Intraoperative Hypotension in Ambulatory Surgery Centers

Study Objectives

To measure the incidence of intraoperative hypotension (IOH) during surgery in ambulatory surgery centers (ASCs) and describe associated characteristics of patients and procedures.

Design

Retrospective analysis.

Setting

20 ASCs.

Patients

16,750 patients having non-emergent, non-cardiac surgery; ASA physical status 2 through 4.

Interventions

None.

Measurements

We assessed incidence of IOH using the definition from the Centers for Medicare & Medicaid Services (CMS) Merit-based Incentive Payment System (MIPS)—mean arterial pressure (MAP) < 65 mmHg for at least 15 cumulative minutes—and three secondary definitions: minutes of MAP <65 mmHg, area under MAP of 65 mmHg, and time-weighted average MAP <65 mmHg.

Main Results

30.9% of ASC cases had a MAP <65 mmHg for at least 15 min. The incidence of IOH varied significantly, and was higher among younger adults (age 18–39; 36.2%), females (35.2%), and patients with ASA physical status 2 (32.8%). IOH increased with increasing surgery length, even when time-weighted, and was higher among low complexity (30.6%) than moderate complexity (28.8%) procedures, and highest among high complexity procedures (44.1%).

Conclusions

There was substantial occurrence of IOH in ASCs, similar to that described in academic hospital settings in previous literature. We hypothesize that this may reflect clinician preference not to intervene in perceived healthy patients or assumptions about ability to tolerate lower blood pressures on behalf of these patients. Future research will determine whether IOH in ACSs is associated with adverse outcomes to the same extent as described in more complex hospital-based surgeries.