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Efficacy and safety of potential irrigation diluents following ‘caustic cocktail’ ingestion 

Adam Lee^1,*, Catherine Moore^1,*, Adam Griffiths¹

¹ Underwater Medicine Department, Institute of Naval Medicine, Portsmouth, UK
^* Drs Lee and Moore contributed equally to this paper

Corresponding author: Adam Lee, Surgeon Lieutenant Commander Royal Navy, Institute of Naval Medicine, Gosport, Portsmouth, UK
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Keywords
Diving medicine; First aid; Injuries; Military diving; Rebreathers - closed circuit; Treatment

Abstract

(Lee A, Moore C, Griffiths A. Efficacy and safety of potential irrigation diluents following ‘caustic cocktail’ ingestion.  Diving and Hyperbaric Medicine. 2026 31 March;56(1):83−87. doi: 10.28920/dhm56.1.83-87. PMID: 41875445.)
Closed circuit rebreather (CCR) diving sets use soda lime, a sodium hydroxide-based ‘scrubber’ substance to remove CO₂ from exhaled breathing gas thus prolonging dive time and efficiency. Inadvertent water ingress into the set may result in reaction with the scrubber and a highly alkaline solution known as a ‘caustic cocktail’ may be formed. Ingestion or aspiration of this solution can cause severe chemical burns. Irrigation with freshwater is the mainstay of initial treatment of ‘caustic cocktail’ injuries in CCR divers. Published advice advises divers never to use acidic diluents to irrigate and neutralise a caustic cocktail solution due to concerns over the potentially exothermic nature of the neutralisation reaction. However, there is limited available evidence to support this advice, and it was felt that further research into the best treatment options available for caustic cocktails is required. This study used an in vitro model of an ingested caustic cocktail to investigate pH and temperature changes after adding different diluents (including acidic diluents orange juice or coca cola) to a solution of sodium hydroxide. Acidic diluents reduce pH significantly more than neutral diluents with a respective mean drop in pH of 5.99 compared to 0.78 (P = 0.015). There is no statistically significant difference in temperature change noted between the two types of diluent (P = 0.32) with no exothermia generated. We propose that orange juice or coca cola are more effective irrigation solutions than fresh or seawater, and that advice to divers who use CCRs could change.

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