A comparative study of epidural ropivacaine and epidural ropivacaine with fentanyl for perioperative analgesia in patients undergoing elective gynaecologial surgery

 

 

Abstract               Background: Different drugs have been tried as adjuvants to local anaesthestic agents administered epidurally to prolong postoperative analgesia. This randomised prospective study was designed to assess and compare the efficacy of fentanyl used as adjuvant to ropivacaine for epidural analgesia in patients undergoing elective gynaecological surgery. Methods: Eighty female patients of ASA Grade I and II, within age group of 20 to 60 years undergoing elective gynaecological surgery were included in one of the two following groups. Patients with pre-existing neurological, cardiac, spinal deformity, local infection in the lumber region and known hypersensitivity to amide local anaesthetics were excluded from the study. Group A patients received 15 – 20 ml of 0.75% ropivacaine hydrochloride epidurally and Group B patients received 15- 20 ml of 0.75% ropivacaine hydrochloride plus 50 mcg of fentanyl citrate. Results: Group B patients had early onset of sensory and motor block and longer duration of analgesia compared to Group A. There was no significant difference in heart rate, mean arterial pressure, distribution of block height and duration of sensory and motor block in both groups. Conclusion: Addition of fentanyl citrate to ropivacaine hydrochloride in epidural anaesthesia, significantly hasten the onset of both sensory and motor block; though, height of the sensory block, duration of sensory (two segment regression) and motor (full motor power and joint movement) block do not alter much. However it causes significant prolongation in duration of analgesia without significant cardiovascular instability and side effects.

Key Words: Fentanyl, Ropivacaine, Epidural Analgesia.

 

 

 

 

INTRODUCTION

Epidural anaesthesia is a popular method of anaesthesia for gynaecological surgery. It has been shown to blunt the stress response to surgery, decrease intraoperative blood loss, reduces the incidence of postoperative thromboembolic events and decrease morbidity and mortality in high risk surgical patients¹. It can be used to extend analgesia into postoperative period, where their use has been shown to provide better analgesia than can be achieved with parenteral opioids.² Ropivacaine, the S-enantiomer of 1-propyl-2,6-pipecoloxylidide, is an amide local anaesthetic with a chemical structure related to mepivacaine and bupivacaine. A number of studies suggest that ropivacaine is associated with less central nervous system and cardiac-toxicity with less motor block potency but anaesthetic and analgesic property is comparable with bupivacaine.^{3, 4} On the other hand, since the introduction of epidural opioids into clinical practice of anaesthesia in 1979, it has gained widespread popularity and acceptance⁵. Epidural administration of combination of opioids and ropivacaine for postsurgical pain relief has resulted in better pain scores. Several authors have suggested that this combination may produce a synergistic effect, while reducing the incidence of side effects.^{6, 7} Since hydrophilic opioids such as morphine, remain in the cerebrospinal fluid for long duration and may be responsible for undesirable side effects like delayed onset of peak analgesic effect and late respiratory depression, highly lipophilic opioids such as fentanyl have been used to reduce the side effects of extradural opioid administration.^8.9 Fentanyl, a potent opioid receptor agonist is largely used to provide analgesia for acute pain and to enhance the quality of epidural block for perioperative analgesia.¹⁰ With this previous review, this study was conducted to compare epidural ropivacaine and epidural ropivacaine with fentanyl in respect of onset, duration and height of sensory anaesthesia and analgesia, onset and duration of motor blockade and incidence of side effects if any.

 MATERIALS AND METHODS

The study protocol was approved by the Institutional Ethics Committee and informed written consent was taken from the patients. The study was carried out in the Department of Anaesthesiology, Burdwan Medial College and Hospital, Burdwan during the period March 2010 to June 2011. Eighty ASA grade - I and II patients of age between 20 yrs to 60 yrs, who underwent elective gynaecological surgeries were included in the study. Patients with pre-existing neurological, cardiac, spinal deformity, local infection in the lumber region and known hypersensitivity to amide local anaesthetics were excluded from the study. Any patient requiring added systemic analgesics or needing general anaesthesia was excluded from the study. Patients were randomly into two groups. Group A patients received 15 – 20 ml of 0.75% ropivacaine hydrochioride. Group B patients received 15 -20 ml of 0.75% ropivacaine hydrochloride plus 50 mcg fentanyl citrate. The dose of ropivacine hydrochloride was calculated according to height of the patients (height upto 160 cm: 15 ml and 161 cm onwards: 20ml). Solutions were prepared by an anaesthesist who was totally unaware of the nature of the study. All Patients after preanaesthetic check up and were explained in detail about the procedure of lumber epidural block. All their queries and doubts were answered informed written consent was taken from the patients. Night before surgery all patients received Tablet Diazepam 10mg orally, Inj. metoclopramide 10 mg and Inj. ranitidine 50 mg IM were given 1 to 2 hrs before operation. On arrival in the operation theatre (OT) the baseline pulse rate, blood pressure, ECG, respiratory rate, SpO2 were recorded. All patients were preloaded with 15ml/kg of Ringer’s lactate solution over 15mins before administering epidural block. The patients were kept in sitting position, the overlying skin was prepared with spirit- povidone iodine - sprit, followed by antiseptic draping. After proper identification of space, 2ml of Inj. lignocaine 2% was infiltrated into the skin and subcutaneous tissue at L_2-3 or L_3-4 inter space. Epidural block was administered For epidural using 18G Tuohy needle. Epidural space was identified by loss of resistance technique. After negative aspiration, a test dose was administered with 3 ml of inj. 2% Lignocaine hydrochlorid with adrenaline and monitoring was done to note any haemodynamic changes to rule out inadvertent intravascular injection. After ensuring proper epidural placement of the needle tip, the study drug solution was slowly injected, following which epidural needle was removed and antiseptic dressing was applied over the puncture site. Monitoring of vital parameters was recorded throughout the procedure. The patients were made supine. The patients were administered O₂, 5 L/min through face mask. The surgery was allowed after 20 minutes of epidural injection after checking satisfactory sensory and motor block. The following parameters were recorded:

• Onset of sensory block - assessed by pin prick method every 3 minutes from local anaesthetic solution administration to total loss of pain sensation.
• Onset of motor block - assessed every 3 minutes by modified Bromage scale as follows: 0 - no paralysis, 1-inability to raise extended leg, 2-inability to flex knee, 3- Inability to flex ankle and first toe. Time duration (minute) was assessed from the time of injection of local anaesthetic solution till motor scale 2 or more.
• Duration of sensory block - assessed every 15 minutes postoperatively by pin prick method. Time duration (minute) was assessed from onset of sensory block to regression of dermatome of two segments.
• Duration of motor block - assessed by modified Bromage scale every 15 minutes post operatively. Time duration (minute) was assessed from onset of motor block to regaining of full motor power and joint movement.
• Duration of analgesia - assessed every 15 minutes postoperatively by 10 cm Visual Analogue Scale (VAS). Time duration (minute) was assessed from onset of sensory block to first request for rescue analgesic or VAS score 4 or more. The numeric pain scale was of 0-10 cm (0 = no pain and 10 = worst possible pain). Rescue analgesic injection diclofenac sodium 1.5mg/kg was given intramuscularly.
• Hemodynamic parameters - pulse, blood pressure (systolic and diastolic and mean) were recorded at 5 minutes, 15 minutes, 30 minutes, 60minutes, 120 minutes, 240minutes after administration of epidural block.
• Side effects - nausea, vomiting, pruritus, hypotension, respiratory depression, shivering, urinary retention etc and others (if any) were noted.

All measurements and assessments were recorded by an anaesthesiologist who was unaware of the medication.

Statistical Analysis: Statistical analysis was performed with the help of statistical package for social sciences (SPSS software version 16.0).numerical variables compared between groups by Student’s unpaired t-test if normally distributed or by Mann-Witney U-test if otherwise. Categorical variables would be compared between groups by Chi-square test or Fisher’s exact test as appropriate. Analysis would be two tailed and p<0.05 would be considered statistically significant.

RESULTS

There was no statistically significant difference in age (p=0.102), body weight (p=0.877), height (p=0.89) distribution among the study groups and hence the groups were comparable to each other in terms of age, body weight, height (Table-1).

There was no statistically significant difference in distribution of block height achieved in different patients between Group-A and Group-B (Table 4).

Table 4: Comparison between group a and group b according to height of sensory block

In present study the duration of sensory block in the two groups was calculated by counting time required to two segment regression of sensory block after surgery under epidural anaesthesia. There was no statistically significant difference (p=0.254) among the Group-A and Group-B in respect to the duration of sensory block shown in the Table – 5. There was no statistically significant difference (p=0.619) among the Group-A and Group-B in respect to the duration of motor block (Table – 5).

 

Table 5: Distribution of Duration of Sensory Block (Two Segment Regression) and Motor Block Between Two Groups:

Duration of analgesia was assessed every 15 minutes postoperatively by 10 cm Visual Analogue Scale (VAS). There was a statistically significant difference (p=0.000) between the Group-A and Group-B in respect to the duration of analgesia (Table 6). This was assessed on the basis of VAS score in the post-operative period (When VAS score≥4) or patient demand for analgesics in the post-operative period. Thus duration of analgesia was longer in Group-B (252.38 min) as compared to Group-A (231.25 min).

 

Table 6: Distribution of Duration of Analgesia (min) Between Two Groups:

In our study there was no statistically significant difference between the patients of Group-A and Group-B as per as mean arterial pressure (MAP) and heart rate variability were concerned at any time in the study period (p value >0.05). Table 7, showing the comparison of the side effects between the study groups.

 

Table 7: Comparison Between Group-A and Group-B According To The Incidence Of Side-Effects:

DISCUSSION

Regional anaesthesia is now increasingly used for gynaecological surgery compared to general anaesthesia. Epidural anaesthesia has several advantages over general anaesthesia like decrease in stress response to surgery, improved postoperative analgesia, decrease incidence of nausea and vomiting, less respiratory and cardiac depression. Many local anaesthetic agents have been used for epidural anaesthesia. Bupivacaine is a well established long acting local anaesthetic which like all amide anaesthetic has been associated with cardiac-toxicity when used in high concentration or when accidentally administered intravascularly. A number of studies suggest that ropivacaine is associated with less central nervous system and cardiac-toxicity with less motor block potency but anaesthetic and analgesic property are comparable with bupivacaine.^4,11 Since the introduction of epidural opioids⁵, it has gained wide spread popularity and acceptance. The advantage of epidural opioids is the synergistic effect with local anaesthetics, allowing a marked decrease in the dose of both the drugs to achieve the same level of analgesia^8,12. Several opioids like morphine^13,14 pethidine¹⁵, fentanyl ^16-18, tramadol ^19,20 have been used epidurally with their merits and demerits. The duration of action of epidurally administered fentanyl is short and excellent results have been reported with continuous infusion of fentanyl for postoperative analgesia²¹. Fentanyl added to local anaesthetic improves the onset and duration of action and provides better quality of anaesthesia^22,23. In our study, there was no statistically significant difference between the two groups in terms of age (p=0.102), body weight (p=0.877) and height (p=0.441) distribution. Hence, the groups were comparable with respect to the demographic characteristics. Our study shows that patients in group-B have earlier onset of sensory and motor block than patients in group-A. There was significant difference (p<0.05) in the time of onset of both sensory and motor block between the two groups. Chen-Hwan Cherng et al in a similar study found that the onset time of sensory block to the T10 dermatome was significantly more rapid in patients received epidural fentanyl (13.0±3.0 min) than in the intravenous fentanyl group (16.2±3.5min) or control group (17.7±3.6min) ²⁴. The onset times of motor block up to Bromage scale 1 and 2 were also significantly more rapid in the epidural fentanyl group (11.9±4.6 and 24.4±5.9min) than in the intravenous fentanyl group (16.9±4.7 and 30.8±5.6min) or control group (18.3±4.9 and 32.7±5.7min). These observations were close to our findings. We observed in our study that highest level achieved in both the groups was up to T₄ dermatome and lowest level was up to T₇ dermatome. Statistically there was no difference in the height of sensory block in the two groups. Wahedi W et al ²⁵ studied with ropivacaine 0.75% (epinephrine 1:200,000) in different doses (15,20 and 25 ml). In the thoracic region T 6, T 5 and T 4 were reached. Similar levels of sensory block were found with 15 ml volume of ropivacaine (0.75%) solution with or without fentanyl in our study. Statistically there was no significant difference in the duration of sensory block in the two groups in the present study. Wahedi W, et al²⁵, in their study with single shot epidural anaesthesia found two-segment regression time was 124 +/- 29 minutes for ropivacaine 0.75% which was similar to our study findings. And there was no significant prolongation (p=0.254) in duration of sensory block or two segment regression time with addition of 50µg of fentanyl to ropivacaine 0.75% in our study. We observed that there was no significant difference (p=0.619) among the Group-A and Group-B in respect to the duration of motor block. Peduto VA et al²⁶ in their comparative study with epidural ropivacaine and levo-bupivacaine found that complete resolution of motor block required 95 ± 48 minutes with ropivacaine which was close to the duration we found in ropivacaine group (group-A) of our study. The duration was not prolonged significantly with addition of 50 µg of fentanyl. In our study the differences between two groups were statistically significant in respect to duration of analgesia. Ray M et al²⁷ in their study found that ropivacaine produced postoperative analgesia of about 405±18 minutes when given caudal epidural route in children posted for uro-genital surgery. Whereas Crosby E et al²⁸ found ropivacaine produced median duration of analgesia which varied between 1.7 and 4.2 hr which was similar to our study. But it was lower than that found by Ray M et al²⁷. This different may be due to age group (children) of the patients or type of surgery (urogenital surgery) in their study. Interestingly we found mean duration of analgesia about 252.38 ± 12.19 minutes (median = 252.50 minutes) in patients who received 50 µg of fentanyl along with ropivacaine (group-B). This was significantly higher than patients who received ropivacaine alone (p = 0.000). Opioid increases in potentiality of local anaesthetics by direct action on opioid receptor or because of systemic absorption of opioid. This may be the reason behind the longer duration of analgesia in epidural anaesthesia with adjunction of opioid. Fentanyl is a synthetic opioid agonist, highly lipophilic and as an analgesic fentanyl is 50-100 times more potent than morphine. Milon D et al²⁹ in their prospective study of epidural anaesthesia using the bupivacaine-fentanyl combination for caesarean section, found similar potentiation of analgesia with fentanyl. We observed that there was no incidence of hypotension (reduction of blood pressure >20% of base line) or bradycardia or any other haemodynamic instability in any of the groups. However, hypovolemia was not allowed during perioperative period and corrected with infusion of Ringer’s Lactate solution. 10% in group-A and 7.5% of group-B had incidence of nausea and vomiting.7.5% in group-B complaint about pruritus, while none in group-A. There was no incidence of respiratory depression and urinary retention in any of the group. The incidence of side effect was not statistically significant in any of the groups in the present study.

CONCLUSION

In conclusion, 15-20 ml of (0.75%) ropivacaine hydrochloride provides adequate anaesthesia and analgesia for the patients undergoing elective gynaecological surgery under lumber epidural anaesthesia. Addition of 50µg fentanyl citrate to 0.75% ropivacaine hydrochloride in epidural anaesthesia, significantly hasten the onset of both sensory and motor block; though, height of the sensory block, duration of sensory (two segment regression) and motor (full motor power and joint movement) block do not alter much. However it causes significant prolongation in duration of analgesia without significant cardiovascular instability and side effects.

 

REFERENCES