Zinc supplementation in intensive care: results of a UK survey

Our laboratory receives many routine requests for plasma zinc analysis from intensive care units (ICUs) throughout Scotland. However, such requests are inappropriate because plasma zinc concentrations fall independently of nutritional deficiency during the systemic inflammatory response and, therefore, in critically ill patients. This survey was performed to investigate how widespread this practice was and if low plasma zinc concentrations were interpreted as zinc deficiency so triggering inappropriate initiation of zinc supplementation.

A questionnaire was sent to ICUs throughout the UK; nonresponders were contacted by telephone, and the questionnaire details were recorded. The questionnaire asked if plasma zinc was routinely requested, the frequency of requests, whether patients were supplemented with zinc, and if so, the grounds for supplementation and the dose given.

Plasma measurement of zinc was routinely performed in 18% of UK ICUs. Zinc supplementation was given in 10%, usually as a result of finding low plasma zinc concentrations. Dosages of supplementation varied widely between ICUs: from 0.4 to 135 mg zinc per day. Approximately 6% of ICUs gave very high supplements of zinc of 90 and 135 mg/d.

The finding of a low plasma zinc concentration in Intensive Therapy Unit patients is often misinterpreted as indicating zinc deficiency and inappropriately prompts zinc supplementation. There is no evidence base to support high-dose zinc supplementation in ICU patients. This practice is justifiable only if future randomized trials demonstrate a benefit.