Intravenous dexmedetomidine infusion for labour analgesia in patient with preeclampsia

Editor, Epidural anaesthetic techniques continue to be the most effective and popular methods employed to provide analgesia for the parturient patient for labour and delivery. Patients with preeclampsia and eclampsia may present an increased risk of serious complications from neuraxial anaesthesia [1]. Alternative efficacious and safe analgesic methods would be useful adjuncts to obstetric anaesthesia, especially for this high-risk patient group. Dexmedetomidine is a highly selective α2-adrenoreceptor agonist that, when administered as an intravenous infusion, possesses analgesic, sedative and haemodynamic controlling properties with minimal respiratory depression [2,3]. The placental transfer is minimal and, therefore, little or no effect on the fetus should be seen. α2-Adrenoreceptor agonists have been shown to provide neuraxial analgesia via central α2-adrenoreceptors [4] and have been used successfully in the management of cancer pain [5]. Dexmedetomidine modulates the release of catecholamines and, therefore, may be useful when administered intravenously to patients with eclampsia in controlling the blood pressure [6]. A 37-year-old pregnant woman was admitted for induction of labour because of the development of mild-to-moderate preeclampsia. She was at 38 weeks' gestation and gravida 5 para 3 + 1 with a single cephalic presentation pregnancy. Her blood pressure was 150/90 mmHg at admission, and she had 3+ proteinuria. She had a history of insulin-dependent diabetes and a random blood sugar level of 198 mg dl−1. There was no history of recent headache, visual disturbances or preseizure activity. She was 1.6 m tall and weighed 98 kg. There was no lower limb oedema. Shortly after admission to the obstetric unit, her blood pressure was 170/105 mmHg, and she still had 3+ proteinuria. Her vaginal examination revealed that the Bishop score was less than 3; so induction of labour was initiated with the insertion of a prostaglandin E2 vaginal tablet. Three hours later the patient started to have regular uterine contractions every 3–5 min, each lasting for 35 s. She had 2 cm cervical dilatation with 60% effacement and a nonengaged fetal head. Her pain during uterine contractions was increasing in intensity with a visual analogue scale (VAS) score of 6–7. Laboratory data included a haemoglobin concentration of 11.8 g dl−1 (normal range: 12–16 g dl−1), platelet count 183 000 l−1 (normal range: 140 000–440 000 l−1), prothrombin time 14.1 s (normal range: 11.5–15.5 s), activated prothombin time 34.1 s (normal 27–35 s), normal liver enzymes and normal renal function tests. Total serum protein was 6.6 g dl−1 (normal range: 6–8 g dl−1) and serum albumin of 3.3 g dl−1 (normal range: 3.5–5 g dl−1). A magnesium sulphate intravenous infusion was started as prophylaxis against the development of eclampsia. Epidural analgesia was offered as an option for labour pain relief but was declined by the patient. The intravenous infusion of dexmedetomidine was discussed with the patient. After written informed consent and approval by our ethics committee was obtained, this ‘off-label’ use of the drug was commenced. A bolus dose of dexmedetomidine was not given. The infusion was started with a low dose of 0.2 μg kg−1 h−1. Dexmedetomidine was diluted (200 μg in 48 ml of normal saline) and infused via an infusion syringe pump. The patient's pain was monitored using the VAS, and the dexmedetomidine infusion was increased by 0.1 μg kg−1 h−1 every 30 min to a maximum of 0.5 μg kg−1 h−1 to reduce the VAS score to a range of 0–3. Sedation was monitored with the Ramsay Sedation Score (RSS) and the patient was maintained with an RSS of 2–3 by adjusting the dexmedetomidine infusion rate [7]. An oxytocin infusion was administered to accelerate the course of labour. During labour, blood pressure remained elevated with a diastolic pressure around 100 mmHg despite an infusion of dexmedetomidine of 0.4 μg kg−1 h−1. The VAS score was well controlled with scores of 3, 3, 2, and 2 at 30, 60, 120 and 180 min, respectively. The RSS was well maintained at 2, and the arterial oxygen saturation (SpO2), respiratory rate and pulse rate were maintained in the normal range (Fig. 1). After 3 h of the dexmedetomidine infusion it was decided to undertake a Caesarean section because of the presence of persistent late decelerations in fetal heart rate. This was performed under general anaesthesia. A lively 3.7 kg female infant was delivered successfully with an Apgar score of 8–9. The infant was admitted to the neonatal intensive care unit as a precaution because the mother was a diabetic patient. After delivery, the mother and the baby did well and were discharged home in excellent condition after 7 days.Fig. 1When a labour epidural is contraindicated or declined by the patient, the alternatives include natural childbirth techniques [8] or opioid-based techniques [9]. However, both techniques may be associated with poor analgesia and the opioid technique with maternal and fetal respiratory depression. Although dexmedetomidine has not been approved for intravenous use during pregnancy, it is reported to have been used in pregnant patients undergoing nonobstetric surgery [10]. Dexmedetomidine was shown to decrease the total dose of opioids, promote haemodynamic stability and maintain maternal homeostasis and uteroplacental blood flow. In-vitro studies on human placentas have demonstrated a low maternal–fetal transfer of dexmedetomidine, presumably because of its high lipophilicity [11]. These characteristics of dexmedetomidine may make it an ideal intravenous analgesic for labour when an epidural technique is contraindicated. There were no incidences of maternal bradycardia or hypotension. In this case, there was fetal heart rate deceleration associated with uterine contraction, but the underlying fetal heart rate was normal. The potential specific advantages of dexmedetomidine in patients with preeclampsia with its specific action for blood pressure control potentially offer a very significant advantage over current techniques. A pilot study is indicated to explore the role of dexmedetomidine administered intravenously in this high-risk parturient group.