Comparison of hyperbaric and plain ropivacaine 15 mg in spinal anaesthesia for lower limb surgery

H. Kallio1,*, E.-V. T. Snäll1, C. A. Tuomas1 and P. H. Rosenberg2

1 Department of Anaesthesia, Forssa Hospital, Forssa, Finland. 2 Department of Anaesthesiology and Intensive Care Medicine, Helsinki University Central Hospital, Helsinki, Finland

* Corresponding author. E-mail: helena.kallio{at}fstky.fi

Accepted for publication June 10, 2004.


    Abstract
 Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
 References
 
Background. Previously, plain ropivacaine 15 mg given intrathecally has been shown to be feasible for ambulatory surgery of lower-extremities. Hypothetically, hyperbaric solution could improve and shorten the block.

Methods. This prospective, randomized, double-blind study included 56 patients undergoing surgery of lower extremities. They received intrathecally either 1.5 ml of ropivacaine 10 mg ml–1 and 0.5 ml of glucose 300 mg ml–1 (HYP) or 2 ml of ropivacaine 7.5 mg ml–1 (PL).

Results. All patients in Group HYP achieved T10 dermatome analgesia but only 64% (18/28) of Group PL. T10 analgesia was reached in 5 min (median, range 5–20 min) in the HYP group vs 10 min (5–45 min) in the PL group (P=0.022), and full motor block in 10 min (5–45 min) vs 20 min (5–60 min) (P=0.003), respectively. Group HYP had a longer duration of analgesia at T10; 83 min (5–145 min) vs 33 min (0–140 min) (P=0.004). Duration of sensory block from injection of the anesthetic to complete recovery was shorter in Group HYP than in Group PL, 210 min (120–270 min) vs 270 min (210–360 min) (P<0.001), as was duration of motor block, 120 min (5–150 min) vs 210 min (120–330 min) (P<0.001). Patients of Group HYP attained discharge criteria earlier than those of Group PL (P=0.009).

Conclusion. In comparison with the plain solution, 15 mg of intrathecal hyperbaric ropivacaine produced a faster onset, greater success rate of analgesia at the level of T10 dermatome, and faster recovery of the block.

Keywords: anaesthetic techniques, subarachnoid ; anaesthetic techniques, hyperbaric anaesthetics local, ropivacaine


    Introduction
 Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
 References
 
In recent years ropivacaine has been found useful for spinal anaesthesia1 2 and its sensorimotor dissociation property3 4 has suggested faster recovery of motor function than after the use of bupivacaine. This was substantiated in our previous study where recovery of motor block was faster after intrathecal plain ropivacaine 15 mg compared with plain bupivacaine 10 mg.5 In spinal anaesthesia, hyperbaric solutions of local anaesthetics are known to produce a more predictable extension of the sensory block,1 6 shorter duration of block, and faster recovery than plain solutions. Therefore, we investigated the efficacy and usefulness of hyperbaric ropivacaine 15 mg in comparison with plain ropivacaine 15 mg for spinal anaesthesia. The rationale for selection of the dose was that in an earlier study5 15 mg of plain ropivacaine was suitable for 1-h surgery of the lower-extremities, but the highest extent of sensory analgesia was unpredictable.


    Methods
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 Abstract
 Introduction
 Methods
 Results
 Discussion
 References
 
The ethics committee of the institution approved the study and all 56 patients gave their written informed consent. Elective, day-case patients undergoing minor lower-extremity surgery were enrolled into the study. Inclusion criteria of the patients were BMI ≤35 and age 18–65 yr. Randomization was performed with random sampling numbers with stratification of 10. The 56 patients were prospectively allocated into two groups: 1.5 ml of ropivacaine 10 mg ml–1 (Naropin®, AstraZeneca AB, Sweden) and 0.5 ml of glucose 300 mg ml–1 (Glucosteril® Baxter) (Group HYP), or 2 ml ropivacaine 7.5 mg ml–1 (Naropin®,AstraZeneca AB, Sweden) (Group PL). In a blinded fashion, 2 ml of local anaesthetic solution was injected intrathecally, corresponding to hyperbaric ropivacaine 15 mg (with 7.5% glucose) or plain ropivacaine 15 mg.

One hour before spinal anaesthesia diazepam (approximately 0.1 mg kg–1) was given orally. The patients were continuously monitored with ECG and pulse oximetry. Non-invasive arterial pressure was recorded every 5 min in the operating room (OR) and every 5–10 min in the recovery room, and at least once on the day-case ward. Haemodynamic changes were treated only if clinically indicated. Before spinal anaesthesia, 0.2 mg of glycopyrronium bromide and for sedation fentanyl 0.001 mg kg–1 were given to the patients in addition to an i.v. pre-load of 500 ml of acetated Ringer's solution. The patients were positioned in the position of right decubitus. A horizontal position of the spine was verified using a spirit level. A staff anaesthetist (E.-V.S.) performed all spinal blocks. The skin at the puncture site was infiltrated with lidocaine 10 mg ml–1 using a 25-G Microlance® needle (Becton Dickinson, Ireland). The subarachnoid puncture was performed using a 27-G pencil-point needle (Pencan® 0.42x88 mm/27Gx31/2'', B.Braun AG) through an introducer (0.73x35 mm/22Gx1 3/8'', B.Braun AG) in the midline of the L3–L4 inter-space. In case of anatomy-related technical difficulties, an adjacent inter-space was chosen. Without turning the needle (the orifice facing to the left side of the patient), 2 ml of anaesthetic solution was injected over 20 s without barbotage or aspiration. Immediately after the puncture, the patient was placed supine and at the same time the operating table was placed horizontally.

An anaesthetist (C.A.T.), who was blinded to which solution was being used, assessed sensory and motor block at timed intervals: 5, 10, 15, 20, 25, 30, 45, 60, 90, 120, 150, 180, 210, 240, 270, 300, 330, and 360 min after injection. The segmental level of sensory block to pinprick was assessed on both sides and the caudal limit of sensory block testing was restricted to S2. Motor block of both legs was tested using the modified Bromage scale: 0=full movement; 1=inability to raise extended leg, can bend knee; 2=inability to bend knee, can flex ankle, 3=no movement. If the sensory block was not adequate in 30 min for the planned operation, general anaesthesia was induced using fentanyl, propofol and a laryngeal mask airway, and anaesthesia was maintained with sevoflurane. At 15–30 min after injecting the intrathecal anaesthetic, median thigh tourniquet pressure of 300 mm Hg (range, 250–300 mm Hg) was used in all patients with the exception of patients undergoing varicose vein surgery (n=7) and one trauma patient in the hyperbaric group. The indication for giving any supplemental sedation or opioid was recorded.

After surgery all patients were allowed free oral fluids and the time of the first oral intake was registered. Recovery of sensory block to at least L1 dermatome and full cardiorespiratory stability were used as discharge criteria from recovery room. The time of first spontaneous micturition and the time to reach discharge criteria were recorded by a ward nurse. The discharge criteria were as follows: no difficulties in breathing, stability of arterial pressure and heart rate, full orientation of the patient in time and place, ability to walk and dress, ability to drink without nausea or vomiting, micturition, and no more than slight pain. On the first day after operation, one of the investigators interviewed the discharged patients by telephone or in case of hospitalization, on the ward unit. Any adverse effects, including pain, nausea, vomiting, headache, backache, or neurological symptoms were recorded.

Estimation of sample size
The primary outcome variable was recovery from motor block (Bromage 0) and results of Khaw and coworkers1 were used to estimate the sample size. In their study, the mean time (min) (SD) of complete motor recovery (Bromage 0) was 145 (5.8 min mg–1) (28) min and 219 (8.76 min mg–1) (57) min in the hyperbaric and plain ropivacaine 25 mg groups, respectively. When extrapolated from their study to our study with hyperbaric and plain solutions of ropivacaine 15 mg, the mean time to Bromage 0 could be calculated as 87 and 131.4 min. The difference between the means was 44.4 min and SD was estimated to be 42.5 min from the study of Khaw and coworkers.1 As we chose {alpha} 0.05 and power 0.97, we calculated the sample size to be 28 in each group.

Statistical analysis
In case of continuous numeric values, mean (SD) are described, and the groups were compared using the t-test; if the data were not normally distributed the Mann–Whitney U-test was used. Non-continuous numeric values, are expressed as medians (range), and were tested with the Mann–Whitney U-test. Binominal data were compared using {chi}2 or Fisher's exact test. Significant changes of sensory and motor block were tested within the groups with Wilcoxon's test. Differences between the groups in sensory and motor block assessments were tested with Mann–Whitney U-test. When sensory onset and duration times at T10 were assessed, patients not reaching T10 were excluded. A P-value <0.05 was considered statistically significant. The statistics were calculated with SigmaStat for Windows, version 2.03® (Jandel Corporation).


    Results
 Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
 References
 
The groups did not differ in patient characteristics, tourniquet times, and duration, or type of surgery (Table 1). The L2–L3 inter-space was used for the puncture in one patient in both groups. The groups did not differ in haemodynamics in the OR, recovery room, or on the day-case ward (Table 2). None of the study patients needed sympathomimetics for hypotension, and none had nausea or vomiting. In the OR, one patient in Group HYP received meperidine 15 mg i.v. because of shivering.


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Table 1 Characteristics of patients and types of surgery in the hyperbaric ropivacaine group (HYP) and the plain ropivacaine group (PL). Values of height, weight, and BMI are expressed as mean ± SD and tested with t-test. Age is expressed as median (range) and tested with Mann–Whitney U-test. ASA physical status is expressed as numbers of patients and is tested with Mann–Whitney U-test. Surgical procedures are expressed as numbers of patients and tested by Fisher's exact test

 

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Table 2 Haemodynamics in the operating room (OR) and the recovery room of the hyperbaric ropivacaine group (HYP) and the plain ropivacaine group (PL). Data are expressed in mean ± SD (t-test) or numbers of patients and percentages (Fisher's exact test). The anticholinergic was glycopyrrolate 0.1–0.2 mg or atropine 0.5 mg

 
Sensory block
Sensory block reached the T10 dermatomal level in all patients of Group HYP, but there were 10 patients (36%) in Group PL in whom the block failed to reach the T10 level (Table 3). Figure 1 presents the changes of median sensory block of both groups at timed intervals. Figure 2 presents the maximum cephalad dermatomal extent of the sensory block in each patient. The range of the maximum upper level of sensory block was 8.5 and 15 dermatomes, in Groups HYP and PL, respectively.


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Table 3 Development and recovery of sensory block after intrathecal injection of 15 mg of hyperbaric (HYP) or plain ropivacaine (PL). Medians (range) are used with Mann–Whitney U-test

 


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Fig 1 Cephalad dermatomal spread of pinprick analgesia (median) in the patients after 15 mg of intrathecal hyperbaric or plain ropivacaine. Statistical significance within the groups was tested with Wilcoxon's test and between the two groups with Mann–Whitney U-test, *P<0.05.

 


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Fig 2 Maximum cephalad extent of sensory block of each patient in groups HYP and PL. The median level is indicated with a horizontal line, P=0.002.

 
In those 10 patients of Group PL, in whom the analgesia level did not reach T10 dermatome, sensory block increased until 20 min, and they maintained a plateau of sensory block until 120 min. Median time to reach total recovery from sensory block was 300 min, which did not differ from the rest of the patients in Group PL (n=18), having a median recovery time of 240 min. Median times to reach the highest level of sensory block did not differ significantly between these subgroups.

Motor block
Development of motor block at timed intervals is presented in Figure 3 and numerical values in Table 4. Overall the motor block parameters indicated a shorter duration in Group HYP and, notably, the difference in latency until complete recovery was both statistically and clinically significant (Fig. 3).



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Fig 3 Motor block on the modified Bromage scale (0–3) in Groups HYP and PL. Statistical significance within the groups was tested with Wilcoxon's test and between the two groups with Mann–Whitney U-test. Motor block increased until 20 min in the group HYP and until 30 min in Group PL, *P<0.05.

 

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Table 4 Development and duration of motor block after intrathecal injection of 15 mg of hyperbaric (HYP) or plain ropivacaine (PL). Medians (range) are used with Mann–Whitney U-test

 
Need for general anaesthesia and i.v. analgesics
In Group PL, at a median time of 35 min (range 30–42 min) from injecting the spinal anaesthetic and before starting surgery, general anaesthesia had to be given to three patients because of insufficient analgesia (L5, L4, and L2). On the other hand, at the end of the surgical procedure (90, 100, and 115 min from injecting the block, when the level of pinprick analgesia was L1, T11, and T4) three patients of Group HYP needed general anaesthesia. Two of these three patients had meniscectomy of the knee, one with additional shaving and the other with synovectomy. The third patient required surgery for a metatarsal fracture. In addition, one patient in Group HYP received general anaesthesia 25 min after spinal anaesthetic injection because of anxiety (pinprick analgesia was at the T10 level).

At the end of the procedure (87 and 90 min) two patients in Group HYP, with analgesia levels T12 and L2, received 0.075 and 0.1 mg fentanyl i.v. One patient in Group PL received 0.05 mg fentanyl for pain at the operative site during the operation, 80 min from injecting the anaesthetic, when an L1/L2 level of analgesia was recorded. Pressure from the thigh tourniquet was disturbing in one patient of Group HYP (sensory block at T6) and in four patients of Group PL (sensory block at L1–T10) and they received 0.05–0.2 mg fentanyl at 15–125 min from injecting the spinal anaesthetic.

Patients who did not receive rescue medication (fentanyl or general anaesthesia) in Group HYP had a higher level of sensory block (median T8/T9, range S2–T3) at the end of operation than patients who received rescue medication (median T12, range S2–T9, P=0.012). In contrast, in Group PL, the median T12 level analgesia was registered at the end of the operation in cases of fentanyl or general anaesthesia (range L4–T9) and without any rescue medication (range L5–T4/T5).

Supplemental sedation was given to seven patients (13%) using 2.5–5 mg of diazepam i.v. in four patients of Group HYP and one patient in Group PL, and 0.05–0.1 mg of fentanyl in one patient of both groups.

Postanaesthetic care and discharge parameters
In the recovery room two patients in Group HYP and one patient in Group PL needed 0.05–0.1 mg of fentanyl for pain in the wound region. In addition, one patient in Group HYP, who had arthroscopic meniscectomy, received 0.1 mg of fentanyl because of shoulder pain. Meperidine 15 mg i.v. was given to one patient in Group HYP and three patients in Group PL to relieve shivering. Mean duration of stay in the recovery room did not differ between the groups: 69 and 66 min in Groups HYP and PL, respectively.

In Group HYP the patients voided earlier and met the discharge criteria earlier than in Group PL (Table 5). Four patients in both groups were hospitalized because of surgical reasons. In addition, three patients in Group PL needed to stay overnight in hospital; two because of social reasons, and one patient had to be followed up for cardiovascular reasons unrelated to anaesthesia and surgery.


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Table 5 Time to attainment of certain discharge criteria in the hyperbaric ropivacaine group (HYP) and the plain ropivacaine group (PL). Medians (range) are used with Mann–Whitney U-test. Numbers of patients are tested with Fisher's exact test

 
In the interview on the first day after operation, three patients in Group HYP and two patients in Group PL complained of a slight headache, which was managed with a non-steroidal anti-inflammatory drug. Two patients in Group HYP and one patient in Group PL complained of back pain at the puncture site. One patient in Group PL experienced right side paresthesia during the spinal puncture, but she did not have any symptoms thereafter.


    Discussion
 Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
 References
 
Spinal anaesthesia with hyperbaric ropivacaine 15 mg resulted in significantly faster recovery of both motor and sensory block, as well as shorter time to first voluntary micturition and home-readiness in comparison with 15 mg of plain ropivacaine. In all Group HYP patients the cephalad spread reached at least the T10 level of analgesia, which occurred in only two-thirds of patients in Group PL. The median maximum cephalad extent of sensory block was five dermatomes greater in Group HYP. Three patients in Group PL needed general anaesthesia because the sensory block was initially insufficient for surgery. In the other three who needed general anaesthesia because of pain, all from Group HYP, this was needed at the end of prolonged surgery (median 1 h 40 min from injecting the anaesthetic).

The T10 level of analgesia was chosen as an arbitrary study parameter assumed to represent sufficient block level for patients undergoing day-surgery of the lower-extremities including the use of a thigh tourniquet. In this respect, adequate level of analgesia was achieved in all patients in Group HYP. When we compare the duration of analgesia at the T10 dermatome, 15 mg of hyperbaric ropivacaine provided longer analgesia than 15 mg of plain ropivacaine. It can be assumed that the total dose was delivered correctly into the subarachnoid space also in those 10 Group PL patients where T10 level analgesia was not achieved, as the duration of measurable residual analgesia was similar to that of the others in that particular group.

In our study, the 90-min regression of the sensory block to the T10 level was comparable with that (115.8 min) in an earlier study by Chung and coworkers7 with a slightly larger dose of hyperbaric ropivacaine (18 mg). Their overall median two-dermatome regression of sensory block was 64.3 min, which was similar to this (60 min). In our Group PL, the median two-segment regression of sensory block (90 min) was comparable with the mean time reported after 14 mg of plain solution (98 min).8

There was a significant difference to the benefit of Group HYP in the time to first micturition. However, we actually believe that these patients would have been able to void even earlier than that recorded in this study. The reason for this speculation is that the median time between recovery from sensory block and first voluntary micturition was significantly longer in Group HYP than in Group PL (67 vs 30 min) (P=0.037).

When we were performing our study, Khaw and coworkers'1 study was the only one to compare plain and hyperbaric solutions of intrathecal ropivacaine. Although the type of surgery was different, our anaesthetic results of hyperbaric and plain intrathecal ropivacaine were in full accordance with their results. In both studies, the hyperbaric ropivacaine solution was superior to the plain solution with respect to analgesia and maximal extent of sensory block, faster onset and offset of sensory as well as motor block. In their study, complete recovery from motor block was achieved in 145 and 219 min in the hyperbaric and plain groups, respectively, while in our study the corresponding durations were 120 and 210 min.

Our motor block durations seem to be comparable also with results from other studies. For instance, the median full motor recovery in 120 min after spinal anaesthesia with 15 mg hyperbaric ropivacaine is comparable with the mean time of 113.7 min after 18 mg hyperbaric ropivacaine in the study by Chung and coworkers.7 Similarly, our result of median full motor recovery in 210 min in the 15 mg plain group is comparable with the result of the study by Gautier and coworkers8 who reported a mean of 189 min with 14 mg plain ropivacaine. The median time from injection to first micturition after 15 mg hyperbaric ropivacaine was similar in our study (264 min) to the median (276 min) in the study by Whiteside and coworkers.9

In agreement with previous work,1 6 in our study, the sensory block with the plain solution of local anaesthetic spread unpredictably; one-third of patients in Group PL did not reach T10 analgesia and the highest extent of sensory block varied widely (Fig. 2). This 1.8 times greater variability of the plain solution compared with the hyperbaric solution was the same as reported with bupivacaine.6 Also, this is in accordance with the results of Khaw and coworkers,1 who reported that all patients in the hyperbaric group had sufficient analgesia for Caesarean section, but 25% of patients in Group PL needed rescue medication. The highest median extent of sensory block (T4) in the present study with ropivacaine 15 mg was significantly greater in Group HYP than in Group PL (T9), which is comparable with an earlier study with 15 mg of bupivacaine having a mean cephalad spread to T3.6 and T9.5 in the hyperbaric (8% glucose) and nearly plain (0.33% glucose) groups6 and the median spread with hyperbaric ropivacaine 18 mg to T3.7 Whiteside and coworkers9 studied hyperbaric ropivacaine 15 mg and reported a somewhat lower median extent of cephalad spread of sensory block (T7) than in our study with hyperbaric ropivacaine 15 mg (T4). Their median duration of analgesia at and above the T10 level was somewhat shorter than ours (56.5 vs 83 min).

We conclude that spinal anaesthesia with 15 mg of hyperbaric ropivacaine is suitable for ambulatory lower-extremity surgery, including the use of a thigh tourniquet, of approximately 1 h duration. In comparison with a plain solution, the major advantage of 15 mg of hyperbaric ropivacaine was a greater success rate of achieving sufficient analgesia (at least T10 level sensory block) and faster recovery.


    Acknowledgments
 
We thank Dr Mikko Pitkänen for critical advice during preparation of the manuscript.


    References
 Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
 References
 
1 Khaw KS, Kee WDN, Wong M, Ng F, Lee A. Spinal ropivacaine for cesarean delivery: a comparison of hyperbaric and plain solutions. Anesth Analg 2002; 94: 680–5[Abstract/Free Full Text]

2 Whiteside JB, Burke D, Wildsmith JAW. Spinal anaesthesia with ropivacaine 5 mg ml–1 in glucose 10 mg ml–1 or 50 mg ml–1. Br J Anaesth 2001; 86: 241–4[Abstract/Free Full Text]

3 Rosenberg PH, Heinonen E. Different sensitivity of A and C fibres to long-acting amide local anaesthetics. Br J Anaesth 1983; 55: 163–7[Abstract]

4 Bader AM, Datta S, Flanagan H, Covino BG. Comparison of bupivacaine- and ropivacaine-induced conduction blockade in the isolated rabbit vagus nerve. Anesth Analg 1989; 68: 724–7[Abstract]

5 Kallio H, Snäll E-VT, Kero MP, Rosenberg PH. A comparison of intrathecal plain solutions containing ropivacaine 20 mg or 15 mg versus bupivacaine 10 mg. Anesth Analg 2004; in press

6 Bannister J, McClure JH, Wildsmith JAW. Effect of glucose concentration on the intrathecal spread of 0.5% bupivacaine. Br J Anaesth 1990; 64: 232–4[Abstract]

7 Chung CJ, Choi SR, Yeo KH, Park HS, Lee SI, Chin YJ. Hyperbaric spinal ropivacaine for cesarean delivery: a comparison to hyperbaric bupivacaine. Anesth Analg 2001; 93: 157–61[Abstract/Free Full Text]

8 Gautier PhE, De Kock M, Van Steenberge A, et al. Intrathecal ropivacaine for ambulatory surgery: a comparison between intrathecal bupivacaine and intrathecal ropivacaine for knee arthroscopy. Anesthesiology 1999; 91: 1239–45[ISI][Medline]

9 Whiteside JB, Burke D, Wildsmith JAW. Comparison of ropivacaine 0.5% (in glucose 5%) with bupivacaine 0.5% (in glucose 8%) for spinal anaesthesia for elective surgery. Br J Anaesth 2003; 90: 304–8[Abstract/Free Full Text]





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