Hyponatremia at autopsy: an analysis of etiologic mechanisms and their possible significance

Abstract

While electrolyte measurements after death may be confounded by a number of variables, vitreous humor sodium tends to remain stable for some time, enabling correlation between ante- and postmortem levels. Review of natural and unnatural causes of reduced vitreous humor sodium levels at autopsy was undertaken to demonstrate the range of diseases that may result in this finding. Natural diseases affecting the vasopressin-renin-angiotensin axis may cause reduction in sodium levels with associated hypovolemia, euvolemia, and hypervolemia. Low sodium measurements may also occur with redistribution of water, and artefactually when there are underlying lipid and protein disorders. Unnatural causes of hyponatremia at autopsy include water intoxication from psychogenic polydipsia, environmental polydipsia, ingestion of dilute infant formulas, beer potomania, endurance exercise, fresh water immersion (including water births) and iatrogenic causes including drug and parenteral fluid administration, and surgical irrigation. A knowledge of the range of conditions that may result in lowered postmortem sodium levels will help to exclude or confirm certain diseases at autopsy. In addition, significant vitreous hyponatremia may be a useful finding to help clarify mechanisms of unnatural deaths.

Vitreous Humor: A Short Review on Post-mortem Applications

“…The degree of change in vitreous electrolytes is dependent on conditions such as the storage condition of the body, the PMI, and the method of sampling the body fluid [26,27]. Post-mortem levels of vitreous electrolytes are dependent on the effects of cellular hypoxia, which lead to an increase in the cell membrane and blood vessel wall permeability, and the reduction of Adenosine Triphosphate (ATP), preventing electrolyte pumps from maintaining physiological cell membrane electrical gradients.…”

“…VH sodium levels of greater than 155 meq/L have been cited as evidence of dehydration [50]. Although changes occur in post-mortem sodium levels these often remain stable for sufficient time to provide information that may be useful in determining the mechanism of death [26] For example, the ante-mortem serum sodium and chloride concentrations are reflected in post-mortem vitreous values, making it possible to diagnose hyponatremia or hypernatremia at the time of death [1,6,13,14,16,[25][26][27][28]44,49,[51][52][53][54][55][56][57][58][59].…”

Postmortem chemistry update part I

“…Byramji et al [97] and Ingham and Byard [98] reviewed Unnatural cases of hyponatremia upon autopsy [97,[104][105][106][107][108][109][110][111][112][113] include water intoxication from psychogenic polydipsia, environmental polydipsia, ingestion of dilute infant formulas, beer potomania, endurance exercise, fresh water immersion and iatrogenic causes including drug and parenteral fluid administration and surgical irrigation. If antemortem findings are not available, vitreous sodium levels lower than 120 mmol/l could support the diagnosis of fatal hyponatremia [104].…”

“…According to several authors abnormalities in antemortem serum sodium concentrations are reflected in postmortem vitreous values, making it possible to diagnose hypo-or hypernatremia at the time of death. Like sodium, vitreous chloride concentrations show minimal falls in values during the early postmortem period and abnormalities in antemortem serum chloride are reflected in postmortem vitreous values[1,4,6,9,19,[21][22][23][24][25][26][27][28][97][98][99].Cases of hypernatremia showing vitreous sodium concentrations ranging from 155 to 210 mmol/l and chloride concentrations ranging from 139 to 147 mmol/l have been reported in the literature[1,[100][101][102]. Madea and Lachenmeier[103] mentioned 17 cases of hypertonic dehydration showing increased vitreous sodium and urea values.…”

Postmortem biochemistry performed on vitreous humor after postmortem CT-angiography

“…According to several authors, abnormalities in antemortem sodium concentrations in serum are reflected in postmortem vitreous levels, making it possible to diagnose hypo-or hypernatremia at the time of death. Postmortem vitreous chloride levels track with sodium, suggesting that abnormalities in antemortem serum chloride may be demonstrated with postmortem vitreous analyses, allowing diagnosis of electrolyte disturbances present at the time of death [9,10,24,29,35,36].…”