Effects of low-dose IV ketamine on peripheral and central pain from major limb injuries sustained in combat

Abstract

Objective: Examine response patterns to low-dose intravenous (IV) ketamine continuous infusions on multiple pain outcomes, and demonstrate effectiveness, safety, and tolerability of ketamine administration on general wards. Design.: Retrospective case series of consecutive patients given low-dose IV ketamine continuous infusions. Setting.: Walter Reed Army Medical Center, Washington, DC. Patients.: Nineteen eligible inpatients with neuropathic pain from major limb injuries sustained in combat with inadequate pain control from multimodal analgesia. Interventions.: A 3-day IV infusion of ketamine at doses ≤120μg/kg/h. Outcome Measures.: Daily present (PPI), average (API), and worst (WPI) pain intensity (0-10), global pain relief (GPR) (1 "no relief" to 5 "complete relief"), daily assessments of adverse events, and daily opioid requirements measured during therapy. Results.: A significant reduction in PPI (P<0.001) and improvement in GPR (P=0.031) was noted over time. Higher baseline WPI (≥7; N=14) was associated with a significant decrease in WPI (P=0.0388), but lower baseline WPI (N=5) was not. Significant mean percent decreases in PPI with higher baseline PPI (N=8; P=0.0078) and WPI with no phantom limb pain (PLP) (N=10; P=0.0436) were observed. Mean percent increase in overall GPR was better for those reporting GPR scores ≤3 (N=13) in the first 24 hours of therapy (P=0.0153). While not significant, mean opioid requirement (IV morphine equivalents) decreased from 129.9mgs±137.3 on day 1 to 112.14±86.3 24 hours after therapy. Conclusions.: Low-dose ketamine infusions for complex combat injury pain were safe and effective, and demonstrated response patterns over time and by baseline pain score stratification and presence or absence of PLP. © 2013.