{'fraction_non_alphanumeric': 0.017036450079239304, 'fraction_numerical': 0.009112519809825673, 'mean_word_length': 5.662269129287599, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Commentary: what conclusions can we draw from recent analyses of anesthesia provider model and patient outcomes?

In the April 2009 issue of Health Services Research, Needleman and Minnick (2009) explore the relationship between anesthesia provider credentials and maternal outcomes. They pose questions with potentially significant implications for the delivery of obstetric care in the United States, where hospitals vary in the models they employ for the provision of anesthetic care for labor and delivery. 
 
This study builds upon the authors' prior work, which describes five distinct anesthesia provider models based on reports from 613 hospitals in eight states (Minnick and Needleman 2008). In the present study, they compare rates of mortality and key complications among mothers following delivery at facilities distinguished by the relative participation of anesthesiologists and Certified Registered Nurse Anesthetists (CRNAs) in obstetric anesthesia care at each hospital. Needleman and Minnick use multivariable regression models in an effort to adjust for a number of observed confounders, including patient comorbidities and hospital characteristics, and conduct propensity score-matched analyses in an effort to control for patient selection according to hospital type. 
 
Despite the authors' efforts to limit the effect of important biases in this work, our review of the paper leaves us with concerns surrounding the authors' conclusions. Having found no systematic differences in the rates of patient complications in hospitals employing different anesthesia provider models, Needleman and Minnick (2009) conclude that “these findings do suggest, that at least in the area of obstetrical anesthesia services, there may be no gain in anesthesia safety from restricting which licensed providers can provide these services.” The authors cite work by an author of the present commentary that emphasizes the need for caution in making clinical or health policy recommendations based on retrospective analyses of cross-sectional data (Fleisher and Anderson 2002). In the present commentary, we discuss sources of bias that may remain in Needleman and Minnick's work due to the influence of unmeasured but potentially important clinical confounders. We ultimately find that the authors' results support multiple conflicting interpretations with drastically different implications for health policy, and put forward a similar caution in using their analyses to generate specific health policy recommendations.