Serial Postoperative Blood and Peritoneal Fluid Analysis and Ultrasonographic Assessment in Client-Owned Horses Undergoing Ventral Midline Exploratory Celiotomy for Colic.

Overview

• This study investigated changes in blood and peritoneal fluid markers, along with ultrasound imaging, in horses after abdominal surgery for colic, to identify signs that might predict postoperative complications.

Study Purpose and Objectives

• The main goal was to track serial changes in venous blood and peritoneal fluid parameters—particularly L-lactate levels—in horses after ventral midline exploratory celiotomy (a common surgery to diagnose and treat colic).
• A secondary goal was to assess whether postoperative abdominal ultrasonography could help predict which horses might develop complications after surgery.

Study Design and Methods

• Thirty-six client-owned horses presenting with colic and undergoing ventral midline exploratory celiotomy were prospectively enrolled.
• Samples of peripheral venous blood and peritoneal (abdominal cavity) fluid were collected at four key timepoints:
  • Preoperatively (T0)
  • 48 hours post-op (T1)
  • 72 hours post-op (T2)
  • 120 hours post-op (T3)
• Abdominal ultrasonographic exams were also performed at these same timepoints.

Key Measurements

• L-lactate concentrations were measured in both peripheral blood and peritoneal fluid. L-lactate is a metabolic marker often linked to tissue hypoxia or ischemia and can indicate ongoing injury or compromised blood flow.
• Ultrasonography focused on assessing the diameter of the small intestine, as distension can be a sign of postoperative ileus or other complications.

Results

• Ultrasound findings showed normalization of small intestinal diameter postoperatively in all horses, regardless of whether complications developed.
• Peripheral venous blood L-lactate levels decreased over time:
  • T0 (pre-op): about 1.9 mmol/L (±1.5)
  • T1 (48h): 0.9 mmol/L (±0.5)
  • T2 (72h): 0.8 mmol/L (±0.3)
  • T3 (120h): 0.9 mmol/L (±0.3)
• Peritoneal fluid L-lactate was higher than in blood at all timepoints:
  • T0: 3.8 mmol/L (±2.4)
  • T1: 2.8 mmol/L (±1.8)
  • T2: 1.1 mmol/L (±0.9)
  • T3 could not be evaluated due to insufficient fluid volume.
• Of the 36 horses, 32 survived to discharge. Among these survivors, 25/32 (around 78%) experienced postoperative complications, with postoperative colic being the most common complication.
• Horses that developed complications showed higher peripheral blood L-lactate levels at all measured postoperative timepoints compared to those without complications.
• Peritoneal L-lactate remained above blood L-lactate even in horses without complications, indicating a higher metabolic activity or inflammation in the abdominal cavity post-surgery regardless of outcome.

Interpretation and Significance

• The study suggests that monitoring peripheral blood L-lactate serially after colic surgery could be a useful marker for identifying horses at risk of postoperative complications.
• Peritoneal fluid L-lactate was consistently elevated compared to blood but was less predictive of complications on its own.
• Despite normalization of ultrasound metrics like small intestinal diameter, complications still frequently occurred, indicating ultrasound alone may not be a sensitive predictor of postoperative problems in this context.
• The most common complication—postoperative colic—highlights the ongoing challenges faced in managing recovery after colic surgery.

Limitations

• The relatively small sample size (36 horses) limits the statistical power and the ability to generalize findings broadly.
• Lack of data at 120 hours for peritoneal fluid L-lactate reduces the completeness of serial postoperative measurement.
• The study was observational, so it cannot definitively establish cause-effect relationships between measured variables and outcomes.

Conclusion

• Serial monitoring of blood and peritoneal L-lactate levels after ventral midline exploratory celiotomy in horses offers valuable information, with peripheral blood L-lactate being particularly associated with postoperative complications.
• Ultrasound evaluation of the intestine diameter showed normalization postoperatively but did not differentiate between horses with or without complications.
• These findings can help guide postoperative monitoring strategies to potentially improve detection and management of complications following equine colic surgery.