Characteristics and outcomes of patients hospitalized following pulmonary aspiration.

BACKGROUND: Pulmonary aspiration is an important recognized cause of ARDS. Better characterization of patients who aspirate may allow identification of potential risks for aspiration that could be used in future studies to mitigate the occurrence of aspiration and its devastating complications. METHODS: We conducted a secondary analysis of the Lung Injury Prediction Score cohort to better characterize patients with aspiration, including their potential risk factors and related outcomes. RESULTS: Of the 5,584 subjects at risk for ARDS and who required hospitalization, 212 (3.8%) presented with aspiration. Subjects who aspirated were likely to be male (66% vs 56%, P < .007), slightly older (59 years vs 57 years), white (73% vs 61%, P = .0004), admitted from a nursing home (15% vs 5.9%, P < .0001), have a history of alcohol abuse (21% vs 8%, P < .0001), and have lower Glasgow Coma Scale (median, 13 vs 15; P < .0001). Aspiration subjects were sicker (higher APACHE [Acute Physiology and Chronic Health Evaluation] II score), required more mechanical ventilation (54% vs 32%, P < .0001), developed more moderate to severe ARDS (12% vs 3.8%, P < .0001), and were twofold more likely to die in-hospital, even after adjustment for severity of illness (OR = 2.1; 95% CI, 1.2-3.6). Neither obesity nor gastroesophageal reflux was associated with aspiration. CONCLUSIONS: Aspiration was more common in men with alcohol abuse history and a lower Glasgow Coma Scale who were admitted from a nursing home. It is independently associated with a significant increase in the risk for ARDS as well as morbidity and mortality. Findings from this study may facilitate the design of future clinical studies of aspiration-induced lung injury.

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.

Contemporary ventilator management in patients with and at risk of ALI/ARDS.

BACKGROUND: Ventilator practices in patients at risk for acute lung injury (ALI) and ARDS are unclear. We examined factors associated with choice of set tidal volumes (VT), and whether VT < 8 mL/kg predicted body weight (PBW) relates to the development of ALI/ARDS. METHODS: We performed a secondary analysis of a multicenter cohort of adult subjects at risk of lung injury with and without ALI/ARDS at onset of invasive ventilation. Descriptive statistics were used to describe ventilator practices in specific settings and ALI/ARDS risk groups. Logistic regression analysis was used to determine the factors associated with the use of VT < 8 mL/kg PBW and the relationship of VT to ALI/ARDS development and outcome. RESULTS: Of 829 mechanically ventilated patients, 107 met the criteria for ALI/ARDS at time of intubation, and 161 developed ALI/ARDS after intubation (post-intubation ALI/ARDS). There was significant intercenter variability in initial ventilator settings, and in the incidence of ALI/ARDS and post-intubation ALI/ARDS. The median VT was 7.96 (IQR 7.14-8.94) mL/kg PBW in ALI/ARDS subjects, and 8.45 (IQR 7.50-9.55) mL/kg PBW in subjects without ALI/ARDS (P = .004). VT decreased from 8.40 (IQR 7.38-9.37) mL/kg PBW to 7.97 (IQR 6.90-9.23) mL/kg PBW (P < .001) in those developing post-intubation ALI/ARDS. Among subjects without ALI/ARDS, VT ≥ 8 mL/kg PBW was associated with shorter height and higher body mass index, while subjects with pneumonia were less likely to get ≥ 8 mL/kg PBW. Initial VT ≥ 8 mL/kg PBW was not associated with the post-intubation ALI/ARDS (adjusted odds ratio 1.30, 95% CI 0.74-2.29) or worse outcomes. Post-intubation ALI/ARDS subjects had mortality similar to subjects intubated with ALI/ARDS. CONCLUSIONS: Clinicians seem to respond to ALI/ARDS with lower initial VT. Initial VT, however, was not associated with the development of post-intubation ALI/ARDS or other outcomes.

Sex, race, and the development of acute lung injury.

BACKGROUND: Prior studies suggest that mortality differs by sex and race in patients who develop acute lung injury (ALI). Whether differences in presentation account for these disparities remains unclear. We sought to determine whether sexual and racial differences exist in the rate of ALI development and ALI-related mortality after accounting for differences in clinical presentations. METHODS: This was a multicenter, observational cohort study of 5,201 patients at risk for ALI. Multivariable logistic regression with adjustment for center-level effects was used to adjust for potential covariates. RESULTS: The incidence of ALI development was 5.9%; in-hospital mortality was 5.0% for the entire cohort, and 24.4% for those patients who developed ALI. Men were more likely to develop ALI compared to women (6.9% vs 4.7%, P , .001) and had a nonsignificant increase in mortality when ALI developed (27.6% vs 18.5%, P 5 .08). However, after adjustment for baseline imbalances between sexes these differences were no longer significant. Black patients, compared to white patients, presented more frequently with pneumonia, sepsis, or shock and had higher severity of illness. Black patients were less likely to develop ALI than whites (4.5% vs. 6.5%, P 5 .014), and this association remained statistically significant after adjusting for differences in presentation (OR, 0.66; 95 % CI, 0.45-0.96). CONCLUSIONS: Sex and race differences exist in the clinical presentation of patients at risk of developing ALI. After accounting for differences in presentation, there was no sex difference in ALI development and outcome. Black patients were less likely to develop ALI despite increased severity of illness on presentation.

Early identification of patients at risk of acute lung injury: evaluation of lung injury prediction score in a multicenter cohort study.

RATIONALE: Accurate, early identification of patients at risk for developing acute lung injury (ALI) provides the opportunity to test and implement secondary prevention strategies. OBJECTIVES: To determine the frequency and outcome of ALI development in patients at risk and validate a lung injury prediction score (LIPS). METHODS: In this prospective multicenter observational cohort study, predisposing conditions and risk modifiers predictive of ALI development were identified from routine clinical data available during initial evaluation. The discrimination of the model was assessed with area under receiver operating curve (AUC). The risk of death from ALI was determined after adjustment for severity of illness and predisposing conditions. MEASUREMENTS AND MAIN RESULTS: Twenty-two hospitals enrolled 5,584 patients at risk. ALI developed a median of 2 (interquartile range 1-4) days after initial evaluation in 377 (6.8%; 148 ALI-only, 229 adult respiratory distress syndrome) patients. The frequency of ALI varied according to predisposing conditions (from 3% in pancreatitis to 26% after smoke inhalation). LIPS discriminated patients who developed ALI from those who did not with an AUC of 0.80 (95% confidence interval, 0.78-0.82). When adjusted for severity of illness and predisposing conditions, development of ALI increased the risk of in-hospital death (odds ratio, 4.1; 95% confidence interval, 2.9-5.7). CONCLUSIONS: ALI occurrence varies according to predisposing conditions and carries an independently poor prognosis. Using routinely available clinical data, LIPS identifies patients at high risk for ALI early in the course of their illness. This model will alert clinicians about the risk of ALI and facilitate testing and implementation of ALI prevention strategies. Clinical trial registered with www.clinicaltrials.gov (NCT00889772).

Perioperative management of obstructive sleep apnea.

Obstructive sleep apnea (OSA) is the most common breathing disorder, with a high prevalence in both the general and surgical populations. OSA is frequently undiagnosed, and the initial recognition often occurs during medical evaluation undertaken to prepare for surgery. Adverse respiratory and cardiovascular outcomes are associated with OSA in the perioperative period; therefore, it is imperative to identify and treat patients at high risk for the disease. In this review, we discuss the epidemiology of OSA in the surgical population and examine the available data on perioperative outcomes. We also review the identification of high-risk patients using clinical screening tools and suggest intraoperative and postoperative treatment regimens. Additionally, the role of continuous positive airway pressure in perioperative management of OSA and a brief discussion of ambulatory surgery in patients with OSA is provided. Finally, an algorithm to guide perioperative management is suggested.

Assessing the predictive value of the bispectral index vs patient state index on clinical assessment of sedation in postoperative cardiac surgery patients.

PURPOSE: To compare the depth of sedation determined by Ramsay sedation scale (RSS) with electroencephalogram-based bispectral index (BIS) and patient state index (PSI). MATERIALS AND METHODS: Fifty mechanically ventilated cardiac surgical patients undergoing propofol and morphine sedation were assessed hourly for up to 6 hours or until tracheal extubation using the BIS, PSI, and RSS. Correlation between RSS, BIS, and PSI was determined, as well as the interrater reliability of RSS, BIS, and PSI. kappa statistics was used to further evaluate the agreement between BIS and PSI. RESULTS: There was positive correlation between BIS and PSI values (rho = 0.731, P < .001). The average weighted kappa coefficient was .40 between the BIS and PSI, 0.28 between the RSS and BIS, and 0.16 between the RSS and PSI. Intraclass correlation was consistently higher between the BIS and PSI at all time intervals during the study. Logistic regression modeling over study duration showed that the BIS was consistently better at predicting oversedation (area under the curve, 0.92) than the PSI (area under the curve, 0.78). A comparison of BIS and PSI receiver operating characteristic curves showed that the BIS monitor was a better predictor of oversedation compared with the PSI (P = .02). CONCLUSIONS: There is significant positive correlation between the BIS and PSI but poor correlation and poor test agreement between the RSS and BIS as well as RSS and PSI. The BIS is a better predictor of oversedation compared with the PSI. There was no significant difference between the BIS and PSI with respect to the prediction of undersedation.

Trends and outcomes of malignant hyperthermia in the United States, 2000 to 2005.

BACKGROUND: Malignant hyperthermia (MH) is a potentially fatal pharmacogenetic disorder with an estimated mortality of less than 5%. The purpose of this study was to evaluate the current incidence of MH and the predictors associated with in-hospital mortality in the United States. METHODS: The Nationwide Inpatient Sample, which is the largest all-payer inpatient database in the United States, was used to identify patients discharged with a diagnosis of MH during the years 2000-2005. The weighted exact Cochrane-Armitage test and multivariate logistic regression analyses were used to assess trends in the incidence and risk-adjusted mortality from MH, taking into account the complex survey design. RESULTS: From 2000 to 2005, the number of cases of MH increased from 372 to 521 per year. The occurrence of MH increased from 10.2 to 13.3 patients per million hospital discharges (P = 0.001). Mortality rates from MH ranged from 6.5% in 2005 to 16.9% in 2001 (P < 0.0001). The median age of patients with MH was 39 (interquartile range, 23-54 yr). Only 17.8% of the patients were children, who had lower mortality than adults (0.7% vs. 14.1%, P < 0.0001). Logistic regression analyses revealed that risk-adjusted in-hospital mortality was associated with increasing age, female sex, comorbidity burden, source of admission to hospital, and geographic region of the United States. CONCLUSIONS: The incidence of MH in the United States has increased in recent years. The in-hospital mortality from MH remains elevated and higher than previously reported. The results of this study should enable the identification of areas requiring increased focus in MH-related education.

Intraoperative fluid restriction predicts improved outcomes in major vascular surgery.

BACKGROUND: Traditional fluid resuscitation during general anesthesia has been questioned in recent studies. One study of patients undergoing abdominal surgery showed decreased postoperative weight gain, earlier return of bowel function, and shorter intensive care unit (ICU) and hospital length of stay (LOS) when intraoperative crystalloid infusion was restricted. The authors conducted a retrospective study of major vascular surgery patients (neo-aorto iliac system surgery) to correlate clinical outcomes with intraoperative crystalloid fluid administration. METHODS: The charts of 41 patients who underwent major vascular surgery at our institution were reviewed. Patients were grouped according to the crystalloid volume infused intraoperatively into <3 L (group 1) and >3 L (group 2). Preoperative and postoperative weights, intraoperative crystalloid administration, intraoperative vasopressor use, preoperative and postoperative creatinine, number of days to clear liquid diet, and the time to discharge from the ICU (ICU LOS) and hospital (hospital LOS) were collected. RESULTS: There were statistically significant differences in duration of mechanical ventilation (0.55 +/- 0.934 vs 2.03 +/- 2.735 days, P = .013) and ICU LOS (3.0 +/- 1.48 vs 5.79 +/- 3.938, P = .029) in favor of the fluid restriction group. Major postoperative complications, such as sepsis, acute myocardial infarction, and graft thrombosis, were less frequent in the fluid restriction group but not statistically significant (5 vs 9, P = .742). Intraoperative crystalloid volume was found to be an independent predictor of ICU LOS after adjusting for estimated blood loss and duration of surgery. There was no statistically significant difference in preoperative serum albumin in both groups. CONCLUSIONS: Restricted intraoperative administration of crystalloid fluids (<3 L) may be beneficial in major vascular surgery patients. These benefits are similar to those previously described in patients undergoing abdominal surgery.

Hospitalists and anesthesiologists as perioperative physicians: Are their roles complementary?

In recent years, there has been an increased emphasis on the role of anesthesiologists as perioperative physicians. However, a new group of physicians called hospitalists has emerged and established a role as perioperative physicians. Most hospitalists have specialized in internal medicine and its subspecialties. We reviewed American medical literature over the last 13 years on the roles of anesthesiologists and hospitalists as perioperative physicians. Results showed that the concept of the anesthesiologist as the perioperative physician is strongly supported by the American Board of Anesthesiology and the leaders of the specialty. However, most anesthesiologists limit their practice to intraoperative care and immediate acute postoperative care in the postanesthesia care unit. The hospitalists may fill a different role by caring for patients in the preoperative and sometimes in the postoperative period, allowing the surgeon to focus on surgery. These roles of the anesthesiologists and the hospitalists as perioperative physicians may be complementary. We conclude that if anesthesiologists and hospitalists work together as peri-operative physicians, with each specialty bringing its expertise to the care of the perioperative patient, care is likely to improve. It is necessary to be proactive and identify areas of future cooperation and collaboration.

Risk of noncardiac surgery after coronary drug-eluting stent implantation.

We examined the records of 38 patients who underwent 41 major and 18 minor noncardiac surgeries after successful drug-eluting stent (DES) implantation (57% sirolimus-eluting stents and 43% paclitaxel-eluting stents) at the Dallas Veterans Affairs Medical Center from April 2003 to January 2006. The mean patient age was 62 +/- 9 years, and all patients were men. A total of 41 major noncardiac surgeries (34% abdominal, 22% vascular, 17% genitourinary, and 27% other) were performed in 28 patients a median of 260 days after DES implantation. Also, 18 minor noncardiac surgeries (44% skin surgery, 44% injections, and 12% other) were performed in 10 patients a median of 297 days after DES implantation. No major adverse cardiac events or death occurred during or after the 41 major (0%, 95% confidence interval 0% to 9%) and 18 minor noncardiac (0%, 95% confidence interval 0% to 19%) surgeries. In conclusion, although our data were limited by the small sample size, they suggest a low risk of major cardiac complications in patients undergoing noncardiac surgery after coronary DES implantation.

Management of perioperative myocardial infarction in noncardiac surgical patients.

Perioperative myocardial infarction (PMI) is a major cause of morbidity and mortality in patients undergoing noncardiac surgery. The incidence of PMI varies depending on the method used for diagnosis and is likely to increase as the population ages. Studies have examined different methods for prevention of myocardial infarction (MI), including the use of perioperative beta-blockers, alpha(2)-agonists, and statin therapy. However, few studies have focused on the treatment of PMI. Current therapy for acute MI generally involves anticoagulation and antiplatelet therapy, raising the potential for surgical site hemorrhage in this population. This article reviews the possible mechanisms, diagnosis, and treatment options for MI in the surgical setting. We also suggest algorithms for treatment.

Comparison of knowledge of perioperative care in primary care residents versus anesthesiology residents.

Primary care physicians (internal medicine and family practice) are often asked to evaluate patients before surgery and prepare them for the procedure. The goal of our study was to examine primary care and anesthesiology resident physicians' knowledge of preoperative evaluation and preparation as well as perioperative changes during anesthesia and surgery. To this end, a questionnaire was sent to primary care resident physicians and anesthesiology resident physicians in our university hospital system. One hundred twenty questionnaires were distributed, and the overall response rate was 50.8%. Although there was agreement between anesthesiology and primary care residents in many of the areas surveyed, differences were observed in questions related to appropriateness of preoperative instructions regarding medications, utility of routine preoperative testing, and identification of expected physiologic changes during anesthesia and surgery. Of the maximum possible 36 points, the mean score for anesthesiology residents (27.55) was higher than the mean scores for primary care residents (21.4 and 20.24 for internal medicine and family practice, respectively), although overall scores were generally lower than expected for both anesthesiology and primary care residents. The level of training of the respondents did not significantly affect the responses. We conclude that primary care resident physicians were knowledgeable about most perioperative care, although some deficiencies were identified when these residents were compared with anesthesiology residents. Surveys such as ours may be used to identify areas of deficiencies that require further education for both groups of residents.

Ventilator-associated lung injury in patients without acute lung injury at the onset of mechanical ventilation.

OBJECTIVE: Although ventilation with small tidal volumes is recommended in patients with established acute lung injury, most others receive highly variable tidal volume aimed in part at normalizing arterial blood gas values. We tested the hypothesis that acute lung injury, which develops after the initiation of mechanical ventilation, is associated with known risk factors for ventilator-induced lung injury such as ventilation with large tidal volume. DESIGN: Retrospective cohort study. SETTING: Four intensive care units in a tertiary referral center. PATIENTS: Patients who received invasive mechanical ventilation for > or = 48 hrs between January and December 2001. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: The main outcome of interest, acute lung injury, was assessed by independent review of daily digital chest radiographs and arterial blood gases. Ventilator settings, hemodynamics, and acute lung injury risk factors were extracted from the Acute Physiology and Chronic Health Evaluation III database and the patients' medical records. Of 332 patients who did not have acute lung injury from the outset, 80 patients (24%) developed acute lung injury within the first 5 days of mechanical ventilation. When expressed per predicted body weight, women were ventilated with larger tidal volume than men (mean 11.4 vs. 10.4 mL/kg predicted body weight, p <.001) and tended to develop acute lung injury more often (29% vs. 20%, p =.068). In a multivariate analysis, the main risk factors associated with the development of acute lung injury were the use of large tidal volume (odds ratio 1.3 for each mL above 6 mL/kg predicted body weight, p <.001), transfusion of blood products (odds ratio, 3.0; p < 0.001), acidemia (pH < 7.35; odds ratio, 2.0; p =.032) and a history of restrictive lung disease (odds ratio, 3.6; p =.044). CONCLUSIONS: The association between the initial tidal volume and the development of acute lung injury suggests that ventilator-associated lung injury may be an important cause of this syndrome. Height and gender should be considered when setting up the ventilator. Strong consideration should be given to limiting large tidal volume, not only in patients with established acute lung injury but also in patients at risk for acute lung injury.