A Least Absolute Shrinkage and Selection Operator-Derived Predictive Model for Postoperative Respiratory Failure in a Heterogeneous Adult Elective Surgery Patient Population

BACKGROUND

Postoperative respiratory failure (PRF) is associated with increased hospital charges and worse patient outcomes. Reliable prediction models can help to guide postoperative planning to optimize care, to guide resource allocation, and to foster shared decision-making with patients.

RESEARCH QUESTION

Can a predictive model be developed to accurately identify patients at high risk of PRF?

STUDY DESIGN AND METHODS

In this single-site proof-of-concept study, we used structured query language to extract, transform, and load electronic health record data from 23,999 consecutive adult patients admitted for elective surgery (2014-2021). Our primary outcome was PRF, defined as mechanical ventilation after surgery of > 48 h. Predictors of interest included demographics, comorbidities, and intraoperative factors. We used logistic regression to build a predictive model and the least absolute shrinkage and selection operator procedure to select variables and to estimate model coefficients. We evaluated model performance using optimism-corrected area under the receiver operating curve and area under the precision-recall curve and calculated sensitivity, specificity, positive and negative predictive values, and Brier scores.

RESULTS

Two hundred twenty-five patients (0.94%) demonstrated PRF. The 18-variable predictive model included: operations on the cardiovascular, nervous, digestive, urinary, or musculoskeletal system; surgical specialty orthopedic (nonspine); Medicare or Medicaid (as the primary payer); race unknown; American Society of Anesthesiologists class ≥ III; BMI of 30 to 34.9 kg/m2; anesthesia duration (per hour); net fluid at end of the operation (per liter); median intraoperative FIO2, end title CO2, heart rate, and tidal volume; and intraoperative vasopressor medications. The optimism-corrected area under the receiver operating curve was 0.835 (95% CI,0.808-0.862) and the area under the precision-recall curve was 0.156 (95% CI, 0.105-0.203).

INTERPRETATION

This single-center proof-of-concept study demonstrated that a structured query language extract, transform, and load process, based on readily available patient and intraoperative variables, can be used to develop a prediction model for PRF. This PRF prediction model is scalable for multicenter research. Clinical applications include decision support to guide postoperative level of care admission and treatment decisions.

Quality of Life Improvement: A Novel Framework and Approach to Well-Being

Physician burnout is a complex problem that requires creative solutions. Despite increasing awareness of the importance of systems approaches to address physician well-being, few tools exist for organizations to bridge the gap between well-being theory and practice. As demonstrated during the COVID-19 pandemic, new threats to well-being can arise at any time, necessitating an iterative approach. Here we outline the quality of life improvement (QOLI) approach, a novel framework and approach that incorporates principles of human-centered design (HCD), quality improvement (QI), and implementation science (IS) to address clinician well-being. Additionally, we share our experience using this approach in a large academic anesthesiology department.

Outcomes and risk factors for delayed-onset postoperative respiratory failure: a multi-center case-control study by the University of California Critical Care Research Collaborative (UC3RC)

BACKGROUND

Few interventions are known to reduce the incidence of respiratory failure that occurs following elective surgery (postoperative respiratory failure; PRF). We previously reported risk factors associated with PRF that occurs within the first 5 days after elective surgery (early PRF; E-PRF); however, PRF that occurs six or more days after elective surgery (late PRF; L-PRF) likely represents a different entity. We hypothesized that L-PRF would be associated with worse outcomes and different risk factors than E-PRF.

METHODS

This was a retrospective matched case-control study of 59,073 consecutive adult patients admitted for elective non-cardiac and non-pulmonary surgical procedures at one of five University of California academic medical centers between October 2012 and September 2015. We identified patients with L-PRF, confirmed by surgeon and intensivist subject matter expert review, and matched them 1:1 to patients who did not develop PRF (No-PRF) based on hospital, age, and surgical procedure. We then analyzed risk factors and outcomes associated with L-PRF compared to E-PRF and No-PRF.

RESULTS

Among 95 patients with L-PRF, 50.5% were female, 71.6% white, 27.4% Hispanic, and 53.7% Medicare recipients; the median age was 63 years (IQR 56, 70). Compared to 95 matched patients with No-PRF and 319 patients who developed E-PRF, L-PRF was associated with higher morbidity and mortality, longer hospital and intensive care unit length of stay, and increased costs. Compared to No-PRF, factors associated with L-PRF included: preexisiting neurologic disease (OR 4.36, 95% CI 1.81-10.46), anesthesia duration per hour (OR 1.22, 95% CI 1.04-1.44), and maximum intraoperative peak inspiratory pressure per cm H₂0 (OR 1.14, 95% CI 1.06-1.22).

CONCLUSIONS

We identified that pre-existing neurologic disease, longer duration of anesthesia, and greater maximum intraoperative peak inspiratory pressures were associated with respiratory failure that developed six or more days after elective surgery in adult patients (L-PRF). Interventions targeting these factors may be worthy of future evaluation.

A Tale of Two Supercities: Early COVID-19 Outcomes Reflect Social Vulnerability in New York City and San Francisco

In this narrative review, anesthesiologists at 2 large hospital systems in New York City and San Francisco compare early coronavirus disease 2019 (COVID-19) public health outcomes while considering the role played by social vulnerability and relevant approaches in their 2 cities. An iterative search process allowed for a broad review of medical and public policy research, as well as newspaper reports, expert opinion, and multimedia sources, with the goal of exploring the importance of crowding, the labor force, and social identity in pandemic experiences. Related struggles, pitfalls, and successful interventions in both locales are summarized. Although technology in the form of vaccination will likely play an outsize role in the next phase of the pandemic, our review concludes that we must carefully consider how social vulnerabilities have and will continue to inform equitable and effective access to life-saving resources.

Risk Factors Associated With Early Postoperative Respiratory Failure: A Matched Case-Control Study

BACKGROUND

Postoperative respiratory failure is the most common serious postoperative pulmonary complication, yet little is known about factors that can reduce its incidence. We sought to elucidate modifiable factors associated with respiratory failure that developed within the first 5 d after an elective operation.

MATERIALS AND METHODS

Matched case-control study of adults who had an operation at five academic medical centers between October 1, 2012 and September 30, 2015. Cases were identified using administrative data and confirmed via chart review by critical care clinicians. Controls were matched 1:1 to cases based on hospital, age, and surgical procedure.

RESULTS

Our total sample (n = 638) was 56.4% female, 71.3% white, and had a median age of 62 y (interquartile range 51, 70). Factors associated with early postoperative respiratory failure included male gender (odds ratio [OR] 1.72, 95% confidence interval [CI] 1.12-2.63), American Society of Anesthesiologists class III or greater (OR 2.85, 95% CI 1.74-4.66), greater number of preexisting comorbidities (OR 1.14, 95% CI 1.004-1.30), increased operative duration (OR 1.14, 95% CI 1.06-1.22), increased intraoperative positive end-expiratory pressure (OR 1.23, 95% CI 1.13-1.35) and tidal volume (OR 1.13, 95% CI 1.004-1.27), and greater net fluid balance at 24 h (OR 1.17, 95% CI 1.07-1.28).

CONCLUSIONS

We found greater intraoperative ventilator volume and pressure and 24-h fluid balance to be potentially modifiable factors associated with developing early postoperative respiratory failure. Further studies are warranted to independently verify these risk factors, explore their role in development of early postoperative respiratory failure, and potentially evaluate targeted interventions.

Dexmedetomidine or Propofol for Sedation in Mechanically Ventilated Adults with Sepsis

BACKGROUND

Guidelines currently recommend targeting light sedation with dexmedetomidine or propofol for adults receiving mechanical ventilation. Differences exist between these sedatives in arousability, immunity, and inflammation. Whether they affect outcomes differentially in mechanically ventilated adults with sepsis undergoing light sedation is unknown.

METHODS

In a multicenter, double-blind trial, we randomly assigned mechanically ventilated adults with sepsis to receive dexmedetomidine (0.2 to 1.5 μg per kilogram of body weight per hour) or propofol (5 to 50 μg per kilogram per minute), with doses adjusted by bedside nurses to achieve target sedation goals set by clinicians according to the Richmond Agitation-Sedation Scale (RASS, on which scores range from -5 [unresponsive] to +4 [combative]). The primary end point was days alive without delirium or coma during the 14-day intervention period. Secondary end points were ventilator-free days at 28 days, death at 90 days, and age-adjusted total score on the Telephone Interview for Cognitive Status questionnaire (TICS-T; scores range from 0 to 100, with a mean of 50±10 and lower scores indicating worse cognition) at 6 months.

RESULTS

Of 432 patients who underwent randomization, 422 were assigned to receive a trial drug and were included in the analyses - 214 patients received dexmedetomidine at a median dose of 0.27 μg per kilogram per hour, and 208 received propofol at a median dose of 10.21 μg per kilogram per minute. The median duration of receipt of the trial drugs was 3.0 days (interquartile range, 2.0 to 6.0), and the median RASS score was -2.0 (interquartile range, -3.0 to -1.0). We found no difference between dexmedetomidine and propofol in the number of days alive without delirium or coma (adjusted median, 10.7 vs. 10.8 days; odds ratio, 0.96; 95% confidence interval [CI], 0.74 to 1.26), ventilator-free days (adjusted median, 23.7 vs. 24.0 days; odds ratio, 0.98; 95% CI, 0.63 to 1.51), death at 90 days (38% vs. 39%; hazard ratio, 1.06; 95% CI, 0.74 to 1.52), or TICS-T score at 6 months (adjusted median score, 40.9 vs. 41.4; odds ratio, 0.94; 95% CI, 0.66 to 1.33). Safety end points were similar in the two groups.

CONCLUSIONS

Among mechanically ventilated adults with sepsis who were being treated with recommended light-sedation approaches, outcomes in patients who received dexmedetomidine did not differ from outcomes in those who received propofol. (Funded by the National Institutes of Health; ClinicalTrials.gov number, NCT01739933.).

Consensus-based perioperative protocols during the COVID-19 pandemic

OBJECTIVE

During the COVID-19 pandemic, quaternary-care facilities continue to provide care for patients in need of urgent and emergent invasive procedures. Perioperative protocols are needed to streamline care for these patients notwithstanding capacity and resource constraints.

METHODS

A multidisciplinary panel was assembled at the University of California, San Francisco, with 26 leaders across 10 academic departments, including 7 department chairpersons, the chief medical officer, the chief operating officer, infection control officers, nursing leaders, and resident house staff champions. An epidemiologist, an ethicist, and a statistician were also consulted. A modified two-round, blinded Delphi method based on 18 agree/disagree statements was used to build consensus. Significant disagreement for each statement was tested using a one-sided exact binomial test against an expected outcome of 95% consensus using a significance threshold of p < 0.05. Final triage protocols were developed with unblinded group-level discussion.

RESULTS

Overall, 15 of 18 statements achieved consensus in the first round of the Delphi method; the 3 statements with significant disagreement (p < 0.01) were modified and iteratively resubmitted to the expert panel to achieve consensus. Consensus-based protocols were developed using unblinded multidisciplinary panel discussions. The final algorithms 1) quantified outbreak level, 2) triaged patients based on acuity, 3) provided a checklist for urgent/emergent invasive procedures, and 4) created a novel scoring system for the allocation of personal protective equipment. In particular, the authors modified the American College of Surgeons three-tiered triage system to incorporate more urgent cases, as are often encountered in neurosurgery and spine surgery.

CONCLUSIONS

Urgent and emergent invasive procedures need to be performed during the COVID-19 pandemic. The consensus-based protocols in this study may assist healthcare providers to optimize perioperative care during the pandemic.

Postoperative respiratory failure: An update on the validity of the Agency for Healthcare Research and Quality Patient Safety Indicator 11 in an era of clinical documentation improvement programs

BACKGROUND

Administrative data can be used to identify cases of postoperative respiratory failure (PRF). We aimed to determine if recent changes to the Agency for Healthcare Research and Quality Patient Safety Indicator 11 (PSI 11) and adoption of clinical documentation improvement programs have improved the validity of PSI 11. We also analyzed reasons why PSI 11 was falsely triggered.

STUDY DESIGN

Cross-sectional study of all eligible discharges using health record data from five academic medical centers between October 1, 2012 and September 30, 2015.

RESULTS

Of 437 flagged records, 434 (99.3%) were accurately coded and 414 (94.7%) represented true clinical PRF. None of the false positive records involved respiratory failure present on admission. Most (78.3%) false positive records required airway protection but did not have respiratory failure.

CONCLUSION

The validity of PSI 11 has improved with recent changes to the code criterion and adoption of clinical documentation improvement programs.

The Feasibility and Utility of Continuous Sleep Monitoring in Critically Ill Patients Using a Portable Electroencephalography Monitor

BACKGROUND

Sleep disruption in critically ill adults can result in acute decrements in cognitive function, including delirium, but it is underdiagnosed in the setting of the intensive care unit (ICU). Although sleep stages can be assessed by polysomnography (PSG), acquisition and interpretation of PSG is costly, is labor intensive, is difficult to do over an extended period of time with critically ill patients (multiple days of continuous recording), and may interfere with patient care. In this pilot study, we investigated the feasibility and utility of monitoring sleep in the ICU setting using a portable electroencephalography (EEG) monitor, the SedLine brain monitor.

METHODS

We first performed a baseline comparison study of the SedLine brain monitor by comparing its recordings to PSG recorded in a sleep laboratory (n = 3). In a separate patient cohort, we enrolled patients in the ICU who were monitored continuously with the SedLine monitor for sleep disruption (n = 23). In all enrolled patients, we continuously monitored their EEG. The raw EEG was retrieved and sleep stages and arousals were analyzed by a board-certified technologist. Delirium was measured by a trained research nurse using the Confusion Assessment Method developed for the ICU.

RESULTS

For all enrolled patients, we continuously monitored their EEGs and were able to retrieve the raw EEGs for analysis of sleep stages. Overall, the SedLine brain monitor was able to differentiate sleep stages, as well as capture arousals and transitions between sleep stages compared with the PSG performed in the sleep laboratory. The percentage agreement was 67% for the wake stage, 77% for the non-rapid eye movement (REM) stage (N1 = 29%, N2 = 88%, and N3 = 6%), and 89% for the REM stage. The overall agreement was measured with the use of weighted kappa, which was 0.61, 95% confidence interval, 0.58 to 0.64. In the ICU study, the mean recording time for the 23 enrolled patients was 19.10 hours. There were several signs indicative of poor-quality sleep, where sleep was distributed throughout the day, with reduced time spent in REM (1.38% ± 2.74% of total sleep time), and stage N3 (2.17% ± 5.53% of total sleep time) coupled with a high arousal index (34.63 ± 19.04 arousals per hour). The occurrence of ICU delirium was not significantly different between patients with and without sleep disruption.

CONCLUSIONS

Our results suggest the utility of a portable EEG monitor to measure different sleep stages, transitions, and arousals; however, the accuracy in measuring different sleep stages by the SedLine monitor varies compared with PSG. Our results also support previous findings that sleep is fragmented in critically ill patients. Further research is necessary to develop portable EEG monitors that have higher agreement with PSG.

A Typology of ICU Patients and Families from the Clinician Perspective: Toward Improving Communication

This paper presents an exploratory case study of clinician-patient communications in a specific clinical environment. It describes how intensive care unit (ICU) clinicians' technical and social categorizations of patients and families shape the flow of communication in these acute care settings. Drawing on evidence from a year-long ethnographic study of four ICUs, we develop a typology of patients and families as viewed by the clinicians who care for them. Each type, or category, of patient is associated with differing communication strategies, with compliant patients and families engaged in greater depth. In an era that prioritizes patient engagement through communication for all patients, our findings suggest that ICU teams need to develop new strategies for engaging and communicating with not just compliant patients and families, but those who are difficult as well. We discuss innovative methods for developing such strategies.

An Ethnographic Study of Health Information Technology Use in Three Intensive Care Units

OBJECTIVES

To identify the impact of a full suite of health information technology (HIT) on the relationships that support safety and quality among intensive care unit (ICU) clinicians.

DATA SOURCES

A year-long comparative ethnographic study of three academic ICUs was carried out. A total of 446 hours of observational data was collected in the form of field notes. A subset of these observations-134 hours-was devoted to job-shadowing individual clinicians and conducting a time study of their HIT usage.

PRINCIPAL FINDINGS

Significant variation in HIT implementation rates and usage was noted. Average HIT use on the two "high-use" ICUs was 49 percent. On the "low-use" ICU, it was 10 percent. Clinicians on the high-use ICUs experienced "silo" effects with potential safety and quality implications. HIT work was associated with spatial, data, and social silos that separated ICU clinicians from one another and their patients. Situational awareness, communication, and patient satisfaction were negatively affected by this siloing.

CONCLUSIONS

HIT has the potential to accentuate social and professional divisions as clinical communications shift from being in-person to electronically mediated. Socio-technically informed usability testing is recommended for those hospitals that have yet to implement HIT. For those hospitals already implementing HIT, we suggest rapid, locally driven qualitative assessments focused on developing solutions to identified gaps between HIT usage patterns and organizational quality goals.

Interprofessional rhetoric and operational realities: an ethnographic study of rounds in four intensive care units

Morning interprofessional rounds (MIRs) are used in critical care medicine to improve team-based care and patient outcomes. Given existing evidence of conflict between and dissatisfaction among rounds participants, this study sought to better understand how the operational realities of care delivery in the intensive care unit (ICU) impact the success of MIRs. We conducted a year-long comparative ethnographic study of interprofessional collaboration and patient and family involvement in four ICUs in tertiary academic hospitals in two American cities. The study included 576 h of observation of team interactions, 47 shadowing sessions and 40 clinician interviews. In line with best practices in ethnographic research, data collection and analysis were done iteratively using the constant comparative method. Member check was conducted regularly throughout the project. MIRs were implemented on all units with the explicit goals of improving team-based and patient-centered care. Operational conditions on the units, despite interprofessional commitment and engagement, appeared to thwart ICU teams from achieving these goals. Specifically, time constraints, struggles over space, and conflicts between MIRs' educational and care-plan-development functions all prevented teams from achieving collaboration and patient-involvement. Moreover, physicians' de facto control of rounds often meant that they resembled medical rounds (their historical predecessors), and sidelined other providers' contributions. This study suggests that the MIRs model, as presently practiced, might not be well suited to the provision of team-based, patient-centered care. In the interest of interprofessional collaboration, of the optimization of clinicians' time, of high-quality medical education and of patient-centered care, further research on interprofessional rounds models is needed.

Predicting mortality in the intensive care unit: a comparison of the University Health Consortium expected probability of mortality and the Mortality Prediction Model III

Background

Quality benchmarks are increasingly being used to compare the delivery of healthcare, and may affect reimbursement in the future. The University Health Consortium (UHC) expected probability of mortality (EPM) is one such quality benchmark. Although the UHC EPM is used to compare quality across UHC members, it has not been prospectively validated in the critically ill. We aimed to define the performance characteristics of the UHC EPM in the critically ill and compare its ability to predict mortality with the Mortality Prediction Model III (MPM-III).

Methods

The first 100 consecutive adult patients discharged from the hospital (including deaths) each quarter from January 1, 2009 until September 30, 2011 that had an intensive care unit (ICU) stay were included. We assessed model discrimination, calibration, and overall performance, and compared the two models using Bland-Altman plots.

Results

Eight hundred ninety-one patients were included. Both the UHC EPM and the MPM-III had excellent performance (Brier score 0.05 and 0.06, respectively). The area under the curve was good for both models (UHC 0.90, MPM-III 0.87, p = 0.28). Goodness of fit was statistically significant for both models (UHC p = 0.002, MPM-III p = 0.0003), but improved with logit transformation (UHC p = 0.41; MPM-III p = 0.07). The Bland-Altman plot showed good agreement at extremes of mortality, but agreement diverged as mortality approached 50 %.

Conclusions

The UHC EPM exhibited excellent overall performance, calibration, and discrimination, and performed similarly to the MPM-III. Correlation between the two models was poor due to divergence when mortality was maximally uncertain.

An analysis of near misses identified by anesthesia providers in the intensive care unit

Background

Learning from adverse events and near misses may reduce the incidence of preventable errors. Current literature on adverse events and near misses in the ICU focuses on errors reported by nurses and intensivists. ICU near misses identified by anesthesia providers may reveal critical events, causal mechanisms and system weaknesses not identified by other providers, and may differ in character and causality from near misses in other anesthesia locations.

Methods

We analyzed events reported to our anesthesia near miss reporting system from 2009 to 2011. We compared causative mechanisms of ICU near misses with near misses in other anesthesia locations.

Results

A total of 1,811 near misses were reported, of which 22 (1.2 %) originated in the ICU. Five causal mechanisms explained over half of ICU near misses. Compared to near misses from other locations, near misses from the ICU were more likely to occur while on call (45 % vs. 19 %, p = 0.001), and were more likely to be associated with airway management (50 % vs. 12 %, p < 0.001). ICU near misses were less likely to be associated with equipment issues (23 % vs. 48 %, p = 0.02).

Conclusions

A limited number of causal mechanisms explained the majority of ICU near misses, providing targets for quality improvement. Errors associated with airway management in the ICU may be underappreciated. Specialist consultants can identify systems weaknesses not identified by critical care providers, and should be engaged in the ICU patient safety movement.

Preoperative medical testing in Medicare patients undergoing cataract surgery

BACKGROUND

Routine preoperative testing is not recommended for patients undergoing cataract surgery, because testing neither decreases adverse events nor improves outcomes. We sought to assess adherence to this guideline, estimate expenditures from potentially unnecessary testing, and identify patient and health care system characteristics associated with potentially unnecessary testing.

METHODS

Using an observational cohort of Medicare beneficiaries undergoing cataract surgery in 2011, we determined the prevalence and cost of preoperative testing in the month before surgery. We compared the prevalence of preoperative testing and office visits with the mean percentage of beneficiaries who underwent tests and had office visits during the preceding 11 months. Using multivariate hierarchical analyses, we examined the relationship between preoperative testing and characteristics of patients, health system characteristics, surgical setting, care team, and occurrence of a preoperative office visit.

RESULTS

Of 440,857 patients, 53% had at least one preoperative test in the month before surgery. Expenditures on testing during that month were $4.8 million higher and expenditures on office visits $12.4 million higher (42% and 78% higher, respectively) than the mean monthly expenditures during the preceding 11 months. Testing varied widely among ophthalmologists; 36% of ophthalmologists ordered preoperative tests for more than 75% of their patients. A patient's probability of undergoing testing was associated mainly with the ophthalmologist who managed the preoperative evaluation.

CONCLUSIONS

Preoperative testing before cataract surgery occurred frequently and was more strongly associated with provider practice patterns than with patient characteristics. (Funded by the Foundation for Anesthesia Education and Research and the Grove Foundation.).

Cytokines and clinical predictors in distinguishing pulmonary transfusion reactions

BACKGROUND

Pulmonary transfusion reactions are important complications of blood transfusion, yet differentiating these clinical syndromes is diagnostically challenging. We hypothesized that biologic markers of inflammation could be used in conjunction with clinical predictors to distinguish transfusion-related acute lung injury (TRALI), transfusion-associated circulatory overload (TACO), and possible TRALI.

STUDY DESIGN AND METHODS

In a nested case-control study performed at the University of California at San Francisco and Mayo Clinic, Rochester, we evaluated clinical data and blood samples drawn before and after transfusion in patients with TRALI (n = 70), possible TRALI (n = 48), TACO (n = 29), and controls (n = 147). Cytokines measured included granulocyte-macrophage-colony-stimulating factor, interleukin (IL)-6, IL-8, IL-10, and tumor necrosis factor-α. Logistic regression and receiver operating characteristics curve analyses were used to determine the accuracy of clinical predictors and laboratory markers in differentiating TACO, TRALI, and possible TRALI.

RESULTS

Before and after transfusion, IL-6 and IL-8 were elevated in patients with TRALI and possible TRALI relative to controls, and IL-10 was elevated in patients with TACO and possible TRALI relative to that of TRALI and controls. For all pulmonary transfusion reactions, the combination of clinical variables and cytokine measurements displayed optimal diagnostic performance, and the model comparing TACO and TRALI correctly classified 92% of cases relative to expert panel diagnoses.

CONCLUSIONS

Before transfusion, there is evidence of systemic inflammation in patients who develop TRALI and possible TRALI but not TACO. A predictive model incorporating readily available clinical and cytokine data effectively differentiated transfusion-related respiratory complications such as TRALI and TACO.

Recipient clinical risk factors predominate in possible transfusion-related acute lung injury

BACKGROUND

Possible transfusion-related acute lung injury (pTRALI) cases by definition have a clear temporal relationship to an alternative recipient risk factor for acute respiratory distress syndrome (ARDS). We questioned whether transfusion factors are important for the development of pTRALI.

STUDY DESIGN AND METHODS

In this nested case-control study, we prospectively identified 145 consecutive patients with pTRALI and randomly selected 163 transfused controls over a 4-year period at the University of California at San Francisco and the Mayo Clinic (Rochester, Minnesota).

RESULTS

For pTRALI, we found evidence against transfusion being important: receipt of plasma from female donors (odds ratio [OR], 0.82; 95% confidence interval [CI], 0.29-2.3; p = 0.70), total number of units transfused (OR, 0.99; 95% CI, 0.89-1.10; p = 0.86), and number of red blood cell and whole blood units transfused (OR, 0.78; 95% CI, 0.59-1.03; p = 0.079). In contrast, we found that risk for pTRALI was associated with additional recipient factors: chronic alcohol abuse (OR, 12.5; 95% CI, 2.8-55; p < 0.001), current smoker (OR, 4.2; 95% CI, 1.67-10.8; p = 0.0024), shock before transfusion (OR, 4.6; 95% CI, 2.0-10.7; p < 0.001), and positive fluid balance before transfusion (OR, 1.32/L; 95% CI, 1.20-1.44; p < 0.001).

CONCLUSION

Recipient risk factors for ARDS rather than transfusion risk factors predominate in pTRALI.

Interprofessional care in intensive care settings and the factors that impact it: results from a scoping review of ethnographic studies

At the heart of safe cultures are effective interactions within and between interprofessional teams. Critical care clinicians see severely ill patients who require coordinated interprofessional care. In this scoping review, we asked: "What do we know about processes, relationships, organizational and contextual factors that shape the ability of clinicians to deliver interprofessional care in adult ICUs?" Using the 5-stage process established by Levac et al. (2010), we reviewed 981 abstracts to identify ethnographic articles that shed light on interprofessional care in the intensive care unit. The quality of selected articles is assessed using best practices in ethnographic research; their main insights evaluated in light of an interprofessional framework developed by Reeves et al (Interprofessional Teamwork for Health and Social Care. San Francisco, CA: Wiley-Blackwell; 2010). Overall, studies were of mixed quality, with an average (SD) score of 5.8 out of 10 (1.77). Insights into intensive care unit cultures include the importance of paying attention to workflow, the nefarious impact of hierarchical relationships, the mixed responses to protocols imposed from the top down, and a general undertheorization of sex and race. This review highlights several lessons for safe cultures and argues that more needs to be known about the context of critical care if quality and safety interventions are to succeed.

Management of the Potential Organ Donor in the ICU

There is a major gap between supply and demand of organs for transplantation. Organ donation after neurological death is increasing in the United States, and there is potential for this gap to be minimized by focused medical management of the potential donor in the ICU. Increasing organ yield requires early potential donor identification and early referral to organ procurement organizations, and understanding the medical issues specific to the brain-dead patient, such as hemodynamic instability requiring vasopressors, coagulopathy, diabetes insipidus, renal failure, and acute lung injury/acute respiratory distress syndrome. Intensive care with treatment focused on these issues has the potential to increase both the number of potential donors and the number of organs transplanted per donor.

Fresh and stored red blood cell transfusion equivalently induce subclinical pulmonary gas exchange deficit in normal humans

BACKGROUND

Transfusion can cause severe acute lung injury, although most transfusions do not seem to induce complications. We tested the hypothesis that transfusion can cause mild pulmonary dysfunction that has not been noticed clinically and is not sufficiently severe to fit the definition of transfusion-related acute lung injury.

METHODS

We studied 35 healthy, normal volunteers who donated 1 U of blood 4 weeks and another 3 weeks before 2 study days separated by 1 week. On study days, 2 U of blood were withdrawn while maintaining isovolemia, followed by transfusion with either the volunteer's autologous fresh red blood cells (RBCs) removed 2 hours earlier or their autologous stored RBCs (random order). The following week, each volunteer was studied again, transfused with the RBCs of the other storage duration. The primary outcome variable was the change in alveolar to arterial difference in oxygen partial pressure (AaDo(2)) from before to 60 minutes after transfusion with fresh or older RBCs.

RESULTS

Fresh RBCs and RBCs stored for 24.5 days equally (P = 0.85) caused an increase of AaDo(2) (fresh: 2.8 mm Hg [95% confidence interval: 0.8-4.8; P = 0.007]; stored: 3.0 mm Hg [1.4-4.7; P = 0.0006]). Concentrations of all measured cytokines, except for interleukin-10 (P = 0.15), were less in stored leukoreduced (LR) than stored non-LR packed RBCs; however, vascular endothelial growth factor was the only measured in vivo cytokine that increased more after transfusion with LR than non-LR stored packed RBCs. Vascular endothelial growth factor was the only cytokine tested with in vivo concentrations that correlated with AaDo(2).

CONCLUSION

RBC transfusion causes subtle pulmonary dysfunction, as evidenced by impaired gas exchange for oxygen, supporting our hypothesis that lung impairment after transfusion includes a wide spectrum of physiologic derangements and may not require an existing state of altered physiology. These data do not support the hypothesis that transfusion of RBCs stored for >21 days is more injurious than that of fresh RBCs.

Special article: rescue therapies for acute hypoxemic respiratory failure

The recent H1N1 epidemic has resulted in a large number of deaths, primarily from acute hypoxemic respiratory failure. We reviewed the current strategies to rescue patients with severe hypoxemia. Included in these strategies are high-frequency oscillatory ventilation, airway pressure release ventilation, inhaled vasodilators, and the use of extracorporeal life support. All of these strategies are targeted at improving oxygenation, but improved oxygenation alone has yet to be demonstrated to correlate with improved survival. The risks and benefits of these strategies, including cost-effectiveness data, are discussed.

Ventilator-associated pneumonia in a neurologic intensive care unit does not lead to increased mortality

BACKGROUND

Ventilator-associated pneumonia (VAP) is the most common nosocomial infection among medical intensive care unit (ICU) patients and is associated with increased mortality and length of stay (LOS). Neurologic disease is a risk factor for VAP development, but the relationship between VAP and outcomes in patients admitted to the ICU for neurologic reasons remains largely unknown.

METHODS

All mechanically ventilated patients over a 2-year period with neurovascular disease were included in a retrospective study. Data collected included patient demographics, dates of admission and discharge, LOS, and ventilator hours. Comparisons between neurologic patients who did and did not develop VAP were made using univariate and multivariate analysis.

RESULTS

Of 585 intubated neurovascular patients, 24 (4.1%) developed VAP. Compared with those who did not develop VAP, those with VAP were younger (51.8 +/- 13.9 years vs. 58.8 +/- 15.9 years, P = 0.03), had increased LOS (32.6 +/- 29.2 days vs. 14.5 +/- 7.8 days, P < 0.001), and more ventilator hours (272 +/- 257 h vs. 85.9 +/- 140 h, P < 0.001). There was no difference in mortality between patients with and without VAP (25.0% vs. 28.3%, P = 0.72). VAP was not an independent predictor of mortality in a multivariate model (OR 1.11, 95% CI 0.37-3.30, P = 0.855).

CONCLUSIONS

VAP in neurocritical care patients is associated with increased LOS and ventilator hours, but is not associated with increased mortality, contrary to prior studies in medical ICU patients.

Looking forward, looking back: assessing variations in hospital resource use and outcomes for elderly patients with heart failure

BACKGROUND

Recent studies have found substantial variation in hospital resource use by expired Medicare beneficiaries with chronic illnesses. By analyzing only expired patients, these studies cannot identify differences across hospitals in health outcomes like mortality. This study examines the association between mortality and resource use at the hospital level, when all Medicare beneficiaries hospitalized for heart failure are examined.

METHODS AND RESULTS

A total of 3999 individuals hospitalized with a principal diagnosis of heart failure at 6 California teaching hospitals between January 1, 2001, and June 30, 2005, were analyzed with multivariate risk-adjustment models for total hospital days, total hospital direct costs, and mortality within 180-days after initial admission ("Looking Forward"). A subset of 1639 individuals who died during the study period were analyzed with multivariate risk-adjustment models for total hospital days and total hospital direct costs within 180-days before death ("Looking Back"). "Looking Forward" risk-adjusted hospital means ranged from 17.0% to 26.0% for mortality, 7.8 to 14.9 days for total hospital days, and 0.66 to 1.30 times the mean value for indexed total direct costs. Spearman rank correlation coefficients were -0.68 between mortality and hospital days, and -0.93 between mortality and indexed total direct costs. "Looking Back" risk-adjusted hospital means ranged from 9.1 to 21.7 days for total hospital days and 0.91 to 1.79 times the mean value for indexed total direct costs. Variation in resource use site ranks between expired and all individuals were attributable to insignificant differences.

CONCLUSIONS

California teaching hospitals that used more resources caring for patients hospitalized for heart failure had lower mortality rates. Focusing only on expired individuals may overlook mortality variation as well as associations between greater resource use and lower mortality. Reporting values without identifying significant differences may result in incorrect assumption of true differences.

Strategies for success: A PDSA analysis of three QI initiatives in critical care

BACKGROUND

Implementation of evidence-based quality improvement (QI) initiatives is not without its challenges. Recent experience in the design, implementation, and evaluation of three QI initiatives at the University of California, San Francisco Medical Center (UCSF) suggests lessons learned that may be generalizable to other QI initiatives. INITIATIVES: Between December 2002 and May 2006, a ventilator bundle of care and a tight glycemic control (TGC) protocol were implemented in the intensive care units (ICUs), and early goal-directed therapy (EGDT) for patients with severe sepsis or septic shock was implemented in the ICUs and emergency department. The initiatives were selected on the basis of the magnitude of the problem, strength of the evidence regarding associated reductions in morbidity and mortality in the critically ill, and cost-effectiveness.

LESSONS LEARNED

A number of challenges in QI processes and strategies for success were identified via retrospective analysis within the construct of the Plan-Do-Study-Act model, representing a novel use of the model. Pitfalls most commonly occurred in the planning stage. Suggested strategies for success include using an interdisciplinary team, selecting a champion, securing additional resources, identifying specific goals and providing feedback on progress, using work-flow analyses and stepwise implementation and/or pilot testing, creating standard work, eliciting feedback from staff, and celebrating successes. The knowledge gained from these initiatives has been disseminated at UCSF, and the initiatives have helped to raise general awareness regarding the importance of quality.

CONCLUSIONS

The ventilator bundle of care, TGC, and EGDT are still in use at UCSF, with modification of the initiatives occurring as new evidence becomes available.

Postoperative infectious complications of abdominal solid organ transplantation

There is a rapidly growing population of immunocompromised organ transplant recipients. These patients are at risk of a large variety of infections that have significant consequences on mortality, graft dysfunction, and graft loss. The diagnosis and treatment of these infections are facilitated by an understanding of the preoperative, perioperative, and postoperative risk factors; the typical pathogens; and their characteristic time of presentation. On the basis of these factors, we put forth an algorithm for diagnosing and treating suspected infections in solid organ transplant recipients.

Critical care challenges in orthopedic surgery patients

OBJECTIVES

To review common and life-threatening complications resulting in intensive care unit admission for patients undergoing orthopedic surgery procedures. To identify specific diagnostic techniques and treatment modalities that may improve the outcome of critically ill orthopedic surgery patients.

DESIGN

A review of the current literature regarding the care of orthopedic surgery patients was performed.

RESULTS

Orthopedic surgery patients are vulnerable to a number of complications, particularly pulmonary complications related to scoliosis surgery, embolic complications of joint arthroplasty, and complications related to the use of opioids and sedatives in an elderly population. They also are susceptible to transfusion-related complications such as transfusion-related acute lung injury and transfusion-associated circulatory overload. Specific strategies for management of these complex patients are identified.

CONCLUSIONS

Orthopedic surgery patients represent a significant and growing proportion of patients in intensive care units. They develop unique complications, and management of these complications requires understanding of preoperative co-morbidities, intraoperative management, and early recognition and treatment of postoperative complications. Prevention and early identification of these complications are the most efficacious routes to improving outcomes in this patient population.

Recombinant factor VIIa reduces transfusion requirements in liver transplant patients with high MELD scores

Patients undergoing orthotopic liver transplantation (OLT) often experience significant coagulopathy and remain at risk for excessive blood loss and massive transfusion. The ability of recombinant factor VIIa (rFVIIa) to reduce transfusion requirements during OLT has not been well established. This retrospective study investigates whether rFVIIa reduces transfusion requirements in liver transplant patients with a significantly prolonged prothrombin time (PT) and a model of end-stage liver disease (MELD) score of > 20. Eleven patients received a single dose of rFVIIa (58 +/- 18 microg kg(-1)) at the time of incision. This group was matched with a selected control group that fulfilled all of the inclusion/exclusion criteria. Patient characteristics, pre-operative PT, HCT, PLT and MELD were identical between groups. Prophylactic application of rFVIIA reduced packed red blood cells (3.9 +/- 2.6 versus 6.9 +/- 2.3 U, P = 0.01) and fresh-frozen plasma (FFP) (12.6 +/- 6 versus 19.8 +/- 7 U, P = 0.018) transfusion requirements when compared with the control group. FFP administration in the first 24 h after surgery was also significantly less in the rVIIa group when compared with the control group (388 +/- 385 versus 1225 +/- 701 mL, P = 0.003). Hospital stay following transplantation tended to be shorter in the rFVIIa group, albeit statistical significance was not achieved (11 +/- 7.3 versus 7.9 +/- 2.7, P = 0.2). All but one patient in the control group survived for 30 days after transplantation. In a selected group of patients with prolonged PT and high MELD score, the prophylactic application of rFVIIa at the start of the OLT may reduce perioperative transfusion requirements.

Pulmonary edema after transfusion: how to differentiate transfusion-associated circulatory overload from transfusion-related acute lung injury

OBJECTIVE

Pulmonary edema is an under-recognized and potentially serious complication of blood transfusion. Distinct mechanisms include adverse immune reactions and circulatory overload. The former is associated with increased pulmonary vascular permeability and is commonly referred to as transfusion-related acute lung injury (TRALI). The latter causes hydrostatic pulmonary edema and is commonly referred to as transfusion-associated circulatory overload (TACO). In this review article we searched the National Library of Medicine PubMed database as well as references of retrieved articles and summarized the methods for differentiating between hydrostatic and permeability pulmonary edema.

RESULTS

The clinical and radiologic manifestations of TACO and TRALI are similar. Although echocardiography and B-type natriuretic peptide measurements may aid in the differential diagnosis between hydrostatic and permeability pulmonary edema, invasive techniques such as right heart catheterization and the sampling of alveolar fluid protein are sometimes necessary. The diagnostic differentiation is especially difficult in critically ill patients will multiple comorbidities so that the cause of edema may only be determined post hoc based on the clinical course and response to therapy. Guided by available evidence, we present an algorithm for establishing the pretest probability of TRALI as opposed to TACO. The decision to test donor and recipient blood for immunocompatibility may be made on this basis.

CONCLUSIONS

The distinction between hydrostatic (TACO) and permeability (TRALI) pulmonary edema after transfusion is difficult, in part because the two conditions may coexist. Knowledge of strengths and limitations of different diagnostic techniques is necessary before initiation of complex TRALI workup.

Transfusion-related acute lung injury: a review

Transfusion-related acute lung injury (TRALI) is an underreported complication of transfusion therapy, and it is the third most common cause of transfusion-associated death. TRALI is defined as noncardiogenic pulmonary edema temporally related to transfusion therapy. The diagnosis of TRALI relies on excluding other diagnoses such as sepsis, volume overload, and cardiogenic pulmonary edema. Supportive diagnostic evidence includes identifying neutrophil or human leukocyte antigen (HLA) antibodies in the donor or recipient plasma. All plasma-containing blood products have been implicated in TRALI, with the majority of cases linked to whole blood, packed RBCs, platelets, and fresh-frozen plasma. The pathogenesis of TRALI may be explained by a "two-hit" hypothesis, with the first "hit" being a predisposing inflammatory condition commonly present in the operating room or ICU. The second hit may involve the passive transfer of neutrophil or HLA antibodies from the donor or the transfusion of biologically active lipids from older, cellular blood products. Treatment is supportive, with a prognosis substantially better than most causes of clinical acute lung injury.

Evidence-Based Management of Critically Ill Patients: Analysis and Implementation

A number of important clinical trials focusing on critically ill patients have been completed in the last few years. These trials have been among the first critical care clinical trials to demonstrate mortality reduction in the critically ill. As in any adaptation of evidence-based medicine, it is essential to closely examine the trials and to determine whether the demonstrated benefits can be translated to the individual patient. In addition to the primary outcome, usually survival benefit, it is also important to examine cost-effectiveness. All of the trials examined in this review were able to demonstrate mortality reduction. Most focused on patients with severe sepsis, because this population has been associated with both frequent mortality and increased hospital costs. Some of the interventions, such as small tidal volume mechanical ventilation in patients with acute lung injury or the administration of low-dose corticosteroids for patients with septic shock, are cost-effective and relatively simple to implement. Others, such as use of activated protein C in patients with severe sepsis or "tight" glycemic control in patients with hyperglycemia, require either significant pharmaceutical expenditure or, possibly, additional health care personnel. Nevertheless, the trials discussed represent significant advances in the field of critical care medicine and should at least be considered for implementation in all intensive care units.

Injury and repair in lung and airways

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are common causes of morbidity and mortality in the intensive care unit. ALI/ARDS occurs as a result of systemic inflammation, usually triggered by a microorganism. Activation of leukocytes and release of proinflammatory mediators from multiple cellular sources result in both local and distant tissue injury. Tumor necrosis factor-alpha and interleukin-1 beta are the best characterized of the proinflammatory cytokines contributing to ALI/ARDS and subsequent fibrosis. The ultimate clinical course of ALI/ARDS often is determined by the ability of the injured lung to repopulate the alveolar epithelium with functional cells. Death may occur when fibrosis predominates the healing response, as it results in worsening lung compliance and oxygenation. The rodent bleomycin model of lung fibrosis allows the use of molecular tools to dissect the cellular and subcellular processes leading to fibrosis. The elements of this response may provide therapeutic targets for the prevention of this devastating complication of ALI/ARDS.

Postoperative analgesia and sedation in the adult intensive care unit: a guide to drug selection

An essential goal of all critical care physicians should be to maintain an optimal level of pain control and sedation for their patients. This has become increasingly important because of evidence showing that the combined use of sedatives and analgesics may ameliorate the detrimental stress response in critically ill patients. Unfortunately, both pain and anxiety are subjective and difficult to measure, thereby limiting our ability to analyse these states and making management more challenging. Although there is still a lack of high quality, randomised, prospective, controlled trials comparing agents, monitoring techniques and scoring scales, several societies have come together to publish some clinical practice guidelines for sedation and analgesia. Recommended opioids are fentanyl or hydromorphone for short-term use, and morphine or hydromorphone for longer-term therapy. Midazolam or diazepam are recommended for sedation of the acutely agitated patient, while lorazepam is recommended for longer infusions. Propofol is preferred when rapid awakening is desired. The challenge for critical care physicians is to use these medications to provide comfort and safety without increasing morbidity or mortality. Most studies support the use of protocols in order to help achieve these goals. The bottom line is that most protocols end up stressing some common issues. These include daily cessation of drugs to evaluate the patient and frequent reassessment of the level of sedation required by each specific patient. Much is still unknown about the long-term effects of sedative and analgesic drugs used as infusions that may last from days to weeks to months. Hopefully, as more studies are performed, we will have more defined clinical end-points, newer drugs with rapid onset and offset and no active metabolites, and decreased morbidity and mortality for our patients.

Respiratory and Hemodynamic Management After Cardiac Surgery

In this new era of managed care, the emphasis has been on the reduction of intensive-care stay after coronary artery bypass surgery. "Fast-track" or rapid weaning protocols have become increasingly popular due to evidence that shows their cost-effectiveness and safety. With new advances in surgical and anesthetic techniques, the goal is often to have patients extubated within 4 to 6 hours upon arrival in the intensive-care unit. Patients who are not candidates for the fast-track protocol are often those who either have poor respiratory function and a large A-a gradient or those who have hemodynamic instability from poor cardiac function after bypass. These patients need more intensive care and more traditional weaning from mechanical ventilation. Those that are not able to wean from the mechanical ventilator within a few weeks are candidates for tracheostomy in order to avoid complications from prolonged endotracheal intubation and to improve pulmonary toilet. The treatment of perioperative low cardiac output syndrome is another goal after bypass surgery. Poor cardiac function can be managed with a variety of vasopressor and inotropic agents based on what the suspected derangement is from clinical examination and hemodynamic measurements (eg, low preload, low cardiac index, high or low systemic vascular resistance). Another modality that has been shown to have benefit on reducing hospital stay and costs is prophylaxis for atrial fibrillation, which may occur in 40% of patients who undergo bypass surgery and in 60% of those who undergo valve replacement surgery. Beta-blockers and amiodarone have both been found to be effective as prophylaxis against postoperative atrial fibrillation.

Protective effects of low tidal volume ventilation in a rabbit model of Pseudomonas aeruginosa-induced acute lung injury

OBJECTIVE

To determine whether low "stretch" mechanical ventilation protects animals from clinical sepsis after direct acute lung injury with Pseudomonas aeruginosa as compared with high "stretch" ventilation.

DESIGN

Prospective study.

SETTING

Experimental animal laboratory.

SUBJECTS

Twenty-seven anesthetized and paralyzed rabbits.

INTERVENTIONS

P. aeruginosa (109 colony forming units) was instilled into the right lungs of rabbits that were then ventilated at a tidal volume of either 15 mL/kg (n = 11) or 6 mL/kg (n = 7) for 8 hrs. Control animals were ventilated at a tidal volume of either 15 mL/kg (n = 4) or 6 mL/kg (n = 5) for 8 hrs, but an instillate without bacteria was used. A positive end-expiratory pressure of 3-5 cm H2O was used for all experiments. Radiolabeled albumin was used as a marker of alveolar epithelial permeability.

MEASUREMENTS AND MAIN RESULTS

Hemodynamics, arterial blood gas determination, alveolar permeability, wet-to-dry ratios on lungs, and time course of bacteremia were determined. When final values were compared with the values at the beginning of the experiment, there were significant decreases in mean arterial pressure (from 104 +/- 15 to 57 +/- 20 mm Hg), pH (from 7.46 +/- 0.04 to 7.24 +/- 15), Pao2 (from 528 +/- 35 to 129 +/- 104 torr [70.4 +/- 4.7 to 17.2 +/- 13.9 kPa]), and temperature (from 38.2 +/- 1 to 36.2 +/- 1.2 degrees C) in the high tidal volume group, whereas no significant differences were found in the low tidal volume group. Decreased alveolar permeability was shown in the low tidal volume group, as was decreased extravascular lung water in the uninstilled lung in the low tidal volume group (12.7 +/- 2.5 vs. 4.3 +/- 0.45 g H2O/g dry lung). No noteworthy difference was noted in the time course of bacteremia, although there was a trend toward earlier bacteremia in the high tidal volume group.

CONCLUSIONS

In our animal model of P. aeruginosa-induced acute lung injury, low tidal volume ventilation was correlated with improved oxygenation, hemodynamic status, and acid-base status as well as decreased alveolar permeability and contralateral extravascular lung water.

Etiology of acute pulmonary edema during liver transplantation : a series of cases with analysis of the edema fluid

STUDY OBJECTIVES

To describe the clinical features of a group of patients who acutely developed pulmonary edema during orthotopic liver transplantation and to determine the nature (transudate vs exudate) of the edema.

DESIGN

Retrospective review of clinical records and radiographic studies.

SETTING

Operating room and ICU of a tertiary-care medical center hospital.

PATIENTS

End-stage liver disease patients undergoing orthotopic liver transplantation under general anesthesia.

INTERVENTIONS AND MEASUREMENTS

Pulmonary edema fluid obtained from seven patients within 15 min of first appearance was analyzed for protein content and compared with the protein content of a simultaneously obtained plasma sample. Hemodynamic data, fluid administration totals, and length of postoperative intubation and ICU stay were also collected.

RESULTS

Eight patients were identified. Six of the seven patients whose edema fluid was analyzed had edema fluid/plasma protein ratios > or =0.75, characteristic of increased permeability pulmonary edema (the one other patient had a ratio of 0.73). Hemodynamic monitoring at the time of onset of the edema effectively ruled out a cardiogenic etiology. One patient died intraoperatively; at autopsy, the cause of death was determined to be pulmonary fat embolization. In the other seven patients, production of edema fluid resolved within 6 h of admission to the ICU. The duration of ventilatory support ranged from 23 to 96 h, with a mean of 49 h.

CONCLUSIONS

The most likely cause of the reaction is transfusion-related acute lung injury (TRALI). An incidence of TRALI that is higher than previously reported in this population indicates that other elements, such as reperfusion of the newly implanted liver, may be contributing factors.

Additive inhibition of nicotinic acetylcholine receptors by corticosteroids and the neuromuscular blocking drug vecuronium

BACKGROUND

Neuromuscular disorders associated with muscular weakness and prolonged paralysis are common in critically ill patients. Acute myopathy has been described in patients receiving a combination therapy of corticosteroids and nondepolarizing neuromuscular blocking drugs for treatment of acute bronchospasm. The cause of this myopathy is not fully established and may involve drug interactions that perturb neuromuscular transmission. To investigate the interaction of corticosteroids with neuromuscular blocking drugs, the authors determined the effects of methylprednisolone and hydrocortisone alone and in combination with vecuronium on fetal (gamma-subunit containing) and adult (epsilon-subunit containing) subtypes of the muscle-type nicotinic acetylcholine receptor.

METHODS

Functional channels were expressed in Xenopus laevis oocytes and activated with 1 microM acetylcholine. The resulting currents were recorded using a whole cell two-electrode voltage clamp technique.

RESULTS

Both forms of the muscle-type acetylcholine receptor were potently inhibited by methylprednisolone and hydrocortisone, with concentrations producing 50% inhibition in the range of 400-600 microM and 1-2 mM, respectively. The corticosteroids produced noncompetitive antagonism of the muscle-type nicotinic acetylcholine receptor at clinical concentrations. Both receptor forms were also inhibited, even more potently, by vecuronium, with a concentration producing 50% inhibition in the range of 1-2 nM. Combined application of vecuronium and methylprednisolone showed additive effects on both receptor forms, which were best described by a two-site model, with each site independent.

CONCLUSIONS

The enhanced neuromuscular blockade produced when corticosteroids are combined with vecuronium may augment pharmacologic denervation and contribute to the pathophysiology of prolonged weakness observed in some critically ill patients.