You are working at an outpatient surgical center and your next patient presents for a knee arthroscopy. Your patient has a body mass index (BMI) of 50 kg/m2. According to a recent retrospective cohort study that examined the association of BMI with postoperative outcomes after joint arthroscopy, which of the following is MOST likely increased in a patient who has a BMI between 50 and 60 compared with a patient who has a BMI between 30 and 40?

  • □ (A) Likelihood of same-day hospital admission

  • □ (B) Risk of same-day postoperative complications

  • □ (C) Risk of hospital readmission within 30 days

More surgical procedures are being performed on an outpatient basis or in stand-alone outpatient surgical centers. Optimal patient selection for ambulatory surgery is important to prevent postoperative complications and unplanned hospital admissions. Past studies have reported obesity as a risk factor for postoperative complications, but the data have been mixed in regard to specific levels of obesity and specific procedures for risk stratification purposes.

A recent multi-institutional retrospective cohort study reviewed the association of BMI with same-day hospital admission for patients undergoing outpatient joint arthroscopy using the American College of Surgeons National Surgical Quality Improvement Program (ACS NSQIP) dataset. They included 99,410 patients who were 18 years or older, with an ASA Physical Status of III or less, and who had undergone knee, hip, or shoulder arthroscopy between 2012 and 2016. The primary study outcome was same-day hospital admission and secondary outcomes were day of surgery complications and 30-day hospital readmission. Patients were divided into seven cohorts based on BMI, ranging from underweight (<20 kg/m2) to severe obesity (divided into three categories: ≥40 to <50; ≥50 to <60; and ≥60). BMI of ≥30 to <40 was used as the reference range for obesity because this has been defined as the initial obesity BMI range by the U.S. Centers for Disease Control and Prevention.

Multivariable logistic regression was used to determine the correlation of BMI with the primary and secondary outcomes after controlling for several comorbidities including age, diabetes mellitus, smoking status, functional status, case duration, and procedure type. Patients with a BMI between 50 and 60 had an increased likelihood for same-day hospital admission following surgery compared with patients in the reference range (BMI ≥30 to <40 [OR, 1.55; 95% CI, 1.18-2.01]). Overall, the rate of same-day postoperative complications was 0.02% (n=21) and the rate of 30-day readmission was 0.7% (n=707). No differences were found in the rates of same-day postoperative complications and 30-day hospital readmission among the BMI cohorts compared with the reference group.

The authors point out several limitations of their study, including its retrospective nature and available patient variables of interest in the ACS NSQIP dataset. Data regarding obstructive sleep apnea (OSA) status were not recorded. OSA is common in the severely obese patient population and may have influenced admission rates. Although all patients in the study were listed as “outpatient” in the dataset, information was not available regarding the planned or unplanned nature of a hospital admission. Interestingly, an association between increased odds of same-day hospital admission and BMI greater than 60 was not found, perhaps suggesting that these patients had planned hospital admissions prior to surgery. The authors suggested that for patients with a BMI less than 50, BMI alone should not be used as a contraindication in patient selection for outpatient joint arthroscopy.

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, et al
The association of body mass index with same-day hospital admission, postoperative complications, and 30-day readmission following day-case eligible joint arthroscopy: a national registry analysis
J Clin Anesth
. doi:10.1016/j.jclinane.2019.06.012

Answer: A