Noninvasive monitoring of physiologic compromise in acute appendicitis: New insight into an old disease

Introduction: Physiologic compromise in children with acute appendicitis has heretofore been difficult to measure. We hypothesized that the Compensatory Reserve Index (CRI), a novel adjunctive cardiovascular status indicator, would be low for children presenting with acute appendicitis in proportion to their physiological compromise, and that CRI would rise with fluid resuscitation and surgical management of their disease.

Methods: Ninety-four children diagnosed with acute appendicitis were monitored with a CipherOx CRI™ M1 pulse oximeter (Flashback Technologies Inc., Boulder, CO). For clarity, CRI=1 indicates supine normovolemia, CRI=0 indicates hemodynamic decompensation (systolic blood pressure<80mmHg), and CRI values between 1 and 0 indicate the proportion of volume reserve remaining before collapse. Results are presented as counts with proportion (%), or mean with 95% confidence interval (CI).

Results: Mean age was 11years old (95% CI: 10-12), and 49 (52%) of the children were male. Fifty-four (57%) had nonperforated appendicitis and 40 (43%) had perforated appendicitis. Mean initial CRI was significantly higher in those with nonperforated appendicitis compared to those with perforated appendicitis (0.57, 95% CI: 0.52-0.63 vs. 0.36, 95% CI: 0.29-0.43; P<0.001). The significant differences in mean CRI values between the two groups remained throughout the course of treatment, but lost its significance at 2h after surgery (0.63, 95% CI: 0.57-0.70 vs. 0.53, 95% CI: 0.46-0.61; P=0.05).

Conclusion: Low CRI values in children with perforated appendicitis are indicative of their lower reserve capacity owing to peritonitis and hypovolemia. CRI offers a real-time, noninvasive adjunctive tool to monitor tolerance to volume loss in children.

Level of evidence: Study of diagnostic test; Level of evidence: Level III.