Elsevier

Mayo Clinic Proceedings

Volume 76, Issue 9, September 2001, Pages 897-905
Mayo Clinic Proceedings

Original Article
Postoperative Complications in Patients With Obstructive Sleep Apnea Syndrome Undergoing Hip or Knee Replacement: A Case-Control Study

https://doi.org/10.4065/76.9.897Get rights and content

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.

PATIENTS AND 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).

Conclusion

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.

Section snippets

Inclusion Criteria

Mayo Clinic Total Joint Registry and Sleep Center databases were used to identify the patients with a clinically suspected or objectively documented diagnosis of OSAS between January 1995 and December 1998 and undergoing hip or knee replacement at our institution. Patients with OSAS who had their orthopedic surgery within 3 years before or anytime after the diagnosis were included. We assumed that, if the operation was done within 3 years before the diagnosis, the patient had unrecognized OSAS

RESULTS

A total of 122 patients met the time period criterion set forth for inclusion. Of these, 21 patients were excluded, 18 because they lacked objective data (oximetry or PSG) to confirm clinical suspicion of OSAS and 3 because their PSG was performed elsewhere and no details were available. For the sake of simplicity in data presentation, the remaining 101 study patients were grouped by diagnostic status.

Group 1A consisted of 36 patients with OSAS undiagnosed before their joint replacement. These

DISCUSSION

Unexpected and unexplained postoperative deaths, within 7 days of an operation, most often occur at night.18 Cardio-pulmonary events related to sleep have been proposed as the most likely cause of postoperative mortality at night.19 Gill et al20 showed that prolonged episodes of myocardial ischemia, as recorded by electrocardiogram, occurred during hypoxemia.

Many factors influence the development of respiratory instability and episodic desaturation in the postoperative period, including sleep,

CONCLUSIONS

In this study, we have shown that the presence of OSAS in patients undergoing elective hip replacement or knee replacement is associated with a considerable number of complications in the postoperative period. Almost one third of the patients with OSAS in our study suffered a substantial respiratory or cardiac complication. Patients who were not using CPAP prior to hospitalization had a significantly higher incidence of serious complications. Patients diagnosed with OSAS have been shown to be

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