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REVIEW ARTICLE
Year : 2019  |  Volume : 13  |  Issue : 4  |  Page : 340-351

Efficacy of low dose bupivacaine with intrathecal fentanyl for cesarean section on maternal hemodynamic: Systemic review and meta-analysis


1 Department of Anesthesiology, College of Health and Medical Sciences, Dilla University, Ethiopia
2 Department of Public Health, College of Health and Medical Sciences, Debre Berhan University, Ethiopia

Correspondence Address:
Semagn Mekonnen Abate
Department of Anesthesiology, College of Health and Medical Sciences, Dilla University, PO. Box: 914
Ethiopia
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/sja.SJA_17_19

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Date of Web Publication5-Sep-2019
 

  Abstract 


Hypotension during spinal Anesthesia is the most common complication with maternal and neonatal morbidity and mortality. Low dose bupivacaine with intrathecal fentanyl is recommended as strategy to prevent spinal Anesthesia induced hypotension and related complications. The aim of this systemic review is to evaluate the efficacy of low dose bupivacaine with Intrathecal fentanyl on the improvement of maternal and neonatal outcomes compared to conventional dose bupivacaine among mothers who undergone cesarean section. We conducted a systemic search of the electronic databases of Pubmed, Medline, LILACS and others with PICO strategy for randomized controlled clinical trials comparing low dose bupivacaine with fentanyl and conventional dose bupivacaine for cesarean section. Joanna Briggs Institute (JBI) standardized data extraction form was used for data extraction and finally entered into Review Manager for data synthesis. Ten Randomized trials (552) were included in this review. Incidence of hypotension was less likely in mothers who received low dose bupivacaine with Fentanyl as compared to those with conventional dose of bupivacaine alone (RR = 0.43, 95% confidence interval (CI) 0.12-0.47, ten trials, 552 participants). The review revealed that Low dose bupivacaine combined with intrathecal Fentanyl decrease incidence of hypotension.

Keywords: Bupivacaine; cesarean section; hypotension; spinal Anesthesia


How to cite this article:
Abate SM, Belihu AE. Efficacy of low dose bupivacaine with intrathecal fentanyl for cesarean section on maternal hemodynamic: Systemic review and meta-analysis. Saudi J Anaesth 2019;13:340-51

How to cite this URL:
Abate SM, Belihu AE. Efficacy of low dose bupivacaine with intrathecal fentanyl for cesarean section on maternal hemodynamic: Systemic review and meta-analysis. Saudi J Anaesth [serial online] 2019 [cited 2019 Sep 22];13:340-51. Available from: http://www.saudija.org/text.asp?2019/13/4/340/265990




  Introduction Top


Spinal anesthesia is the most common techniques of regional anesthesia for cesarean section with minimal maternal and neonatal complications as compared to general anesthesia which is associated with difficult airway and risk of aspiration.[1],[2],[3],[4] However, hypotension during spinal anesthesia for cesarean section is the most common complication associated with nausea and vomiting, altered mental status and risk of aspiration.[1],[4],[5],[6],[7],[8],[9]

Incidence of hypotension during spinal anesthesia for cesarean section varies in different studies based on the definition of hypotension which ranges from 55-100 percent.[5],[10],[11] Recent systemic review on definition of hypotension showed that systolic blood pressure less than 94 mmHg or systolic blood pressure less than 24% of the baseline is the accepted value.[10]

Bupivacaine is the most commonly used local anesthetics in spinal anesthesia for cesarean section. The dose of bupivacaine for spinal anesthesia in non-obstetric patient is 13-15 mg where as it is about 12.5 mg for pregnant mothers to avoid high and extensive block due to physiologic and mechanical effects of pregnancy. Even with standard doses of bupivacaine (12.5 mg) for pregnant lady, there are evidences of severe hypotension and related maternal and neonatal complications.[3],[12],[13],[14]

Different adjuvant like Opioids and non-Opioids have been tried to improve intraoperative anesthesia, and to prolong postoperative analgesic duration. Fentanyl, a lipophilic opioid, has rapid onset of action after intrathecal administration.[2],[3],[5],[8],[12],[15] After intrathecal administration, fentanyl diffuses into epidural space and subsequently into the plasma, suggesting that it acts not only through spinal opioid receptors but also systemically. Delayed respiratory depression is less likely associated with fentanyl, as it does not reach to 4th ventricle in sufficient concentrations.[9],[16]

Though high dose of bupivacaine provides sensory and motor block, it is also associated with high incidence of hypotension and poor neonatal outcomes.[16],[17],[18],[19] On the other hand, low dose bupivacaine (<8 mg) is associated with inadequate anesthesia despite low incidence of hypotension.[17],[18],[19] Low dose bupivacaine with fentanyl provides adequate anesthesia with stable maternal hemodynamic and neonatal outcomes. However, there are discrepancies on the efficacy of low dose bupivacaine with fentanyl.[17],[18] Therefore, we conducted this systemic review and meta-analysis to assess the efficacy of low dose bupivacaine with intrathecal fentanyl on maternal and neonatal outcomes.


  Objective and Research Question Top


Objective

The objectives of this systemic review and meta-analysis is to assess the efficacy of low dose bupivacaine with intrathecal fentanyl for cesarean section on maternal hemodynamic as compared with that of conventional doses of bupivacaine.

Research question

Does low dose bupivacaine with intrathecal fentanyl prevent spinal induced hypotension and associated complications as compared with that of conventional dose of bupivacaine in mothers who are undergoing cesarean section?


  Methods Top


Types of studies

We considered randomized controlled trials comparing low dose bupivacaine with intrathecal fentanyl and conventional dose bupivacaine for cesarean section.

Types of participants

All parturient scheduled for cesarean section.

Types of Intervention

Intervention

Parturient mothers receiving intrathecal fentanyl with low dose bupivacaine.

Control

Parturient mothers receiving spinal anesthesia with conventional dose bupivacaine

Outcomes

The primary outcome interest was incidence of hypotension. The secondary outcomes were onset of sensory block, duration of block, block failure, nausea and vomiting, and neonatal outcomes.

Criteria for selection of clinical trials

The inclusion criteria of this search articles include the following:

  1. Randomized controlled trial received low dose bupivacaine with intrathecal fentanyl for cesarean section
  2. Control group received conventional dose bupivacaine
  3. Articles comparing hypotension as primary outcomes
  4. Articles with full text available.


The exclusion criteria of the search articles include the following:

  1. Studies comparing ASA III and above parturient
  2. Observational studies
  3. Cross sectional studies
  4. Cross over and Quasi-expermental studies.


Searching strategy

Databases were searched for randomized clinical trials comparing intrathecal fentanyl and low bupivacaine without date and language restriction as shown below with medical subject heading (MeSH) terms of parturient, hemodynamic stability, pain, nausea and vomiting, and spinal anesthesia were searched as follows:

  1. Cesarean section
  2. Intrathecal fentanyl
  3. Low dose bupivacaine
  4. Spinal hypotension
  5. Analgesia
  6. #1 and #2 and #3 and #4 or #5
  7. Clinical trial
  8. #6 and #7
  9. Randomized control
  10. #8 and #9.


Data extraction

Different databases were explored to identify controlled clinical trials comparing fentanyl co-administered with low dose bupivacaine and conventional bupivacaine dose for spinal anesthesia in cesarean section. Full reports of all controlled clinical trials were searched without date and language restriction. There have been 14 controlled trails collected for eligibility assessment and eleven trials were incorporated for extraction of outcomes. Two review authors independently assess the eligibility of studies with customized checklist that was adopted from Joana Briggs Institute [Table 1], and disagreement was fixed by consensus. Characteristics of Included studies [Table 2], and the reason for exclusion of studies was described in detail [Table 3]. The study selection process was summarized using PRISMA chart [Figure 1].
Table 1: Study Eligibility Assessment Tool

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Table 2: Description of included studies

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Table 3: Descriptions of excluded studies

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Figure 1: PRISMA flow diagram

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Methods of the review

The corresponding author had chosen appropriate trials from those identified by the search strategy and retrieved the full articles, and duplicate publications from the same data set were only used once. The two authors independently assessed the methodological quality of the included trials using tools that were adapted from Cochrane Handbook for systemic reviews and Jadad scale [Table 4], which incorporates generation of allocation sequence, allocation concealment, blinding and loss to follow up. For all trials, each quality component apart from blinding was classed as adequate, inadequate or unclear. For loss to follow up, inclusion of 90% of participants was considered adequate. Blinding was assessed using the following criteria: blinding of participants, blinding of Health care providers and blinding of outcome assessment. Blinding was assessed as open or single blind. Disagreements between authors were resolved by discussion.
Table 4: Risk of Bias within studies

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Data analysis

The data were analyzed using Review Manager (RevMan 5.3, Cochrane Collaboration) and comprehensive meta-analysis (CMA). Statistical combination of data from two or more separate trials in a meta-analysis was decided based on the evaluation of the clinical and methodological heterogeneity. The inconsistency throughout trials was quantified with the I 2 statistic proposed by Higgins and colleagues, assuming a value more than 50% as a substantial heterogeneity and subgroup analysis were conducted to see the source of heterogeneity. We conducted logarithmic transformation of the risk ratio (RR) effect estimates and its standard errors by construction of Begg's funnel plots, and assessment of the degree of symmetry with Egger's test to explore publication bias. The summary effect measure were risk ratio (RR) and odd ratio for dichotomous variables and mean Difference and standard deviation for continuous variables along with their corresponding 95% confidence intervals (CI). This systematic review was carried out using the methods established by the Cochrane Handbook for Systematic Reviews of Interventions and we followed the recommendations and checklist items from the PRISMA Statement for Reporting Systematic Reviews and Meta-analysis [Table 5].
Table 5: Prisma statement checklist

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  Qualitative Data Synthesis Top


Description of included studies

There were about 811 randomized trials identified from different databases as described in methodology section [Figure 1]. There were about 20 trials that were selected for evaluation after successive screening. About 10 trials with 552 participants were included for final analysis, and the rest were excluded with reasons [Table 3]. Population sizes ranged from 32–90. Power analysis was mentioned in two studies and the variables considered for calculations were ephedrine requirements, and duration of analgesia.

The study included clinical trials that were published from 2000 up to 2017. The mean age of the patients included and ranged from 24–37 years whereas the mean weight reported was between 58 and 62 kg. The majority of trials reported an appropriate method of randomization.[1],[2],[3],[5],[6],[7],[8],[20] There was a large variety of working hypotheses and primary outcomes. In 7 reports, the principal aim of the study was to test whether improved analgesia with fewer adverse effects could be achieved with the combination of a small dose of an opioid with a reduced dose of local anesthesia.[2],[3],[5],[6],[7],[8],[20] The local anesthetic used was bupivacaine with dose range from 7–13.5 mg and added fentanyl dose that was 10–25 μg. Ringer's lactate solution was most commonly used for preloading, in the range of 500–1500 ml. Hypotension was managed with ephedrine as a sole drug in five studies [1],[5],[6],[7],[9] and mephentermine was used in one study.[3] Bradycardia (defined as a heart rate <45–50 min/min) was managed with IV atropine in three studies.[3],[8],[20]


  Results Top


Primary outcomes

Incidence of hypotension

All the included trials reported the presence or absence of maternal arterial hypotension. Various criteria were used to define hypotension in included studies. Some studies recorded hypotension as systolic blood pressure (SBP) decreased by 20-30% or <90–95 mmHg and others defined hypotension when systolic blood pressure decreased by 20-30% from baseline. Incidence of hypotension was reported in all included studies.[1],[2],[3],[5],[6],[7],[8],[9],[12],[20] Assessment of reduction in mean systolic and diastolic blood pressure was reported in five studies.[1],[2],[3],[5],[12]

Nausea/vomiting

Incidence was reported either separately as nausea, vomiting in two trials [1],[3] or combined nausea/vomiting in seven studies.[5],[6],[7],[8],[9],[12],[20]

Analgesia

Time to sensory onset was reported in eight studies,[1],[2],[3],[6],[7],[8],[12],[20] whereas complete sensory regression was mentioned in six studies.[1],[2],[3],[7],[8],[20]

Four trials reported the duration of postoperative analgesia, which defined as the time from the end of surgery until the first request for rescue analgesia.[1],[2],[3],[20]

Failed block and conversion to general anesthesia occurred in only one study and supplemental fentanyl required in bupivacaine-fentanyl group.[6] There were no reported events of conversion to general anesthesia for bupivacaine group in any of the study.

Secondary outcomes

Sedation

Sedation was assessed with objective score based on Ramsay sedation scale in one of the study [9] and in the other study using categories (alert, drowsy, dozes-rouses spontaneously, dozes-arousable, and not arousable as an outcome.[6]

Shivering

Shivering was reported in five studies.[1],[3],[7],[9],[12] There was not much statistically significant differences.

Urinary retention

One study reported the risk of postoperative urinary retention. None of the patients complained urinary retention in both groups.[12]

Pruritus

Pruritus was reported in five studies.[1],[3],[7],[9],[12]

Maternal Bradycardia

Maternal Bradycardia was reported in three studies.[3],[8],[12] But there was no significant difference between the groups.

Patient satisfaction

Participants were asked to grade their level of overall satisfaction with the anesthesia quality using scores or categories as that of excellent, good, average, or poor based on incidence of side effect.[6],[7]

Quantitative data analysis

Spinal anesthesia is compared with low dose bupivacaine combined with fentanyl and conventional dose of bupivacaine for cesarean section. About 10 randomized trials were included in the meta-analysis for data extraction.

In the pooled analysis, incidence of hypotension was higher in mothers who received conventional dose of bupivacaine alone as that compared to those with low dose bupivacaine with fentanyl (RR = 0.43, 95% confidence interval (CI) 0.12-0.47, 8 trials, 532 participants) [Figure 2].
Figure 2: Forest plot for incidence of hypotension low dose bupivacaine-fentanyl vs bupivacaine alone: individual trials and meta-analysis. Events: the total numbers with the events. Total: the total number of participants in intervention and control. Weight: sample size contribution of the study relative to the pooled sample size of the meta-analysis. M–H, Mantel–Haenszel methods

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There were about five studies that reported the mean intraoperative systolic blood pressure and the result of meta-analysis showed relative stable systolic blood pressure in low dose bupivacaine combined with intrathecal fentanyl when compared with conventional bupivacaine alone (MD = 9.52, (95% confidence interval (CI) 6.01 to 13.03, 5 trials, 280 participants) [Figure 3].
Figure 3: Forest plot for mean intraoperative systolic blood pressure comparing low dose bupivacaine-fentanyl vs bupivacaine alone: individual trials and meta-analysis total: the total number of participants in intervention (BF) and control (B). Weight: sample size contribution of the study relative to the pooled sample size of the meta-analysis. IR: Inverse Variance

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From the pooled analysis of four results showed that mean intraoperative diastolic blood pressure was found to be better in mothers who received spinal anesthesia with low dose bupivacaine with fentanyl as compared to that of the conventional bupivacaine dose (MD = 3.23, 95% confidence interval (CI) 0.02 to 6.45, 4 trials, 220 participants) [Figure 4].
Figure 4: Forest plot for mean intraoperative diastolic blood pressure comparing low dose bupivacaine-fentanyl vs bupivacaine alone: individual trials and meta-analysis total: the total number of participants in intervention (BF) and control (B). Weight: sample size contribution of the study relative to the pooled sample size of the meta-analysis. IR: Inverse Variance

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Nausea and vomiting was very common in patient with conventional bupivacaine dose as compared to that of low dose bupivacaine combined with intrathecal fentanyl as shown with pooled results of meta-analysis (RR = 0.35, confidence interval (CI) 0.24 to 0.51, 9 trials, 482 participants) [Figure 5].[20]
Figure 5: Forest plot for incidence of nausea/vomiting comparing low dose bupivacaine-fentanyl vs bupivacaine alone: individual trials and meta-analysis. Events, the total numbers with the events total: the total number of participants in intervention (SA) and control (GA). Weight: sample size contribution of the study relative to the pooled sample size of the meta-analysis. M–H, Mantel–Haenszel methods

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Adequacy of sensory and motor block was reported in majority of included studies. Peak sensory block was faster in low dose bupivacaine with fentanyl as compared to conventional dose bupivacaine (MD = −0.8, (95% confidence Interval (CI) -1.43 to 0.18, 8 trials, 222 participants). However, complete motor block (bromage scale >3) was faster in conventional dose bupivacaine as compared to low dose bupivacaine with fentanyl (MD = 0.07, 95% confidence interval (CI) 0.01 to 0.04, 5 trials, 300 participants) [Figure 6] and [Figure 7].
Figure 6: Forest plot for time to sensory block comparing low dose bupivacaine-fentanyl vs bupivacaine alone: individual trials and meta-analysis. Total: the total number of participants in intervention (BF) and control (B). Weight: sample size contribution of the study relative to the pooled sample size of the meta-analysis. IR: Inverse Variance

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Figure 7: Forest plot for time to two segment regression comparing low dose bupivacaine-fentanyl vs bupivacaine alone: individual trials and meta-analysis. Total: the total number of participants in intervention (BF) and control (B). Weight: sample size contribution of the study relative to the pooled sample size of the meta-analysis. IR: Inverse Variance

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Complete sensory recovery was prolonged in low dose bupivacaine with fentanyl as compared to bupivacaine alone (MD = 4.3, 95% confidence interval (CI) 2.55 to 6.05, 6 trials, 350 participants), whereas complete motor recovery was shorter in low dose bupivacaine with fentanyl when compared with bupivacaine alone (MD = 0.07, 95% confidence interval CI), 5 trials, 300 participants) [Figure 8] and [Figure 9].
Figure 8: Forest plot for complete sensory recovery comparing low dose bupivacaine-fentanyl vs bupivacaine alone: individual trials and meta-analysis total: the total number of participants in intervention (BF) and control (B). Weight: sample size contribution of the study relative to the pooled sample size of the meta-analysis. IR: Inverse Variance

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Figure 9: Forest plot for complete motor recovery comparing low dose bupivacaine-fentanyl vs bupivacaine alone: individual trials and meta-analysis total: the total number of participants in intervention (BF) and control (B). Weight: sample size contribution of the study relative to the pooled sample size of the meta-analysis. IR: Inverse Variance

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From the secondary outcomes, incidence of Pruritus was 13 times more likely in low dose bupivacaine with fentanyl (OR = 12.60, 95% confidence interval CI) 3.56 to 44.61, 5 trials, 290 participants whereas the risk of shivering was higher in bupivacaine alone (OR = 0.43, 95% confidence interval (CI) 0.28 to 0.86, 5 trials, 270 participants. There was no significant difference between the group regarding Bradycardia (OR = 2.07, 95% confidence interval 0.36 to 11.79, 3 trials, 180 participants) [Figure 10].
Figure 10: Forest plot for Incidence of adverse effects comparing low dose bupivacaine-fentanyl vs bupivacaine alone: individual trials and meta-analysis. Events, the total numbers with the events total: the total number of participants in intervention (SA) and control (GA). Weight: sample size contribution of the study relative to the pooled sample size of the meta-analysis. M–H, Mantel–Haenszel methods

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  Discussion Top


This review was conducted to explore the efficacy of low dose bupivacaine combined with intrathecal fentanyl as the conventional bupivacaine dose is associated with hemodynamic instability despite its adequate analgesia and anesthesia for cesarean section.

Maternal and neonatal mortality was not reported in included randomized trials and this might witness the relative safety of low dose bupivacaine combined with intrathecal fentanyl for cesarean section.

The review has shown that incidence of hypotension is less likely in mothers with low dose bupivacaine with intrathecal fentanyl. This finding is consistent with another meta-analysis that conducted with low dose bupivacaine and conventional doses of bupivacaine for cesarean section.

The mean intraoperative systolic blood pressure was relatively stable in low dose bupivacaine with fentanyl unlike the mean diastolic blood pressure which did not show any significant difference in pooled analysis of four randomized trials.

The pooled analysis of the included randomized clinical trials showed that incidence of intraoperative nausea and vomiting was lower in low dose bupivacaine combined with intrathecal fentanyl when compared with that of conventional dose of bupivacaine alone.

The finding of this review is consistent with included individual trials and another meta-analysis conducted somewhere else. This might be due to fewer episodes of hypotension incidents in low dose bupivacaine with fentanyl as a result of relatively less tense sympathetic blockade in which parasympathetic vagal dominance in gastrointestinal tract is balanced unlike with high bupivacaine dose where vagal dominance is pronounced.

The pooled analysis of included trials showed fast sensory onset and prolonged complete sensory recovery in low dose bupivacaine with fentanyl. This finding is inconsistent with some of included trials and one meta-analysis where there was inadequate sensory block and additional analgesic supplementations that were required. This might be the variation in definition of low dose bupivacaine and fentanyl in different included studies which ranges from 4-8 mg and 10-25 μg respectively.

Motor onset was slower in low dose bupivacaine with fentanyl whereas complete motor regression was faster in low dose bupivacaine with Bupivacaine as compared to that of conventional dose alone.

In included trials reporting neonatal outcomes it did not show any significant difference between the groups but qualitative data extraction was not done due to dissimilarities in method of reporting outcomes.

From the adverse events, incidence of Pruritus was 15 times more likely in low dose bupivacaine with fentanyl whereas incidence of shivering was more common in Bupivacaine dose alone compared with low dose bupivacaine with fentanyl.

Comparison with other systemic reviews

As of our information, there is no systemic review conducted with low dose bupivacaine with intrathecal fentanyl and conventional bupivacaine alone. However, there is one systemic review and meta-analysis comparing low dose and conventional dose of bupivacaine irrespective of intrathecal fentanyl. They incorporated studies comparing low dose and conventional dose with or without intrathecal adjuvant besides fentanyl with which comparison with our systemic review and meta-analysis is inappropriate.

Conclusion and clinical applicability

This systemic review and meta-analysis shows low dose bupivacaine combined with intrathecal fentanyl improves maternal hemodynamic parameters without significant difference in adequacy of analgesia and anesthesia. Many institutions in Ethiopia did not use low dose bupivacaine and intrathecal fentanyl despite having the advantages of stable hemodynamic and adequate anesthesia. However, further randomized clinical trials are required to set out the standard low dose bupivacaine to be used with fentanyl as there is variation in defining how low is low. Overall, intrathecal fentanyl in spinal anesthesia prevents complications associated with profound sympathetic blockade.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

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    Figures

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    Tables

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5]



 

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