Risk Factors for Ambulatory Surgery Conversion to Extended Stay Among Patients Undergoing One-level or Two-level Posterior Lumbar Decompression : Spine

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Risk Factors for Ambulatory Surgery Conversion to Extended Stay Among Patients Undergoing One-level or Two-level Posterior Lumbar Decompression

Dodo, Yusuke MD, PhDa,b; Okano, Ichiro MD, PhDa,b; Kelly, Neil A. MDc; Sanchez, Leonardo A. BAc; Haffer, Henryk MDa; Muellner, Maximilian MDa; Chiapparelli, Erika MDa; Oezel, Lisa MDa; Shue, Jennifer MSa; Lebl, Darren R. MDa; Cammisa, Frank P. MDa; Girardi, Federico P. MDa; Hughes, Alexander P. MDa; Sokunbi, Gbolabo MDa; Sama, Andrew A. MDa

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Spine 48(11):p 748-757, June 1, 2023. | DOI: 10.1097/BRS.0000000000004621


Study design: 

A retrospective observational study.


The objective of this study was to investigate the factors associated with the conversion of patient status from ambulatory surgery (AMS) to observation service (OS) (<48 h) or inpatient (>48 h).

Summary of Background Data. 

AMS is becoming increasingly common in the United States because it is associated with a similar quality of care compared with inpatient surgery, significant costs reduction, and patients’ desire to recuperate at home. However, there are instances when AMS patients may be subjected to extended hospital stays. Unanticipated extension of hospitalization stays can be a great burden not only to patients but to medical providers and insurance companies alike.

Materials and Methods. 

Data from 1096 patients who underwent one-level or two-level lumbar decompression AMS at an in-hospital, outpatient surgical facility between January 1, 2019, and March 16, 2020, were collected. Patients were categorized into three groups based on length of stay: (1) AMS, (2) OS, or (3) inpatient. Demographics, comorbidities, surgical information, and administrative information were collected. Simple and multivariable logistic regression analyses were conducted comparing AMS patients and OS/inpatient as well as OS and inpatients.


Of the 1096 patients, 641 (58%) patients were converted to either OS (n=486) or inpatient (n=155). The multivariable analysis demonstrated that age (more than 80 yr old), high American Society of Anesthesiologists Physical Status (ASA) grade, history of sleep apnea, drain use, high estimated blood loss, long operation, late operation start time, and a high pain score were considered independent risk factors for AMS conversion to OS/inpatient. The risk factors for OS conversion to inpatient were an ASA class 3 or higher, coronary artery disease, diabetes mellitus, hypothyroidism, steroid use, drain use, dural tear, and laminectomy.


Several surgical factors along with patient-specific factors were significantly associated with AMS conversion. Addressing modifiable surgical factors might reduce the AMS conversion rate and be beneficial to patients and facilities.

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