Although
electrolyte analysis of
pleural effusion at autopsy is useful for the diagnosis of water aspiration (i.e.,
drowning), the method of comparing each level of
sodium (Na(+)),
potassium (K(+)), and
chloride (Cl(-))
ions does not clearly differentiate between freshwater
drowning, seawater
drowning, and non-
drowning. Therefore, here we introduce the summation of Na(+), K(+), and Cl(-) levels, that is SUM(Na+K+Cl), as a modified diagnostic
indicator. In 21 autopsy cases of freshwater
drowning, 32 cases of seawater
drowning, and 43 non-
drowning controls (with
pleural effusion), mean SUM(Na+K+Cl) differed significantly between the groups (188.8±33.2, 403.5±107.9, and 239.3±21.7 mEq/L, respectively). We defined a SUM(Na+K+Cl) cut-off value of <195.9 mEq/L as strongly suggestive of freshwater aspiration and that of >282.7 mEq/L as strongly suggestive of seawater aspiration. When these values were applied to the two
drowning groups, 15 cases (71%) of freshwater
drowning and 29 cases (91%) of seawater
drowning were diagnosed correctly. This new approach may be more valid than previous methods in cases found >2 days after death or those with substantial
pleural effusion (>100 mL). For an additional 15 bathtub deaths, mean SUM(Na+K+Cl) was 198.8±40.0 mEq/L, and in 14 of these cases (93%) the relationship between cause of death and SUM(Na+K+Cl) could be explained using this method. Forensic pathologists should not depend exclusively on chemical findings and should consider also typical pathological indicators of
drowning. This new method may be useful as a supplementary diagnostic tool when used alongside consideration of the pathological findings.