Minimal Effective Weight-based Dosing of Ondansetron to Reduce Hypotension in Cesarean Section Under Spinal Anesthesia

A Randomized Controlled Superiority Trial

Maliwan Oofuvong; Thitikan Kunapaisal; Orarat Karnjanawanichkul; Nussara Dilokrattanaphijit; Jaranya Leeratiwong

BMC Anesthesiol. 2018;18(105)

Conclusions

Ondansetron administered at a dose of 0.05 mg/kg or 0.1 mg/kg before spinal anesthesia was not effective in reducing the incidence of hypotension in pregnant women undergoing cesarean section. Higher weight-based dosing of ondansetron should be examined keeping the safety issues in mind.

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Abbreviations
CI: Confidence interval; DBP: Diastolic blood pressure; MAP: Mean arterial blood pressure; RR: Relative risk ratio; SBP: Systolic blood pressure

Acknowledgements
We would like to thank Assistant Professor Edward McNeil for editing the manuscript and Glenn Shingledecker for correcting some grammatical errors in the manuscript.

Funding
This work was funded by the Faculty of Medicine, Prince of Songkla University, Hat Yai, Songkhla, Thailand.

Availability of data and materials
The datasets used and analyzed during the current study are available from the corresponding author upon reasonable request.

Ethics approval and consent to participate
The study was approved by the Institutional Ethics Committee of the Faculty of Medicine, Prince of Songkla University, Songkhla, Thailand, Chairperson Assoc. Prof. Boonsin Tangtrakulwanich, EC number EC 58382081 on March 22, 2016. A written informed consent was obtained from all participants.

Consent for publication
Not applicable.

Publisher's Note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Table 1. Comparison of demographic and anesthesia related data between the three groups
Parameter	Normal saline (n = 72)	Ondansetron 0.05 mg/kg (n = 71)	Ondansetron 0.1 mg/kg (n = 72)	P-value
Age (years)^a	31.8 (4.5)	32.2 (5.5)	32.7 (4.8)	0.55
Weight (kg)^a	67.5 (9.6)	68.7 (9.1)	69.6 (8.9)	0.39
Height (cm)^a	157.2 (5.5)	156.9 (5.7)	157.9 (5.2)	0.48
Body mass index (kg/m²)^a	27.3 (3.5)	27.9 (3.0)	27.9 (3.2)	0.47
Type of operation
CS only	49 (68.1)	49 (69)	46 (63.9)	0.79
CS with tubal resection	23 (31.9)	22 (31)	26 (36.1)
Site of spinal anesthesia
L2–3	2 (2.8)	0 (0)	0 (0)	0.33
L3–4	70 (97.2)	71 (100)	72 (100)
Number of blocks
1	70 (97.2)	70 (98.6)	69 (95.8)	0.87
2	2 (2.8)	1 (1.4)	3 (4.2)
Anesthesia level^b	T7 (T6–T8)	T6 (T6–T8)	T6 (T6–T8)	0.33
Analgesia level^b	T4 (T3–T4)	T3 (T3–T4)	T4 (T3–T4)	0.43
Premedication with metoclopramide	25 (34.7)	21 (29.6)	21 (29.2)	0.73
Premedication with ranitidine	25 (34.7)	21 (29.6)	21 (29.2)	0.73

Data are presented as frequency (%) unless stated otherwise
^amean (SD)
^bmedian (IQR)
CS cesarean section

Table 2. Comparison of incidence and episodes of hypotension between the three groups
Parameter	Normal saline (n = 72)	Ondansetron 0.05 mg/kg (n = 71)	Ondansetron 0.1 mg/kg (n = 72)	P-value
Total incidence,
n (%)	59 (81.9)	60 (84.5)	53 (73.6)	0.23
(95% CI)	(73.1–90.8)	(76.1–92.9)	(63.4–83.8)
Episodes, median (IQR)	2 (0–4.0)	3 (0.5–5.0)	1 (0–3.2)	0.07
Before delivery
Incidence,
n (%)	57 (79.2)	59 (83.1)	50 (69.4)	0.13
(95% CI)	(69.8–88.5)	(74.4–91.8)	(58.8–80.1)
Episodes, median (IQR)	2 (1–6.0)^a	5 (1.5–8.0)^b	2 (0–5.0)^ac	0.015
After delivery
Total incidence,
n (%)	37 (52.1)	41 (57.7)	39 (54.9)	0.80
(95% CI)	(40.5–63.7)	(46.3–69.2)	(43.4–66.5)
Episodes, median (IQR)	0 (0–2.0)	1 (0–3.0)	1 (0–1.5)	0.64

IQR interquartile range, CI confidence interval
^acGroups sharing the same superscript were not significantly different, ^bGroup was significantly different compared to the others

Table 3. Comparison of surgical and anesthetic parameters between the three groups
Parameter	Normal saline (n = 72)	Ondansetron 0.05 mg/kg (n = 71)	Ondansetron 0.1 mg/kg (n = 72)	P-value
Duration of surgery (min)	56.6 (18.1)	58.9 (22.3)	55.2 (16.5)	0.52
Ephedrine (mg), median (IQR)	6 (0–18)	12 (0–18)	6 (0–18)	0.21
Norepinephrine (mcg), median (IQR)	0 (0–10)	0 (0–10)	0 (0–10)	0.47
Oxytocin (unit)	22.7 (8.5)	21.3 (9.1)	22.4 (9.7)	0.62
Methylergometrine (mg), median (IQR)	0 (0–0.2)	0 (0–0.2)	0 (0–0.2)	0.77
Blood loss (mL)	447.9 (201.3)	490.8 (241.2)	440.3 (198.2)	0.32
Crystalloid (mL)	1934.7 (303.3)	1884.5 (346.2)	1891.7 (284.8)	0.58
Packed red cells (mL)	0 (0)	2.8 (23.9)	0 (0)	0.36
Metoclopramide, n (%)	12 (16.7)^a	6 (8.5)^ab	2 (2.8)^b	0.02

Data are presented as mean (SD) unless stated otherwise
^abGroups sharing the same superscript were not significantly different
IQR interquartile range

Table 4. Comparison of maternal and newborn adverse events between the three groups
Adverse event	Normal saline (n = 72)	Ondansetron 0.05 mg/kg (n = 71)	Ondansetron 0.1 mg/kg (n = 72)	P-value
Mother
Urticaria	1 (1.4)	0 (0)	2 (2.8)	0.78
Arrhythmia	2 (2.8)	0 (0)	1 (1.4)	0.78
Vomiting	10 (13.9)	10 (14.1)	3 (4.2)	0.09
Itching	10 (13.9)	4 (5.6)	7 (9.7)	0.25
Newborn
Apgar 1, median (IQR)	9 (8–9)	9 (8–9)	9 (8–9)	0.94
Apgar 5, median (IQR)	9 (9–9)	9 (9–9)	9 (9–9)	0.14
Hypotension	0 (0)	1 (1.4)	0 (0)	0.33
Tachypnea	2 (2.8)	5 (7.0)	0 (0)	0.04*