This article was presented at the annual meeting of the Obstetric Anaesthetists Association, June 5–6, 2003, Cardiff, Wales, UK, and the 35th annual meeting of the Society for Obstetric Anesthesia and Perinatology, May 14–17, Phoenix, Arizona, USA, May 2003.
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Magnesium-induced vasodilation in the dorsal hand vein†
Article first published online: 19 APR 2004
DOI: 10.1111/j.1471-0528.2004.00114.x
Issue
BJOG: An International Journal of Obstetrics & Gynaecology
Volume 111, Issue 5, pages 446–451, May 2004
Additional Information
How to Cite
Landau, R., Scott, J. A. and Smiley, R. M. (2004), Magnesium-induced vasodilation in the dorsal hand vein. BJOG: An International Journal of Obstetrics & Gynaecology, 111: 446–451. doi: 10.1111/j.1471-0528.2004.00114.x
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Publication History
- Issue published online: 19 APR 2004
- Article first published online: 19 APR 2004
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Objective Magnesium affects blood pressure by modulating vascular tone and reactivity. In obstetric patients, magnesium is administered to prevent eclamptic seizures and as a tocolytic to treat preterm labour. Prior to studying vascular sensitivity in women with pre-eclampsia, we sought to determine the effect of magnesium on venous tone in healthy women of childbearing age.
Design Dose–response study.
Setting Columbia-Presbyterian Medical Center, New York.
Population Ten healthy non-pregnant women (age range 21–47 years).
Methods Vascular response to magnesium sulphate (MgSO4) was measured in a dorsal hand vein using the linear variable differential transformer (LVDT) technique. Complete dose–response curves to MgSO4 (0.0000275–0.088 mmol/min) were determined after 50% preconstriction of the vein with phenylephrine.
Main outcome measures The ED50 of MgSO4 (dose resulting in 50% of maximal effect, Emax) was determined. Blood samples from the contralateral upper extremity were obtained to assess total plasma magnesium levels at baseline and at the highest infused dose of magnesium. ED50 results are expressed as geometric mean (95% confidence interval, CI). Emax results and magnesium plasma concentrations are expressed as mean [SD].
Results The ED50 of MgSO4 was 0.000307 mmol/min (95% CI 0.138, 0.666) and Emax was 102% [20%].
Conclusion Magnesium induces dose-dependent venodilation in healthy women in the absence of systemic haemodynamic effects. The dose resulting in vasodilation using the LVDT/hand vein model is two to three orders of magnitude less than the therapeutic doses of magnesium used for tocolysis or seizure prophylaxis. Studies of the effect of systemically administered therapeutic doses of magnesium on vascular reactivity in pre-eclampsia will be of interest.