|Year : 2017 | Volume
| Issue : 2 | Page : 46-50
Role of intramuscular injections of vasopressors in combating spinal hypotension during caesarean sections: A prospective, randomized, double-blinded controlled clinical trial
Ananth Srikrishna Somayaji, Gayathri Bhat
Department of Anaesthesiology, K. S. Hegde Medical Academy, Mangalore, Karnataka, India
|Date of Submission||23-Jun-2017|
|Date of Acceptance||09-Nov-2017|
|Date of Web Publication||12-Dec-2017|
Ananth Srikrishna Somayaji
Department of Anaesthesiology, K. S. Hegde Medical Academy, Derlakatte, Mangalore, Karnataka
Source of Support: None, Conflict of Interest: None
Background: Hypotension following spinal anaesthesia (SA) is a common problem. Vasopressors play an important role in its management. The common approach in the routine clinical setting is immediate action after detection of hypotension rather than as a preventive measure. There are studies which compare bolus and intravenous (IV) infusion in the management of maternal hypotension, but literature about comparison of efficacy of intramuscular (IM) vasopressors is very limited. Hence, this study was planned in elective caesarean deliveries to compare the efficacy of IM phenylephrine, ephedrine, and mephentermine for the maintenance of arterial pressure during SA.
Materials and Methods: A prospective, randomized, double-blind study was conducted where 120 parturients belonging to American Society of Anaesthesiologists II undergoing elective caesarean section under SA were evaluated after being randomized into four groups receiving either preemptive phenylephrine 4 mg IM, ephedrine 45 mg IM, mephentermine 30 mg IM, or normal saline 0.9% 2 ml IM as placebo, immediately following SA. The mean arterial blood pressure and heart rate were primarily evaluated and any other complications were also recorded.
Results: It points toward significantly decreased incidence of hypotension in phenylephrine group compared to the other groups (P = 0.034). The incidence of rescue IV ephedrine requirement was maximum with the placebo group, least with mephentermine compared to ephedrine and placebo group. However, there was no statistical difference between the groups with respect to doses of IV ephedrine used (P = 0.08). Maternal nausea, vomiting, and newborn Apgar score were also comparable.
Conclusion: All the vasopressors are effective in reducing the severity of hypotension, though phenylephrine was found to be better for the prevention of hypotension.
Keywords: Intramuscular vasopressors, maternal hypotension, phenylephrine, vasopressors
|How to cite this article:|
Somayaji AS, Bhat G. Role of intramuscular injections of vasopressors in combating spinal hypotension during caesarean sections: A prospective, randomized, double-blinded controlled clinical trial. Indian Anaesth Forum 2017;18:46-50
|How to cite this URL:|
Somayaji AS, Bhat G. Role of intramuscular injections of vasopressors in combating spinal hypotension during caesarean sections: A prospective, randomized, double-blinded controlled clinical trial. Indian Anaesth Forum [serial online] 2017 [cited 2021 Jul 29];18:46-50. Available from: http://www.theiaforum.org/text.asp?2017/18/2/46/220549
| Introduction|| |
Hypotension is a major concern during spinal anaesthesia (SA) for Caesarean section. The Anaesthesiologist has to ensure that the hypotension does not have its ill effects on mother (nausea, vomiting, loss of consciousness, and pulmonary aspiration) and fetus (hypoxia leading to respiratory acidosis). It can be controlled with crystalloids, colloids and vasopressors, positional changes (15° left lateral tilt), and lower leg compressions.,
Recent studies show that the main cause for maternal hypotension is the reduced systemic vascular resistance. Hence, the management has been directed more toward the use of vasopressors in adjunct with fluids.
Different vasopressors have varying degrees of effectiveness; the most common is the bolus of ephedrine and phenylephrine.
Intramuscular (IM) administration of vasopressors has been tried in the past with good outcomes,, but there have been no studies comparing IM routes for different vasopressors. Time for the onset of action after IV administration is 15–30 s, whereas it is 10–20 min after IM administration. This time gap can buy enough time for slow and gradual action of the drug, thus providing better hemodynamic stability during the intraoperative period with lesser side effects on mother and the fetus.
Hence, this study was contemplated in elective caesarean deliveries to compare the efficacy of IM phenylephrine, ephedrine, and mephentermine for the maintenance of arterial pressure during SA in parturients.
Our primary objective was to compare the efficacy of IM vasopressors (phenylephrine, ephedrine, and mephentermine). The secondary objective was to evaluate and compare the dose of rescue ephedrine used along with the assessment of fetal and maternal outcome.
| Materials and Methods|| |
After approval from the institutional ethics committee, this prospective, randomized, double-blinded study was conducted at a tertiary care center from January to July 2015. A total of 120 parturients aged between 18 and 40 years with singleton pregnancy scheduled for elective caesarean section were included in our study. Written informed consent was taken from every participant. They were divided into four groups of 30 each where Group 1 received preemptive phenylephrine 4 mg IM (0.4 ml + 1.6 ml NS), Group 2 received ephedrine 45 mg IM (1.5 ml + 0.5 ml NS), Group 3 received mephentermine 30 mg IM (1 ml + 1 ml NS), and Group 4 received normal saline 0.9% 2 ml IM as placebo, immediately following SA. Pregnant women on thyroid supplements, with gestational diabetes mellitus, hypertension, or any other comorbidities were excluded from the study in addition to other general contraindications of SA. Preoperative checkup was done. In the operating room, venous access was secured on the nondominant hand of every patient by 18-gauge/20-gauge cannula and intravenous (IV) fluid was started. Baseline parameters including heart rate, systolic blood pressure, diastolic blood pressure, mean arterial pressure (MAP), respiratory rate (RR), and SpO2% were recorded. These were again recorded at regular intervals of 2 min until cord clamping. Rescue doses of IV ephedrine were given in necessary cases, and its total requirement was noted. Maternal nausea, vomiting, and newborn Apgar score were also documented. Simple random sequence was generated from the computer. Participants were randomized into four groups with a 1:1 allocation ratio. The allocated intervention was written on slips of paper, placed in serially numbered, opaque envelopes, and sealed. As consecutive eligible participants got enrolled, the envelopes were serially opened, and the allocated intervention was implemented. The chief investigator, medical, and nursing personnel were all blinded. Participants were followed from the point of randomization until complete recovery.
During the procedure, any hypotension (MAP levels <60 mmHg or 25% less than the baseline) was observed, recorded, and treated with rescue doses of IV ephedrine 6mg, and increased as necessary. Apgar scores were recorded at 1 min and 5 min. Any other complications were also noted.
Data was analyzed using SPSS software version 22.0. (IBM SPSS Statistics for Windows, Armonk, NY: IBM Corp.). Descriptive statistics were used to determine the mean and standard deviation for continuous variables like age. Other demographic and obstetric data were compared between the four groups using inferential statistics such as Chi-square test and ANOVA.
| Results|| |
Demographic data and the baseline vitals were comparable in all the groups [Table 1] and [Table 2]. The incidence of hypotension in phenylephrine group was found to be 30%, 40% in ephedrine group, 46.6% in mephentermine group, and 73.3% in placebo group.
The results of the study point toward significantly lesser incidence of hypotension in phenylephrine group compared to the other groups (P = 0.034) [Table 3]. The incidence of rescue IV ephedrine requirement was maximum with the placebo group and least with phenylephrine group. Among mephentermine and ephedrine, mephentermine group was found to have lesser requirements of repeated ephedrine rescue doses. However, there was no statistical difference between the groups with respect to doses of IV ephedrine used for rescue (P = 0.08) [Table 4].
The incidence of maternal nausea and vomiting were similar in all the four study groups. Newborn Apgar scores were also comparable [Table 5].
| Discussion|| |
Vasopressors are often used for counteracting hypotension following SA in caesarean sections. Sahu et al. have reported that maternal hypotension during SA for caesarean section is seen in nearly 85% of patients. This high incidence could be due to factors such as the amount of drug (local anaesthetic) injected, sympathetic blockade, and compression of the inferior vena cava by the gravid uterus compromising the venous return.
Phenylephrine is a synthetic noncatecholamine which directly stimulates alpha-1– adrenergic receptors.
Ephedrine is an indirectly acting synthetic noncatecholamine which stimulates alpha- and beta-adrenergic receptors. Mephentermine is also an indirect-acting synthetic noncatecholamine that acts on beta-adrenergic receptors.
Vasopressors can be administered either through IM or IV route. Despite prior concerns of reactive hypertension with IM administration of vasopressors, multiple studies has reported better outcomes with IM prophylactic vasopressors in preventing hypotension associated with SA for lower-segment caesarean section.,
In fact, Webb and Shiptonhave indicated that IM ephedrine prevents hypotension and provides more sustained cardiovascular parameters than IV ephedrine. In addition, a meta-analysis by Lin et al. have reported equal effectiveness of IV and IM route of administration of vasopressor agents, that is, IV (RR = 1.08; 95% confidence interval [CI], 0.66–1.75) and IM (RR = 1.24; 95% CI, 0.71–2.18).
A few studies comparing IM with IV route; such as a study by Raskaran et al. has reported that IM ephedrine helps in the adequate management of hypotension with lesser incidences of side effects such as nausea and vomiting. Varathan et al. have also reported lesser incidence of hypotension and better hemodynamic stability with IM administration of ephedrine with no incidence of any maternal or fetal adverse effects.
In this study, we found that phenylephrine is the best vasopressor among the three (phenylephrine, mephentermine, and ephedrine) for the effective management of hypotension following SA in cases of caesarean section. Ganeshanavar et al. also compared the efficacy of IV bolus phenylephrine, ephedrine, and mephentermine for the maintenance of arterial blood pressure during SA in caesarean section and concluded that all the three vasopressors effectively maintain hemodynamic stability.
Although this study did not have a comparison between IV and IM routes of administration of vasopressors, it was clinically seen that there was better hemodynamic stability with IM route.
The incidence of hypotension in phenylephrine group was found to be least compared to ephedrine, mephentermine, and placebo group. This was seen to be in accordance with a study done by Ayorinde et al. where they found a lesser incidence of hypotension with prophylactic phenylephrine than with ephedrine.
On comparison between the four study groups, incidences of maternal nausea and vomiting were similar in each of the groups, and there was no statistically significant difference. Newborn Apgar scores were also comparable. Umbilical cord pH was not used as an assessment tool in our study, even though recent studies by Allen et al., Casey et al., and Finster et al.,, have shown that Apgar score is a good predictor of neonatal well-being status.
| Conclusion|| |
IM administration of vasopressors was found to have an added benefit of conferring hemodynamic stability and lesser side effects. The onset of action being longer, it provides a comparatively better effect in the management of hypotension following SA for the caesarean delivery.
Phenylephrine group had minimum incidences of nausea and vomiting while mephentermine group patients needed least number of repeated rescue doses of ephedrine.
To conclude, all vasopressors were found to be effective in reducing the severity of hypotension, with phenylephrine being the overall better drug for the prevention of hypotension in parturients.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2], [Table 3], [Table 4], [Table 5]