European Journal of Cardiovascular Medicine

Sub arachnoid block is the preferred obstetric, regional anaesthetic technique for lower segment caesarean section, as it offers several advantages over general anaesthesia, such as, reduced maternal mortality, reduced blood loss and early ambulation. However, it is associated with maternal hypotension leading to reduced uteroplacental blood flow and fetal compromise.

Several techniques are used to minimize spinal anaesthesia induced maternal hypotension, such as left uterine displacement, reducing the dose of local anaesthetic, usage of intrathecal opioids, preloading and co-loading with different intravenous fluids. However, the evidence is inconclusive and no technique reliably produces decrease in the incidence of hypotension.

Opioids are the most frequently used local anesthetic adjuvants and their use in neuraxial blocks have evolved over the last 50 years. The dose, site of injection, lipophilicity and the acid-base milieu of the site of drug deposition determine the extent of efficacy of the block. Intrathecal fentanyl in the dose range of 10-30 μg has also been shown to prolong the duration and extent of sensory block with a favorable adverse effect profile.[1]

In our clinical study, we investigated a novel method of administering spinal anaesthesia in pregnant patients undergoing elective caesarean section wherein, the hemodynamic effects and block characteristics in spinal anaesthesia given as a single bolus dose was compared to fractionated dose where two third of total dose was initially administered followed by the remaining one third dose after an interval of 90 seconds.

This was a randomized, comparative clinical study conducted between December 2020 to August 2021 involving 60 pregnant patients undergoing elective caesarean section under spinal anaesthesia between 18 to 40 years of age belonging to ASA physical status II without comorbidities. The study subjects were divided into two groups Group BD and Group FD of 30 patients each. Spinal anaesthesia was administered at L3-L4 intervertebral space with 25guage Quincke Spinal needle. Group BD received single bolus dose of 2.2ml of solution which included 1.8ml (9mg) of 0.5% hyperbaric Bupivacaine with 0.4ml (20mcg) of Fentanyl. Group FD received fractionated dose of spinal anaesthesia where, out of the total 2.2ml of drug preparation, 1.6ml was administered initially and the remaining 0.6 ml was given after 90 seconds interval. Hemodynamic parameters in the intraoperative and postoperative periods were recorded. Time to onset of sensory block at T6 and that of Motor block to Bromage Scale 3, duration of sensory and motor block were noted. SAS 9.2, SPSS 15.0, Stata 10.1, MedCalc 9.0.1, Systat 12.0 and R environment ver.2.11.1 were used for the analysis of the data. Chi-square/ Fisher Exact test was used to find the significance of study parameters on categorical scale between two groups. P value: less than 0.05 was Suggestive of significance (0.05<P<0.10) and P<0.01: Strongly significant

The mean age of Group BD was 26.37±4.271 years and in Group FD it was 28.20±4.916 years, as shown in Table 1. No Statistical significance (p>0.05) was observed in the age of the study population.

The mean height of the patient in Group BD was 160.07±5.994 cms and in Group FD was 158.03±5.768 cms. The mean weight of Group BD 60.80±4.444 kgs was and Group FD was 67.87±5.251 kgs. There was no statistically significant difference between the two groups with p>0.05 for these parameters.

The mean duration of surgery in Group BD was 85.77±11.043 minutes and in Group FD it was 87.33±14.368 minutes, both the groups were comparable in terms of duration of surgery. (p- 0.615)

The onset of sensory block in Group FD was 1.60± 0.246 minutes and Group BD was 2.18±0.254 minutes, which was statistically significant with p<0.001. The onset of motor block in Group FD was 6.18±0.381 minutes and Group BD was 5.12±0.200 minutes. Group FD had statistically significant shorter onset of motor block compared to Group BD with p<0.001 (Table 2).

As shown in Table 3, the mean duration of sensory block in Group BD was 186.17± 8.375 minutes and in Group FD it was 225.43±9.679 minutes, which was statistically significant with p<0.001. The mean duration of motor block in Group FD was 178.33±10.317 minutes, which was significantly longer than Group BD 153.47±9.108 and statistically significant with p<0.001.

Heart rate was measured in the intraoperative period every 2 minutes for the first ten minutes, followed by every 5 minutes until the end of surgery, On comparing the heart rate between the two groups, no statistical significance was observed with p values >0.05.

Intraoperative systolic blood pressure was measured every 2 minutes for the first ten minutes followed by every 5 minutes until the end of surgery. Group BD had statistically significant fall in systolic blood pressure between 6 minutes to 25-minute interval when compared to Group FD, with p<0.001.

On comparison of diastolic blood pressure between the two groups, there was statistically significant fall in diastolic blood pressure in Group BD compared to Group FD at time intervals of 6 minutes to 25 minutes with p values <0.001

There was statistically significant drop in the intraoperative mean arterial blood pressure in Group BD in time intervals from 6 minutes to 25 minutes when compared to Group FD, with p<0.05.

There was no statistically significant difference in the intraoperative Spo2 between the two groups with p>0.05. 10 patients (33.33%) in Group BD required vasopressor (Inj. Ephedrine) to treat intraoperative hypotension. Whereas, 5 patients (16.7%) required Ephedrine in Group FD, which was statistically significant with p<0.001.

Bradycardia was seen in 5 patients (16.67%) in Group BD that received bolus dose of spinal anaesthesia and 2 patients (6.67%) in Group FD that received fractionated dose which was managed with Inj. Atropine 0.6mg IV. which was statistically not significant with p= 0.228.

Post-operative heart rate was measured at every 15 minutes for the first hour followed by every hourly for the first 24 hours of the post-operative period. No significant difference was found between the two groups. (p>0.05). Post-operative systolic, diastolic and mean blood pressures measured in the first 24 hours showed no statistical significance between the groups (p>0.05). Pain scores (visual analog scale) were 0 for the first four hours in both the groups, the highest score was achieved at 8 hours in both the groups which was statistically not significant, with p>0.05.

The primary objective of this prospective randomized clinical study was to compare the hemodynamic changes occurring in the technique of administering spinal anaesthesia as a bolus dose compared to fractionated dose after 90 seconds interval and the secondary objective was to study the onset, duration of sensory and motor blockade [2]. The demographic parameters in both the groups such as age, weight and height were comparable. There was a statistically significant fall in the intraoperative systolic blood pressure, diastolic blood pressure as well as the mean arterial pressure from time intervals of 6 minutes to 40 minutes in Group BD when compared to Group FD (p<0.05). However, no significant differences in the intraoperative heart rate or the postoperative hemodynamic parameters were observed.

Onset of sensory block in Group BD was 2.18 ± 0.254 minutes and in Group FD it was 1.60 ± 0.246 minutes which was statistically significant with p<0.001. The onset of motor block was assessed using Bromage scale and it was observed that Group BD had a longer onset of motor block compared to Group FD. The onset of motor block in Group BD was 6.18±0.381 minutes and in 5.12±0.2 minutes which was found to be statistically significant with p<0.001. The duration of sensory block, which was defined in our study as duration from the onset of sensory block to need for rescue analgesic was 186.17± 8.375 minutes and in Group BD and 225.43±9.679 minutes in Group FD which was statistically significant with p<0.001. Group FD that received fractionated dose had a longer duration of sensory block. Duration of motor block in our study for complete motor recovery in Group FD was 151.47±9.10 minutes and 178.33±10.31 minutes in Group BD, which was also statistically significant with p<0.001.33.3% of parturients in Group BD required Ephedrine whereas only 16.7% of patients required Ephedrine to teat hypotension after administering spinal anaesthesia which was statistically significant with p<0.001.

In a similar randomized, double blinded study conducted by Badheka et al[3] sixty patients undergoing elective caesarean section reported fractionated group to have an increase in duration of sensory block of 236±42 min and motor block of 204±42 min with p<0.001, which was similar to our findings. However, they observed no difference in the time of onset of sensory block (p=0.07).

In a prospective randomized study conducted by Bina B Patel et al[4] 60 parturients, the authors reported a significantly shorter onset of sensory and motor block in fractionated Group, F 1.27±0.19 min and 4.55±0.52 min compared to onset of sensory and motor blocks in Bupivacaine Group, B which were 1.44±0.12 min and 5.36±0.79 min with p<0.001. Similar observations were made in our study.

Nugroho AM[5] et al observed no difference in mean arterial pressure or block characteristics between bolus and fractionated dose administration in spinal anaesthesia, they conducted a prospective randomized study on 42 parturients with pregnancy induced hypertension and observed no significant difference (p>0.05) in mean arterial pressure, total ephedrine use or levels of sensory blockade between the fractionated dose and the bolus dose groups. Similarly, Kumar VS et al.[6] found no significant difference in hemodynamic parameters in their prospective double blinded study where, 60 parturients were randomized into two groups. A fixed dose of 2ml 0.5% Bupivacaine for spinal anaesthesia was used. Group A received blous dose and Group B received fractionated dose after 60 second interval. Block characteristics, hemodynamic parameters and APGAR scores at 1 min and 5 min were studied. Contrary to our study, statistically significant faster onset of sensory and motor block was seen in Group A who received bolus dose (p<0.05). But, the duration of sensory block was prolonged in the fractionated Group B (188.97±18.80 min) when compared to Group A (154±22.56 min) with p<0.05. They also noted no difference in APGAR scores between the groups.

Kishor Kabir K et al.[7] in their prospective study on 200 parturients undergoing elective caesarean section noted significant hypotension (p<0.05) in bolus group in time intervals between 5 min and 30 min after induction. Similar observations were made in our study where statistically significant hypotension (p<0.05) was observed between 6min to 40 min intervals after giving spinal anaesthesia.

They also noted 39% of patients in bolus group required vasopressors and only 15% of patients who received fractionated dose required vasopressors no statistical significance was observed in heart rate variation between the groups which was also observed in our study.

Hossain MM et al.[8] in their prospective randomized study compared fractionated dose with bolus dose of spinal anaesthesia in sixty patients undergoing elective caesarean section. They observed the mean pulse rate of the fractionated group between 5 minutes and 60minutes after administration of spinal anaesthesia was higher when compared to blous group (p<0.05) but the mean arterial pressure in both the groups were similar with no statistical significance, which is contrary to our findings where we observed the bolus group (Group BD) statistically significant drop in the systolic BP, diastolic BP as well as mean arterial pressure between time intervals of 6min to 40 min after giving spinal. They also noted a longer duration of sensory block in the fractionated group (254±38.8 minutes) compared to the bolus group with p<0.001 which was similar to our findings.

A sub arachnoid block with 9mg (1.8ml) of 0.5% hyperbaric Bupivacaine and 20mcg (0.4ml) of Fentanyl, administered as a fractionated dose, provides early onset and prolonged duration of sensory and motor blocks with better hemodynamic stability compared to a single bolus dose in patients undergoing caesarean section.

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