Magnesium Therapy in Pre-eclampsia Prolongs Analgesia Following Spinal Anaesthesia with Fentanyl and Bupivacaine: An Observational Study

Preeklampside Magnezyum Tedavisi, Fentanil ve Bupivakain ile Yapılan Spinal Anestezisi Sonrası Analjeziyi Uzatıyor: Gözlemsel Çalışma

Tülay Özkan Seyhan ¹, Meltem Karadeniz ¹, Kemalettin Koltka ¹, Mukadder Orhan Sungur ¹, Olgaç Bezen ², İbrahim Kalelioğlu ³

¹Department of Anesthesiology, İstanbul University İstanbul Faculty of Medicine, İstanbul, Turkey
²Department of Anesthesiology, İstanbul Bilim University Faculty of Medicine, İstanbul, Turkey
³Department of Obstetrics and Gynecology, İstanbul University İstanbul Faculty of Medicine, İstanbul, Turkey

DOI : 10.5152/balkanmedj.2014.13116

Pages : 143-148

Abstract

Background: Magnesium has anti-nociceptive effects and potentiates opioid analgesia following its systemic and neuraxial administration. However, there is no study evaluating the effects of intravenous (IV) magnesium sulphate (MgSO4) therapy on spinal anaesthesia characteristics in severely pre-eclamptic patients.

Aims: The aim of this study was to compare spinal anaesthesia characteristics in severely pre-eclamptic parturients treated with MgSO4 and healthy preterm parturients undergoing caesarean section. Thus, our primary outcome was regarded as the time to first analgesic request following spinal anaesthesia.

Study Design: Case-control Study.

Methods: Following approval of Institutional Clinical Research Ethics Committee and informed consent of the patients, 44 parturients undergoing caesarean section with spinal anaesthesia were enrolled in the study in two groups: Healthy preterm parturients (Group C) and severely pre-eclamptic parturients with IV MgSO4 therapy (Group Mg). Following blood and cerebrospinal fluid (CSF) sampling, spinal anaesthesia was induced with 9 mg hyperbaric bupivacaine and 20 µg fentanyl. Serum and CSF magnesium levels, onset of sensory block at T4 level, highest sensory block level, motor block characteristics, time to first analgesic request, maternal haemodynamics as well as side effects were evaluated.

Results: Blood and CSF magnesium levels were higher in Group Mg. Sensory block onset at T4 were 257.1±77.5 and 194.5±80.1 sec in Group C and Mg respectively (p=0.015). Time to first postoperative analgesic request was significantly prolonged in Group Mg than in Group C (246.1±52.8 and 137.4±30.5 min, respectively, p<0.001; with a mean difference of 108.6 min and 95% CI between 81.6 and 135.7). Side effects were similar in both groups. Group C required significantly more fluids.

Conclusion: Treatment with IV MgSO4 in severe pre-eclamptic parturients significantly prolonged the time to first analgesic request compared to healthy preterm parturients, which might be attributed to the opioid potentiation of magnesium.