Open Access Highly Accessed Research article

Influence of the timing of administration of crystalloid on maternal hypotension during spinal anesthesia for cesarean delivery: preload versus coload

Ah-Young Oh12, Jung-Won Hwang12*, In-Ae Song2, Mi-Hyun Kim3, Jung-Hee Ryu12, Hee-Pyoung Park1, Yeong-Tae Jeon12 and Sang-Hwan Do12

Author Affiliations

1 Department of Anesthesiology and Pain Medicine, Seoul National University College of Medicine, Seoul, South Korea

2 Department of Anesthesiology and Pain Medicine, Seoul National University Bundang Hospital, Seongnam, South Korea

3 Department of Anesthesiology and Pain Medicine, St. Mary’s Hospital, Catholic University of Korea School of Medicine, Seoul, Korea

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BMC Anesthesiology 2014, 14:36  doi:10.1186/1471-2253-14-36

Published: 16 May 2014



Prophylactic fluid preloading before spinal anesthesia has been a routine procedure to prevent maternal hypotension during cesarean delivery. Unlike colloid, timing of infusion of crystalloid may be important because of its short stay in intravascular space. We hypothesized that crystalloid loading just after intrathecal injection compared to preload would be more effective in preventing maternal hypotension.


In this prospective controlled study, sixty parturients were randomized to receive 15 ml/kg of crystalloid before (preload group) or after (coload group) intrathecal drug injection for spinal anesthesia. Hypotension was defined if systolic arterial pressure decreased below 80% of baseline and ephedrine was administered to treat hypotension. The incidence of hypotension and the total dose of ephedrine were checked. Blood pressure, heart rate and nausea before childbirth were assessed. Neonatal outcomes were evaluated with Apgar scores and umbilical blood gas analysis.


The incidence of hypotension was lower in the coload group compared to the preload group (53% vs. 83%, P = 0.026). The blood pressure showed the bigger drop during spinal anesthesia in the preload group (34 ± 13 vs. 25 ± 10 mmHg, P = 0.002) and smaller dose of ephedrine was required in the coload group (7.5 [0–30] vs. 15 [0–40] mg, P = 0.015). The incidence of nausea was also lower in the coload group (27% vs. 60%, P = 0.019). Neonatal outcome measures were comparable between two groups.


In case of using crystalloids for cesarean delivery, coload is more effective than preload for the prevention of maternal hypotension after spinal anesthesia.

Trial registration

Clinical Research Information Service KCT0000324 (Jan 12th, 2012)

Cesarean delivery; Hypotension; Spinal anesthesia; Crystalloid