A comparative study of low dose Bupivacaine vs high dose Bupivacaine along with Fentanyl and Phenylephrine on Pregnant women undergoing elective Caesarean Section under Spinal Anesthesia

A Sivaram1, Govardhani Y2, Varaprasad U S S A3

1Post graduate Student,2Senior resident,3Professor. All are affiliated with Department of Anesthesiology & Intensive Care, Dr Pinnamaneni Siddhardha Institute of Medical Sciences, Chinaoutpalli, Krishna District, A P, INDIA

Corresponding author: Dr A Sivaram, Email: drsivaram79@gmail.com

Abstract

Background: This randomized study was conducted to evaluate the effect of low dose vs high dose Bupivacaine+Fentanyl, with or without Phenylephrine infusion on hemodynamics, motor recovery, adequacy of block and side effects, on pregnant  women undergoing caesarean section under spinal anaesthesia. Methods: One hundred sixty pregnant  women were randomized into four groups of fourty each. Group-A (n=40) received 10 mg(2ml) of Bupivacaine + Fentanyl 25µg(0.5ml) along with Phenylephrine i.v. infusion of 0.25µg/Kg/min. Group-B (n=40) recieved same drugs, without Phenylephrine infusion. Group-C (n=40) received 7 mg(1.4ml) of Bupivacaine+Fentanyl 25µg(0.5ml) along with Phenylephrine i.v. infusion of 0.25µg/Kg/min. Group-D (n=4) received same drugs , without Phenylephrine infusion. Result:  When given with fentanyl,  low dose bupivacaine (1.4 ml / 7 mg) was as effective as of high dose buypivacaine (2ml/ 10mg) in producing adequate relaxation and analgesia. Addition of low dose phenylephrine infusion decreased the incidence of hypotension maintains the pulse rate nearer to baseline for better hemodynamic stability. The motor recovery was quick in case of low dose bupivacaine groups with or without phenylephrine which aids in early mobilization of pregnant women. Conclusion: When given along with an opioid like fentanyl, low dose bupivacaine (1.4 ml / 7 mg) was as effective as of high dose buypivacaine (2ml/ 10mg) in producing adequate relaxation and analgesia. Addition of low dose phenylephrine infusion decreased the incidence of hypotension and maintained better hemodynamic stability

Key words: Bupivacaine, Fentanyl, Phenylephrine infusion, caesarean section, hemodynamic stability.

Manuscript received: 15th Feb 2014, Reviewed: 25th Feb 2014
Author Corrected: 13th Mar 2014, Accepted for Publication: 15thMar 2014

Introduction
 
Prevention of hemodynamic instability during lower segment caesarean section under spinal anesthesia has been the aim of several studies. Noninvasive monitoring has been used in previous studies but spinal anesthesia for caesarean section has become popular in recent decade & it has been the preferred technique for the majority of anesthesiologist. This is primarily due to increased maternal mortality with general anesthesia and benefits conveyed to the mother. But, spinal anesthesia is associated with major or minor complications in the pregnant pregnant women, the commonest being maternal hypotension. It is believed to occur in up to 95% of the pregnant  women and may lead to a reduction in utero-placental perfusion resulting in fetal acid-base abnormalities [1]. Local anesthetics plus opioids administered together intrathecally have been shown to have a synergistic analgesic effect [2, 3]. Intrathecal opioids increase the quality of analgesia and reduces local anesthetic requirements, with some studies showing favourable effects on haemodinamics stability [4, 5]. Therefore, it may be possible to achieve spinal anesthesia with less hypotension by using a reduced dose of local anesthetic.

Opioids have been proved to give more intensity of block and quicker onset time when added as an adjunct to spinal anaesthetic without altering hemodynamic stability in pregnant women undergoing ceasarean section. Since, low dose bupivacaine will be better effective along with an opioid like fentanyl, it was added in this study in all the groups of pregnant women along with  bupivacaine. Studies show the dose dependent effects of hyperbaric bupivacaine on maternal hemodynamics and showed that small dose of bupivacaine with fentanyl better preserves hemodynamic stability resulting in equally effective anaesthesia.

Phenylephrine, an alpha agonist is more prominent venoconstrictor.  During caesarean sections phenylephrine maintains maternal systolic blood pressure at baseline and is associated with low incidence of fetal acidosis than that of ephedrine (6,7). The aim of this randomized trial was to compare the effects of two different intrathecal doses of bupivacaine, with or without intravenous phenylephrine infusion, on cardiac output and systolic blood pressure as general anesthesia increase maternal mortality; spinal anesthesia is advantageous to pregnant mothers with fewer side effects, in the form of maternal hypotension and maintaing hemodynamic stability.

Methods

After obtaining hospital ethical committee’s approval, 160 uncomplicated pregnant mothers of age between 19-29 years, weighing between 55–65 Kg., height between 150 -160 cms scheduled to have caesarean section were chosen for this randomized comparative study. Pregnant women with foetal malposition, hypertention, cardiac disease, renal disease, diabetes mellitus and on chronic medication were excluded from the study. Informed consent was obtained and hemodynamic variables were noted. Pregnant women were randomly divided into four groups of 40 each, without any bias. With all aseptic precautions lumbar puncture was performed with 25G Quinke needle in L3-L4 inter space  in left lateral position and group specified drugs were injected according to random assignment and pregnant women was immediately placed in supine position with a wedge under the  hip.

Group-A (n=40):  Received 0.5% Bupivacaine heavy 10mg (2ml) and Fentanyl citrate 25 mcg (0.5ml) making a total of 2.5ml, intrathecally. They also received continuous infusion of phenylepherine 0.25µ/Kg/minute intravenously by separate I.V line through an infusion pump, till the end of surgery.

Group-B (n=40):  Received 0.5% Bupivacaine heavy 10mg (2ml) and Fentanyl citrate 25 µg (0.5ml) making a total of 2.5ml, intrathecally, without phenylephrine infusion.

Group-C (n=40): Received 0.5% Bupivacaine heavy 7mg (1.4ml) and Fentanyl citrate 25 µg(0.5ml) and 0.6ml of normal saline making a total of 2.5ml, intrathecally. They also received phenylepherine 0.25µ/Kg/minute .  
Group-D (n=40): Received 0.5% Bupivacaine heavy 7mg.(1.4ml) and Fentanyl citrate 25 mcg(0.5ml) and without  phenylephrine infusion.

All pregnant women received supplemental Oxygen of 4 L/min  via polymask. Pulse rate, SpO2, B.P (systolic, diastolic and mean) were recorded every 2 minutes till the completion of delivery of placenta and firm uterine contraction, then at every 5 minutes till the completion of surgery and thereafter at every 15 minutes, until pregnant women able to perform bilateral straight leg lift indicating complete motor recovery.  The onset of upper sensory level was noted by pinprick method 5 minutes after initiation of spinal blockade.  All the pregnant women were pre hydrated during the procedure the pregnant women received maintainance fluid of just 30 drops/min of Ringer solution, unless hypotension is warranted. The observations and results were analysed.

Results

In this study, 160 uncomplicated pregnant women planed to undergo elective caesarean section were chosen for this randomized comparative study .The results encountered in the present study are enumerated in table 1-10

Table 1: Demographic profile of the participants of the 4 study group

Group A Group B Group C Group D
No. of patients 40 40 40 40
Age in years 25 + 1.39 24 + 1.40 24 + 1.98 24 + 1.50
Weight in Kgs 60 + 6.48 61 + 5.05 60 + 5.62 61 + 5.09
Height in cms 154 + 3.73 154 + 3.38 154 + 3.04 154 + 3.18
       
Table 2: level of sensory blockade and Motor blockade

Group A Group C Group C Group D
·         Height of  Sensory Level  ( Median) T4 [T3 – T6] T4 [T3 – T6] T4 [T3 – T6] T4 [T3 – T6]
·         Time for injection to highest sensory level in minutes 5.7 + 1.34 5.8 + 1.22 5.8 + 0.98 6.0 + 1.20
·         Onset of grade 3 motor block (Min) 5.7 + 0.65 6.0 + 0.79 6.0 + 0.82 + 0.91
·         Duration of  motor block  (Min) 145 + 4.43 142 + 4.12 98 + 4.99 101 + 9.11
  
Table 3:  Baseline of Hemodynamics before starting of Anaeshesia induction
  
Group A Group B Group C Group D
Systolic blood pressure( mmHg) 126 + 4.76 129  + 4.31 121  + 5.30 124  +  5.68
Mean arterial pressure(mmHg) 92 + 3.78 92 + 4.65 92 + 7.70 92 + 4.00
Diastolic blood pressure(mmHg) 76 + 4.21 75 + 4.18 79 + 6.54 77 + 3.81
Pulse rate(beats / min) 89 + 3.96 91 + 5.89 89 + 4.12 90 + 4.83

Table 4: Hemodynamic changes encountered during LSCS

Group A Group B Group C Group D
SBP (mmHg)
Minimum (mmHg) 97 91 111 101
Change 29 38 10 23
% Change 23 30 8 19
Time (Min) 8 8 10 8
MAP, mmHg
Minimum 72 65 81 74
Change, mmHg 20 27 12 18
% Change 22 29 13 20
Time, (Min) 8 8 8 10
Hypotension 7 14 2 6
Bradycardia [ < 60 min] 3 0 2 0

Table 5: Distribution of  Mephentermine doses  among 4 groups
No. of Mephentermine (1 doses = 3mg

Group A

[B10 + Fentanyl +
Phenylephrine]
n=14

Group B

[B10 + Fentanyl]

(n=28)

Group C

[B7 + Fentanyl +

Phenylephrine]

(n=4)

Group D

[B7 + Fentanyl]

(n=12)
1 dose 8 10 4 8
2 dose 6 12 - 4
3 dose - 6 - -
Total 14 28 4 12
n=number of patients

The data was   analysed by using   SPSS 15.0 version and Microsoft Excel software. Independent sample ‘t’ test  was used     to assess the significance of difference of  means between the cases and controls . P<0.05 is considered as significant.

Table-6: Comparision of  Hemodynamic changes between four Groups

 

Group –A and Group-B

Group–C and Group-D

Group–A and Group-D

t-value

p-value

t-value

p-value

t-value

p-value

Systolic blood pressure( mmHg)

1.62

>0.05

5,59

<0.05*

-3.51

<0.05*

Mean arterial pressure(mmHg)

2.07

<0.05*

5.01

<0.05*

-3.82

<0.05*

Diastolic blood pressure(mmHg)

2.32

<0.05*

5.15

<0.05*

-5.35

<0.05*

Pulse rate(beats / min)

9.5

<0.05*

-7.2

<0.05*

0.7

>0.05
p-value <0.05* is significant

DISCUSSION

This randomized study was conducted to show the hemodynamic  stability under spinal anaesthesia during ceasarean section deliveries, by reducing the dose of bupivacaine from 10 mg to 7mg.  Most of the pregnant  women in our maternity ward, coming for elective caesarean sections are less than 160 cm of height and below 65 kgs of weight so these pregnant  women may not require the traditional dose (10 mg of bupivacaine) which has been advocated since long time and is the established practice (table-1).  So an attempt has been made to study the level of sensory block, effectiveness of motor blockade (table-2) and recovery by using low dose bupivacaine (7mg) along with fentanyl, with or without low dose phenylephrine infusion.
 
Marc Vande velde et al (5) studied the dose dependent effects of hyperbaric bupivacaine on maternal hemodynamics and showed that small dose of bupivacaine with fentanyl better preserves hemodynamic stability resulting in equally effective anaesthesia. To prevent hemodynamic instability in most of the previous studies recorded blood pressure non-invasively at 1-2 minutes interval or even less frequently.[6-10] Tejwani et. al [11] study showed that opioids and local anaesthetics administred together intrathecally had synergistic analgesic effect possible to achieve spinal anaesthesia using otherwise inadequate doses of local anaesthetics with less hypotension (table-4). The first study with continuous invasive monitoring in healthy pregnant women was done by Langestear et al.[12]  During caesarean sections phenylephrine maintains maternal systolic  blood pressure at baseline and is associated with low incidence of fetal acidosis than that of ephedrine proven by cooper et al.(13,14,15) .  

The hemodynamic curves depicted clearly shows that there is a maximum fall of SBP and MAP around 6 – 12 minutes after induction of spinal anaesthesia in all groups of pregnant  women(table-3). Group B pregnant  women who received high dose bupivacaine 10 mg with 25mcg fentanyl without phenylephrine has faired poorly and has resulted in maximum fall of SBP and MAP (B-10 mg without phenylephrine -70%).  It is minimal in group C (B-7mg with phenylephrine -10%). The mean pulse rate was little lower in case of pregnant  women who received phenylephrine than in pregnant  women who does not receive phenylephrine. This was same in high dose and low dose bupivacaine groups.This shows a low dose phenylephrine infusion produce better hemodynamic stability and maintains the pulse rate nearer to baseline which is in correlation with studies of Anna Lee et al(16,17)

Level of sensory blockade and onset of motor blockade were almost similar in all pregnant  women in all groupswith average T4 [T3– T6] in all groups. So,we indicates low dose bupivacaine group pregnant  women can be made ambulatory at the earliest and also had better hemodynamic stabilty.[18]  Lowering the dose of spinal anesthetic is associated with reduced incidence of maternal hypotension, requirement of vasopressors and episodes of nausea or vomiting.[19-21]( table-6) Roofthooft and Van de Velde reported that using 6.5 mg with sufenatnil as a part of combined spinal epidural (CSE) technique, but take more time .[21]It is successful use of a low dose with efficient anesthesia and minimal incidence of hypotension. [22-26] Owing to the risk of failed intubation and hemodynamic responses to intubation, GA is hazardous in this population and should be reserved for women for whom neuraxial anesthesia is contraindicated.[27]

Conclusion

The result shows that, keeping in view of the average height and weight of pregnant  women who are coming for LSCS, they just need a minimal dose of hyperbaric bupivacaine along with of fentanyl for adequate level and degree of block, maintaining better hemodynamic stability if it is added with continuous infusion of low dose phenylephrine.

Funding: Nil, Conflict of interest: Nil
Permission from IRB: Yes

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How to cite this article?

A Sivaram, Govardhani Y, Varaprasad U S S A. A comparative study of low dose Bupivacaine vs high dose Bupivacaine along with Fentanyl and Phenylephrine on Pregnant women undergoing elective Caesarean Section under Spinal Anesthesia. Int J Med Res Rev 2014;2(2):124-129.doi:10.17511/ijmrr.2014.i02.010