Application of scanning electron microscopy in the auxiliary diagnosis of death caused by potassium chloride intravenous injection: a case report

To determine the cause of death, in addition to routine autopsy, some assisted techniques are imperative to achieve a definite diagnosis. Herein, we report a case of 36-year-old man who was found dead in his apartment. Medical drug containers (potassium chloride, zolpidem, and propofol) and medical instruments (syringes and indwelling needles) were also found at the scene. An autopsy revealed large amounts of whitish foamy and brown liquid in the trachea and bronchi, and histopathological findings showed remarkable pulmonary congestion and edema. An injection mark with hemorrhage on the right wrist was found on external examination. Results of forensic pathology excluded the presence of mechanical injuries, mechanical asphyxia, embolism, and other fatal diseases. The data of toxicological analysis showed that concentrations of zolpidem and propofol in blood were appreciably higher than the therapeutic dose but they did not reach the absolute lethal dose. Moreover, the level of potassium in the blood and vitreous humor was higher than the expected concentration after death. A scanning electron microscope (SEM) combined with energy-dispersive X-ray microanalyzer (EDX) was subsequently applied to assess the skin samples collected from bilateral wrists. Ultrastructural observation discovered continuous visible interruption of the skin around the injection mark, and energy spectrum analysis revealed statistically significantly higher potassium content of the skin over the right wrist than the left wrist. Comprehensive analysis concluded that the deceased had died of potassium chloride intravenous injection under the zolpidem and propofol effects.