Usomoto et al measured the concentration of various electrolytes in the pleural fluid of people who drowned. The concentration of sodium and chloride can indicate whether the person drowned in sea or fresh water.
Site of Drowning
Sodium
Chloride
sea water
very high
very high
fresh water
very low
very low
A pleural fluid sodium concentration > 100 mmol/L was seen with drowning in sea water, with many cases showing a concentration > 150 mmol/L.
A pleural fluid sodium concentration < 100 mmol/L was seen with drowning in fresh water.
Limitations:
• A short period of time in the water may impact the concentrations.
• A person drowning in brackish water might have a more normal concentration.
• A pre-existing pleural effusion might impact the concentrations.
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