Electrolyte analysis in pleural effusion as an indicator of the drowning medium.

In medico-legal autopsies for drowned bodies, the location of drowning needs to be determined. To investigate the usefulness of electrolyte analysis in pleural effusion as an indicator of the location where the deceased has drowned, we determined the concentrations of electrolytes in the pleural effusion of rats drowned in four kinds of water. The concentrations of sodium and chloride ions in the pleural effusion of rats that drowned in seawater were significantly greater than those of rats that drowned in freshwater at both 1 day and 3 days after drowning. The concentration of potassium ions in pleural effusion 1 day after drowning showed no difference between each group, although it then increased from 1 to 3 days after seawater drowning, whereas it decreased from 1 to 3 days after freshwater drowning. The concentration of total protein in pleural effusion increased from 1 to 3 days after drowning, however, there was no significant difference in the concentration of total protein in pleural effusion between each group at either 1 day or 3 days after drowning. These results suggest that analysis of electrolytes in pleural effusion may be useful for determining whether drowning has occurred in seawater or in freshwater.