SYSTEMIC ABSORPTION OF GENTAMICIN IRRIGATION IN JOINT REPLACEMENT SURGERY: A CAUSE OF CONCERN

Abstract

Gentamicin is one of the most widely used antibiotics in Orthopaedic practice. It is commonly used as prophylaxis either through intravenous route, incorporated into bone cement or topical intraoperative irrigation. The former two are well studied. However, there is limited study on the therapeutic efficacy and safety of topical Gentamicin irrigation.

To assess the safety and infection rate of joint replacement surgery when topical gentamicin irrigation was used. This is a non-randomised, prospective study whereby patients undergoing joint replacement surgery were treated with gentamicin irrigation intra-operatively.

A total of 138 patients were divided into two groups in this study. Group A (98 patients) were patients with Total Joint Replacement and group B (40 patients) were patients with hemi arthroplasty of the hips and shoulders. Patients with pre-existing renal impairment were excluded. Two ampoules of Gentamicin (160mg) were irrigated into the wound before implants insertion and wound closure respectively. Intravenous Cefuroxime was also given prophylactically to all patients but none of them had intravenous gentamicin. Plasma Gentamicin level was assayed 4 hours and 24 hours post-operatively.

There were 16 patients in group A (16%; p< 0.001) and 12 patients in group B (30%; p< 0.001)) found to have plasma Gentamicin level > 2mcg/ml. All but 6 had plasma gentamicin level dropped to < 2mcg/ml at 24 hours. Although none of them developed systemic complications, the raise in plasma gentamicin was alarming. The incidence of infection was 6.1% (6 patients) in group A. These were superficial wound infection responded to antibiotics. No infection was reported in group B.

This study did not show apparent reduction in infection rate as compared to the reported literatures. Nevertheless, there was significant systemic absorption of topical gentamicin irrigation. Therefore, monitoring of post-operative plasma gentamicin levels is mandatory to avoid unforseen toxicity.