Michael D. Maile

A Description of Intraoperative Ventilator Management in Patients with Acute Lung Injury and the Use of Lung Protective Ventilation Strategies

Background:The incidence of acute lung injury (ALI) in hypoxic patients undergoing surgery is currently unknown. Previous studies have identified lung protective ventilation strategies that are beneficial in the treatment of ALI. The authors sought to determine the incidence and examine the use of lung protective ventilation strategies in patients receiving anesthetics with a known history of ALI. Methods:The ventilation parameters that were used in all patients were reviewed, with an average preoperative Paco2/Fio2 ratio of ≤ 300 between January 1, 2005 and July 1, 2009. This dataset was then merged with a dataset of patients screened for ALI. The median tidal volume, positive end-expiratory pressure, peak inspiratory pressures, fraction inhaled oxygen, oxygen saturation, and tidal volumes were compared between groups. Results:A total of 1,286 patients met criteria for inclusion; 242 had a diagnosis of ALI preoperatively. Comparison of patients with ALI versus those without ALI found statistically yet clinically insignificant differences between the ventilation strategies between the groups in peak inspiratory pressures and positive end-expiratory pressure but no other category. The tidal volumes in cc/kg predicted body weight were approximately 8.7 in both groups. Peak inspiratory pressures were found to be 27.87 cm H2O on average in the non-ALI group and 29.2 in the ALI group. Conclusion:Similar ventilation strategies are used between patients with ALI and those without ALI. These findings suggest that anesthesiologists are not using lung protective ventilation strategies when ventilating patients with low Paco2/Fio2 ratios and ALI, and instead are treating hypoxia and ALI with higher concentrations of oxygen and peak pressures.

Worsening preoperative heart failure is associated with mortality and noncardiac complications, but not myocardial infarction after noncardiac surgery: a retrospective cohort study.

BACKGROUND:Heart failure (HF) is an important risk factor for perioperative morbidity and mortality. While these patients are at high risk for cardiac adverse events, there are few current data describing the types of noncardiac complications that occur in this population. METHODS:We performed a multicenter cohort study of patients undergoing noncardiac surgery from 2005 to 2010 as part of the American College of Surgeons National Surgical Quality Improvement Program. A HF cohort (HF that is new or worsening within 30 days of surgery) was compared with a control cohort that was matched regarding other surgical risk factors. RESULTS:Five thousand ninety-four patients with worsening preoperative HF were compared with an otherwise similar cohort of patients without worsening preoperative HF. Worsening preoperative HF was associated with increased risk of 30-day all-cause mortality (relative risk [RR] 2.08; 95% confidence interval [CI], 1.75–2.46; P < 0.001) and increased risk of morbidity (any recorded postoperative complication) (RR 1.54; 95% CI, 1.40–1.69; P < 0.001). HF patients had increased risk of developing renal failure (RR 1.85; 95% CI, 1.37–2.49; P < 0.001), need for mechanical ventilation longer than 48 hours (RR 1.81; 95% CI, 1.52–2.15; P < 0.001), pneumonia (RR 1.73; 95% CI, 1.44–2.08; P < 0.001), cardiac arrest (RR 1.69; 95% CI, 1.29–2.21; P < 0.001), unplanned intubation (RR 1.68; 95% CI, 1.41–1.99; P < 0.001), renal insufficiency (RR 1.64; 95% CI, 1.10–2.44; P = 0.014), sepsis (RR 1.43, 95% CI, 1.24–1.64; P < 0.001), and urinary tract infection (RR 1.29; 95% CI, 1.06–1.58; P = 0.011). The incidence of myocardial infarction in the sample was similar between the 2 groups (RR 1.07; 95% CI, 0.75–1.52; P = 0.719). CONCLUSIONS:Worsening preoperative HF is associated with a significant increase in postoperative morbidity and mortality when controlling for other comorbidities. Although these likely have a multifactorial etiology, patients are much more likely to suffer from respiratory, renal, and infectious complications than cardiac complications.

Automated Alerting and Recommendations for the Management of Patients with Preexisting Hypoxia and Potential Acute Lung Injury: A Pilot Study

Background:Acute lung injury (ALI) is associated with high mortality. Low tidal volume (Vt) ventilation has been shown to reduce mortality in ALI patients in the intensive care unit. Anesthesiologists do not routinely provide lung-protective ventilation strategies to patients with ALI in the operating room. The authors hypothesized that an alert, recommending lung-protective ventilation regarding patients with potential ALI, would result in lower Vt administration. Methods:The authors conducted a randomized controlled trial on anesthesia providers caring for patients with potential ALI. Patients with an average or last collected ratio of partial pressure of arterial oxygen to inspired fraction of oxygen less than 300 were randomized to providers being sent an alert with a recommended Vt of 6 cc/kg predicted body weight or conventional care. Primary outcomes were Vt/kg predicted body weight administered to patients. Secondary outcomes included ventilator parameters, length of postoperative ventilation, and death. Results:The primary outcome was a clinically significant reduction in mean Vt from 508–458 cc (P = 0.033), with a reduction in Vt when measured in cc/kg predicted body weight from 8 to 7.2 cc/kg predicted body weight (P = 0.040). There were no statistically significant changes in other outcomes or adverse events associated with either arm. Conclusions:Automated alerts generated for patients at risk of having ALI resulted in a statistically significant reduction in Vt administered when compared with a control group. Further research is required to determine whether a reduction in Vt results in decreased mortality and/or postoperative duration of mechanical ventilation.

Timing of Preoperative Troponin Elevations and Postoperative Mortality After Noncardiac Surgery.

BACKGROUND:Even small elevations in preoperative troponin levels have been shown to be associated with adverse outcomes. However, there are currently limited data on the relationship between troponin increase and timing of surgery. METHODS:We performed a single-institution, retrospective cohort study of 6030 individuals with a troponin measurement made during the 30 days preceding a noncardiac surgical procedure. Subjects with detectable troponin levels were separated into terciles based on both the magnitude of the value and the time elapsed between this value and the surgery. For those undergoing nonemergent procedures, these 9 cohorts were compared with the group of individuals with undetectable preoperative troponin levels using bivariable and multivariable logistic regression. RESULTS:Thirty-day mortality was 4.7% in the group with undetectable troponin levels and increased with higher concentrations, with rates of 8.9%, 12.7%, and 12.7% in the low, medium, and high tercile groups, respectively. Unadjusted risk of 30-day mortality was highest in those with the highest troponin levels and shortest duration between the measurement and surgery (odds ratio, 4.497; 95% confidence interval, 2.058–9.825). After adjusting for subject characteristics, troponin remained associated with 30-day mortality in several groups, including individuals with troponin levels in the normal range. CONCLUSIONS:Higher levels of preoperative cardiac troponin I were associated with higher postoperative mortality, and longer time to surgery appeared to reduce this risk for individuals with mild preoperative troponin elevations. Prospective studies are needed to determine whether delaying surgery in patients with elevated preoperative troponin levels improves postoperative outcomes.

U-Shape Association Between Hemoglobin A1c and Late Mortality in Patients With Heart Failure After Cardiac Surgery

Hemoglobin A1c (HbA1c) levels are used as a measure of glycemic control, with greater levels indicating poorer control and a greater risk of death. However, recent studies have found a U-shaped association between the HbA1c levels and mortality in patients with heart failure, with the lowest risk of death associated with elevated HbA1c levels, usually >7%. Cardiac surgery is frequently used to mitigate the signs and symptoms of heart failure. The purpose of the present study was to determine the association between HbA1c levels and late mortality in cardiac surgery patients with and without heart failure. Patients with and without New York Heart Association class III or IV heart failure were divided into quartiles according to the preoperative HbA1c level. Mortality was determined for each group and compared using chi-square tests and Cox modeling. Of the 311 patients with heart failure, 65 (21%) were dead at follow-up compared to 57 of 669 patients (9%) without heart failure (p <0.001). After adjusting for confounders, the patients without heart failure and with HbA1c ≤5.7% had the lowest risk of death. In patients with preoperative heart failure, we found a U-shaped association between HbA1c levels and late mortality, with those patients with HbA1c levels of 5.8% to 6.2% having the lowest risk of death. HbA1c levels ≤5.7% and ≥7.2% were associated with statistically significant greater risks of death. In conclusion, we found in patients with heart failure that the lowest risk of death was associated with HbA1c levels of 5.8% to 6.2%.

A case of malignant hyperthermia captured by an anesthesia information management system

Many cases of malignant hyperthermia triggered by volatile anesthetic agents have been described. However, to our knowledge, there has not been a report describing the precise changes in physiologic data of a human suffering from this process. Here we describe a case of malignant hyperthermia in which monitoring information was frequently and accurately captured by an anesthesia information management system.

Impact of ejection fraction on infectious, renal, and respiratory morbidity for patients undergoing noncardiac surgery

OBJECTIVE We sought to determine if decreased left ventricular systolic function was associated with an increased risk of postoperative infectious, respiratory, or renal complications in patients undergoing noncardiac surgery. DESIGN Retrospective cohort study. SETTING Single tertiary-care, university-based medical center. PATIENTS We studied individuals who participated in the American College of Surgeons National Quality Improvement Program and had a preoperative echocardiogram conducted at our institution. INTERVENTIONS None. MEASUREMENTS The incidences of postoperative respiratory (need for postoperative mechanical ventilation or unplanned intubation), renal (acute renal failure or renal insufficiency), and infectious (pneumonia, urinary tract infection, sepsis, or wound infection) complications were analyzed. MAIN RESULTS Postoperative infections (n=175, 10%) represented the most common postoperative complication seen in the study population of 1692 individuals. Respiratory complications occurred in 77 (5%) and renal complications occurred in 29 (2%) participants. The time between the echocardiogram and surgery ranged from 7 months (interquartile range [IQR] 1.8-15.7) for those with severely reduced left ventricular ejection fraction (LVEF) to 24 months (IQR 2.5-38.6) for those with a normal LVEF (P=.038). Univariate analysis demonstrated a relationship between decreased preoperative LVEF and infectious and renal complications, but not respiratory complications. After adjusting for preoperative characteristics, decreased preoperative LVEF was associated with infectious (odds ratio, 1.33; 95% confidence interval, 1.03-1.68; P=.0265) and renal (odds ratio, 1.69; 95% confidence interval, 1.12-2.48; P=.0142) complications. CONCLUSIONS Decreased preoperative LVEF is associated with postoperative infections and renal complications.

Kinetic estimated glomerular filtration rate and acute kidney injury in cardiac surgery patients.

PURPOSE To determine how a formula to estimate kinetically changing glomerular filtration rate (keGFR) relates to serum creatinine changes and to compare the discriminatory ability of keGFR to that of perioperative change in serum creatinine to predict acute kidney injury (AKI) and mortality. MATERIALS AND METHODS Retrospective cohort study at a single-tertiary-care Midwestern university hospital of 4022 patients admitted to the intensive care unit between January 2006 and January 2012 immediately after cardiac surgery. MEASUREMENTS AND MAIN RESULTS Of 4022 patients, 1031 (25.6%) developed at least AKI stage 1 and 1106 (27.5%) developed AKI-min. Patients who developed AKI stage 1 or AKI-min had a greater decrease in keGFR, both by absolute amounts and by percentage. After adjusting for other factors with logistic regression, keGFR had good discrimination (c statistic = 0.787 and 0.749, respectively) in predicting AKI and operative mortality. CONCLUSION Despite no change in immediate perioperative serum creatinine levels, keGFR fell and this predicted subsequent AKI. Using keGFR enables identification of patients who, despite unchanged postoperative creatinine, incur clinically significant kidney injury based on reduction in GFR and increased mortality.

Variability of Automated Intraoperative ST Segment Values Predicts Postoperative Troponin Elevation.

BACKGROUND:Intraoperative electrocardiographic monitoring is considered a standard of care. However, there are no evidence-based algorithms for using intraoperative ST segment data to identify patients at high risk for adverse perioperative cardiac events. Therefore, we performed an exploratory study of statistical measures summarizing intraoperative ST segment values determine whether the variability of these measurements was associated with adverse postoperative events. We hypothesized that elevation, depression, and variability of ST segments captured in an anesthesia information management system are associated with postoperative serum troponin elevation. METHODS:We conducted a single-institution, retrospective study of intraoperative automated ST segment measurements from leads I, II, and III, which were recorded in the electronic anesthesia record of adult patients undergoing noncardiac surgery. The maximum, minimum, mean, and SD of ST segment values were entered into logistic regression models to find independent associations with myocardial injury, defined as an elevated serum troponin concentration during the 7 days after surgery. Performance of these models was assessed by measuring the area under the receiver operator characteristic curve. The net reclassification improvement was calculated to quantify the amount of information that the ST segment values analysis added regarding the ability to predict postoperative troponin elevation. RESULTS:Of 81,011 subjects, 4504 (5.6%) had postoperative myocardial injury. After adjusting for patient characteristics, the ST segment maximal depression (e.g., lead I: odds ratio [OR], 1.66; 95% confidence interval [CI], 1.26–2.19; P = 0.0004), maximal elevation (e.g., lead I: OR, 1.70; 95% CI, 1.34–2.17; P < 0.0001), and SD (e.g., lead I: OR, 0.16; 95% CI, 0.06–0.42; P = 0.0002) were found to have statistically significant associations with myocardial injury. Increased SD was associated with decreased risk when accounting for the maximal amount of ST segment depression and elevation and for patient characteristics. The ST segment summary statistics model had fair discrimination, with an area under the receiver operator characteristic curve of 0.71 (95% CI, 0.68–0.73). Addition of ST segment data produced a net reclassification improvement of 0.0345 (95% CI, 0.00016–0.0591; P = 0.0474). CONCLUSIONS:Analysis of automated ST segment values obtained during anesthesia may be useful for improving the prediction of postoperative troponin elevation.

Years of Life Lost After Complications of Coronary Artery Bypass Operations

BACKGROUND We currently have an incomplete understanding of which postoperative complications after coronary artery bypass grafting (CABG) are associated with long-term death. The purpose of this study was to find the associations between complications and attributable death. METHODS Prospectively collected data on patient characteristics, risk factors, and complications of patients undergoing isolated CABG with 20-year follow-up were analyzed with a Cox regression model to calculate the overall hazard of dying associated with each postoperative complication. An individuals age and hazard of dying from each complication were then used to calculate years of life lost to each complication. RESULTS The postoperative mortality rate was 0.79% (69 of 8,773) at 30 days, 2.85% (250 of 8,773) at 180 days, and 6.38% (560 of 8,773) at 2 years. At a median follow-up of 9.8 years, 1,891 patients (21.6%) had died. Postoperative complications occurred in 3,438 patients (39.2%). Cardiac arrest (hazard ratio, 2.153), reoperation (hazard ratio, 1.679), and new dialysis (hazard ratio, 1.64) were the complications with the greatest hazard of death. After adjusting for complication incidence and patient age, cardiac arrest (703 years), reoperation (544 years), atrial fibrillation (470 years), and prolonged mechanical ventilation (371 years) were associated with the greatest number of years of life lost. CONCLUSIONS Acute cardiac arrest, reoperation for other cardiac reasons, new dialysis, atrial fibrillation, and prolonged mechanical ventilation are associated with the largest increase in attributable deaths. Prevention and treatment of these complications may improve mortality rates after cardiac operations.