Derivation and diagnostic accuracy of the surgical lung injury prediction model. Anesthesiology. 2011;115:117-128. [PMID: 21694510 DOI: 10.1097/aln.0b013e31821b5839]

Postoperative acute respiratory distress syndrome in patients with previous exposure to bleomycin

OBJECTIVE

To determine the incidence and risk factors for postoperative acute respiratory distress syndrome (ARDS) in a large cohort of bleomycin-exposed patients undergoing surgery with general endotracheal anesthesia.

PATIENTS AND METHODS

From a Mayo Clinic cancer registry, we identified patients who had received systemic bleomycin and then underwent a major surgical procedure that required more than 1 hour of general anesthesia from January 1, 2000, through August 30, 2012. Heart, lung, and liver transplantations were excluded. Postoperative ARDS (within 7 days after surgery) was defined according to the Berlin criteria.

RESULTS

We identified 316 patients who underwent 541 major surgical procedures. Only 7 patients met the criteria for postoperative ARDS; all were white men, and 6 were current or former smokers. On univariate analysis, we observed an increased risk of postoperative ARDS in patients who were current or former smokers. Furthermore, significantly greater crystalloid and colloid administration was found in patients with postoperative ARDS. We also observed a trend toward longer surgical duration and red blood cell transfusion in patients with postoperative ARDS, although this finding was not significant. Intraoperative fraction of inspired oxygen was not associated with postoperative ARDS. In bleomycin-exposed patients, the incidence of postoperative ARDS after major surgery with general anesthesia is approximately 1.3% (95% CI, 0.6%-2.6%). For first major procedures after bleomycin therapy, the incidence is 1.9% (95% CI, 0.9%-4.1%).

CONCLUSION

The risk of postoperative ARDS in patients exposed to systemic bleomycin appears to be lower than expected. Smoking status may be an important factor that modifies the risk of postoperative ARDS in these patients.

Towards prevention of acute syndromes: electronic identification of at-risk patients during hospital admission

BACKGROUND

Identifying patients at risk for acute respiratory distress syndrome (ARDS) before their admission to intensive care is crucial to prevention and treatment. The objective of this study is to determine the performance of an automated algorithm for identifying selected ARDS predisposing conditions at the time of hospital admission.

METHODS

This secondary analysis of a prospective cohort study included 3,005 patients admitted to hospital between January 1 and December 31, 2010. The automated algorithm for five ARDS predisposing conditions (sepsis, pneumonia, aspiration, acute pancreatitis, and shock) was developed through a series of queries applied to institutional electronic medical record databases. The automated algorithm was derived and refined in a derivation cohort of 1,562 patients and subsequently validated in an independent cohort of 1,443 patients. The sensitivity, specificity, and positive and negative predictive values of an automated algorithm to identify ARDS risk factors were compared with another two independent data extraction strategies, including manual data extraction and ICD-9 code search. The reference standard was defined as the agreement between the ICD-9 code, automated and manual data extraction.

RESULTS

Compared to the reference standard, the automated algorithm had higher sensitivity than manual data extraction for identifying a case of sepsis (95% vs. 56%), aspiration (63% vs. 42%), acute pancreatitis (100% vs. 70%), pneumonia (93% vs. 62%) and shock (77% vs. 41%) with similar specificity except for sepsis and pneumonia (90% vs. 98% for sepsis and 95% vs. 99% for pneumonia). The PPV for identifying these five acute conditions using the automated algorithm ranged from 65% for pneumonia to 91 % for acute pancreatitis, whereas the NPV for the automated algorithm ranged from 99% to 100%.

CONCLUSION

A rule-based electronic data extraction can reliably and accurately identify patients at risk of ARDS at the time of hospital admission.

Airway pepsin levels in otherwise healthy surgical patients receiving general anesthesia with endotracheal intubation

BACKGROUND

Airway pepsin has been increasingly used as a potentially sensitive and quantifiable biomarker for gastric-to-pulmonary aspiration, despite lack of validation in normal control subjects. This study attempts to define normal levels of airway pepsin in adults and distinguish between pepsin A (exclusive to stomach) and pepsin C (which can be expressed by pneumocytes).

METHODS

We performed a prospective study of 51 otherwise healthy adult patients undergoing elective extremity orthopedic surgery at a single tertiary-care academic medical center. Lower airway samples were obtained immediately following endotracheal intubation and just prior to extubation. Total pepsin and pepsin A concentrations were directly measured by an enzymatic activity assay, and pepsin C was subsequently derived. Pepsinogen/pepsin C was confirmed by Western blot analyses. Baseline characteristics were secondarily compared.

RESULTS

In all, 11 (22%; 95% CI = 9.9%-33%) had detectable airway pepsin concentrations. All 11 positive specimens had pepsin C, without any detectable pepsin A. Pepsinogen/pepsin C was confirmed by Western blot analyses. In a multivariate logistic regression, men were more likely to have airway pepsin (OR, 12.71, P = .029).

CONCLUSIONS

Enzymatically active pepsin C, but not the gastric-specific pepsin A, is frequently detected in the lower airways of patients who otherwise have no risk for aspiration. This suggests that nonspecific pepsin assays should be used and interpreted with caution as a biomarker of gastropulmonary aspiration, as pepsinogen C potentially expressed from pneumocytes may be detected in airway samples.

Predicting postoperative pulmonary complications in the general population

PURPOSE OF REVIEW

Postoperative pulmonary complications (PPCs) are common and lead to longer hospital stays and higher mortality. A wide range of patient, anaesthetic and surgical factors have been associated with risk for PPCs. This review discusses our present understanding of PPC risk factors that can be used to plan preoperative risk reduction strategies. The methodological and statistical basis for building risk scores is also described.

RECENT FINDINGS

Studies in specific surgical populations or large patient samples have identified a range of predictors of PPC risk. Factors such as age, types of comorbidity and surgical characteristics have been found to be relevant in most of these studies. Recently, researchers have begun to develop risk scoring systems for a PPC composite outcome or for specific PPCs, especially pneumonia and respiratory failure. Preoperative arterial oxyhaemoglobin saturation is an objective measure that is easy to record and discriminates level of risk for impaired cardiorespiratory function. Preoperative anaemia and recent respiratory infection are factors that have lately been found to confer risk for PPCs.

SUMMARY

PPC risk prediction scales based on large population studies are being developed. New studies to confirm the validity of these scales in different geographic areas will be needed before we can be sure of their generalizability.

Nonventilatory strategies to prevent postoperative pulmonary complications

PURPOSE OF REVIEW

In this review, we aimed at providing the most recent and relevant clinical evidence regarding the use of nonventilatory strategies to prevent postoperative pulmonary complications (PPCs) after noncardiac surgery.

RECENT FINDINGS

Although nonavoidable, most comorbidities can be modified in order to reduce the incidence of pulmonary events postoperatively. The physical status of patients suffering from chronic obstructive pulmonary disease, asthma, obstructive sleep apnea, and congestive heart failure can be improved preoperatively, and a number of measures can be undertaken to prevent PPCs, including physiotherapy for pulmonary rehabilitation and drug therapies. Also, smokers may benefit from both short and long-term smoke cessation. Furthermore, the risk of PPCs may be reduced upon: choice of an adequate anesthesia strategy (e.g. regional vs. general); appropriate neuromuscular blockade and reversal; use of volatile instead of intravenous anesthetics in lung surgery; judicious intravascular volume expansion (restrictive vs. liberal strategy); regional instead of systemic analgesia after major surgery in high-risk patients; more strict indication for nasogastric decompression in order to avoid silent aspiration; and laparoscopic instead of open bariatric surgery.

SUMMARY

Nonventilatory strategies can play an important role in reducing PPCs and improving clinical outcome after noncardiac surgery, especially in high-risk patients.

Predicting postoperative pulmonary complications in high-risk populations

PURPOSE OF REVIEW

Our objective is to describe prediction models for surgical patients who have suspected obstructive sleep apnea (OSA) at risk for postoperative respiratory complications and for surgical patients at risk for postoperative acute respiratory distress syndrome (ARDS).

RECENT FINDINGS

Because of the increased rate of severe perioperative respiratory complications in patients with OSA, the American Society of Anesthesiologists issued practice guidelines for perioperative management. When OSA is diagnosed preoperatively, the rate of postoperative pulmonary complications is low and not associated with OSA severity. However, OSA continues to be an important risk because a substantial proportion of patients in the contemporary surgical population have undiagnosed OSA. Strategies based on preoperative and immediate postoperative clinical signs and symptoms can help identify patients with a high likelihood of OSA, postoperative desaturations, and pulmonary complications. ARDS is another serious postoperative complication associated with high mortality rate and limited treatment options, and its prevention is critical. Practice changes have led to a dramatic reduction in ARDS incidence. A recently developed prediction model can help identify high-risk patients.

SUMMARY

Evidence is emerging that early identification of modifiable risk factors and implementation of 'protective' management strategies may lead to reduction of severe postoperative pulmonary complications.

Plasma angiopoietin-2 predicts the onset of acute lung injury in critically ill patients

RATIONALE

Current clinical prediction scores for acute lung injury (ALI) have limited positive predictive value. No studies have evaluated predictive plasma biomarkers in a broad population of critically ill patients or as an adjunct to clinical prediction scores.

OBJECTIVES

To determine whether plasma angiopoietin-2 (Ang-2), von Willebrand factor (vWF), interleukin-8 (IL-8), and/or receptor for advanced glycation end products (sRAGE) predict ALI in critically ill patients.

METHODS

Plasma samples were drawn from critically ill patients (n = 230) identified in the emergency department. Patients who had ALI at baseline or in the subsequent 6 hours were excluded, and the remaining patients were followed for development of ALI.

MEASUREMENTS AND MAIN RESULTS

Nineteen patients developed ALI at least 6 hours after the sample draw. Higher levels of Ang-2 and IL-8 were significantly associated with increased development of ALI (P = 0.0008, 0.004, respectively). The association between Ang-2 and subsequent development of ALI was robust to adjustment for sepsis and vasopressor use. Ang-2 and the Lung Injury Prediction Score each independently discriminated well between those who developed ALI and those who did not (area under the receiver operating characteristic curve, 0.74 for each), and using the two together improved the area under the curve to 0.84 (vs. 0.74, P = 0.05). In contrast, plasma levels of sRAGE and vWF were not predictive of ALI.

CONCLUSIONS

Plasma biomarkers such as Ang-2 can improve clinical prediction scores and identify patients at high risk for ALI. In addition, the early rise of Ang-2 emphasizes the importance of endothelial injury in the early pathogenesis of ALI.

Risk factors for postoperative respiratory mortality and morbidity in patients undergoing coronary artery bypass grafting

ABSTRACT

Nowadays, coronary artery bypass grafting (CABG) is considered to be one of the most common surgical procedures. This procedure has been the main topic in many clinical research studies, which have assessed the effect of the procedure on patients’ outcomes. Like other surgical procedures, this procedure is also accompanied by a number of unwanted complications, including those of the respiratory system. Since the respiratory system plays an integral role in defining the clinical outcome of patients, improvements in studies that can assess and predict clinical outcomes of the respiratory system, assume greater importance. There are a number of predictive models which can assess patients in the preoperative period and introduce a number of risk factors, which could be considered as prognostic factors for patients undergoing CABG. The respiratory system is among the clinical systems that are assessed in many prediction scoring systems. This review assesses the main studies which have evaluated the possible risk factors for postoperative respiratory mortality and morbidity, in patients undergoing CABG.

Electronic health record surveillance algorithms facilitate the detection of transfusion-related pulmonary complications

BACKGROUND

Transfusion-related acute lung injury (TRALI) and transfusion-associated circulatory overload (TACO) are leading causes of transfusion-related mortality. Notably, poor syndrome recognition and underreporting likely result in an underestimate of their true attributable burden. We aimed to develop accurate electronic health record-based screening algorithms for improved detection of TRALI/transfused acute lung injury (ALI) and TACO.

STUDY DESIGN AND METHODS

This was a retrospective observational study. The study cohort, identified from a previous National Institutes of Health-sponsored prospective investigation, included 223 transfused patients with TRALI, transfused ALI, TACO, or complication-free controls. Optimal case detection algorithms were identified using classification and regression tree (CART) analyses. Algorithm performance was evaluated with sensitivities, specificities, likelihood ratios, and overall misclassification rates.

RESULTS

For TRALI/transfused ALI detection, CART analysis achieved a sensitivity and specificity of 83.9% (95% confidence interval [CI], 74.4%-90.4%) and 89.7% (95% CI, 80.3%-95.2%), respectively. For TACO, the sensitivity and specificity were 86.5% (95% CI, 73.6%-94.0%) and 92.3% (95% CI, 83.4%-96.8%), respectively. Reduced PaO2 /FiO2 ratios and the acquisition of posttransfusion chest radiographs were the primary determinants of case versus control status for both syndromes. Of true-positive cases identified using the screening algorithms (TRALI/transfused ALI, n = 78; TACO, n = 45), only 11 (14.1%) and five (11.1%) were reported to the blood bank by physicians, respectively.

CONCLUSIONS

Electronic screening algorithms have shown good sensitivity and specificity for identifying patients with TRALI/transfused ALI and TACO at our institution. This supports the notion that active electronic surveillance may improve case identification, thereby providing a more accurate understanding of TRALI/transfused ALI and TACO epidemiology.

Low Tidal Volume Ventilation in Patients without Acute Respiratory Distress Syndrome: A Paradigm Shift in Mechanical Ventilation

Protective ventilation with low tidal volume has been shown to reduce morbidity and mortality in patients suffering from acute lung injury (ALI) and acute respiratory distress syndrome (ARDS). Low tidal volume ventilation is associated with particular clinical challenges and is therefore often underutilized as a therapeutic option in clinical practice. Despite some potential difficulties, data have been published examining the application of protective ventilation in patients without lung injury. We will briefly review the physiologic rationale for low tidal volume ventilation and explore the current evidence for protective ventilation in patients without lung injury. In addition, we will explore some of the potential reasons for its underuse and provide strategies to overcome some of the associated clinical challenges.