No benefit from the addition of low-dose ketamine infusion to standard evidence-based care of patients with multiple rib fractures.

Background: Multiple rib fractures from blunt thoracic trauma cause significant morbidity. Optimal current management includes multimodal analgesia, pulmonary hygiene, and early mobilization. Low-dose ketamine infusion (LDKI) has been proposed as an adjunctive analgesic in this setting. A prior study reported decreased pain scores with LDKI in patients with multiple rib fractures. We hypothesized that LDKI would decrease morphine milligram equivalents (MMEs) in patients with multiple rib fractures.

Methods: A prospective randomized placebo-controlled trial was performed in adult (18 years or older) patients with three or more rib fractures. A prestudy power analysis calculated an 80% chance of identifying a 15% decrease in MMEs with 50 subjects. The study was approved by the institutional review board and informed consent obtained in all subjects. Demographic (age, sex) and injury specific information (Injury Severity Score, number of rib fractures) were obtained. Subjects were randomized 1:1 to receive continuous LDKI (0.1 mg/kg/h) or placebo infusion (0.9% NaCl) for ≤48 hours. All patients received a standard evidence-based multidisciplinary protocol for rib fractures management. Primary outcome measure was MME use or pulmonary complications. Statistical comparison of LDKI versus placebo was performed using the Mann-Whitney U test.

Results: All 50 enrolled subjects (placebo, 25; LDKI, 25) received study drug infusion. The two groups were well matched for age, Injury Severity Score, and number of rib fractures. We observed no differences in the Day 1 (p = 0.961), Day 2 (p = 0.373), or total MMEs (p = 0.946) between groups. Similar total MME use was observed when subjects who received ≥40 hours of study drug and were compared (p = 0.924). Use of LDKI did not alter subsequent need for opiate analgesics postinfusion, hospital length of stay, pulmonary complications, or need for readmission.

Conclusion: The addition of LDKI to an established multimodal, evidence-based protocol for management of multiple rib fractures did not decrease opiate usage or impact pulmonary complications.

Level of evidence: Therapeutic/Care Managaement; Level I.