Lung Injury and Acute Respiratory Distress Syndrome After Cardiac Surgery

Postoperative Critical Care of the Adult Cardiac Surgical Patient. Part I: Routine Postoperative Care

OBJECTIVES

Cardiac surgery, including coronary artery bypass, cardiac valve, and aortic procedures, is among the most common surgical procedures performed in the United States. Successful outcomes after cardiac surgery depend on optimum postoperative critical care. The cardiac intensivist must have a comprehensive understanding of cardiopulmonary physiology and the sequelae of cardiopulmonary bypass. In this concise review, targeted at intensivists and surgeons, we discuss the routine management of the postoperative cardiac surgical patient.

DATA SOURCE AND SYNTHESIS

Narrative review of relevant English-language peer-reviewed medical literature.

CONCLUSIONS

Critical care of the cardiac surgical patient is a complex and dynamic endeavor. Adequate fluid resuscitation, appropriate inotropic support, attention to rewarming, and ventilator management are key components. Patient safety is enhanced by experienced personnel, a structured handover between the operating room and ICU teams, and appropriate transfusion strategies.

Extracorporeal life support for severe acute respiratory distress syndrome

PURPOSE OF REVIEW

To provide a summary of the recent literature on extracorporeal membrane oxygenation (ECMO) in adults with severe acute respiratory distress syndrome (ARDS), focusing on advances in equipment, current conventional and unconventional indications, complications, and future applications.

RECENT FINDINGS

ECMO use has increased during the past 5 years. Advances in cannulation, circuit design, and patient selection have made it a safer therapeutic option in severe ARDS, and its use has become more widespread for nonconventional indications.

SUMMARY

High-quality evidence for the routine use of ECMO for management of adult patients with severe ARDS is still lacking. An ongoing randomized controlled trial (ECMO to rescue lung injury in severe ARDS) will contribute valuable data to guide clinical decisions to opt for this supportive therapy.

Multiorgan protection of remote ischemic perconditioning in valve replacement surgery

BACKGROUND

Remote ischemic perconditioning (RIPerc) is a new alternative of remote ischemic conditioning and has not been well studied. RIPerc attenuates myocardial injury when applied during cardiac surgery. However, its protective effects on other organs remain unknown.

MATERIALS AND METHODS

Patients with rheumatic heart disease undergoing valve replacement surgery were randomized into the RIPerc group (n = 101) or the control group (n = 100). RIPerc was achieved by three cycles of 5-min ischemia-5-min reperfusion in the right thigh during surgery. Clinical data and the levels of injury biomarkers for the heart, lungs, liver, and kidneys within 48 h after surgery were compared using one-way or repeated measurement analysis of variance.

RESULTS

In the RIPerc group, the release of serum cardiac troponin I (128.68 ± 102.56 versus 172.33 ± 184.38, P = 0.04) and the inotropic score (96.4 ± 73.8 versus 121.5 ± 89.6, P = 0.032) decreased compared with that of the control; postoperative drainage (458.2 ± 264.2 versus 545.1 ± 349.0 ml, P = 0.048) and the incidence of acute lung injury was reduced (36.6% versus 51%, P = 0.04), and the extent of hyperbilirubinemia was also attenuated. No significant difference was observed in the levels of biomarkers for renal injury and systemic inflammation response.

CONCLUSIONS

RIPerc applied during the valve replacement surgery induced multiple beneficial effects postoperatively including reduced drainage and myocardial damage, lower incidence of acute lung injury, and attenuated hyperbilirubinemia.

Predictive factors for bleeding-related re-exploration after cardiac surgery: A prospective cohort study

BACKGROUND

Bleeding-related re-exploration is a life-threatening complication after cardiac surgery. Nurses must be aware of important risk factors for this complication so that their assessment, monitoring and evaluation activities can be prioritized, focused and anticipated.

AIMS

To identify the predictive factors for bleeding-related re-exploration after cardiac surgery and to describe the sources of postoperative bleeding.

METHODS

This is a prospective cohort study at a tertiary cardiac school-hospital in São Paulo/SP, Brazil. Adult patients (n=323) submitted to surgical correction of acquired cardiac diseases were included. Potential risk factors for bleeding-related re-exploration within the 24 hours following admission to the intensive care unit were investigated in the patients' charts. A univariate analysis and a multiple analysis through logistic regression were conducted to identify the outcome predictors. The area under the receiver-operating characteristic curve was calculated as a measure of accuracy considering the cut-off points with the highest sensitivity and specificity.

RESULTS

The univariate factors significantly associated with bleeding-related re-exploration were a lower preoperative platelet count, a lower number of bypasses in coronary artery bypass surgery and postoperatively, a lower body temperature, infusion of lower intravenous volume, a higher positive end-expiratory pressure during mechanical ventilation and transfusion of blood products. The independent predictors of bleeding-related re-exploration included postoperative red blood cell transfusion, and transfusion of fresh frozen plasma, platelet or cryoprecipitate units. These predictors had a sensitivity of 87.5%, a specificity of 99.28% and an accuracy of 97.93%.

CONCLUSIONS

Blood product transfusion postoperatively is an independent predictor of bleeding-related re-exploration. Surgical errors prevailed as sources of bleeding.

Fluid management in the cardiothoracic intensive care unit: diuresis--diuretics and hemofiltration

PURPOSE OF REVIEW

The present review discusses the current concepts of fluid management in cardiothoracic surgery, and its clinical implications with special reference to organ-related complications and their prevention.

RECENT FINDINGS

Current strategies in fluid management for cardiothoracic patients, various fluid formulation, and the preventive strategies for minimizing fluid-related complications are described, with particular reference to new discoveries and controversies that have arisen from recent literature.

SUMMARY

The optimal fluid management in cardiothoracic patients has not been settled. Results of recent clinical published trials highlight the need for minimizing fluid administration and attempting to use diuretics to achieve a negative fluid, although hypovolemia and hypoperfusion should be carefully considered. An individualized optimization of fluid status, using goal-directed therapy, has emerged as a possible preferable approach. The old debate between crystalloid and colloid solutions has been partially solved, as some colloids have demonstrated deleterious effect on renal function and coagulation system. Various preventive strategies have also emerged for minimizing fluid-related complications.

Procalcitonin as a predictor of moderate to severe acute respiratory distress syndrome after cardiac surgery with cardiopulmonary bypass: a study protocol for a prospective cohort study

INTRODUCTION

Procalcitonin (PCT) is activated during cardiopulmonary bypass (CPB) and may be a predictor of acute respiratory distress syndrome (ARDS). The objective of this study is to determine whether patients with different serum PCT concentrations exhibit different rates of developing moderate to severe ARDS.

METHODS AND ANALYSIS

This is a prospective, single centre, observational cohort study. All patients admitted to the cardiosurgery department for cardiac surgery with CPB were screened for study eligibility. All eligible patients received a CPB procedure. Blood samples were obtained to determine white cell counts as well as N-terminal pro-B-type natriuretic peptide, C reactive protein and PCT levels. Patients were assigned to the PCT elevated cohort or the control cohort based on serum PCT concentrations on the first postoperative day with a cut-off value of 7.0 ng/mL. Data, including baseline, perioperative and outcome data, were collected daily for 7 days. The primary end point was the incidence of moderate to severe ARDS, which was diagnosed according to the Berlin definition.

ETHICS AND DISSEMINATION

The study was approved by the Institutional Review Board of Fujian Provincial Hospital. Study findings are disseminated through peer-reviewed publications and conference presentations.

STUDY REGISTRATION

Chinese Clinical Trial Registry (ChiCTR-OCH-14005076).

Predicting risk of postoperative lung injury in high-risk surgical patients: a multicenter cohort study

BACKGROUND

Acute respiratory distress syndrome (ARDS) remains a serious postoperative complication. Although ARDS prevention is a priority, the inability to identify patients at risk for ARDS remains a barrier to progress. The authors tested and refined the previously reported surgical lung injury prediction (SLIP) model in a multicenter cohort of at-risk surgical patients.

METHODS

This is a secondary analysis of a multicenter, prospective cohort investigation evaluating high-risk patients undergoing surgery. Preoperative ARDS risk factors and risk modifiers were evaluated for inclusion in a parsimonious risk-prediction model. Multiple imputation and domain analysis were used to facilitate development of a refined model, designated SLIP-2. Area under the receiver operating characteristic curve and the Hosmer-Lemeshow goodness-of-fit test were used to assess model performance.

RESULTS

Among 1,562 at-risk patients, ARDS developed in 117 (7.5%). Nine independent predictors of ARDS were identified: sepsis, high-risk aortic vascular surgery, high-risk cardiac surgery, emergency surgery, cirrhosis, admission location other than home, increased respiratory rate (20 to 29 and ≥30 breaths/min), FIO2 greater than 35%, and SpO2 less than 95%. The original SLIP score performed poorly in this heterogeneous cohort with baseline risk factors for ARDS (area under the receiver operating characteristic curve [95% CI], 0.56 [0.50 to 0.62]). In contrast, SLIP-2 score performed well (area under the receiver operating characteristic curve [95% CI], 0.84 [0.81 to 0.88]). Internal validation indicated similar discrimination, with an area under the receiver operating characteristic curve of 0.84.

CONCLUSIONS

In this multicenter cohort of patients at risk for ARDS, the SLIP-2 score outperformed the original SLIP score. If validated in an independent sample, this tool may help identify surgical patients at high risk for ARDS.

Lung injury after simulated cardiopulmonary bypass in an isolated perfused rat lung preparation: Role of mitogen-activated protein kinase/Akt signaling and the effects of theophylline

Objectives

Lung deflation and inflation during cardiac surgery with cardiopulmonary bypass contributes to pulmonary dysfunction postoperatively. Theophylline treatment for lung diseases has traditionally been thought to act by phosphodiesterase inhibition; however, increasing evidence has suggested other plausible mechanisms. We investigated the effects of deflation and reinflation on signaling pathways (p38-mitogen-activated protein kinase [MAPK], extracellular signal-regulated kinase 1 and 2 [ERK1/2], and Akt) and whether theophylline influences the deflation-induced lung injury and associated signaling.

Methods

Isolated rat lungs were perfused (15 mL/min) with deoxygenated rat blood in bicarbonate buffer and ventilated. After 20 minutes' equilibration, the lungs were deflated (60 minutes, aerobic perfusion 1.5 mL/min), followed by reinflation (60 minutes, anaerobic reperfusion 15 mL/min). Compliance, vascular resistance, and kinase phosphorylation were assessed during deflation and reinflation. The effects of SB203580 (50 μM), a p38-MAPK inhibitor, and theophylline (0.083 mM [therapeutic] or 3 mM [supratherapeutic]) on physiology and signaling were studied.

Results

Deflation reduced compliance by 44% compared with continuously ventilated lungs. p38-MAPK and Akt phosphorylation increased (three to fivefold) during deflation and reinflation, and ERK1/2 phosphorylation increased (approximately twofold) during reinflation. SB203580 had no effect on lung physiology or ERK1/2 and Akt activation. Both theophylline doses increased cyclic adenosine monophosphate, but only 3 mM theophylline improved compliance. p38-MAPK phosphorylation was not affected by theophylline; 0.083 mM theophylline inhibited reinflation-induced ERK1/2 phosphorylation (72% ± 3%); and 3 mM theophylline inhibited Akt phosphorylation during deflation (75% ± 5%) and reinflation (87% ± 4%).

Conclusions

Lung deflation and reinflation stimulates differential p38-MAPK, ERK1/2, and Akt activation, suggesting a role in lung injury during cardiopulmonary bypass. However, p38-MAPK was not involved in the compromised compliance. A supratherapeutic theophylline dose protected lungs against deflation-induced injury and was associated with inhibition of phosphoinositide 3-kinase/Akt rather than phosphodiesterase.

Postoperative hypoxia and length of intensive care unit stay after cardiac surgery: the underweight paradox?

OBJECTIVE

Cardiac operations with cardiopulmonary bypass can be associated with postoperative lung dysfunction. The present study investigates the incidence of postoperative hypoxia after cardiac surgery, its relationship with the length of intensive care unit stay, and the role of body mass index in determining postoperative hypoxia and intensive care unit length of stay.

DESIGN

Single-center, retrospective study.

SETTING

University Hospital. Patients. Adult patients (N = 5,023) who underwent cardiac surgery with CPB.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

According to the body mass index, patients were attributed to six classes, and obesity was defined as a body mass index >30. POH was defined as a PaO2/FiO2 ratio <200 at the arrival in the intensive care unit. Postoperative hypoxia was detected in 1,536 patients (30.6%). Obesity was an independent risk factor for postoperative hypoxia (odds ratio 2.4, 95% confidence interval 2.05-2.78, P = 0.001) and postoperative hypoxia was a determinant of intensive care unit length of stay. There is a significant inverse correlation between body mass index and PaO2/FiO2 ratio, with the risk of postoperative hypoxia increasing by 1.7 folds per each incremental body mass index class. The relationship between body mass index and intensive care unit length of stay is U-shaped, with longer intensive care unit stay in underweight patients and moderate-morbid obese patients.

CONCLUSIONS

Obese patients are at higher risk for postoperative hypoxia, but this leads to a prolonged intensive care unit stay only for moderate-morbid obese patients. Obese patients are partially protected against the deleterious effects of hemodilution and transfusions. Underweight patients present the "paradox" of a better lung gas exchange but a longer intensive care unit stay. This is probably due to a higher severity of their cardiac disease.

The relationship between total red blood cells and plasma transfusion and acute lung injury risk after cardiac surgery: a retrospective study

The aim of our study was to determine whether red blood cells (RBCs) and fresh frozen plasma (FFP) transfusion is independently associated with the development of acute lung injury (ALI) in patients after cardiac surgery. In retrospective study, 165 patients were included. The results showed total fresh RBCs transfusion were not significantly increased in patients who developed ALI compared with patients who did not develop ALI (4.7 ± 2.4, 4 [0-12] units VS 4.0 ± 1.9, 3 [0-9] units, P = 0.119). FFP transfusion were also not significantly increased (704.1 ± 832.5, 600 [150-6500] ml VS 533.9 ± 323.6, 400 [125-3100] ml, P = 0.053). Multivariable logistic regression analysis showed that only age and CPB time were independent factors for ALI, but not for total RBCs and FFP transfused, with the adjusted OR 0.952 (95% CI 0.762-1.189, P=0.664), and 1.000 (95% CI 0.999-1.001, P = 0.480), respectively. In subgroup analysis, female patients showed a lower ALI incidence in low RBCs transfused group (23.9% VS 45.0%, OR 0.38, 95% CI 0.15-0.98) and in low FFP transfused group (22.0% VS 44.4%, OR 0.35, 95% CI 0.14-0.90). Our study demonstrates that red blood cells and fresh-frozen plasma transfusion are not related with ALI after cardiac surgery in our institution.

The postoperative airway: unique challenges?

PURPOSE OF REVIEW

The review is focused on the challenge of managing airway and ventilation in the intraoperative and postoperative period.

RECENT FINDINGS

In past years, a lot of attention was focused on tracheal intubation in difficult airway, whereas only in recent years extubation time of difficult airway is also covering an important role. Protective ventilation strategies have been studied in acute respiratory distress syndrome and then in general anesthesia, either for thoracic or bariatric surgery, whereas in general abdominal surgery, in healthy lung, few studies are present demonstrating the effective protective role of low tidal volume, lung recruitment maneuvers (LRM) and positive end-expiratory pressure (PEEP). In the early postoperative period, the role of noninvasive ventilation is growing as it reduces postoperative pulmonary complications, postoperative length of stay and costs.

SUMMARY

The combination of planning extubation of predicted and unpredicted difficult airway, both intraoperative low tidal volume and low FiO2 with LRM and PEEP at different points of surgery and postoperative noninvasive ventilation should be considered in patients undergoing surgery to decrease the rate of postoperative pulmonary complications and major fatal complications such as brain damage and death.

Adult respiratory distress syndrome following cardiac surgery

BACKGROUND

Severe lung injury with the development of acute respiratory distress syndrome (ARDS) is a serious complication of cardiac surgery. The aim of this study was to determine the incidence, risk factors, and mortality of ARDS following cardiac surgery.

METHODS

We retrospectively analyze data in the period between January 2005 and March 2013.

RESULTS

Of 6069 patients who underwent cardiac surgery during the study period, 37 patients developed ARDS during the postoperative period. The incidence of ARDS was 0.61%, with a mortality of 40.5% (15 patients). Multivariate regression analysis identified previous cardiac surgery, complex cardiac surgery, and more than three transfusions with packed red blood cells (PRBC) were independent predictors for developing ARDS.

CONCLUSIONS

ARDS remains a serious, but very rare complication associated with significant mortality. In our study, previous cardiac surgery, complex cardiac surgery, and more than three transfusions of PRBC were independent predictors for the development of ARDS.

Expression of cytotoxic T-lymphocyte antigen 4 on CD4+ and CD8+ T cells is increased in acute lung injury

Acute lung injury (ALI) is a severe form of diffuse lung disease, which imposes a substantial health burden all over the world. The immune system plays a key role in the development of ALI. The aim of the study was to investigate the expression of cytotoxic T-lymphocyte antigen 4 (CTLA4) in ALI. Levels of CTLA4 were tested on CD4+ and CD8+ T cells in 62 ALI cases and 75 healthy controls by flow cytometry. Data revealed that prevalence of CTLA4 on CD4+ T cells was significantly increased in ALI patients (3.7%±2.1%) than in controls (0.7%±0.3%). Similarly, the proportion of CTLA4 on CD8+ T cells was also significantly elevated in cases (1.0%±0.4% versus 0.5%±0.1%, p<0.05). Further analysis showed that the frequency of CTLA4+CD4+ T cells was positively correlated with the score of Acute Physiology and Chronic Health Evaluation II (APACHE II) (p=0.0005). In addition, when investigating CTLA4 expression with ALI patient mortality, we observed that the level of CTLA4+CD4+ T cells in patients was higher at the time before death than at the time of recruitment (p=0.001). These data suggested that CTLA4 was involved in the pathogenesis and progression of ALI and could be used as a potential target for treating this disease.