Abstract
Background and objective:
Ropivacaine owing to its propensity of causing motor blockade of reduced duration, is preferred for ambulatory day care surgery. Intrathecal ropivacaine has shown effective analgesia for lower limb surgery. Our study plans to evaluate spinal ropivacaine in three different doses in patients undergoing day care perineal surgery.
Methodolgy:
90 ASA-I patients scheduled to undergo day care perineal surgery were randomized to receive intrathecal ropivacaine. Group I (n=30) received 15mg of intrathecal ropivacaine, Group II (n=30) received 18.75 mg of intrathecal ropivacaine and Group III (n=30) received 22.5 mg of intrathecal ropivacaine. Onset of sensory block at T 10, peak sensory block level, duration of sensory block, onset and duration of motor block and relevant safety data were recorded.
Result:
Onset of analgesia was significantly shorter in Group III (3.5 min ; P <0.0001). However, time taken for peak sensory blockade was comparable in group II and III (12.76 and 11.93 mins). Duration of analgesia was longer and statistically significant in Group III (201.6 mins: P <0.0001) when compared to Group I and II. Onset of motor block was observed to be shortest in Group III (6.7 mins) and duration of motor block was longest in Group III (153.73 mins). These two parameters were statistically significant than Group I and II (P <0.0001).
Conclusion:
Intrathecal ropivacaine in a dose of 18.75 and 22.5 mg were observed to be equally effective in providing satisfactory analgesia. However, higher dose was associated with profound sensory and motor block.
Keywords: Intrathecal, isobaric, perineal surgery, ropivacaine
INTRODUCTION
Spinal anesthesia is a common, economical method of achieving rapid and reliable onset of analgesia with adequate muscle relaxation. Ropivacaine is a long-acting, amide local anesthetic developed and promoted as a potential replacement for bupivacaine, citing reduced cardiotoxicity and neurotoxicity.[1] Ropivacaine is more selective in inhibiting Aδ and C nerve fibers when compared to Aβ nerve fibers. This results in sensory analgesia with a motor blockade of reduced duration.[2] Ropivacaine is being extensively used for peripheral nerve blockade, epidural analgesia, and labor analgesia. Intrathecal administration of ropivacaine has attracted attention owing to its propensity to cause motor blockade of reduced duration, thereby facilitating early ambulation, a requisite for day care surgery.
We conducted this study to evaluate the effect of intrathecal ropivacaine in three different concentrations in patients undergoing day care perineal surgeries.
PATIENTS AND METHODS
After obtaining approval from the hospital's ethical committee, ninety patients of American Society of Anesthesiologists (ASA) class I and II, of either sex and age between 18 and 50 years scheduled to undergo day care perineal surgeries, were enrolled for this prospective, randomized, double-blind study held in our hospital over a period of 6 months from December 2016 to May 2017. Written informed consent was obtained from all the ninety patients.
Exclusion criteria included patients with known contraindications to spinal anesthesia, resting heart rate <60 bpm, known allergy to amide local anesthetic, pregnancy, and history of substance abuse. Visual analog scale (VAS) for pain assessment was explained to the patients preoperatively wherein “0” indicated no pain and “10” indicated worst imaginable pain.[3] Patients were randomly allocated to one of the three groups of thirty patients each using the computer randomization table.
Group I received 3 ml of 0.5% ropivacaine (15 mg)
Group II received 3 ml of 0.625% ropivacaine (18.75 mg)
Group III received 3 ml of 0.75% ropivacaine (22.5 mg).
On arrival in the operating room, an intravenous (i.v.) cannula of appropriate size was placed. 500 ml of normal saline was administered. ASA standard monitors were placed, and baseline readings of heart rate, blood pressure (BP), and oxygen saturation were recorded. Supplemental oxygen was administered in every case.
Under complete aseptic precautions, spinal anesthesia was administered using a 25-gauge Quincke's spinal needle in L3–L4 interspace in lateral decubitus position. Drug was injected over 15 s without aspiration or barbotage.[4] Drug in three different dosage under study was prepared and loaded in a syringe by an anesthetist in a separate operating room and was not involved in the study. The patient and the anesthetist administering the drug were blinded to the concentration of the drug being administered.
The level of sensory and motor block was assessed at 2, 4, 6, 8, 10, and 15 min and thereafter every 30 min for 8 h. Pinprick sensation was assessed using a 20-gauge hypodermic needle. During the tracking of sensory level, time taken for loss of pinprick sensation at T10 (onset of analgesia), time taken to achieve T6 block level (maximal block level), and duration of analgesia (time taken for sensory level to recede to S1) were recorded. Motor block was assessed using modified Bromage scale (0 = able to raise leg, 1 = able to flex knee, 2 = able to flex ankle, and 3 = no movement).[5]
A fall in systolic BP >20% and a drop in heart rate to <50 bpm were considered as hypotension and bradycardia, respectively, and intervention in the form of i.v. mephentermine (5 mg) and i.v. atropine (0.2 mg) was planned., Rescue analgesia if needed was administered in the form of midazolam and fentanyl. The quality of anesthesia (judged by the anesthetist), the quality of muscle relaxation (opinion of the surgeon), and the degree of intraoperative comfort (judged by the patient) were recorded as excellent, satisfactory, or unsatisfactory, respectively.
Postoperatively, patients were assessed for pain using VAS scale, and injection diclofenac (75 mg) was administered on encountering a VAS score of 4. It was recorded as time for first analgesic demand. Patients were also observed for nausea, vomiting, bradycardia, and hypotension. A follow-up visit was done after 24 h to assess the patient for headache and any neurological deficits.
Statistical Package for the Social Sciences 20 (SPSS 20) software (IBM, ARMONK, NEW YORK, USA) was used for statistical calculation. Continuous variables were tested for normal distribution by the Kolmogorov–Smirnov test. Data were expressed as either mean and standard deviation or numbers and percentages. Demographic data were compared using ANOVA test. The monitored and calculated parameters were analyzed using ANOVA test.
Based on clinical experience and review of literature, it was seen that 30 min difference in mean duration of analgesia between the two groups can be considered, being clinically significant. Within group, standard deviation was assumed to be 45 min. Using these data and assuming a study power of 80% and a 5% probability of type I error, a sample size of 90 patients was found to be required for this study. Therefore, a total of 90 patients were incorporated in the study, who were distributed randomly into three equal study groups (n = 30).
RESULTS
Demographic data did not differ among study groups [Tables 1 and 2]. Spinal anesthesia was easy and uneventful in all patients. The relevant aspects of the spinal block are presented in Table 3. Onset of analgesia was significantly shorter in Group III (3.5 min; P < 0.0001) [Table 3]. However, time taken for peak sensory blockade was comparable in Group II and Group III (12.76 and 11.93 min, respectively). Duration of analgesia was longer and statistically significant in Group III (201.6 min: P <0.0001) when compared to Group I and Group II. Onset of motor block was observed to be shortest in Group III (6.7 min) and duration of motor block was longest in Group III (153.73 min). These two parameters were statistically significant than Group I and Group II (P < 0.0001). The mean VAS score was higher in Group I at each time interval, which shows that Group III offers more smooth and early onset of analgesia [Figure 1]. VAS score of 4 was set as a cutoff for first analgesic dose. VAS score of 4 was observed at 180 min in Group III which was longer and statistically significant than Group I and Group II.
Table 1.
Group-wise representation of demographic data
Table 2.
Sex-wise distribution of patients among groups
Table 3.
Characteristic of spinal block
Figure 1.
Evolution of visual analog scale score in three groups
Intraoperative motor blockade and muscle relaxation were assessed as excellent by the anesthetist and surgeon, respectively, in majority of patients across three groups. The great majority (>90%) of the patients across three groups evaluated their intraoperative analgesia as adequate. In Group I, this proportion was significantly lower. [Figures 2 and 3] depict mean pulse rate and mean BP in three groups at different time intervals, respectively. Three patients, one in Group I, one in Group II, and one in Group III, received i.v. atropine for hypotension combined with bradycardia, and two patients, one in Group I and one in Group III, received mephentermine for treatment of hypotension. Rescue analgesia was not required in any of the patients. The mean duration of surgeries was 120 min. None of the patients reported any complaint suggestive of transient neurologic symptoms. The postoperative course was uneventful for all the patients.
Figure 2.
Mean pulse rate in three groups at different time intervals
Figure 3.
Mean blood pressure in three groups at different time intervals
DISCUSSION
Ropivacaine is a enantiomerically pure, long-acting, lipid-soluble, amide local anesthetic with reduced propensity for motor blockade.[1,2]
Ropivacaine in comparison to bupivacaine has been found to be 20% less potent when administered through epidural route and 50% when administered intrathecally.[6] Studies conducted in the past have primarily compared ropivacaine with bupivacaine in terms of quality and duration of analgesia and motor block achieved when administered through epidural route or intrathecally.[7]
The spread of isobaric ropivacaine is primarily dependent on the local current generated by the speed of injection and diffusion. Most of the drug is restricted to the site of its deposition, the lumbar and sacral nerve making it reliable for perineal, lower limb, and lower abdominal surgery.[8]
Our study evaluated intrathecal ropivacaine in three different doses (15, 18.75, and 22 mg) in patients undergoing day care perineal surgery.
Lee et al. in their dose–response study on intrathecal ropivacaine concluded that ED50 and ED95 for spinal ropivacaine in lower limb surgery of 50 min duration or less were 7.6 and 11.4 mg, respectively.[9] Gautier et al. compared the effects of three different doses of intrathecal ropivacaine (10, 12, and 14 mg) in patients undergoing knee arthroscopy. They deduced that doses of 12 and 14 mg were comparable in their effects barring the fact that patients administered with 14 mg took more time to void.[6]
However, Wong et al. suggested that intrathecal ropivacaine in a dose of 18.75 and 22.5 mg were comparable in terms of safety and efficacy in Chinese parturients undergoing cesarean section.[10]
In common with a previous study, an increase in the dose of intrathecal ropivacaine led to an increased duration of profound sensory and motor block.[11] Our study observed that intrathecal ropivacaine in a dosage of 18.75 and 22.5 mg was equally effective in providing adequate analgesia for the required duration with statistically significant reduced duration of motor blockade in Group II (92.3 min) when compared with Group III (153 min) making the use of a dose of 18.75 mg prudent for day care surgery.
Although both general anesthesia and regional anesthesia have their advantages and disadvantages when it comes to day care surgery, studies have shown postoperative nausea and vomiting to be the main reason for prolonged stay in hospital, complication common with general anesthesia but rare with regional anesthesia. Regional anesthesia with use of agents such as ropivacaine is associated with early recovery of motor function and ability to void urine, therefore making them ideal for day care surgery.
Our study stands unique by evaluating three different doses of intrathecal ropivacaine and further reinforces that ropivacaine results in motor blockade of reduced duration when compared to sensory blockade. In terms of safety, the three doses of intrathecal ropivacaine provided a high degree of cardiovascular stability with a low incidence of bradycardia. Limitation of the study seems to be the lack of use of adjunct.
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Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
REFERENCES
- 1.Kuthiala G, Chaudhary G. Ropivacaine: A review of its pharmacology and clinical use. Indian J Anaesth. 2011;55:104–10. doi: 10.4103/0019-5049.79875. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 2.Graf BM, Abraham I, Eberbach N, Kunst G, Stowe DF, Martin E, et al. Differences in cardiotoxicity of bupivacaine and ropivacaine are the result of physicochemical and stereoselective properties. Anesthesiology. 2002;96:1427–34. doi: 10.1097/00000542-200206000-00023. [DOI] [PubMed] [Google Scholar]
- 3.Gould D. Visual analogue scale. J Clin Nurs. 2001;10:697–706. doi: 10.1046/j.1365-2702.2001.00525.x. [DOI] [PubMed] [Google Scholar]
- 4.Hocking G, Wildsmith JA. Intrathecal drug spread. Br J Anaesth. 2004;93:568–78. doi: 10.1093/bja/aeh204. [DOI] [PubMed] [Google Scholar]
- 5.Bromage PR. Philadelphia: WB Saunders; 1978. Epidural Analgesia; p. 144. [Google Scholar]
- 6.Gautier PE, De Kock M, Van Steenberge A, Poth N, Lahaye-Goffart B, Fanard L, et al. Intrathecal ropivacaine for ambulatory surgery. Anesthesiology. 1999;91:1239–45. doi: 10.1097/00000542-199911000-00013. [DOI] [PubMed] [Google Scholar]
- 7.Bang EC, Lee HS, Kang YI, Cho KS, Kim SY, Park H, et al. Onset of labor epidural analgesia with ropivacaine and a varying dose of fentanyl: A randomized controlled trial. Int J Obstet Anesth. 2012;21:45–50. doi: 10.1016/j.ijoa.2011.10.002. [DOI] [PubMed] [Google Scholar]
- 8.Fettes PD, Hocking G, Peterson MK, Luck JF, Wildsmith JA. Comparison of plain and hyperbaric solutions of ropivacaine for spinal anaesthesia. Br J Anaesth. 2005;94:107–11. doi: 10.1093/bja/aei008. [DOI] [PubMed] [Google Scholar]
- 9.Lee YY, Ngan Kee WD, Chang HK, So CL, Gin T. Spinal ropivacaine for lower limb surgery: A dose response study. Anesth Analg. 2007;105:520–3. doi: 10.1213/01.ane.0000267523.66285.57. [DOI] [PubMed] [Google Scholar]
- 10.Wong JO, Tan TD, Leung PO, Tseng KF, Cheu NW. Spinal anesthesia with two different dosages of 0.75% glucose-free ropivacaine: A comparison of efficacy and safety in Chinese parturients undergoing cesarean section. Acta Anaesthesiol Sin. 2003;41:131–8. [PubMed] [Google Scholar]
- 11.McNamee DA, Parks L, McClelland AM, Scott S, Milligan KR, Ahlén K, et al. Intrathecal ropivacaine for total hip arthroplasty: Double-blind comparative study with isobaric 7.5 mg ml(-1) and 10 mg ml(-1) solutions. Br J Anaesth. 2001;87:743–7. doi: 10.1093/bja/87.5.743. [DOI] [PubMed] [Google Scholar]
