|Year : 2012 | Volume
| Issue : 1 | Page : 16-22
Comparison of hydroxyethyl starch versus normal saline for epidural volume extension in combined spinal epidural anesthesia for cesarean section
Sunanda Gupta, Udita Naithani, Niyati Sinha, Vimla Doshi, Karthik Surendran, Vikram Bedi
Department of Anaesthesiology and Critical Care, RNT Medical College, Udaipur, Rajasthan, India
|Date of Web Publication||4-Aug-2012|
26, Navratna Complex, Bedla Road, Udaipur-313004, Rajasthan
Source of Support: None, Conflict of Interest: None
Background: Epidural volume extension (EVE) with saline in the epidural space during a CSE technique can result in cephalad extension of the block and may be accompanied by episodes of hypotension. It also allows CSE to be performed with small initial intrathecal doses of local anesthetic.
Objectives: We investigated the difference in block characteristics and hemodynamic profile with CSE-EVE using either saline or colloid in the epidural space.
Materials and Methods: This prospective, randomized, controlled study was conducted in 99 parturients, ASA grade I or II, with gestational age 37 weeks or more, undergoing elective cesarean section under CSEA. Women were randomly distributed into three groups: Group NEVE (CSE with no EVE), Group EVE-S (CSE followed by EVE using 5 ml of 0.9% saline), and Group EVE-H (CSE followed by EVE using 5 ml of 6% hydroxyethyl starch (HES) 200/0.5). All the groups received 6 mg of 0.5% hyperbaric bupivacaine with 25 mcg fentanyl intrathecally, while Groups EVE-S and EVE-H also received 5 ml of saline or HES in the epidural space. All blocks were performed using needle through needle CSE technique via midline approach at the L 4-5 interspace with the women in the left lateral position. Block characteristics and hemodynamic parameters were recorded by an independent anesthesiologist. Data were compared with Chi-square, t test, and ANOVA using Epi info 6 with P < 0.05 as significant.
Results: The peak sensory level and the time taken to achieve it was significant in Group EVE-S (P = 0.003 temperature, P = 0.007 pinprick, P = 0.000 time) as compared to Group NEVE while Group EVE-H was intermediate as compared to the other two groups. In Group EVE-S, there was a difference in the mean peak sensory levels as assessed by temperature (thoracic T 4.88±1.01 ) and pinprick (T 5.04±1.02 ), whereas it was the same in the other two groups (T 6.10±1.41 in Group NEVE and T 5.44±1.35 in Group EVE-H). The requirement for ketamine supplementation was significantly more in Group NEVE (54.5%) as compared to Group EVE-S (24.2%) and Group EVE-H (27.3%), P = 0.018. The motor block characteristics were comparable in all the three groups (P > 0.05).The lowest attained values of heart rate, systolic, and diastolic blood pressure were significantly less in Group EVE-S versus Group NEVE (P = 0.019, 0.008, and 0.001, respectively), while hemodynamic parameters in Group EVE-H were intermediate. Incidence of hypotension was significantly more in Group EVE-S (n = 20, 60.6%), as compared to Group NEVE (n = 9, 27.3%, P = 0.02) and Group EVE-H (n = 13, 39.4%).
Conclusion: We conclude that an intrathecal dose of 6 mg hyperbaric bupivacaine with 25 mcg fentanyl is adequate for cesarean section when used in CSE with the EVE technique, using 0.9% saline or 6% HES. However, EVE with HES provides optimal hemodynamic profile as compared to EVE with saline.
Keywords: Cesarean section, combined spinal epidural, epidural volume extension, Colloids for epidural volume extension, Saline versus colloid in epidural volume extension
|How to cite this article:|
Gupta S, Naithani U, Sinha N, Doshi V, Surendran K, Bedi V. Comparison of hydroxyethyl starch versus normal saline for epidural volume extension in combined spinal epidural anesthesia for cesarean section. J Obstet Anaesth Crit Care 2012;2:16-22
|How to cite this URL:|
Gupta S, Naithani U, Sinha N, Doshi V, Surendran K, Bedi V. Comparison of hydroxyethyl starch versus normal saline for epidural volume extension in combined spinal epidural anesthesia for cesarean section. J Obstet Anaesth Crit Care [serial online] 2012 [cited 2019 Jun 26];2:16-22. Available from: http://www.joacc.com/text.asp?2012/2/1/16/99310
| Introduction|| |
Combined spinal epidural anesthesia (CSEA) is now a well-accepted technique for cesarean section (CS).  A modification of CSE is the epidural volume extension (EVE) technique, wherein normal saline is injected into the epidural space, soon after the intrathecal dose, as part of CSEA.  This increases the sensory block height which is attributed to a "volume effect" as the injected volume of the fluid in the epidural space compresses the dural sac and causes cephalad spread of the local anesthetic already present in the subarachnoid space.  Thus, one of the suggested benefits of EVE is a reduction in the local anesthetic requirement that may result in better hemodynamic stability and early motor recovery. 
Hypotension remains an important side effect of spinal anesthesia for cesarean delivery and is strongly associated with lower umbilical cord blood gases.  However, some authors have documented that CSE with EVE cause more hypotension than a single shot spinal (SSS). 
EVE has usually been performed with either saline  or local anesthetics.  There is a paucity of data on the use of colloids for EVE,  though colloids (Dextran 40 and hydroxyethyl starch (HES)) have been successfully used in an experimental postdural puncture rat model  as well as clinically to treat postdural puncture headache (PDPH) in humans  without neurotoxic side effects. 
Since no published data are available regarding the effects of saline versus colloid in EVE for LSCS, we hypothesized that this technique could result in differences in block characteristics and hemodynamic profile. Thus, the present study was designed to compare the effects of colloid (6% HES) versus normal saline (0.9%) for EVE in CSEA for elective CS and to assess the quality of block and concurrent hemodynamic stability.
| Materials and Methods|| |
After taking approval from the institutional ethics committee, a prospective single-blinded randomized controlled clinical trial was conducted in a tertiary care teaching hospital. A written informed consent was taken from parturients of ASA grades I and II with more than 37 weeks of gestation, having singleton uncomplicated pregnancy, scheduled to undergo elective CS under CSEA. Exclusion criteria included parturients weighing more than 100 kg, having pregnancy-induced hypertension, coagulopathy, antepartum hemorrhage, in active labour, or emergency CS.
Sample size estimation was based on the detection of any fall in systolic blood pressure (SBP) between groups; with an alpha error of 0.05 and a power of 80%, a sample size of 30 in each group was calculated. We enrolled 33 patients in each group to compensate for dropouts. Ninety-nine patients were randomized using the sealed envelope technique into three groups of 33 each, comprising Group NEVE (CSE with no EVE), Group EVE-S (CSE followed by EVE with 0.9% normal saline), and Group EVE-H (CSE followed by EVE with 6% HES (200/0.5).
All subjects were adequately fasted and received 500 ml Ringer lactate as preload before induction of regional anesthesia. Standard monitoring included noninvasive blood pressure (NIBP), electrocardiography (ECG), and pulse oximetry (SpO 2 ). Baseline heart rate (HR), SBP, and diastolic blood pressure (DBP) were recorded. After taking aseptic precautions, the CSEA block was performed using a CSE kit (B-Braun containing 27-gauge Whitacre spinal needle and an 18 G Tuohy epidural needle) with the patient in the left lateral position at the L3-4 interspace using a midline approach. Epidural space was identified using loss of resistance to air (<2 ml). A 27 G Whitacre pencil point needle was advanced through the Tuohy needle into the subarachnoid space and the intrathecal drug was injected. The intrathecal drug dose with a total volume of 1.7 ml was identical in the three groups and consisted of 0.5% 6 mg hyperbaric bupivacaine (1.2 ml in a 2 ml disposable syringe) with fentanyl 25 mcg (0.5 ml). The spinal needle was withdrawn and depending on group allocation, the patient either received EVE with 5 ml of 0.9% saline (Group EVE-S) or 6% HES (Group EVE-H) via epidural needle or no EVE (Group NEVE). After withdrawing the epidural needle, patients were turned supine with a left lateral tilt of 15°.
To provide blindness to the study, data were recorded by an independent anesthesiologist who was unaware about group allocation. SBP, DBP, and HR were recorded every min until delivery, and then every 5 min. Lowest attained value of SBP, DBP, and HR in each patient was noted and their percent of fall from baseline was calculated. Hypotension (20% fall from baseline or SBP less than 100 mmHg) was treated with ephedrine 6 mg boluses and bradycardia (HR less than 60/ min) was treated with atropine 0.4 mg bolus. Sensory and temperature sensation blockade was determined as a complete loss of sensation to pinprick (25G hypodermic needle) and cold (ice cube sensation) in the midaxillary line, respectively. The motor block was measured by the Bromage score as 0-3. Sensory and motor block were assessed at 1 min interval until there was no change in three consecutive readings, to record the onset data. Following completion of surgery, recovery was recorded by assessing sensory and motor block every 5 min till regression of sensory block occurred to L 1 and the Bromage score reached to zero. The block characteristics were noted with all times calculated from time 0 (Time of intrathecal drug) as the peak sensory block level achieved, Time peak : time to reach the maximum sensory level, Time (peak-L1) : time for sensory block regression to L 1 , time to attain maximum motor blockade, time for complete regression of motor blockade (Bromage score = 0).
Surgery was allowed to proceed once the sensory block reached T 6 . If the block height was less than T 6 and the patient complained of pain anytime during the surgery, supplemental analgesia with ketamine (0.5 mg/kg IV) was administered and the total ketamine requirement was noted. If the block was less than T 8 , it was considered as block failure and surgery was conducted under general anesthesia and was excluded from the study. Intraoperative adverse effects noted included nausea, vomiting, pruritus, and shivering. Neonatal outcome was assessed by a pediatrician with 1 and 5 min Apgar scores.
The statistical analysis was done using SPSS version 16.0 and Epi Info 6. Data were presented as mean ± SD, median (range), or number (proportion) as appropriate. Demographic variables were analyzed using the Student's t test while the hemodynamic parameters and sensory and motor block characteristics were analyzed using analysis of variance (ANOVA). A Chi- square test was used to analyze the incidence of intra- and postoperative adverse events. A P value less than 0.05 was considered as significant.
| Results|| |
All the three groups were comparable regarding mean age, weight, height, baseline hemodynamic parameters, and duration of surgery [Table 1].
The peak sensory level as assessed by temperature and pinprick were significantly higher in Group EVE-S as compared to Group NEVE (P = 0.003 and P = 0.007, respectively). The peak sensory level was also achieved significantly earlier in Group EVE-S as compared to Group NEVE (P = 0.000) and Group EVE-H (P > 0.05). In Group EVE-S, there was a difference in peak sensory levels as assessed by temperature and pinprick (thoracic T 4.88±1.01 (temp) versus T 5.04±1.02 (pinprick)), whereas it was the same in the other two groups (T 6.10±1.41 in Group NEVE and T 5.44±1.35 in Group EVE-H). The median value of peak sensory level for temperature was higher in Group EVE-S (median T 4, range T 4- T 6 ) as compared to Group NEVE and Group EVE-H (median T 6, range T 4- T 8 ). However, the median value of peak sensory level to pinprick was T 6 in all the three groups, which was adequate for LSCS. The need for ketamine supplementation was significantly more in Group NEVE (54.5%) than in Group EVE-S and Group EVE-H (24.2% and 27.3%, P = 0.02, respectively) showing the differences in the quality of block in the three groups [Table 2].
Complete motor block (Bromage score 3) was achieved in 13(39.4%) patients of Group NEVE, 18 (54.5%) of Group EVE-H, and 22 (66.7%) of Group EVE-S, which was comparable, P = 0.083 as also the mean time to attain maximum motor block (P = 0.164). The mean modified Bromage score at the end of surgery was significantly higher in Group EVE-S (2.2 ± 0.8) than in Group NEVE (1.6 ± 0.9) and EVE-H (1.4 ± 1.0), P = 0.004 [Table 3]. The time taken for sensory block regression to L1 and motor block regression to Bromage score 0 was significantly more in Group EVE-S as compared to Group NEVE (P = 0.000), while Group EVE-H was intermediate [Table 2] and [Table 3].
HR, SBP, and DBP were significantly lower in Group EVE-S than in Group NEVE (P = 0.019, 0.008, and 0.001 respectively), while vital parameters in Group EVE-H were intermediate. The lowest value of SBP was observed significantly earlier in Group EVE-S (7.9 ± 4.5 min) as compared to Group NEVE (14.6 ± 4.8 min), P = 0.000. However, total doses (in mg) of ephedrine and atropine showed no statistically significant difference among the three groups (P > 0.05) [Table 4], [Figure 1].
Incidence of hypotension (60.6%), bradycardia (18.2%), nausea (24.2%), and shivering (21.2%) was more in group EVE-S, whereas hallucinations were seen only in Group NEVE (18.2%) [Table 4], [Figure 2]. Apgar scores of neonates in the three groups were comparable. None of the patients in the study had pruritus or PDPH.
| Discussion|| |
SSS is noted to be the most commonly used anesthetic technique for CS offering a dense block with rapid onset.  Nowadays CSEA is another well-accepted technique for CS that allows intraoperative as well as postoperative analgesia supplementation.  A further modification of the CSE is EVE, where normal saline is injected in the epidural space soon after the intrathecal injection which increases sensory block height and has been used successfully for CS. ,
EVE allows CSE to be performed with small intrathecal doses of local anesthetics. , Earlier studies in parturients have shown augmentation of spinal block with CSE compared to SSS,  EVE compared to CSE, ,, and EVE compared to SSS.  The mechanism of higher sensory block with CSE is postulated to be an increase in epidural pressure following communication of the epidural space with atmospheric pressure through the epidural needle, leading to thecal compression and cephalad spread of local anesthetic. , With EVE, block augmentation has also been explained by the intrathecal drug being pushed cephalad by the epidural injection (volume effect), over and above that induced by a raised epidural pressure due to CSE without EVE. , The cephalic spread of spinal local anesthetic has been proved clinically, ,, myelographically,  , and by using magnetic resonance imaging. 
It is postulated that reduction of intrathecal local anesthetic dose should provide better maternal hemodynamic stability. However, some authors documented that CSE and EVE were associated with increased incidence of hypotension and lower umbilical cord blood gases. ,,
EVE is usually done with 0.9% saline ,, and also with 0.5% isobaric bupivacaine  but there are only sporadic reports  of use of colloid for EVE. Jain et al.  reported dose reduction of intrathecal bupivacaine when EVE was done with 10 ml of Dextran 40 as compared to plain CSE. It was attributed to slower absorption and less leakage of colloid from epidural space compared with saline. , Though HES has not yet been studied for EVE, it has been used successfully in the epidural space to treat PDPH as an alternative to epidural blood patch without neurotoxic effects. ,, However, no study has compared the difference in block characteristics and hemodynamics, when EVE is used with colloid versus saline.
In our study, laboring women were excluded because variation in epidural pressure during labor can affect the height of spinal block. 
We used 6 mg of 0.5% hyperbaric bupivacaine with 25 mcg fentanyl intrathecally for spinal block in all three groups, because the median effective dose (ED50) of hyperbaric bupivacaine with fentanyl has been reported to be 6.1 mg when used in CSEA without EVE for CS.  But in our study, we found that this low intrathecal dose in CSE without EVE was not adequate for CS because in Group NEVE, the mean peak sensory level was T 6.10±1.41 and supplemental analgesia with ketamine was required by 54.5% patients to accomplish surgery. On the contrary, when CSE was followed by EVE using saline or HES, the mean peak sensory level reached to T 5.04±1.02 (Group EVE-S) and T 5.44±1.35 (Group EVE-H) resulting in the reduction of rescue boluses of ketamine (24.2% and 27.3%, respectively). Similarly Jain et al. have reported an ED50 of intrathecal hyperbaric bupivacaine as 4 mg when EVE was done using Dextran 40 as compared to 7.0 mg in patients without EVE (P < 0.001). 
Controversies regarding optimal volume in EVE have led to the use of varying doses (5-10 ml) of saline in EVE. ,, Many factors seem to influence EVE, including timing, the study population (obstetric versus non-obstetric), position during CSE and EVE (sitting versus lateral), baricity of intrathecal local anesthetics, their additives, and volume used for EVE. ,, Dogunci et al.  investigated the optimal volume of epidural saline administration for EVE using 5, 10, 15, and 20 ml epidural saline after spinal anesthesia. This study indicated that the level of analgesia was higher with administration of 5 ml of saline as compared to the control group and no further change was observed by increasing the saline dose. Higuchi et al.  conducted a study using thoracic and lumbosacral axial magnetic resonance images to know how injected epidural solution is distributed and affects the epidural volume effect in pregnant women. It was found that the epidural volume effect is greater in pregnant than in non-pregnant women. Limited dural sac coating and decreased leakage of epidural saline from the foramina may account for the facilitation of longitudinal spread of epidural analgesia in pregnant women.
We observed in our study that EVE caused augmentation of block in terms of faster onset, higher peak sensory level, intense motor block, and prolonged duration. This block augmentation is attributed to volume effect of EVE in epidural space pushing the intrathecal drug cephalad. , Previous studies showing comparison of EVE with SSS have also shown that EVE caused faster onset and higher peak sensory levels.  In our study, higher levels took more time to regress and caused prolonged duration of block. Most of the authors have reported no effect of EVE on block duration. , It is documented that EVE allows reduction in intrathecal dose of bupivacaine and may result in faster motor recovery. ,
Our study clearly demonstrates that EVE using saline or HES augmented the low-dose spinal block but EVE with saline was associated with increased incidence of hypotension (60.6%) as compared to EVE with HES (39.4%) or without EVE (27.3%). The quantum of fall of SBP, DBP, and HR was also more in EVE-S.
It has been observed that during treatment of PDPH, epidural saline and colloid infusions tend to increase the epidural pressure and immediately relieve headache. , Because of the viscosity, reabsorption of the colloid from the epidural space is delayed, leading to a greater and longer compression enabling closure of the dural rent during treatment of PDPH.  The difference in the volume effect of saline and colloid during EVE as observed in our study could be attributed to the viscosity of HES. When EVE was done with 5 ml saline, the mean peak sensory level reached to a higher level with a difference between the peak autonomic and sensory dermatomal level (T 4.88±1.01 (cold) versus T 5.04±1.02 (pinprick) in EVE-S). The higher autonomic blockade resulted in the increased episodes of hypotension (60.6%). On the contrary, when EVE was done with HES, the peak sensory level as assessed by pinprick and temperature were the same (T 5.44±1.35 ); therefore, incidence of hypotension was less (39.4%). Intraoperative hypotension correlates well with lower umbilical cord blood gases 4 but this could not be carried out in our resource-constrained tertiary centre. However, there was no statistical difference in doses of ephedrine and Apgar score at 1 or 5 min in all the three groups as was also observed by other authors. ,
Among adverse effects, incidence of shivering (21.2%) and nausea (24.2%) were more in patients receiving EVE with saline that could be due to higher autonomic blockade and frequent hypotensive episodes, while hallucinations were observed only in patients receiving CSE without EVE (18.2%).This could be attributed to lower sensory level (T 6.10±1.41 ) in this study group (NEVE) and hence more number of patients required supplemental analgesia with ketamine (54.5%).
The limitation of our study is that the difference in volume effect in EVE using saline versus HES was assessed clinically by noting the level of autonomic and sensory blockade and incidence of hypotension. However, the distribution of epidural saline and HES were not confirmed with MRI images and myelography. The estimation of umbilical cord blood gases could have provided better evaluation of neonatal outcome to assess the effect of maternal hypotension.
We conclude that an intrathecal dose of 6 mg of 0.5% hyperbaric bupivacaine with 25 mcg fentanyl is adequate for CS when used in CSE with EVE using 0.9% saline or 6% HES (HES 200/0.5) and EVE with HES provides optimal hemodynamic profile as compared to saline.
We suggest further studies should be conducted using thoracic and lumbar axial magnetic resonance images and myelography to see the exact distribution of epidural saline versus various colloids to extrapolate our findings. EVE using colloids could thus become a standard technique rather than saline, incorporating the advantage of a dose-sparing effect without significant hypotension as observed in our study.
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[Figure 1], [Figure 2]
[Table 1], [Table 2], [Table 3], [Table 4]
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