Prakash T. S. N1, Ravi V2
The concept of CSE has come into existence with the aims to provide the benefits of spinal block along with flexibility of an epidural catheter so as to modify and prolong the block for a longer period. CSE can be used to reduce or eliminate the disadvantages of spinal and epidural anaesthesia while preserving their advantages. The CSE technique has been used for orthopaedic and trauma surgery of lower limb, general surgery, urologic surgery, gynaecologic surgery, caesarean section, management of labour pain and postoperative pain. CSE blocks have also been used as research tools for controlled comparison between different epidural and subarachnoid techniques. Furthermore, the technique has been used successfully in all age groups including preterm neonates and infants, the very old and other high-risk patients. CSE is a multicompartment block. CSE involves intentional dural puncture followed by epidural drug administration. This introduces the possibility of drug flux from the epidural to the subarachnoid space, which may alter the characteristics of the block. Subarachnoid pressure is normally regarded as greater than epidural pressure by 5-15 cm H2O. This pressure gradient is an obstacle to drug flux into the subarachnoid space. The epidural pressure rises transiently, but dramatically after drug administration, the similar rise in subarachnoid pressure occurs. There is a brief period during, which epidural pressure may exceed subarachnoid pressure. This produces conditions that would allow drug flux into the subarachnoid space.
MATERIALS AND METHODS
This clinical study was conducted in Department of Anaesthesiology in association with Department of Obstetrics and Gynaecology at Victoria General Hospital attached to Andhra Medical College, Visakhapatnam, from October 2013 to August 2014. Clearance was obtained from hospital ethics committee for the study. Written informed consent was obtained from all the patients. 40 parturients with ASA I and ASA II in established labour with cervical dilatation less than 5 cm was selected and randomly allocated into two groups using closed envelope method. Informed written consent was taken from all participants. They were divided into 2 groups of 20 each. Group I received intrathecal Inj. Bupivacaine 1.25 mg and Inj. Fentanyl 20 μg. Group II received intrathecal Inj. Ropivacaine 2.5 mg and Inj. Fentanyl 20 μg for combined spinal epidural. IV line was secured with 18G cannula. Patient was preloaded with 500 mL of Hartmann’s solution. Basal vital parameter like pulse rate, blood pressure, respiration, O2 saturation were recorded. The patient was positioned in a sitting position with the help of an assistant. Under aseptic conditions, the back was prepared with 5% povidone-iodine solution, spirit and area was draped. L3-L4 interspace was identified. Skin was infiltrated with 2 mL of 1% Xylocaine. After infiltration of local anaesthetic by using needle through needle technique 18-gauge Tuohy needle, epidural space was identified with loss of resistance to air technique. Then, a 15 mm (27 G) long ‘Whitacre’ spinal needle was introduced through the epidural needle and the correct position of the tip in the intrathecal space was confirmed by observation of free flow of CSF. Patients were allocated randomly to receive intrathecal injection of bupivacaine 1.25 mg (0.5% bupivacaine 0.25 mL) with fentanyl 20 μg (Group I n=30) or ropivacaine 2.5 mg/0.2% ropivacaine 1.25 mL) with fentanyl 20 μg (Group II, n=30) both made up to total volume of 2 mL with saline. Injection of intrathecal drug was completed in 10 secs., then 20G epidural catheter was threaded through the epidural needle into the epidural space in cephalad direction. The epidural needle was slowly pulled out without disturbing the catheter. About 3 to 5 cm of catheter was left in epidural space. The catheter was well secured with plaster. Patients vitals was recorded every 5, 10, 15, 30, 45, 60, 75, 90, 105 and 120 mins., i.e. (every 5 mins. for 15 mins. and then every 15 mins. for 2 hrs.) until the next request for analgesia. After positioning the patient in supine position, onset of analgesia and dermatome level were checked by loss of sensation to pinprick, time of onset and degree of motor blockade was checked by Bromage classification. VAS pain scores for all patients immediately before and after 15 mins. of the procedure at the next request for analgesia. Vitals were recorded and study was terminated. Continuation of epidural analgesia was done with 0.125% bupivacaine + 2 μg fentanyl in 10 mL. Monitoring - mother’s vital parameters, progress of labour, efficacy of analgesia and foetal welfare were watched in coordination with attending obstetrician. Pulse, NIBP, SpO2, respiratory rate were recorded before and after the start of procedure and every 5 mins. for first 15 mins. and then every 15 mins. for 2 hrs. If bradycardia occurred at any time (<60 bts./mins.), Inj. Glycopyrrolate 0.2 mg was given. If hypotension occurred, then it was treated appropriately with IV fluids and vasopressor. If pruritus occurred, it was treated with pheniramine. Sensory blockade assessed by pinprick and motor blockade was assessed by Bromage scale.
Statistical Analysis- In the present study, results are given as mean±standard deviation and range values for continuous data. Students test was used to compare the two groups, categorical data are expressed as number and percentages and difference between the groups was compared by chi-square test. A p value of 0.05 or less was set for statistical significance.
Maternal hypotension of 15% was noted in both groups, which was statistically significant. Onset of sensory analgesia in seconds showed a standard deviation of 38.12 with a mean difference of 47 seconds between the two groups was found to be statistically highly significant with a p value of <0.001. Maximal dermatomal level of sensory block achieved also showed statistically significant p value of <0.001. Two segment regression of spinal component of CSE showed a mean difference of 13.1 mins. with a mean time of 89.7 mins. for regression.
In conclusion, we found that intrathecal ropivacaine 2.5 mg was as effective as intrathecal bupivacaine 1.25 mg when added to fentanyl 20 μg in providing labour analgesia using combined spinal epidural technique in the first stage of labour with more efficient sensory block in terms of longer duration of action and better VAS scores, minimal motor block and hypotension. Thus, ropivacaine 2.5 mg would provide a suitable alternative to bupivacaine with better analgesia and minimal adverse effects.