The effect of magnesium sulphate on blood flow velocity in the maternal retina in mild pre‐eclampsia: a preliminary colour flow Doppler study

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Abstract
Objectives To investigate the use of colour flow Doppler ultrasound to identify retinal blood vessels in women with mild pre‐eclampsia and to assess the effects of an infusion of magnesium sulphate on the baseline retinal blood flow‐velocity.Design Prospective descriptive study.Setting Ben Taub Hospital, Baylor College of Medicine, Houston, Texas, USA.Subjects Eight women with mild pre‐eclampsiaInterventions Baseline colour flow Doppler ultrasound assessment of the central retinal artery (CRA) and posterior ciliary artery (PCA) blood flow‐velocity before intravenous infusion of 6 g of magnesium sulphate in 100 ml of 5% dextrose water over 20 min, followed by repeat Doppler measurement.Main Outcome Measures Blood pressure, heart rate, pulsatility index (PI), resistance index (RI), angle‐corrected flow‐velocity (cm/s).Results The CRA and PCA were easily and reliably identified. The infusion of 6 g of magnesium sulphate significantly reduced (PP < 0.008) from 0.62 (SD 0.07) to 0.53 (SD 0.10). The PCA PI decreased (P= 0.01) from 0.97 SD (0.14) to 0.78 SD (0.18) and the PCA RI decreased (P= 0.02) from 0.58 SD (0.07) to 0.48 SD (0.09). Angle‐corrected flow‐velocity decreased non‐significantly after the magnesium sulphate infusion.Conclusions Patients with pre‐eclampsia have high CRA and PCA flow‐velocity suggestive of vasospasm. Magnesium sulphate acutely vasodilates the small arteries in the retina, increasing retinal blood flow. Changes in the blood flow in the retina may be indicative of similar changes in other end‐arterial branches of the internal carotid artery. This non‐invasive Doppler method may provide a means to monitor the effects of therapeutic interventions in patients with pre‐eclampsia.