Stability of endogenous GHB in vitreous humor vs peripheral blood in dead bodies.

For the first time, the stability of GHB was tested in post-mortem peripheral blood and vitreous humor samples, collected from 22 dead bodies at two different times: at the external body examination at the place of death and then during autopsy. An ad hoc method for the detection and quantification of GHB in vitreous humor by gas chromatography coupled to mass spectrometry (GC-MS) was developed and validated, with a good linearity between 0.1 and 50μg/mL (r2=0.991) and a precision and accuracy always better than 10% and an analytical recovery higher than 90%. The geometric mean of GHB concentration in the 22 peripheral blood samples at t0 was: 3.6μg/mL (95% CI: 2.3-5.9μg/mL) and at t1 it was 7.4μg/mL (95% CI: 5.0-10.9μg/mL); that of GHB in the 22 vitreous humor at t0 was: 2.5μg/mL (95% CI: 1.5-4.1μg/mL) and at t1 it was 3.0μg/mL (95% CI: 1.9-4.8μg/mL). There was no significant difference between the GHB concentrations in vitreous humor and peripheral blood at t0 in all the samples (p>0.10). Conversely at t1, the increase of GHB in the peripheral blood was significantly increased by a 102% (range: 86-120%) (p<0.001 vs t0), while in the vitreous humor only a slight increase by 19% was observed (range: 16-21%) (p>0.05 vs t0). Finally at t1, GHB values in the two matrices were statistically different, being that of peripheral blood higher (p<0.01). This study demonstrated the usefulness of vitreous humor as a more stable alternative matrix in comparison to peripheral blood for the post-mortem determination of endogenous GHB.