Intraoperative monitoring and anaesthetic complications in horses: A secondary analysis of the CEPEF4 multicentre cohort.

Overview

• This study analyzed detailed intraoperative monitoring data and complications during general anesthesia in horses to understand the frequency of complications, their association with the horses’ health status, and the impact on mortality risk.

Background and Objectives

• The CEPEF4 study provides a large and comprehensive dataset related to anesthesia in horses.
• There was previously limited detailed information on the incidence of intraoperative complications, monitoring practices, and how these relate to the American Society of Anesthesiologists (ASA) physical status grading and mortality.
• The main goals were to:
  • Describe how horses were monitored during anesthesia.
  • Calculate the incidence rates of various intraoperative complications.
  • Examine how complication rates vary with ASA physical status grades.
  • Investigate the relationship between complications and mortality within different ASA groups.

Methods

• Conducted a secondary analysis of the CEPEF4 dataset, which included 47,371 general anesthetic episodes in horses across multiple centers.
• Monitoring data were examined overall and by ASA status, focusing on:
  • Electrocardiography (ECG)
  • Pulse oximetry
  • Capnography (measuring CO₂ levels)
  • Invasive arterial pressure monitoring
• Complications analyzed included:
  • Hypotension (low blood pressure)
  • Hypoxaemia (low blood oxygen)
  • Hypercapnia (high carbon dioxide levels)
  • Arrhythmias (irregular heartbeats)
  • Hypothermia (low body temperature)
  • Intraoperative awakening
  • Severe hemorrhage (heavy bleeding)
• Logistic regression models were used to evaluate the odds of complications across ASA grades.
• Mortality outcomes were classified using a predefined CEPEF4-DEAD endpoint, with sensitivity analyses including euthanasia and accounting for differences between centers and monitoring availability.

Results

• Monitoring coverage was very high:
  • ECG in 92.2% of cases
  • Pulse oximetry in 89.2%
  • Capnography in 86.8%
  • Invasive arterial pressure in 82.0%
• Incidence of complications among monitored cases:
  • Hypotension observed in 40.4% (16,926/41,939)
  • Hypoxaemia in 5.3%
  • Hypercapnia in 5.8%
  • Arrhythmias in 1.6%
  • Hypothermia in 4.6%
• In the full dataset, intraoperative awakening occurred in 11.6%, and severe hemorrhage in 0.8% of cases.
• Higher ASA grades were associated with increased odds of most complications, except that intraoperative awakening showed no clear pattern by ASA grade.
• Mortality (DEAD endpoint) was significantly associated with hypotension, hypoxaemia, arrhythmias, and severe hemorrhage across ASA groups.
• Hypercapnia was associated with mortality only in the higher risk groups (ASA III-V).
• Sensitivity analyses largely supported these associations but suggested careful interpretation particularly when including euthanasia or considering monitoring availability.

Conclusions and Implications

• Monitoring availability influences detection of adverse events and depends on accurate clinical recording, so definitive causal relationships cannot be established from this observational data.
• The frequency of intraoperative complications increases with the ASA physical status score, meaning sicker horses have more complications during anesthesia.
• Hypotension was the most common complication, highlighting it as a key area for clinical attention.
• The findings provide valuable benchmark data for anesthesia monitoring and complication rates in horses.
• This study identifies significant complication patterns linked to mortality, guiding future research focused on improving anesthetic outcomes in equine practice.