|Year : 2017 | Volume
| Issue : 1 | Page : 7-11
Is 5 IU bolus of oxytocin as effective as 10 IU bolus for control of bleeding during cesarean section under spinal anesthesia?
Musa M Yusuf, Elizabeth Ogboli Nwasor, Rabiu I Mohammed
Department of Anaesthesia, Ahmadu Bello University Teaching Hospital, Shika-Zaria, Kaduna State, Nigeria
|Date of Web Publication||13-Sep-2017|
Elizabeth Ogboli Nwasor
Department of Anaesthesia, Ahmadu Bello University Teaching Hospital, Shika-Zaria, Kaduna State
Source of Support: None, Conflict of Interest: None
Aim and Objectives: We sought to compare the hemodynamic effects of 5 international unit (IU) and 10 IU of intravenous (IV) boluses of oxytocin and their efficacy in reducing blood loss during cesarean section and also to determine the incidence of postoperative nausea and vomiting (PONV) and postdural puncture headache (PDPH). Patients and Methods: One hundred and ten parturients of American Society of Anesthesiologists' I and II scheduled for cesarean section under spinal anesthesia were randomized into two groups. Group A (n = 55) received 5 IU IV bolus of oxytocin and Group B (n = 55) received 10 IU IV bolus of oxytocin after delivery. Ten milliliters per kilogram of 0.9% saline was administered to both groups as volume preload. Subarachnoid block was performed with size 24G spinal needles at L2/L3 or L3/L4 intervertebral space with the patients in sitting position. Two milliliters of 0.5% heavy bupivacaine was administered slowly intrathecally. Following delivery of the baby, IV boluses of 5 IU (Group A) or 10 IU (Group B) of oxytocin were administered slowly, and recording of heart rate, systolic, diastolic, and mean arterial blood pressure was done every minute for 5 min after bolus injection. IV infusion of 30 IU of oxytocin in 500 ml of 0.9% saline (60 mU/ml) at a rate of 125 ml/h was continued in both groups till the end of surgery. Estimated blood loss (EBL) was assessed by visual estimation. Patients were monitored continuously until 24 h after surgery to evaluate PDPH and PONV. Results: There were no statistically significant differences in the EBL between the two groups. There was no significant rise in heart rate and no significant decrease in mean arterial blood pressure in Group A compared to Group B. The incidence of PDPH and PONV was also comparable in both groups. Conclusion: Five IU of IV bolus of oxytocin is as effective as 10 IU of IV bolus in reducing blood loss during cesarean section.
Keywords: Cesarean section, hemodynamic, oxytocin, spinal anesthesia
|How to cite this article:|
Yusuf MM, Nwasor EO, Mohammed RI. Is 5 IU bolus of oxytocin as effective as 10 IU bolus for control of bleeding during cesarean section under spinal anesthesia?. Arch Med Surg 2017;2:7-11
|How to cite this URL:|
Yusuf MM, Nwasor EO, Mohammed RI. Is 5 IU bolus of oxytocin as effective as 10 IU bolus for control of bleeding during cesarean section under spinal anesthesia?. Arch Med Surg [serial online] 2017 [cited 2018 Oct 20];2:7-11. Available from: http://www.archms.org/text.asp?2017/2/1/7/214562
| Introduction|| |
Irrespective of the form of anesthesia used for cesarean section, oxytocin 5–10 international unit (IU) bolus is given to the mother immediately after delivery of the new born, to cause uterine contractions and decrease blood loss. It is given either as a slow intravenous (IV) bolus of 5–10 IU, an infusion or combination of both. Even though most literature recommends 5 IU IV bolus of oxytocin following the delivery of a baby and clamping of the cord, there is no agreement as to the bolus dose of oxytocin to be given after delivery among anesthetists. The bolus dose of oxytocin given ranges from 1 IU to 40 IU. Administration of oxytocin as IV bolus is associated with hypotension and tachycardia. Similar hemodynamic changes were also seen with administration of oxytocin by infusion but to a lesser degree as demonstrated by Bhattacharya et al. The hemodynamic changes are related to the dose as well as rate of infusion of oxytocin. Several options have been considered for reducing the hemodynamic response to oxytocin, among which are giving smaller doses of IV boluses of oxytocin and giving oxytocin as an infusion rather than bolus. Therefore, there is need to determine and standardize the dose of IV boluses and the rate of infusion of oxytocin during cesarean section to reduce the adverse hemodynamic responses associated with its use.
| Patients and Methods|| |
This study was carried out at Ahmadu Bello University Teaching Hospital, Zaria. Approval was obtained from the Hospital's Health Research and Ethics Committee. Informed consent was obtained from prospective subjects during the routine preanesthetic assessment. Patients who could not understand English had explanation done in the local dialect. Detailed history was obtained during the preanesthetic visit and physical examination was carried out. Relevant investigations such as packed cell volume (PCV) and urinalysis were ordered for. Ranitidine was routinely prescribed as antacid prophylaxis. Patients for both elective and emergency cesarean section were recruited into the study. Patients were randomized using computer-generated random numbers by (WINPEPI COMPARE2.EXE version 3.85) computer software into two equal Groups (A and B), to receive either 5 or 10 units of oxytocin by slow IV injection given over 5 s. Double blinding was accomplished using sealed opaque envelopes with the help of a study assistant. The study drug, oxytocin injection BP manufactured by the Rotexmedica, Trittau, Germany, was made up to 2 ml using sterile water for injection, irrespective of the dose administered, by the study assistant.
Patients were positioned supine with a left lateral tilt to prevent hypotension. Standard monitoring began 5 min before performing subarachnoid block with recording of the heart rate, noninvasive systolic, diastolic, and mean arterial blood pressures using Dash 4000 (GE) multiparameter monitor. The arterial oxygen saturation was measured using a pulse oximeter. Two IV lines were secured: a separate IV line was dedicated to oxytocin infusion, while a second IV line was used for other fluid and drug requirements. Preloading was done using 10 ml/kg of 0.9% saline just before instituting spinal anesthesia. Lumbar puncture was performed with all patients in sitting position at L3/L4 or L2/L3 intervertebral space with size 24G Quincke bevel-shaped spinal needles using an introducer. Two milliliters of 0.5% heavy bupivacaine was administered intrathecally once clear cerebrospinal fluid was visualized. Patients were positioned supine with a 15° head-up and left lateral tilts. Level of sensory block was tested using blunt pin prick sensation. Bromage scale Motor block was assessed by the ability of the patient to move her legs or feet following the Bromage scale thus:
- No block – full flexion of knees and feet
- Partial block – just able to flex knees plus full flexion of feet
- Almost complete block – unable to flex knees, some foot flexion still
- Complete block – unable to move legs or feet.
Five or ten units of oxytocin was administered depending on the patients' group by slow (over 5 s) IV injection following delivery of the newborn. Both groups subsequently after 5 min of initial bolus received 30 IU oxytocin infusion in 500 ml of 0.9% saline (60 mU/ml) at a rate of 125 ml/h (42 drops/min) till the end of surgery.
In addition to the baseline, recording of the heart rate, systolic, diastolic, and mean arterial blood pressures for the study was done at the time of lumbar puncture, 2 min after lumbar puncture, every minute after administration of oxytocin bolus for 5 min, and subsequently recorded every 5 min during the administration of infusion until end of cesarean section.
Blood loss was monitored continuously throughout the procedure by visual estimation of blood spillage on the drapes, surgeons' gowns, and floor and counting of swabs and suction bottle losses by the same investigator to reduce interobserver bias. While taking suction bottle losses into consideration, the presence of liquor and other nonbloody fluids was considered to avoid overestimation of blood loss. While counting swabs, a 3 × 4 inch swab was considered as containing 15 ml of blood if fully soaked and 10 ml if partially soaked. A large 18 × 18 inch swab was considered as containing 150 ml if fully soaked and 100 ml if partially soaked. Estimated blood loss (EBL) was also recorded and replaced if >15% of the patient's total blood volume. Those who required blood transfusion or additional doses of IV oxytocin were given but were excluded from the study. Patients were reviewed 24 h after surgery to find out whether there was postdural puncture headache (PDPH) and/or other postanesthetic complications.
Between November 2012 and September 2013, a total of 110 patients, n = 55 for each group, of American Society of Anesthesiologists' (ASA) Physical Status Class I and II were studied.
Pregnant women aged 16–45 years undergoing elective or emergency cesarean section under spinal anesthesia, who were of ASA I and II physical status, were included in the study.
All pregnant women who refused to participate in the study or who were of ASA III, IV, and V physical status classification; pregnant women <16 years of age or >45 years; patients with known cardiac diseases such as congestive cardiac failure, hypertensive heart disease, pregnancy induced hypertension, severe preeclampsia, and eclampsia, blood loss in excess of 15% of patient's total blood volume, i.e., blood loss which required blood transfusion; patients who had induction or augmentation of labor with oxytocin, inadequate subarachnoid block (Bromage 1), and uncooperative patients despite effective subarachnoid block were excluded from the study.
The primary outcome measure was to determine the effectiveness of 5 IU and 10 IU IV boluses of oxytocin in reducing blood loss during cesarean section. The secondary outcome measure was to determine whether there are differences on comparison of effects on heart rate and mean arterial blood pressure of 5 IU and 10 IU IV boluses of oxytocin. Other measures include the incidence of side effects such as shivering, epigastric pain, chest pain, postoperative nausea and vomiting (PONV), and PDPH.
Data sources and measurement
The data collected were entered into Statistical Package for Social Sciences version 17.0 (SPSS Inc., 233 South Wacker Drive, 11th Floor, Chicago, IL 60606-6412.) computer package for Windows. The independent sample's t-test was used for intergroup comparisons of means of quantitative variables and frequency and percentages for comparison of means of qualitative variables. Tables, histogram, and figures were used to illustrate the results where necessary. P < 0.05 was considered statistically significant.
Sample size determination
Sample size was calculated using the following formula for comparison of two means, which determines sample size of each group to get a total of 110 patients.
n = number of patients per group, Zα= Zscore corresponding to 95% level of significance = 1.96, Zβ= Zscore corresponding to 80% statistical power of study = 0.84, X1= mean of control group, X2= mean of study group, Sδ1= standard deviation (SD) of control group, Sδ2= SD of study group.
| Results|| |
Six patients (4 in Group B and 2 in Group A) were excluded from the study because they developed severe hypotension and were given ephedrine. Two patients (1 from each group) were excluded following failed subarachnoid block and conversion to general anesthesia. Two patients from Group A who were uncooperative despite an effective subarachnoid block (Bromage scale 4 and 3) were also converted to general anesthesia and excluded from the study.
The two groups were comparable with respect to demographic characteristics. The mean age for Group A was (mean ± SD) 29.22 ± 4.68 and 28.98 ± 6.09 for Group B (P = 0.826) [Table 1].
The parity was also comparable in both groups. The mean parity for Group A was 1.70 ± 1.74 and 1.84 ± 2.07 for Group B with P = 0.715 [Table 1]. The type of operation was also comparable in both groups. Sixteen (32%) patients in Group A had their operations as elective while 34 (68%) patients had theirs as emergency. For Group B, 23 (46%) patients were operated as elective while 27 (54%) were carried out as an emergency. The two groups were also comparable with respect to the indications for cesarean section with 37 (74%) patients in each group having maternal indications such as repeat cesarean section, twin gestation, abnormal presentation and/or lie, antepartum hemorrhage, obstructed labor, and cephalopelvic disproportion. Only 1 (2%) patient had fetal indication, i.e., fetal distress in Group A while 5 (10%) patients had fetal indications (fetal distress) in Group B. Twelve (24%) patients and 8 (16%) patients had maternofetal indications (i.e., also had fetal distress in addition to the maternal indications mentioned earlier) in Group A and B, respectively. The two groups were comparable with respect to ASA physical status. The two groups were also comparable with respect to the preoperative assessment of pulse rate, systolic and diastolic blood pressure as well as PCV. The mean preoperative pulse rate for Group A was (mean ± SD) 85.74 ± 11.00 while that for Group B was 88.48 ± 9.52 with a P = 0.186. The mean preoperative systolic blood pressure for Group A was (mean ± SD) 125.62 ± 15.66 and 122.38 ± 12.17 for Group B with a P = 0.251. The mean preoperative diastolic blood pressures were 78.12 ± 11.25 and 77.32 ± 10.94 for Groups A and B, respectively, with a P = 0.719. The mean preoperative PCV was 34.76 ± 3.79 and 33.38 ± 3.94 for Groups A and B, respectively, with a P = 0.077. Thirty patients (60%) and 29 patients (58%) for Groups A and B, respectively, had their lumbar puncture done at L3/L4 intervertebral space while 20 patients (40%) and 21 patients (42%) for Groups A and B, respectively, had theirs at L2/L3 intervertebral space. Overall, the patients were comparable with respect to the operative conditions. The mean IV crystalloid preload was 690.00 ± 229.24 ml (mean ± SD) and 681.00 ± 143.18 ml for Groups A and B, respectively, with a P = 0.814 while the mean total IV fluid for the entire period of surgery (preload inclusive) was 2776.00 ± 483.85 ml and 2892.00 ± 568.87 ml (mean ± SD) for Groups A and B, respectively, with a P = 0.275. The mean duration of surgery was 61.68 ± 0.81 min (mean ± SD) and 68.88 ± 85.10 min for Groups A and B, respectively, with a P = 0.556 [Table 2].
Assessment of blood loss
There was also no statistically significant difference in blood loss in both groups. The mean blood loss was 685.30 ± 161.04 ml (mean ± SD) and 723.40 ± 242.37 ml for Groups A and B, respectively, with a P = 0.357 [Table 2].
Assessment of motor and sensory block
Overall both groups were comparable with respect to motor and sensory block. Twelve patients (24%) and 24 patients (48%) for Groups A and B, respectively, had sensory block up to T4 level (just above the xiphisternum). The frequencies for T5 and T6 sensory blocks were similar with 19 patients (38%) and 13 patients (26%) for Groups A and B, respectively, having sensory blocks T5 and T6. Forty patients (80%) and 37 patients (74%) for Groups A and B, respectively, had Bromage 4 motor block while 7 patients (14%) and 12 patients (24%) for Groups A and B, respectively, had Bromage 3 motor block. Only 4 patients (3 in Group A and 1 in Group B) had Bromage 2 motor block.
Assessment of heart rate
Overall, the heart rate is slightly higher (from the baseline to the 5th min after oxytocin) in Group B compared to Group A with this difference more markedly seen at the 1st min after oxytocin with a statistically significant P = 0.044 [Figure 1].
Assessment of arterial blood pressure
The two groups are comparable with respect to systolic, diastolic, and mean arterial blood pressures from the baseline measurement to the 5th min after oxytocin.
Assessment of postoperative complications
Shivering was the most frequent complication noted with 26 patients (52%) in Group A compared to 21 patients (42%) in Group B. Four patients (8%) had nausea and vomiting in Group A compared to 6 (12%) in Group B. Four patients (8%) were noted to have had PDPH in each group. Epigastric pain was noted in 2 patients (1 in each group) and chest pain in 3 patients (1 in Group A and 2 in Group B). A significant number of patients had no complications at all (13 in Group A and 12 in Group B).
| Discussion|| |
Visual estimation of blood loss is associated with the risk of either underestimation or overestimation. If three different observers should estimate blood loss following cesarean section, they are likely to come up with three different figures.
In this study, visual estimation of blood spillage on drapes, floor, and surgeons' gowns, counting of swabs, and measurement of suction bottle losses was used to estimate blood loss. Other methods that could have been used include the gravimetric method which entails weighing of swabs before and after use. One milliliter of blood is allowed for every 1 g weight gain in swabs. If the patients' weight and the postoperative PCV had been measured, the formula for allowable blood loss could have been used to estimate blood loss. The gravimetric method of estimation of blood loss was used with considerable accuracy by other researchers. However, the gravimetric methods were not used in our study because of lack of facility. The EBL was comparable in both groups with the 5 IU group even recording a slightly lower blood loss compared to the 10 IU group [Table 2]. This result shows that 5 IU can be as effective as 10 IU in reducing blood loss during cesarean section if other factors affecting blood loss are isolated. This finding was consonance with the finding of Tsima et al., who retrospectively compared among other things the blood loss following different doses of bolus and infusion of oxytocin. This finding was also corroborated by the findings of Jonsson et al., who found that there was no difference in EBL either.
Even though there was a small reduction in mean arterial blood pressure compared to the baseline in both groups following the administration of IV boluses of oxytocin, this study failed to demonstrate a difference in reduction of mean arterial blood pressure in the two groups. This is in keeping with the findings of Pinder et al., where a statistically significant reduction in mean arterial blood pressure was only seen at 30 s after administration of 10 IU IV bolus of oxytocin. However, this is contrary to the findings of other workers, who found a significant difference in reduction of mean arterial blood pressure in the 10 IU group compared to the 5 IU group. A significant reduction in mean arterial blood pressure following the use of a higher dose of oxytocin was corroborated by the findings of Sartain et al., where 2 IU and 5 IU of oxytocin were studied.
As expected, in this study, there was an overall increase in heart rate following administration of IV bolus of oxytocin in both 5 IU and 10 IU groups. Even though not statistically significant, the increase in heart rate was higher in the 10 IU group. It was also noted that the increase was more marked at 1st min after oxytocin. This is consonant with the findings of Pinder et al., which showed that the increase in heart rate was also greatest at 1 min after oxytocin. However, this is at variance with the findings of Abdullah et al. who reported the greatest change in heart rate at the 4th min after oxytocin administration during cesarean section.
The observed incidence of nausea and vomiting in this study was comparable in the two groups, indicating that not only oxytocin but also other factors, for example patient-related factors, anxiety, spinal-induced hypotension contributed to PONV. However, the incidence was low as it did not follow the pattern of findings reported in a similar study. Furthermore, patients who developed severe hypotension were excluded from this study and hypotension is one of the numerous causes of nausea and vomiting seen in these patients. Another complication of subarachnoid block for cesarean section is PDPH. The incidence of PDPH in this study with size 24G Quincke bevel-shaped needles was similar in both groups. Similar incidence of PDPH (8.3%) was found by other researchers, who compared the incidence of PDPH in 3 groups of parturients during cesarean section using 3 different sizes of needles. However, the incidence of PDPH in this study is at variance with the findings of Oberhofer et al., who compared the incidence and clinical significance of PDPH in two groups of patients, i.e., orthopedics and obstetrics. They found an incidence of 14.3% in the parturients group. Given that, sizes 26-G and 27-G Quincke needles were used by Oberhofer et al., an incidence of 14.3% is higher than in the literature. The incidence of PDPH in our study is also contrary to the findings of Imarengiaye and Ekwere  who found a higher incidence (22.7%) using 24G Quincke spinal needle.
The intra- and post-operative hemoglobin values were not obtained for the study.
| Conclusion|| |
Five international units IV bolus of oxytocin is as effective as 10 IU IV bolus in reducing blood loss and has comparable hemodynamic effects during cesarean section. The incidence of shivering PDPH and PONV was also similar with both regimens; we therefore recommend the use of 5 IU bolus followed by 30 IU oxytocin infusion in 500 ml of 0.9% saline during cesarean section.
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Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2]