Could not recruit patients

Magnesium has been shown to decrease the shivering experienced from neuraxial anesthesia. This study aims to investigate whether magnesium decreases the shivering experienced in parturients undergoing labor epidural anesthesia for Cesarean delivery.

Women who have epidurals in place and go on to require a Cesarean delivery typically have their epidurals 'topped-up' with a fast onset local anesthetic to ensure the lower body is fully numb for surgery. This is called an epidural 'top-up'. However, a side effect of epidural top-ups is shivering, which is uncomfortable for the mother and interferes with patient monitoring. Magnesium administration has been shown to decrease shivering in the non-pregnant population. Therefore, in this study the investigators aim to determine if magnesium given prior to an epidural top-up decreases the incidence and severity of shivering in the pregnant population.

Inclusion Criteria:

1. Gestational age of ≥37 weeks
2. Women who are ≥ 19 years old
3. Women undergoing Cesarean delivery under lidocaine top-up via a preexisting epidural catheter inserted for labor analgesia
4. American Society of Anesthesiologist (ASA) Physical Status class 1 or 2

Exclusion Criteria:

1. Emergency Cesarean delivery with limited time for informed consent
2. Women who have received MgSO4 prior to study enrollment
3. Indication for alternative mode of anesthesia for Cesarean delivery (e.g., general anesthesia)
4. Medical conditions or medications that could lead to tremor or shivering. (e.g., movement disorder, untreated thyroid disease) or mask tremor or shivering (e.g., beta-blocker, benzodiazepine, anticonvulsants)
5. Active shivering at time of recruitment
6. Inability to read and understand English for the purpose of informed consent
7. Contraindications to receiving MgSO4 (hypersensitivity reactions, respiratory rate <16breaths/min, absent reflexes, urine output <100 mL during the previous 4 hours, renal failure, or hypocalcemia)
8. History of previous postpartum hemorrhage