title: Postoperative complications in patients with obstructive sleep apnea syndrome undergoing hip or knee replacement: a case-control study.
abstract: OBJECTIVE
  To identify and assess the impact of postoperative complications in patients with unrecognized or known obstructive sleep apnea syndrome (OSAS) undergoing hip replacement or knee replacement compared with control patients undergoing similar operations. Although OSAS is a risk factor for perioperative morbidity, data quantifying the magnitude of the problem in patients undergoing non-upper airway operations are limited.
  
  
  METHODS
  This retrospective, case-control study from a single academic medical institution included patients diagnosed as having OSAS between January 1995 and December 1998 and undergoing hip or knee replacement within 3 years before or anytime after their OSAS diagnosis. Patients with OSAS were subcategorized as having the diagnosis either before or after the surgery and also, regardless of time of diagnosis, by whether they were using continuous positive airway pressure (CPAP) prior to hospitalization. Matched controls were patients without OSAS undergoing the same operation. Interventions were defined specifically as administration of a particular treatment in the context of each complication, eg, supplemental oxygen, implementation of additional monitoring such as oximetry for hypoxemia, or transfer to the intensive care unit (ICU) for cardiac ischemia concerns. Postoperative complications were assessed for all patients in the different categories and included respiratory events such as hypoxemia, acute hypercapnia, and episodes of delirium. Serious complications were noted separately, including unplanned ICU days, reintubations, and cardiac events. The length of hospital stay was also tabulated.
  
  
  RESULTS
  There were 101 patients with the diagnosis of OSAS in this study and 101 matched controls. Thirty-six patients had their joint replacement before OSAS was diagnosed, and 65 had surgery after OSAS was diagnosed. Of the latter 65 patients, only 33 were using CPAP at home preoperatively. Complications were noted in 39 patients (39%) in the OSAS group and 18 patients (18%) in the control group (P=.001). Serious complications occurred in 24 patients (24%) in the OSAS group compared with 9 patients (9%) in the control group (P=.004). Hospital stay was significantly longer for the OSAS patients at a mean +/- SD of 6.8 +/- 2.8 days compared with 5.1 +/- 4.1 days for the control patients (P<.007).
  
  
  CONCLUSIONS
  Adverse postoperative outcomes occurred at a higher rate in patients with a diagnosis of OSAS undergoing hip or knee replacement compared with a group of matched control patients.
authors.affiliation: Sleep Disorders Center, Division of Pulmonary and Critical Care Medicine, Mayo Clinic, Rochester, Minn 55905, USA.
authors.forename: R M
authors.initials: RM
authors.lastname: Gupta
authors.forename: J
authors.initials: J
authors.lastname: Parvizi
authors.forename: A D
authors.initials: AD
authors.lastname: Hanssen
authors.forename: P C
authors.initials: PC
authors.lastname: Gay
mesh_terms: D000328:Adult; D017677:Age Distribution; D000368:Aged; D000369:Aged, 80 and over; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects* / Q000379:methods; D019645:Arthroplasty, Replacement, Knee / Q000009:adverse effects* / Q000379:methods; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D011175:Positive-Pressure Respiration; D011183:Postoperative Complications / Q000175:diagnosis* / Q000453:epidemiology; D011379:Prognosis; D012131:Respiratory Insufficiency / Q000453:epidemiology / Q000209:etiology* / Q000628:therapy; D012189:Retrospective Studies; D018570:Risk Assessment; D012307:Risk Factors; D017678:Sex Distribution; D020181:Sleep Apnea, Obstructive / Q000150:complications* / Q000175:diagnosis / Q000628:therapy