NCT07022951

The Million Anesthesia Cases Study (MACS) - a Cohort Study of Preoperative Fasting and Perioperative Outcomes

The Million Anesthesia Cases Study (MACS) - Retrospective and Prospective Characterization of Perioperative Fasting Practices and Their Effects on Clinical Outcomes

• Status: Recruiting
• Phase: —
• Study type: Observational
• Enrollment: 1,200,000 (estimated)
• Sponsor: Massachusetts General Hospital · Academic / Other
• Sex: All
• Age: —
• Healthy volunteers: Not accepted

Summary

Perioperative fasting has historically been viewed as a low-risk intervention. However, preliminary data indicate that perioperative loss of nutrition and fluids is likely harmful. This study intends to characterize perioperative fasting practices and their potential effects on clinical outcomes through possible effects on patient well-being (anxiety, hunger, thirst), physiology (hypovolemia, hypotension), perioperative aspiration, etc. The research team hypothesized that in addition to known adverse effects on patients' well-being, prolonged preoperative fasting adversely affects circulating blood volume-related (hypotension, decreased urine output etc.) and glucose metabolism-related (e.g., hypo/hyperglycemia) perioperative physiology. The investigators will also test for an association between the duration of preoperative fasting and the risk of perioperative pulmonary aspiration. Additional knowledge on the potential adverse effects of preoperative fasting will inform preoperative fasting policies and research interventions that are relevant to hundreds of millions of patients subjected to preoperative/preprocedural fasting worldwide each year.

Conditions

• Anesthesia
• Sedation
• Monitored Anesthesia Care
• Procedure
• Surgery, Day
• Surgery
• Surgery Scheduled
• Fasting Before Operation
• Aspiration; Gastric Contents, Anesthesia

Interventions

Type	Name	Description
OTHER	Preoperative fasting	This cohort study assesses the duration of preoperative fasting and its clinical effects

Timeline

• Start date: 2016-01-01
• Primary completion: 2028-12-31
• Completion: 2030-12-31
• First posted: 2025-06-15
• Last updated: 2026-04-08

Locations

1 site across 1 country: United States