|Year : 2014 | Volume
| Issue : 1 | Page : 70-75
Temporary application of an additional forearm tourniquet reduces the dose of lidocaine for intravenous regional anesthesia
Waleed M Abdelmageed, Waleed M Al Taher
Department of Anesthesia and Intensive Care, Faculty of Medicine, Ain Shams University, Cairo, Egypt
|Date of Submission||08-Jun-2013|
|Date of Acceptance||02-Sep-2013|
|Date of Web Publication||31-May-2014|
Waleed M Al Taher
Department of Anesthesia and Intensive Care, Faculty of Medicine, Ain Shams University, Cairo
Source of Support: None, Conflict of Interest: None
Local anesthetic toxicity is a serious complication of intravenous regional anesthesia (IVRA). We investigated whether temporary application of an additional forearm tourniquet would permit the reduction of lidocaine dosage for IVRA without affecting the quality of the block.
Patients and methods
One hundred patients undergoing hand surgery under IVRA were randomized to receive ketorolac 10 mg with 40 ml of either 0.5% lidocaine (conventional group, N = 50) or 0.25% lidocaine and an additional simple forearm tourniquet applied for 5 min during and after administration of the local anesthetic (forearm group, N = 50).
Surgical anesthesia occurred more rapidly in the forearm group (6.3 ± 1.4 vs. 8.4 ± 1.8 min in the conventional group, respectively; P < 0.001). There were no statistically significant differences in motor block onset and recovery times, intraoperative sedation requirement and operative conditions assessed by the surgeon between both groups. The mean ± SD verbal numerical scale values of quality of anesthesia were similar in both groups (3.2 ± 1.2 vs. 3.4 ± 1.1, P = 0.387). Time to the first analgesic requirement and the total postoperative analgesic consumption were similar in the studied groups. Significantly more patients in the conventional group experienced postoperative central nervous system manifestations than those in the forearm group (15 vs. three, respectively; P = 0.004). These manifestations were shorter lived in the forearm group (5 ± 2 vs. 16 ± 6 min, in conventional group; P < 0.0001).
Temporary application of an additional forearm tourniquet speeds the onset of IVRA and permits the use of half the dose of lidocaine, hence increasing the safety profile of the block.
Keywords: Intravenous regional anesthesia, lidocaine
|How to cite this article:|
Abdelmageed WM, Al Taher WM. Temporary application of an additional forearm tourniquet reduces the dose of lidocaine for intravenous regional anesthesia. Ain-Shams J Anaesthesiol 2014;7:70-5
|How to cite this URL:|
Abdelmageed WM, Al Taher WM. Temporary application of an additional forearm tourniquet reduces the dose of lidocaine for intravenous regional anesthesia. Ain-Shams J Anaesthesiol [serial online] 2014 [cited 2021 Apr 19];7:70-5. Available from: http://www.asja.eg.net/text.asp?2014/7/1/70/128420
| Introduction|| |
Intravenous regional anesthesia (IVRA) is a simple, reliable and safe anesthetic technique for minor surgical procedures of the extremities that avoids the need for general anesthesia, with a success rate of 96-100% if performed appropriately . This technique allows a rapid return of normal sensory, motor and neurological functions after completion of the surgery, which in turn facilitates early discharge of the patient. Although promising, the conventional technique of IVRA has been limited by tourniquet pain and its inability to provide postoperative analgesia , in addition to the occasional occurrence of adverse effects such as dizziness, tinnitus, convulsion or bradycardia and hypotension. In fact, local anesthetic toxicity remains one of the most serious complications of IVRA , which occurs when a large amount of local anesthetic is released into the systemic circulation  when the tourniquet is deflated either accidentally during the procedure or intentionally at the end of the surgery. Toxicity can also occur from leakage of the local anesthetic past the tourniquet as a result of a rapid increase in the venous pressure when the tourniquet is inflated .
It has been suggested that the application of a tourniquet to the forearm (instead of the conventional upper arm tourniquet) may improve the quality of IVRA and reduce the dose of the local anesthetic used, with preservation of the function of the long flexors and extensor muscles of the hand during the period of operative anesthesia ,. However, the forearm tourniquet technique has not been used routinely because of the potential risk of local anesthetic leakage through the interosseous vessels, incomplete hemostasis, limited surgical exposure and the increased risk of nerve injuries although these risks have not been approved by many studies ,.
The aim of this prospective, randomized study was to determine whether the temporary application of a simple forearm tourniquet during administration of the local anesthetic would permit reduction of the local anesthetic dosage used for IVRA, without affecting the quality of the block, in patients undergoing elective hand or distal forearm surgery.
| Patients and methods|| |
This study was conducted in Ain Shams University Hospital (Cairo, Egypt), from October 2011 to May 2012.The study was approved by the Hospital Ethics Committee, and written informed consent was obtained from each patient. We studied 100 ASA I or II patients of both sex, aged 18-60 years and scheduled for hand or distal forearm surgery (ganglion excision, carpal tunnel release, excision biopsy, tendon repair, foreign body removal, and nerve repair). Patients who were scheduled to undergo surgery that was anticipated to last more than 90 min, those with Raynaud's disease, sickle cell anemia, the use of analgesics within the last 24 h before the study, or a history of allergy to any drug used were excluded from participation.
During the preoperative visit, the procedure was explained to the patients, and they were taught how to represent their postoperative pain on a 10 cm visual analogue scale (VAS) on which 0 cm indicated no pain and 10 cm the worst imaginable pain. On the evening of the operation, all patients were premedicated with lorazepam 2 mg orally.
After application of the standard intraoperative monitors [ECG, heart rate, noninvasive mean arterial blood pressure and peripheral oxygen saturation (SpO 2 )], two 20-G cannulas were placed: one in a vein on the dorsum of the operative hand and the other in the opposite hand. All patients received 2 mg of midazolam and oxygen mask at 6 l/min. A standard technique for IVRA was used. A padded pneumatic double-cuffed (proximal and distal) tourniquet was positioned around the upper arm. The operative arm was elevated for 2 min, and then exsanguinated using an Esmarch bandage that was wrapped around the whole limb distal to the upper arm tourniquet. The proximal tourniquet was then inflated to 250 mmHg and the Esmarch bandage was removed. Circulatory isolation of the arm was verified by inspection, absence of radial pulse and loss of pulse oximetry tracing in the ipsilateral index finger. Patients were randomized using a computer-generated list to one of the two groups before injection of the local anesthetic into the venous compartment of the upper extremity.
The conventional group (N = 50) with an upper arm tourniquet (group UT) received 40 ml of 0.5% lidocaine (200 mg lidocaine diluted in 0.9% normal saline to a volume of 40 ml with ketorolac 10 mg) over 2 min.
In the forearm group (N = 50), in addition to the upper arm tourniquet, a temporary simple forearm tourniquet (the one used during venous cannulation) was applied to the middle of the forearm (group FT), and then 40 ml of 0.25% lidocaine (100 mg lidocaine diluted in 0.9% normal saline to a volume of 40 ml with ketorolac 10 mg) was injected over 2 min. The patients were observed for manifestations of local anesthesia toxicity during lidocaine injection. The forearm tourniquet was removed after 5 min from its application.
The onset of the sensory block was assessed by a surgeon who was unaware of the group to which the patient had been allocated using a pinprick with a 22-G short beveled needle at three separate areas, representing the dermatomal sensory distribution of the three main nerves of the hand, and surgical anesthesia was announced when there was no sensation. Motor function was evaluated by asking the patient to flex and extend his/her wrist and fingers, and complete motor block was noted when voluntary movement was impossible. The sensory and motor block onset times were noted as the time elapsed from injection of lidocaine to complete sensory and motor blocks, respectively. The time between the start and the end of surgery (surgical time) was also noted. Noninvasive mean blood pressure, heart rate and SpO 2 were monitored before and after tourniquet application, 5, 10, 15, 20 and 40 min after the injection of the local anesthetic, and 5, 10 and 20 min after release of the tourniquet.
During surgery, the surgeon assessed the degree of muscle relaxation and the dryness of the operative field. This was on a 10-point verbal numerical scale (VNS), where the 0 point indicates none and the 10 indicates good operative conditions. When the proximal tourniquet pressure became painful, the distal cuff was inflated to the same pressure followed by the release of the proximal cuff. If the tourniquet pain was persistent, the patient was given 2 mg midazolam and 50 mg propofol for sedation, and if unsuccessful, general anesthesia was given.
At the end of operation, the attending anesthetist, who is blinded to the studied groups, was asked to qualify the anesthetic conditions according to a four-point VNS, where a score of 4 (excellent) indicated no complaint from the patient, 3 (good) minor complaint with no need for supplemental sedation, 2 (average) moderate complaint that required supplemental sedation and if the score was 1 (unsuccessful) general anesthesia was given.
Deflation of the tourniquet was performed by the cyclic deflation technique (not before 30 min had been elapsed from injection of the anesthetic solution). The sensory block recovery time (time elapsed after tourniquet deflation, up to recovery of sensation in all dermatomes determined by a pin-prick test), and the motor block recovery time (time elapsed after tourniquet deflation up to movement of the fingers) were noted.
After surgery, patients were transferred to the postanesthesia care unit, where they were monitored and received oxygen through a face mask at 6 l/min. They were free to request rescue analgesics after tourniquet deflation, and the time to the first analgesic requirement (the time elapsed after tourniquet release to the patient's first request for analgesics) was noted. A nurse (not involved in the study) in the postanesthesia care unit and the surgical ward administered the rescue analgesic (lornoxicam 8 mg intravenously) when it was requested (a maximum dose of 24 mg/24 h), and the pain score was assessed by VAS at the time of the first analgesic requirement. The total 24-h postoperative consumption of lornoxicam was recorded. Patients were also observed for the occurrence of unwanted central nervous system (CNS) manifestations (tinnitus, dizziness, circumoral tingling, seizures, and coma), cardiovascular effects such as hypotension and bradycardia (30% decrease from the baseline value) or arrhythmias, a peripheral oxygen saturation less than 90%, nausea and vomiting, or skin rash during the postoperative period, and a suitable management was carried out as clinically indicated.
The required sample size was calculated using G*Power software version 3.1.0 (Institut für Experimentelle Psychologie, Heinrich Heine Universitδt, Düsseldorf, Germany). The primary outcome was the proportion of patients experiencing tourniquet pain and/or discomfort requiring supplemental sedation in the two study groups. It was estimated that a sample of 44 patients in each group would have a power of 80% to detect a medium effect size (w) of 0.3 with regard to the primary outcome. The test used for sample size estimation was the χ2 -test with one degree of freedom and significance of the test was targeted at a type I error of 0.05.
Statistical analysis was performed on a personal computer using IBM SPSS Statistics version 21 (IBM Corp., Armonk, New York, USA). The Shapiro-Wilk test was used to test the normality of numerical data distribution. Normally distributed numerical data were presented as mean and SD, and differences between the two groups were compared using the unpaired Student t-test. Categorical data were presented as number and %, and differences between the two groups were compared using the Pearson χ2 -test with Yates' correction.
All P values are two-sided. P less than 0.05 is considered statistically significant.
| Results|| |
All patients completed the study. There were no differences in the mean age, the sex distribution or the ASA physical status. Patients' characteristics are shown in [Table 1].
Perioperative hemodynamic and respiratory monitoring revealed no statistically significant difference between the two groups (P < 0.05). The duration of surgery was similar in the two groups. The onset of surgical anesthesia had occurred more rapidly in group FT (6.3 ± 1.4 vs. 8.4 ± 1.8 min in the conventional group, P < 0.001). There was no significant difference in the motor block onset time between the two groups (P = 0.124). Sensory and motor block recovery times were comparable in both groups (P = 0.053 and 0.084), respectively [Table 2].
Nine patients in group UT and six patients in group FT received intraoperative sedation (midazolam and propofol) but this was statistically insignificant (P = 0.575). The mean ± SD VNS values of the operative conditions assessed by the surgeon were similar in the two groups (8.3 ± 1.7 in the UT group vs. 7.9 ± 1.4 in the FT group, P = 0.202). There was no statistically significant difference regarding the quality of anesthesia determined by the anesthesiologist between the two groups (P = 0.387) [Table 3].
|Table 3: Operative conditions, quality of anesthesia and the need for supplemental sedation|
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With regard to the postoperative analgesia, the time to the first analgesic requirement and the visual analogue pain score at that time did not differ significantly between the conventional and the temporary forearm tourniquet groups (P = 0.054 and 0.288, respectively). The total 24-h postoperative consumption of lornoxicam was also comparable in the two groups (P = 0.517) [Table 4].
No major complications were seen throughout the study period and no patient had needed any intervention due to perioperative hemodynamic or respiratory problems. Minor local anesthetic side effects were the most prevalent adverse events after completion of the surgery and deflation of the upper arm tourniquet. Significantly more patients in the conventional group experienced tinnitus, light headedness, headache and circumoral numbness than patients in the forearm group (15 vs. three patients, respectively; P = 0.004) [Figure 1]. These side effects were also of shorter duration in the FT group (5 ± 2 min) than in the (16 ± 6 min) UT group and this difference was highly significant (P < 0.0001) [Figure 2].
| Discussion|| |
The results of this study indicate that the application of an additional temporary simple forearm tourniquet for 5 min during and after administration of the local anesthetic for IVRA allowed reduction of the dose of lidocaine used to half and hastened the onset of the surgical aesthesia compared with the conventional upper arm technique, with similar clinical efficacy and postoperative analgesia.
However, the current study failed to demonstrate a significant improvement in all other parameters of IVRA, which could be explained in view of the mechanism of action of IVRA, which is by direct diffusion of the local anesthetic from the veins into the adjacent nerves . The sensory block onset time was shortened by the application of a temporary forearm tourniquet, which confined the intravascular volume to the hand and the distal forearm (the surgical site) and enabled preliminary induction of anesthesia in the hand that resulted in a more rapid development of surgical anesthesia, but due to the low concentration of lidocaine used (0.25%), the sensory nerve fibers were affected more rapidly than the thicker myelinated motor nerve fibers . Thus, the onset of surgical anesthesia had occurred more rapidly in the forearm group, whereas the motor block onset time and the sensory and motor block recovery times were similar in both groups.
Previous studies have suggested several advantages of a forearm-based tourniquet IVRA that included better tolerance and less discomfort than the conventional tourniquet . This could be due to the anatomical differences between the upper arm and the forearm, in which the forearm has the tourniquet around the radius and ulna, whereas the upper arm has only the humorous to absorb the pressure of the tourniquet . Reuben et al.  demonstrated similar pain relief with a forearm tourniquet, and lower doses of lidocaine and ketorolac had been used, improving the safety profile of the technique, compared with the conventional IVRA. Singh et al.  described effective perioperative anesthesia and analgesia with a forearm IVRA. The technique resulted in a clinical profile similar to the upper arm IVRA while using half the doses of both lidocaine and ketorolac. In contrast, several concerns have been raised in the medical literature about the use of a forearm tourniquet. It has been regarded as controversial because the compression forces of an inflated forearm tourniquet may not adequately compress the anterior and the posterior interosseous arteries located between the radius and the ulna, resulting in the inevitable intravascular leakage of the local anesthetic under the tourniquet, especially in hypertensive patients . However, further studies investigating leakage of the local anesthetic during IVRA revealed that tourniquet leaks during forearm IVRA are comparable to upper arm tourniquet leaks 15. Another disadvantage of the forearm IVRA is the occurrence of a burning sensation during injection of the local anesthetic, which is probably due to administration of a large volume into the limited intravascular volume of the hand. In the current study, this complication was avoided by slowing down the rate of lidocaine administration (over 2 min), and the forearm tourniquet was applied only temporarily (removed after 5 min) in order not to hinder the mobility and positioning of the hand during surgery and also not to limit the surgical exposure as well.
Although tourniquet pain is one of the important factors limiting the use of IVRA, its mechanism is not fully understood. It is believed that both mechanical compression and ischemia result in the loss of conduction of the large Aγ fibers, leaving the smaller C pain fibers uninhibited . In this study, the patients in the two groups were comparable regarding their discomfort from the inflated distal upper arm tourniquet and their need for intraoperative sedation despite the application of an additional temporary forearm tourniquet for 5 min in the FT group during and after lidocaine administration. This could be attributed to the proximal migration of the local anesthesia within the veins to reach the nerve endings;  hence, the area between the forearm and the proximal upper arm tourniquet was completely anesthetized in most patients in the FT group after removal of the forearm tourniquet.
IVRA is a simple and valuable technique that is easy to learn and perform. Although CNS side effects are the most common complications (ranging from dizziness and tinnitus to muscle twitching, loss of consciousness, and convulsion), this technique is very safe provided excessive doses of local anesthetics are avoided and the tourniquet pressure is monitored carefully. In addition, excessive lidocaine concentration can cause cardiovascular toxicity, although less common than CNS toxicity, and despite the fact that lidocaine is less cardiotoxic than other lipophilic local anesthetics such as bupivacaine, the risk of cardiac toxicity is the greatest in patients with underlying cardiac arrhythmias or after myocardial infarction. Potential lidocaine cardiovascular effects include negative inotropic action and delirious effect on the myocardial conduction system (widened PR interval, widened QRS duration, sinus tachycardia, sinus arrest and partial or complete atrioventricular dissociation) . Cardiac toxicity is potentiated by acidosis, hypercapnia and hypoxia, which worsen cardiac suppression and increase the chance of arrhythmia.
It is of note that the systemic absorption of the injected local anesthetics depends on the blood flow, which is principally determined by the site of injection, and its rate is proportionate to the vascularity of the site of injection (intravenous>tracheal>intercostals>caudal>epidural>subcutaneous) . Lidocaine toxicity occurs with unintended intravascular administration or with administration of an excessive dose. When lidocaine is used for regional nerve blocks, plasma levels are usually 3-5 μg/ml. Plasma levels of less than 5 μg/ml are unlikely to have cardiovascular toxicities . Levels of 5-10 μg/ml can cause hypotension by inducing both cardiac suppression and vascular smooth muscle relaxation. Levels of more than 30 μg/ml are associated with cardiovascular collapse . In a retrospective review of all postoperative complications associated with IVRA, Guay  found that the lowest dose of local anesthetics associated with seizure was 1.5 mg/kg for lidocaine, and seizures occurring after tourniquet deflation have been reported with a tourniquet time as long as 60 min. It is noteworthy that in our trial to increase the safety profile of IVRA while keeping the same clinical efficacy of the block, the average dose of lidocaine used in the present study was reduced to 1.39 mg/kg in the patients receiving the additional temporary forearm tourniquet. This reduction of lidocaine dosage had an implication on the occurrence of postoperative CNS side effects as significantly more patients in the conventional group experienced CNS manifestations of local anesthetic toxicity compared with the FT group. Moore et al.  have demonstrated that the central manifestations of local anesthetic toxicity may be underreported by premedication. Taking this assumption into consideration, the incidence of CNS manifestations of lidocaine toxicity in the patients receiving conventional IVRA in the current study should have been higher than what was reported because of the premedication of all patients enrolled with midazolam, which could have impaired their ability to describe subjective symptoms. Thus, reduction of the local anesthetics dosage during IVRA could be of extreme significance for minimizing postoperative CNS side effects.
A possible limitation of this study is that the serum levels of lidocaine were not measured due to the unavailability of this facility in our hospital; however, serial monitoring of serum lidocaine levels is recommended during prolonged or high-dose intravenous therapy , and the lidocaine doses used in this study are well within the therapeutic range. Another limitation could be the 'non-blindness' of the patients to the position of the forearm tourniquet, although we believe that a lot of patients in the FT group were not aware of the extra tourniquet application to the forearm.
| Conclusion|| |
The temporary application of a simple forearm tourniquet as an adjuvant to IVRA for 5 min during and after injection of the local anesthetic reduces the dose of lidocaine to half, provides a more rapid onset of surgical anesthesia and decreases the frequency and the duration of the postoperative manifestations of local anesthetic toxicity.
| Acknowledgements|| |
Conflicts of interest
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[Figure 1], [Figure 2]
[Table 1], [Table 2], [Table 3], [Table 4]