Regional anaesthesia for outpatient knee arthroscopy: a randomized clinical comparison of two different anaesthetic techniques

Acta Anaesthesiol Scand 2000; 44: 543–547 Printed in Denmark. All rights reserved

Copyright C Acta Anaesthesiol Scand 2000 ACTA ANAESTHESIOLOGICA SCANDINAVICA

ISSN 0001-5172

Regional anaesthesia for outpatient knee arthroscopy: a randomized clinical comparison of two different anaesthetic techniques A. CASATI1, G. CAPPELLERI1, G. FANELLI1, B. BORGHI2, D. ANELATI1, M. BERTI1 and G. TORRI1 1 University of Milan – Department of Anaesthesiology, IRCCS H. San Raffaele, Milan, 2Department of Anaesthesiology, IRCCS Rizzoli Orthopaedic Institute, Bologna, Italy

Background: The purpose of this prospective, randomized study was to evaluate the time required to perform anaesthesia, achieve surgical block and fulfil standardized discharge criteria in outpatients receiving knee arthroscopy with either spinal anaesthesia or combined sciatic-femoral nerve block. Methods: After a standard midazolam/ketoprofen premedication and baseline measurement of cardiovascular parameters, 50 ASA I–II patients scheduled for elective outpatient knee arthroscopy were randomized to receive spinal anaesthesia with 8 mg of 0.5% hyperbaric bupivacaine (group Spinal, nΩ25), or combined sciatic-femoral nerve block with 25 ml of mepivacaine 20 mg mlª1 and a multiple injection technique (15 ml for femoral nerve block and 10 ml for sciatic nerve block). Times lasting from skin disinfection to the end of local anaesthetic injection (preparation time) and then to achieve surgical anaesthesia (readiness for surgery), as well as times required for block resolution, micturition, unassisted ambulation, and home discharge were recorded by a blinded observer. Occurrence of adverse events was also recorded. Results: Preparation time (mean∫SD) was longer with sciaticfemoral block (8∫2.7 min) than spinal anaesthesia (5∫2.1 min) (PΩ0.0002) while no differences were observed in the time required to achieve readiness for surgery (14∫5 min and 15∫6 min in the Spinal and Sciatic-femoral groups, respectively). No

differences in haemodynamic side effects and need for intraoperative additional analgesia were observed. Patients receiving spinal anaesthesia showed a faster resolution of nerve block and longer time to micturition (137∫49 min and 231∫101 min) than patients receiving peripheral nerve blockade (206∫51 min and 145∫36 min) (P⬍0.0005 and PΩ0.002, respectively); however, no differences were observed in the time required to fulfil standardized discharge criteria (241∫101 min in group Spinal and 209∫70 min in group Sciatic-femoral; PΩ0.86). Conclusion: In patients receiving elective outpatient knee arthroscopy, using a combined sciatic-femoral nerve block with 25 ml of mepivacaine 20 mg mlª1 and a multiple injection technique results in a slightly longer preoperative time but provides similarly effective anaesthesia with no differences in home discharge times as compared to spinal anaesthesia with 8 mg hyperbaric bupivacaine.

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regional anaesthesia for outpatient lower extremity surgery (8), also providing some advantages compared to epidural or general anaesthesia (9); however, at our institution arthroscopic knee surgery is routinely performed using the combined sciatic-femoral nerve block with similarly successful results (10, 11). To obtain more information on use of this peripheral nerve block technique during outpatient knee surgery, we have conducted a prospective, randomized study evaluating the time required to complete the anaesthetic procedure, achieve surgical anaesthesia and fulfil standardized discharge criteria with spinal anaesthesia or combined sciatic-femoral nerve block.

anaesthesia with lidocaine was once considered an ideal choice for outpatient knee arthroscopy; however, transient neurologic symptoms occurring after spinal lidocaine administration has modified clinical practice (1), and spinal block with small doses of a long-acting local anaesthetic like bupivacaine has been suggested for day-case surgery (2–4). Peripheral nerve blocks have been reported to be associated with lower morbidity and cardiovascular effects than central blocks (5, 6), but they are less popular than spinal anaesthesia, mainly due to the increased time and expertise required and delayed recovery (7). Spinal anaesthesia is the most widely used form of PINAL

Received 26 August, accepted for publication 2 November 1999

Key words: Anesthesia, ambulatory; anesthesia, regional: spinal, peripheral nerve blocks; anesthetic, local: bupivacaine, mepivacaine. c Acta Anaesthesiologica Scandinavica 40 (2000)

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Methods After the study protocol had been approved by the local Ethics Committee, written informed consent was obtained from 50 ASA physical status I–II patients, aged 18–65 years, scheduled to have elective ambulatory arthroscopic surgery of the knee. Patients with contraindications to regional anaesthesia, respiratory or cardiac disease, diabetes or peripheral neuropathy as well as patients receiving chronic analgesic therapy were excluded. The required study size was calculated after a pilot study with 10 patients per group: we wished to detect a 5-min difference in the time required to achieve adequate surgical anaesthesia between spinal anaesthesia and combined sciatic-femoral nerve block, accepting a one-tailed a error of 5%, and a b error of 10% (12). Based on these calculations, the required study size was 25 patients per group. After a 20-gauge intravenous (IV) cannula had been inserted in the forearm, all patient received IV premedication with 0.05 mg kgª1 midazolam and 50 mg ketoprofen 20 min before block placement, followed by a 7 ml kgª1 infusion of lactate Ringer’s solution. Then, using a computer generated randomization table, patients were allocated to receive either spinal anaesthesia (group Spinal, nΩ25) or combined sciaticfemoral nerve block (group Sciatic-femoral, nΩ25). Dural puncture was performed at the L3–L4 interspace using a 25-gauge (0.5 mm O.D.) Whitacre spinal needle (Becton-Dickinson, New Jersey, USA) using the midline approach with the patient placed in the lateral position. After free flow of cerebrospinal fluid (CSF) had been observed, 8 mg of 0.5% hyperbaric bupivacaine (Marcaine Spinal Heavy, Astra, Sweden) was injected through a cranially directed needle orifice with three CSF aspirations (barbotage); then patients were immediately turned to the supine position. Combined sciatic-femoral nerve block was performed using 25 ml of mepivacaine 20 mg mlª1 (Carbocaine, Astra, Sweden) with the aid of a nerve stimulator using a short-bevelled, Teflon-coated stimulating needle. Stimulation frequency was set at 2 Hz, while the intensity of stimulating current was initially set to deliver 1 mA and then gradually decreased to less than 0.5 mA. Paraesthesia was never intentionally sought, and a multiple injection technique was used, eliciting specific muscular twitches on nerve stimulation to confirm exact needle location (6, 10, 11). First, we performed the femoral nerve block which was followed by the sciatic nerve block. For the femoral nerve block, the stimulating needle was inserted lateral to the femoral artery at the intersection be-

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tween the femoral artery and a line connecting the anterior superior iliac spine to the pubic tubercle, and then it was reinserted and redirected to elicit each of the three following muscular twitches: contraction of vastus medialis, vastus intermedius and vastus lateralis. Sciatic nerve block was performed according to the classic Labat approach: a line was drawn from the posterior superior iliac spine to the midpoint of the greater trochanter. A perpendicular line was drawn bisecting this line which extended 5 cm caudally. A second line was drawn from the greater trochanter to the sacral hiatus. The intersection of this line with the perpendicular line indicated the point of needle entry. The stimulating needle was inserted and redirected in sequence to elicit each of the following muscular twitches: flexion of the foot and dorsiflexion of the foot. If after each of the considered muscular twitches had been observed, the injection of 1 ml of the study solution immediately stopped the twitch, the needle location was considered adequate. For each of the considered muscular twitches, 5 ml of local anaesthetic solution was injected. Standard monitoring was used throughout the study, including non-invasive arterial blood pressure, heart rate and pulse oximetry. Sensory level was evaluated by loss of pinprick sensation (20-gauge hypodermic needle), whereas motor blockade was evaluated using a modified Bromage scale (0Ωno motor block; 1Ωhip blocked; 2Ωhip and knee blocked; 3Ωhip, knee and ankle blocked). Haemodynamic variables were measured every 5 min during the first 30 min after block placement, then every 15 min until the end of surgery; further assessments were performed every 30 min. Clinically relevant hypotension was defined as a decrease in systolic arterial blood pressure by 30% or more from baseline values, and it was initially treated with 200 ml IV infusion of Ringer’s lactate solution; if this proved to be ineffective, an IV bolus of etilephrine (5 mg) was given. Clinically relevant bradycardia was defined as heart rate decrease below 45 bpm, and it was treated with 0.5 mg IV atropine. The time lasting from skin disinfection to the end of local anaesthetic injection (preparation time) and then to achieve surgical anaesthesia (readiness for surgery) were recorded. Surgical anaesthesia was defined as the presence of adequate motor (complete motor blockade in the Spinal group or inability to move the ankle and the knee of the operated limb in the Sciatic-femoral group) and sensory (loss of pinprick sensation [22-gauge hypodermic needle] at T12 in the Spinal group, or in the femoral and sciatic nerves distribution in the Sciatic-femoral group)

Peripheral or central nerve blocks for knee arthroscopy Table 1

Results

Demographic data.

Age (years) Weight (kg) Height (cm) Male/Female

Spinal (nΩ25)

Sciatic-femoral (nΩ25)

39∫13 73∫17 169∫10 14/11

43∫11 72∫14 170∫8 13/12

Results are presented as mean (∫SD).

blocks. The quality of the block was judged according to the need for supplementary IV analgesics and sedation: adequate nerve blockΩneither sedation nor analgesics required to complete surgery; inadequate nerve blockΩneed for additional analgesia (0.1 mg IV bolus of fentanyl) required to complete surgery; failed nerve blockΩgeneral anaesthesia required to complete surgery. Analgesia consisted of 50 mg oral ketoprofen every 8 h on the operation day, starting 8 h after the operation. Rescue analgesia was given with oral tramadol (50 mg) when the patient asked for more analgesics. Postoperatively, patients were evaluated every 30 min by a blinded observer until readiness for discharge, defined as fulfilment of the following criteria: patient alert, with stable vital signs, able to void and ambulate, with nausea and pain controllable by oral medication. Data regarding the time lasting from the end of local anaesthetic injection to complete resolution of sensory and motor blocks, urination, unassisted ambulation and readiness for discharge, as well as occurrence of adverse events or complications, and pain treatments were also recorded. Postoperative followup was carried out the day after surgery by phone and 1 week after surgery during the routine postoperative visit by asking the patient about postoperative pain, post-dural puncture headache, and dysaesthesias in the buttocks, tights, or lower limbs. The need for rescue tramadol during the first 24 h after surgery was also recorded. Statistical analysis was performed using the program Systat 7.0 (SPSS Inc, Chicago, IL). The twosample Student’s t-test was used to compare demographic data, preparation time, and times for readiness to surgery, block resolution, and home discharge. Analysis of variance for repeated measures was used to analyse changes over time. Ordinal data were analysed using the contingency table analysis with Fisher exact test. A value of P⬍0.05 was considered significant. Continuous variables are presented as mean (∫SD), while ordinal data are presented as number (%).

The two groups had comparable demographic data (Table 1). Hypotension requiring either volume expansion or vasopressor administration was not reported in any patient, while bradycardia was observed in three Spinal group patients (12%) (PΩ0.235). Two patients in the Sciatic-femoral group complained of mild pain at the hip due to the manipulation of the limb during surgery and received additional analgesia (P⬍0.25); however, in no case was general anaesthesia required to complete surgery. While no differences were observed in the time required to achieve surgical anaesthesia, the preparation time was longer in the Sciatic-femoral group (Fig. 1), increasing the total preoperative time in group Sciaticfemoral (25∫5 min) as compared to group Spinal (17∫5 min) (PΩ0.001). Table 2 summarizes the recovery times. Three patients receiving spinal anaesthesia complained of abdominal pain due to urinary retention nearly 4 h after surgery (PΩ0.235): they received bladder catheterization and their data were not considered in the analysis of further recovery times. Even though delayed, these patients fully recovered spontaneous urination, and no hospital admission was required due to urinary retention. Nerve block resolution was faster and time to micturition was longer in the Spinal group as compared with patients receiving peripheral nerve blockade; however, no differences were observed in the time required to fulfil standardized discharge criteria. Postoperative pain relief was adequate in all studied patients. Four patients in the Spinal group

Fig. 1. Mean (∫SD) time lasting from skin disinfection to end of local anaesthetic injection (preparation time) and from local anaesthetic injection to achievement of surgical anaesthesia (ready for surgery) in outpatients receiving knee arthroscopy with either subarachnoid anaesthesia (group Spinal, nΩ25) or combined sciatic-femoral nerve blockade (group Sciatic-femoral, nΩ25). * P⬍0.0005 versus group Sciaticfemoral group.

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A. Casati et al. Table 2 Times to resolution of nerve block, urination and fulfilment of discharging criteria in outpatients receiving knee arthroscopy with either subarachnoid anaesthesia (group Spinal, n Ω 25) or combined sciaticfemoral nerve blockade (group Sciatic-femoral, n Ω 25).

Time Time Time Time

to to to to

nerve block resolution ambulation urination discharge

Spinal (nΩ25)

Sciaticfemoral (nΩ25)

P value

137∫49 179∫58 231∫931 241∫1011

206∫51 205∫56 145∫36 209∫70

0.0005 0.154 0.002 0.867

1

Three patients were excluded because they required bladder catheterization for urinary retention. Results are presented as mean (∫SD).

(16%) required rescue tramadol during the first 24 h after surgery while no rescue analgesic was required in the Sciatic-femoral group (PΩ0.11). No cases of post-dural puncture headache or other complications were reported at the postoperative follow-up.

Discussion This prospective, randomized, blinded study demonstrated that, even though performing a sciatic-femoral nerve block took slightly longer than spinal anaesthesia, the time required to achieve surgical anaesthesia and patient discharge after the end of the anaesthetic procedure was similar when performing outpatient knee arthroscopy using either a combined sciatic-femoral nerve block with 2% mepivacaine and a multiple injection technique or a spinal anaesthesia with 8 mg hyperbaric bupivacaine. The increased time required to perform the anaesthetic procedure in the Sciatic-femoral group is reasonably explained by the need for turning those patients receiving the peripheral nerve blockade from the supine to the lateral position. However, similar preparation times have been reported in other investigations comparing spinal and epidural anaesthesia (9); moreover, even though statistically significant, the clinical relevance of such a small difference in the preoperative time between the two anaesthetic technique may have only minor clinical relevance. As routine in our Department we use low dose hyperbaric bupivacaine as an alternative to lidocaine for spinal anaesthesia, in order to minimize the risk for transient neurologic symptoms (1, 2). The recovery profile observed after 8 mg intrathecal bupivacaine is consistent with that reported in previous investigations with similar doses of bupivacaine (2–4); interestingly, it is also similar to that reported after lido-

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caine spinal block. Liu and colleagues (13) demonstrated that resolution of sensory block required 144 min after 50 mg intrathecal lidocaine; while Urmey and colleagues (14) studied 60 mg 2% plain lidocaine for outpatient knee arthroscopy and found spontaneous micturition after a time ranging between 170 min and 198 min. In this study, we used a multiple injection technique (10, 15), which has been demonstrated to provide successful nerve block with smaller volumes of local anaesthetic solution (11) and shorter onset time (10, 16, 17) compared to the single injection technique: these considerations could also explain the findings of the present investigation. Patient discharge after day-case surgery is known to be influenced by various factors not directly related to the anaesthetic procedure, such as the availability of personnel effecting the patient discharge, or family members to accompany the patient home; however, these factors should have been randomly distributed between the two groups, excluding the risk for a systematic error which would have altered the findings of no significant differences between the two anaesthetic techniques. Moreover, although the sample size of this study is not large enough to provide new information on the incidence of cardiovascular and neurological complications or other adverse events such as post-dural puncture headache and urinary retention, it should be pointed out that peripheral nerve blocks are associated with a lower morbidity than spinal anaesthesia (5), and this must be carefully considered by practitioners when deciding the most appropriate anaesthetic procedure, especially in outpatients. In conclusion, this study demonstrates that, in patients scheduled to have elective outpatient knee arthroscopy, the use of a combined sciatic-femoral nerve block performed with small volumes of 2% mepivacaine and a multiple injection technique results in a slightly longer preoperative time but provides similarly effective anaesthesia with no differences in home discharge times as compared to spinal anaesthesia with low dose bupivacaine.

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Address: Dr A. Casati Department of Anaesthesiology IRCCS H. San Raffaele Via Olgettina 60 20132 Milan, Italy e-mail: casati.andrea/hsr.it

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