPB, was associated with an increased incidence of postoperative pulmonary complications.

Positive end-expiratory pressure and risk of postoperative pulmonary complications in patients living at high altitudes and undergoing surgery at low altitudes: a single-centre, retrospective observational study in China

OBJECTIVES

To examine whether a high positive end-expiratory pressure (PEEP ≥5 cmH₂O) has a protective effect on the risk of postoperative pulmonary complications (PPCs) in a cohort of patients living at high altitudes and undergoing general anaesthesia.

DESIGN

Retrospective, observational study.

SETTING

A tertiary hospital in China.

PARTICIPANTS

Adult Tibetan patients living at high altitudes (≥3000 m) and who went to the low-altitude plain to undergo non-cardiothoracic surgery under general anaesthesia, from January 2018 to April 2020.

MEASUREMENTS

This study included 1905 patients who were divided according to the application of an intraoperative PEEP: low PEEP (<5 cmH₂O, including 0 cmH₂O) or high PEEP (≥5 cmH₂O). The primary outcome was a composite of PPCs within the first 7 postoperative days. The secondary outcomes included reintubation and unplanned intensive care unit (ICU) admission within the first 7 postoperative days and total hospital stays (day).

RESULTS

The study included 1032 patients in the low PEEP group and 873 in the high PEEP group. There were no differences in the incidence of PPCs between the high and low PEEP groups (relative risk (RR) 0.913; 95% CI 0.716 to 1.165; p=0.465). After propensity score matching, 643 patients remained in each group, and the incidence of PPCs in the low PEEP group (18.0%) was higher than in the high PEEP group (13.7%; RR 0.720; 95% CI 0.533 to 0.974; p=0.033). There were no differences in the incidence of reintubation, unplanned ICU admission or hospital stays. The risk factors of PPCs derived from multiple regression showed that the application of >5 cmH₂O PEEP during intraoperative mechanical ventilation was associated with a significantly lower risk of PPCs in patients from a high altitude (OR=0.725, 95% CI 0.530 to 0.992; p=0.044).

CONCLUSIONS

The application of PEEP ≥5 cmH₂O during intraoperative mechanical ventilation in patients living at high altitudes and undergoing surgery at low altitudes may be associated with a lower risk of PPCs. Prospective longitudinal studies are needed to further investigate perioperative lung protection ventilation strategies for patients from high altitudes.

TRIAL REGISTRATION NUMBER

Chinese Clinical Trial Registry (ChiCTR2100044260).

Effect of ventilation strategy during cardiopulmonary bypass on postoperative pulmonary complications after cardiac surgery: a randomized clinical trial

BACKGROUND

To determine whether maintaining ventilation during cardiopulmonary bypass (CPB) with a different fraction of inspired oxygen (FiO₂) had an impact on the occurrence of postoperative pulmonary complications (PPCs).

METHODS

A total of 413 adult patients undergoing elective cardiac surgery with CPB were randomly assigned into three groups: 138 in the NoV group (received no mechanical ventilation during CPB), 138 in the LOV group (received a tidal volume (V_T) of 3-4 ml/kg of ideal body weight with the respiratory rate of 10-12 bpm, and the positive end-expiratory pressure of 5-8 cmH₂O during CPB; the FiO₂ was 30%), and 137 in the HOV group (received the same ventilation parameters settings as the LOV group while the FiO₂ was 80%).

RESULTS

The primary outcomes were the incidence and severity of PPCs during hospitalization. The composite incidence of PPCs did not significantly differ between the NoV (63%), LOV (49%) and HOV (57%) groups (P = 0.069). And there was also no difference regarding the incidence of PPCs between the non-ventilation (NoV) and ventilation (the combination of LOV and HOV) groups. The LOV group was observed a lower proportion of moderate and severe pulmonary complications (grade ≥ 3) than the NoV group (23.1% vs. 44.2%, P = 0.001).

CONCLUSION

Maintaining ventilation during CPB did not reduce the incidence of PPCs in patients undergoing cardiac surgery.

TRIAL REGISTRATION

Chinese Clinical Trial Registry ChiCTR1800015261. Prospectively registered 19 March 2018. http://www.chictr.org.cn/showproj.aspx?proj=25982.

The Impact of Anesthetic Regimen on Outcomes in Adult Cardiac Surgery: A Narrative Review

Despite improvements in surgical techniques and perioperative care, cardiac surgery still is burdened by relatively high mortality and frequent major postoperative complications, including myocardial dysfunction, pulmonary complications, neurologic injury, and acute kidney injury. Although the surgeon's skills and volume and patient- and procedure-related risk factors play a major role in the success of cardiac surgery, there is growing evidence that also optimizing perioperative care may improve outcomes significantly. The present review focuses on the aspects of perioperative care that are strictly related to the anesthesia regimen, with special reference to volatile anesthetics and neuraxial anesthesia, whose effect on outcome in adult cardiac surgery has been investigated extensively.