IV Regional Anesthesia Research Articles

Emergency inguinal hernioplasties in a tertiary public Hospital in Athens Greece, during the economic crisis

BackgroundAlthough the effect of the recent Greek economic crisis and austerity on the population’s health and the health system effectiveness have been discussed a lot recently, data on common surgical conditions affecting large part of the population are missing. Using inguinal hernia as a model we investigated possible changes of citizens’ attitude regarding the time of referral, the perioperative details and the intraoperative findings of the emergency hernioplasties.MethodsThe present retrospective study was conducted by a Department of Surgery in a tertiary public hospital of the Greek capital. We reviewed the records of all hernioplasties performed during two 5-year periods: 2005–2009 and 2012–2016, i.e. before and during the crisis focusing on the emergency ones (either incarcerated or strangulated).ResultsAn equal number of hernioplasties was performed in both periods. During the crisis however, an emergency hernioplasty was significantly more probable (HR 1.269, 95% CI 1.108–1.1454, p = 0.001), at a younger age (p = 0.04), mainly in patients younger than 75 years old (p = 0.0013). More patients presented with intestinal ischemia (7 vs 18, p = 0.002), requiring longer hospitalization (5.2 vs 9.6 days, p = 0.04), with higher cost (560 ± 262.4€ vs 2125 ± 1180.8€ p < 0.001). In contrast the percentage of patients with intestinal resection, their hospitalization length and treatment-cost remained unchanged. During the crisis there was a non-significant increase of emergency patients requiring ICU postoperatively (0 vs 4, p = 0.07) and a non-significant 60% increase of emergency operations in migrants/refugees population (3.5% vs 5.8%, p = 0.28). Epidural anesthesia was significantly more frequent during the crisis.ConclusionDuring the crisis: (i) the emergency hernioplasties increased significantly, (ii) more patients (exclusively Greek) presented with intestinal ischemia requiring longer hospitalization and higher treatment cost, (iii) the mean age of the urgently treated patients decreased significantly (iv) regional (epidural) anesthesia was more frequent. Although a direct causal relation could not be proven by the present study most observations can be explained by an increase of the patients who delayed the elective treatment of their hernia, and by a redistribution of the surgical workload towards big central hospitals. This can be prevented by adequately supporting the small district hospitals.

Single-cuff forearm tourniquet in intravenous regional anaesthesia results in less pain and fewer sedation requirements than upper arm tourniquet

Background A limitation of Bier's block or i.v. regional anaesthesia (IVRA) is tourniquet pain. We hypothesized that tourniquet placement on the forearm vs upper arm during IVRA for distal upper extremity surgery may result in less tourniquet pain, lower the need for analgesic interventions, and decrease post-anaesthesia care unit (PACU) admission. MethodsPatients for distal upper extremity surgery were randomized into upper or forearm single-cuff tourniquet placement. IVRA was either performed with 15 ml of 2% lidocaine and 20 mg ketorolac in the upper group or 8 ml of 2% lidocaine and 10 mg ketorolac in the forearm group. Vital signs and visual analogue scale (VAS) score were recorded. If VAS score was >4, 50 µg fentanyl was injected. If the patient had VAS scores >6 with fentanyl, deep sedation with propofol was administered. ResultsTwenty-eight subjects were in each group. There were no significant differences in patient characteristics, tourniquet time, or pressure between the groups. Ten patients in the forearm vs 27 in the upper arm group had a VAS score >4. The mean fentanyl use was 30 µg in the forearm group vs 104 µg in the upper arm group. One patient in the forearm group required propofol vs 22 in the upper arm group. PACU bypass to phase 2 recovery occurred 19 times in the forearm group vs zero times in the upper arm group (P<0.0001). ConclusionsOur results indicate that the placement of the tourniquet on the forearm resulted in less discomfort, fewer sedation interventions, and greater likelihood of bypassing the PACU when compared with upper arm tourniquet.

The Interaction Between Emulsified Isoflurane and Lidocaine Is Synergism in Intravenous Regional Anesthesia in Rats

Our previous studies have demonstrated that emulsified isoflurane (EI) produced epidural anesthesia and blockade of nerve conduction. We designed this study to observe whether EI could produce an anesthetic effect in IV regional anesthesia (IVRA) and to investigate the underlying interaction between EI and lidocaine when they were combined in IVRA. IVRA was evaluated using tail-flick and tail-clamping tests in a rat model. In experiment 1, Sprague-Dawley rats were assigned to 4 groups (n = 10 per group), receiving 0.5 mL of 8%EI, 0.5% lidocaine, 30% Intralipid, or normal saline to observe whether EI could produce an anesthetic effect in IVRA. In experiment 2, for tail IVRA, EC(50) (median effective concentration) of EI alone and EC(50) of lidocaine alone, as well as EC(50) of lidocaine with the addition of Intralipid (0.0% EI) or with the addition of EI at different concentrations (0.4%, 0.8%, and 1.6%) were determined using an up-and-down method. Isobolographic analysis was used to evaluate the interaction between EI and lidocaine. For experiment 1, successful IVRA was observed in 8 of 10 rats with 8% EI, 10 of 10 rats with 0.5% lidocaine, and 0 of 10 rats with 30% Intralipid or normal saline. The anesthetic effect was not different in onset time (1.5 ± 0.9 vs 1.0 ± 0.0 minutes, P = 0.104) or recovery time (15 ± 9 vs 18 ± 12 minutes, P = 0.394) between 8% EI and 0.5% lidocaine. For experiment 2, EC(50) of EI was 4.467% ± 0.375% and EC(50) of lidocaine was 0.183% ± 0.072%; EC(50) of lidocaine was 0.173% ± 0.036% with the addition of Intralipid, and 0.064% ± 0.008%, 0.035% ± 0.005%, and 0.028% ± 0.006% with the addition of 0.4%, 0.8%, and 1.6% EI, respectively. With the addition of EI, the requirement for lidocaine was reduced in a synergistic manner. EI produced IVRA, and a synergistic interaction was found between EI and lidocaine for IVRA in a rat tail model.

Tramadol/paracetamol combination tablet for postoperative pain following ambulatory hand surgery: a double-blind, double-dummy, randomized, parallel-group trial

This randomized, double-blind, double-dummy, multicenter trial compared efficacy and safety of tramadol HCL 37.5 mg/paracetamol 325 mg combination tablet with tramadol HCL 50 mg capsule in the treatment of postoperative pain following ambulatory hand surgery with iv regional anesthesia. Patients received trial medication at admission, immediately after surgery, and every 6 hours after discharge until midnight of the first postoperative day. Analgesic efficacy was assessed by patients (n = 128 in each group, full analysis set) and recorded in a diary on the evening of surgery day and of the first postoperative day. They also documented the occurrence of adverse events. By the end of the first postoperative day, the proportion of treatment responders based on treatment satisfaction (primary efficacy variable) was comparable between the groups (78.1% combination, 71.9% tramadol; P = 0.24) and mean pain intensity (rated on a numerical scale from 0 = no pain to 10 = worst imaginable pain) had been reduced to 1.7 ± 2.0 for both groups. Under both treatments, twice as many patients experienced no pain (score = 0) on the first postoperative day compared to the day of surgery (35.9% vs 16.4% for tramadol/paracetamol and 36.7% vs 18% for tramadol treatment). Rescue medication leading to withdrawal (diclofenac 50 mg) was required by 17.2% patients with tramadol/paracetamol and 13.3% with tramadol. Adverse events (mainly nausea, dizziness, somnolence, vomiting, and increased sweating) occurred less frequently in patients under combination treatment (P = 0.004). Tramadol/paracetamol combination tablets provided comparable analgesic efficacy with a better safety profile to tramadol capsules in patients experiencing postoperative pain following ambulatory hand surgery.

A Model of Intravenous Regional Anesthesia in Rats

We developed an IV regional anesthesia (IVRA) model using the tails of rats to allow preclinical evaluation of the safety and efficacy of drugs used in IVRA and analgesia. Three sequential experiments were designed to determine local anesthetic and analgesic effects of drugs injected IV in the tail. The anesthesia was assessed by monitoring the response of the tail-clamp (RTC) test on the tail, whereas the analgesia was assessed by recording the latency in the tail-flick test on the tail. In the first 2 experiments, we studied the effects of different environmental temperatures (15 degrees C, 25 degrees C, and 37 degrees C) and length of tourniquet time on the tail-flick and tail-clamp tests, respectively. Based on the outcomes of these 2 experiments, the pharmacological effects of 1% lidocaine (L group) and 0.5% bupivacaine (B group) were compared with normal saline (NS group) to evaluate this model in experiment 3. In experiment 1, compared with its baseline, tail-flick latency increased rapidly in the 15 degrees C group (P < 0.0001), whereas there were no changes in tail-flick latency in the 25 degrees C group (P = 0.3640) and the 37 degrees C group (P = 0.0641) after the first 20 minutes of tail submersion in a water bath. RTCs in all rats were positive during the entire observation period. In experiment 2, tail-flick latency did not change compared with baseline tail-flick latency after the first 20 minutes of tourniquet application (P = 0.0902), but significantly increased at the 30-, 40-, 50-, and 60-minute intervals (P = 0.0001). RTCs in all rats were positive during the experiment. In experiment 3, local anesthesia was generated in the tail (distal to the tourniquet) in the L and B groups with a similar onset time of anesthesia (approximately 1 minute), but with a longer recovery time of anesthesia and analgesia in the B group (56.0 +/- 22.0 minutes) than the L group (31.0 +/- 19.0 minutes), whereas no anesthetic and analgesic effects were observed in the NS group. A reliable model for studying IVRA and analgesia has been developed in rats.

The Analgesic Effect of Paracetamol When Added to Lidocaine for Intravenous Regional Anesthesia

In this study, we evaluated the effect of paracetamol on sensory and motor block onset time, tourniquet pain, and postoperative analgesia, when added to lidocaine in IV regional anesthesia (IVRA). Sixty patients undergoing hand surgery were randomly and blindly divided into three groups. All groups received IVRA lidocaine (3 mg/kg) diluted with saline to a total volume of 40 mL. Group 1 received IVRA lidocaine plus IV saline, Group 2 received IVRA lidocaine and paracetamol (300 mg) admixture plus IV saline, and Group 3 received IVRA lidocaine plus IV paracetamol (300 mg). Sensory and motor block onset time, tourniquet pain, and analgesic use were assessed during operation. After tourniquet deflation, visual analog scale (VAS) scores at 1, 2, 4, 6, 12, and 24 h, the time to first analgesic requirement, total analgesic consumption in first 24 h, and side effects were noted. Onset of motor block was shorter and recovery of motor and sensory block was significantly longer in Group 2 (P < 0.05). Intraoperative VAS scores at intraoperative 20, 30, and 40 min were significantly lower in Group 2 (P < 0.05). Intraoperative fentanyl consumption (78 +/- 12, 58 +/- 14, 78 +/- 11 microg, respectively) and the number of patients who required fentanyl for tourniquet pain (13 patients, 3 patients, 9 patients, respectively) were significantly less in Group 2 (P < 0.05). Time to postoperative fentanyl administration was also prolonged (15 +/- 6, 25 +/- 5, 15 +/- 4 min, respectively) in Group 2 (P < 0.05). The quality of surgical anesthesia was better in Group 2 (P < 0.05). Postoperative VAS scores and time of initial analgesic requirement were similar among groups; however, the total amount of diclophenac use was less in Group 2 (P < 0.05). The addition of paracetamol during IVRA with lidocaine decreased tourniquet pain, increased anesthesia quality, and decreased postoperative analgesic consumption.

Melatonin Improves Tourniquet Tolerance and Enhances Postoperative Analgesia in Patients Receiving Intravenous Regional Anesthesia

Melatonin has anxiolytic and potential analgesic effects. We assessed the efficacy of melatonin premedication in reducing tourniquet-related pain and improving analgesia in patients receiving IV regional anesthesia (IVRA). Forty patients undergoing elective hand surgery under IVRA were randomly assigned into two groups (20 patients each) to receive either melatonin 10 mg (melatonin group) or placebo (control group) as oral premedication. IVRA was achieved with lidocaine, 3 mg/kg, diluted with saline to a total volume of 40 mL. Anxiety scores, hemodynamic changes, sensory and motor block onset and recovery times, tourniquet pain, the quality of intraoperative anesthesia, time to first analgesic request, and 24 h analgesic requirements were recorded. After premedication, the anxiety scores were significantly reduced in the melatonin group (P=0.023). During surgery, patients who received melatonin premedication had better tourniquet tolerance (lower verbal pain scores at 30, 40, and 50 min after tourniquet inflation, P<0.05), lower rescue fentanyl requirements (15.6+/-21.9 vs 45.7+/-33.4 microg, P=0.002), longer time to the first postoperative analgesic request (145.4+/-20.2 min vs 74.6+/-12.8, P<0.001) and lower postoperative diclofenac consumption at 24 h (86.3+/-27.5 mg vs 116.3+/-38.3 mg, P=0.007) compared with the control group. Melatonin is an effective premedication before IVRA since it reduced patient anxiety, decreased tourniquet-related pain, and improved perioperative analgesia.

Premedication with Gabapentin: The Effect on Tourniquet Pain and Quality of Intravenous Regional Anesthesia

Gabapentin, an oral non-opioid analgesic, has been used to decrease pain after a variety of surgical procedures. We hypothesized that premedication with gabapentin would minimize tourniquet-related pain in patients receiving IV regional anesthesia (IVRA). Patients undergoing elective hand surgery with IVRA were randomly assigned to one of two study groups using a double-blind study design. The control group (n = 20) received placebo capsules 1 h before the surgery, and the gabapentin group (n = 20) received gabapentin 1.2 g p.o. before the operation. IVRA was achieved in all patients with lidocaine, 3 mg/kg, diluted with saline to a total volume of 40 mL. Fentanyl, 0.5 microg/kg IV, was administered as a rescue analgesic during surgery. Sensory and motor block onset and recovery times, tourniquet pain, and quality of anesthesia were assessed at specific time intervals during the perioperative period. Visual analog scale pain scores (0-10) were recorded during the 24 h follow-up period, and patients received diclofenac, 75 mg IM, if their pain score was >4. The onset of the sensory and motor block did not differ between the two study groups. However, tourniquet pain scores at 30, 40, 50, and 60 min after cuff inflation were lower in the gabapentin group (P < 0.05). The time to intraoperative analgesic rescue was prolonged in the gabapentin group (35 +/- 10 min vs 21 +/- 13 min, P < 0.05), and less supplemental fentanyl was required (35 +/- 47 microg vs 83 +/- 73 microg, P < 0.05). The quality of anesthesia, as independently assessed by the anesthesiologist and the surgeon, was significantly better in the gabapentin (versus control) group. In the gabapentin group, the time to requesting a rescue analgesic after surgery was prolonged (135 +/- 25 min vs 85 +/- 19 min, P < 0.05), and postoperative pain scores at 60 min (3.8 +/- 0.9 vs 2.2 +/- 0.5) and 120 min (3.2 +/- 1.4 vs 1.8 +/- 0.8), as well as diclofenac consumption (30 +/- 38 mg vs 60 +/- 63 mg), were reduced after surgery. Premedication with oral gabapentin (1.2 g) decreased tourniquet-related pain and improved the quality of anesthesia during hand surgery under IVRA. Gabapentin also reduced pain scores in the early postoperative period.

Comparison of ropivacaine 2 mg ml−1 and prilocaine 5 mg ml−1 for i.v. regional anaesthesia in outpatient surgery

Ropivacaine 2 mg ml(-1) (0.2%) provides longer-lasting analgesia after deflation of the tourniquet cuff, with fewer side-effects, than lidocaine 5 mg ml(-1) (0.5%) after i.v. regional anaesthesia (IVRA). Whether ropivacaine 2 mg ml(-1) also exerts this advantage over prilocaine 5 mg ml(-1), the local anaesthetic of choice in IVRA in most European countries was investigated in this study. Sixty outpatients scheduled for forearm or hand surgery received IVRA with 40 ml of ropivacaine 2 mg ml(-1) (Ropi) or prilocaine 5 mg ml(-1) (Prilo) in a randomized, double-blinded fashion. The development and recovery of pin-prick analgesia and motor power of the hand, as well as ropivacaine and prilocaine plasma concentrations (n=30), were assessed during and after operation. Anaesthesia for surgery was adequate in both groups. Pin-prick analgesia was achieved at a similar rate, except in the radial nerve distribution area where at 10 min 60% of Ropi and 90% of Prilo patients had analgesia (P=0.017). At 10 min 100 and 97% had motor block of the hand in the Ropi and Prilo groups, respectively. Recovery of the sensory block in all innervation areas was already observed 2 min after the tourniquet cuff release. At 10 min after releasing the tourniquet cuff 31% of the Ropi patients and none of the Prilo patients still had analgesia in the median nerve distribution (P=0.004). At 12 min, 42% in the Ropi group and none in the Prilo group had decreased grip strength. After the release of the tourniquet, mean plasma concentrations of ropivacaine were higher than those of prilocaine. The highest individual concentration of ropivacaine was 1.65 microg ml(-1) and that of prilocaine 0.6 microg ml(-1). None of the Ropi patients experienced any symptoms of local anaesthetic toxicity. Compared with prilocaine 5 mg ml(-1), analgesia in IVRA with ropivacaine 2 mg ml(-1) developed slightly more slowly, while motor block developed at a similar rate. After the release of the tourniquet, sensation recovered quickly and at a similar rate in the two groups, except for a slightly slower recovery after ropivacaine in the innervation area of the median nerve, but no surgically useful extended analgesia after the cuff deflation was observed. Despite a 60% lower milligram-dose, ropivacaine plasma concentrations were markedly higher than those of prilocaine.

Does Dexamethasone Improve the Quality of Intravenous Regional Anesthesia and Analgesia? A Randomized, Controlled Clinical Study

We investigated the anesthetic and analgesic effectiveness of adding dexamethasone to lidocaine for IV regional anesthesia (IVRA). Seventy-five patients undergoing ambulatory hand surgery were randomly assigned to one of three groups: group L received 3 mg/kg lidocaine, group LD received 3 mg/kg lidocaine + 8 mg dexamethasone, and group LDc received 3 mg/kg lidocaine for IVRA and 8 mg dexamethasone IV to the nonsurgical arm. IVRA was established using 40 mL of a solution. Visual analog scale and verbal pain scores were recorded intraoperatively and for 2 h postoperatively. Postoperative pain was treated with oral acetaminophen 500 mg every 4 h when visual analog scale score was more than 3. Time to request for the first analgesic and the total dose in the first 24 h were noted. Times to onset of complete sensory and motor block were similar in the 3 groups. The times to recovery of motor block (L = 8 [5.91-10.08] min, LD = 13 [6.76-20.19] min, LDc = 6 [4.44-8.43] min) and sensory block (L = 7 [5.21-10.30] min, LD = 12 [6.11-19.40] min and LDc = 6 [4.2-8.11] min) were longer in group LD (P < 0.05). Patients in group LD reported significantly lower pain scores and required less acetaminophen in the first 24 h after surgery. In conclusion, the addition of 8 mg dexamethasone to lidocaine for IVRA in patients undergoing hand surgery improves postoperative analgesia during the first postoperative day.

The addition of magnesium sulfate to IV regional anaesthesia (IVRA) with lidocaine reduces tourniquet pain,

The addition of magnesium sulfate to IV regional anaesthesia (IVRA) with lidocaine reduces tourniquet pain,

Intravenous Regional Anesthesia Using Lidocaine and Magnesium

We conducted this study to evaluate the effects of magnesium, when added to lidocaine for IV regional anesthesia (IVRA), on tourniquet pain. Thirty patients undergoing elective hand surgery during IVRA were randomly assigned to two groups. IVRA was achieved with 10 mL of saline plus 3 mg/kg lidocaine 0.5% diluted with saline to a total of 40 mL in group C or with 10 mL of 15% magnesium sulfate (12.4 mmol) plus 3 mg/kg lidocaine 0.5% diluted with saline to a total of 40 mL in group M. Injection pain, sensory and motor block onset and recovery time, tourniquet pain, and anesthesia quality were noted. Patients were instructed to receive 75 mg of IM diclofenac when the visual analog scale (VAS) score was >4, and analgesic requirements were recorded. Sensory and motor block onset times were shorter and recovery times were prolonged in group M (P < 0.05). VAS scores of tourniquet pain were lower in group M at 15, 20, 30, 40, and 50 min (P < 0.001). Anesthesia quality, as determined by the anesthesiologist and surgeon, was better in group M (P < 0.05). Time to the first postoperative analgesic request in group C was 95 +/- 29 min and in group M was 155 +/- 38 min (P < 0.05). Postoperative VAS scores were higher for the first postoperative 6 h in group C (P < 0.05). Diclofenac consumption was significantly less in group M (50 +/- 35 mg) when compared with group C (130 + 55 mg) (P < 0.05). We conclude that magnesium as an adjunct to lidocaine improves the quality of anesthesia and analgesia in IVRA.

Meperidine in Forearm Intravenous Regional Anesthesia?

We congratulate Reuben et al. (1) on their study assessing the minimally effective concentration of meperidine in IV regional anesthesia (IVRA). Unfortunately, the 30-mg dose results in excessive systemic side effects; hence, despite a significant increase in the duration of postoperative analgesia, the problems may outweigh the benefits. We wish to suggest a possible solution to this problem, using the forearm method of IVRA, a safe technique (2–4) used often at our institution. The dose of local anesthetic required for successful blockade using the forearm method is approximately 50% of that used in the conventional technique, i.e., 0.3 mL/kg lidocaine 0.5% (approximately 20 mL), compared with 0.6 mL/kg (40 mL) (3). As the prolonged analgesia associated with meperidine is believed to be a local effect, the addition of 15 mg of meperidine to 20 mL of lidocaine for forearm IVRA should result in a similar duration of postoperative analgesia of 30 mg of meperidine diluted in 40 mL of lidocaine, for conventional IVRA. However this 15-mg dose should maintain a low side-effect profile. The forearm technique is suitable for carpal tunnel surgery and is especially useful in tenolysis, in which tendon function is preserved intraoperatively. Using 15 mg of meperidine in forearm IVRA may be beneficial in solving the problem of postoperative pain. Margaret M. Coleman FFARCSI Vincent W. S. Chan FRCP

Peripheral Antihyperalgesic Effect of Morphine to Heat, but Not Mechanical, Stimulation in Healthy Volunteers after Ultraviolet-B Irradiation

The objective of this study was to evaluate direct peripheral analgesic effects of morphine using a peripheral model of hyperalgesia and the technique of IV regional anesthesia (IVRA), thus allowing the differentiation between central and peripheral mechanisms of action. Two spots on the ventral sides of both forearms in 12 volunteers were irradiated with ultraviolet (UV)-B to induce thermal and mechanical hyperalgesia. One day after the induction of the inflammatory reaction, 40 mL of morphine hydrochloride 0.01% was administered via IVRA. Calibrated heat and phasic mechanical stimuli were applied to differentially determine impairments of tactile and nociceptive perception. Touch and phasic mechanical stimuli of noxious intensity to normal skin did not reveal altered responsiveness caused by morphine. In contrast, the administration of morphine significantly increased heat pain thresholds in the UV-B-pretreated skin areas. The peripheral antihyperalgesic effects of morphine were demonstrated only in inflamed skin areas. Direct central analgesic effects were ruled out by the lack of measurable plasma concentrations of morphine and its metabolites. Morphine 0.01% significantly diminished thermal, but not mechanical, hyperalgesia by a peripheral mode of action, which suggests inhibition of effector pathways leading to heat, but not mechanical, sensitization. The peripheral analgesic effects of morphine were studied using modified IV regional anesthesia. When administered 1 day after the induction of dermal inflammation, morphine 0.01% diminished heat, but not primary mechanical, hyperalgesia. Therefore, suppression of mechanical hyperalgesia seen in previous studies could be predominantly due to inhibition of secondary (central) mechanical hyperalgesia.

The dose-response relationship of ketorolac as a component of intravenous regional anesthesia with lidocaine.

Ketorolac (K) is a useful addition to lidocaine for i.v. regional anesthesia (IVRA). However, the minimal dose of K that is effective for this purpose has not been established. We added 0, 5, 10, 15, 20, 30, and 60 mg of K to 0.5% lidocaine IVRA for either carpal tunnel release or tenolysis. Pain was assessed in the postanesthesia care unit by using a visual analog scale. The duration of analgesia (time to first request for pain relief) and the use of Tylenol No. 3 tablets (T3) were measured. A linear dose-response relationship was observed between the dose of K and the duration of analgesia (r = 0.988) up to 20 mg of K. Similarly, the number of T3 tablets used was inversely related to the dose of K (r = 0.960) over the same range. There were no significant differences among the groups who received 20, 30, or 60 mg of K. We conclude that 20 mg of K is the optimal dose for inclusion with 0.5% lidocaine for IVRA under the conditions of our study. The antiinflammatory drug ketorolac is a useful addition to lidocaine for i.v. regional anesthesia. This study showed that 20 mg of ketorolac is equally effective as 60 mg in this context. However, smaller doses provided less effective pain relief, and a linear dose-response relationship was demonstrated.

The Dose-Response Relationship of Ketorolac as a Component of Intravenous Regional Anesthesia with Lidocaine

Ketorolac (K) is a useful addition to lidocaine for IV regional anesthesia (IVRA).However, the minimal dose of K that is effective for this purpose has not been established. We added 0, 5, 10, 15, 20, 30, and 60 mg of K to 0.5% lidocaine IVRA for either carpal tunnel release or tenolysis. Pain was assessed in the postanesthesia care unit by using a visual analog scale. The duration of analgesia (time to first request for pain relief) and the use of Tylenol No. 3 tablets (T3) were measured. A linear dose-response relationship was observed between the dose of K and the duration of analgesia (r = 0.988) up to 20 mg of K. Similarly, the number of T3 tablets used was inversely related to the dose of K (r = 0.960) over the same range. There were no significant differences among the groups who received 20, 30, or 60 mg of K. We conclude that 20 mg of K is the optimal dose for inclusion with 0.5% lidocaine for IVRA under the conditions of our study. Implications: The antiinflammatory drug ketorolac is a useful addition to lidocaine for IV regional anesthesia. This study showed that 20 mg of ketorolac is equally effective as 60 mg in this context. However, smaller doses provided less effective pain relief, and a linear dose-response relationship was demonstrated. (Anesth Analg 1998;86:791-3)

Haemostatic changes caused by i.v. regional anaesthesia with lignocaine

The various components of i.v. regional anaesthesia (IVRA), that is ischaemia, tourniquet compression and the presence of high concentrations of local anaesthetics in the blood vessels of the extremity, may affect haemostatic mechanisms. We performed a cross-over study in 10 healthy male volunteers to examine the role of lignocaine in IVRA on several haemostatic variables, and those indicating fibrinolysis and platelet function in particular. Venous blood samples were obtained from the test arm and the opposite arm before IVRA, at the time of tourniquet cuff deflation and 30 min thereafter. Metal needle punctures were used, and for the sample from the test arm at the time of cuff deflation, cuff pressure was reduced from 300 mm Hg to individual mean arterial pressure. The IVRA technique included exsanguination by arm elevation and axillary artery compression, inflation of the tourniquet cuff for 20 min and deflation of the cuff in one step (after obtaining the venous sample). Each subject received, in random order, either 0.5% lignocaine 3 mg kg-1 or the corresponding volume of saline i.v. All fibrinolysis markers, that is, D-dimer, tissue plasminogen activator antigen (t-PA antigen), tissue plasminogen activator activity (t-PA activity), plasminogen activator inhibitor activity (PAI) and protein C indicated enhanced fibrinolysis by IVRA, but only t-PA antigen and PAI showed greater changes in the lignocaine compared with the saline group in the exposed arm at the time of cuff deflation. Platelet function tests (ADP-induced platelet aggregation, beta-thromboglobulin and thrombelastogram (TEG)) indicated no differences between the lignocaine and saline groups. Although IVRA appeared to induce some platelet dysfunction, there was a small increase in TEG amplitude indicative of improved fibrin-platelet interaction in the lignocaine-exposed arm at the time of cuff deflation. We conclude that the presence of high i.v. lignocaine concentrations (median 144.4 micrograms ml-1 in cubital veins at the end of the tourniquet time) potentiated ischaemia-induced fibrinolysis activation during IVRA. Concomitant platelet dysfunction was not aggravated by lignocaine.

Quantitative evaluation of tourniquet leak during i.v. regional anaesthesia of the upper and lower limbs in human volunteers

Although it is accepted that during i.v. regional anaesthesia (IVRA) local anaesthetic can leak under the tourniquet into the systemic circulation, no published study has evaluated this leak quantitatively. In volunteers, during two random sessions, we have simulated IVRA using standard techniques with a radiolabelled compound which is chemically similar to lignocaine and has comparable tissue distribution (0.1 mg of HIDA labelled with 100 muCi of 99mTc in 40 ml of saline). The decrease in radioactivity was measured with a gamma camera for the 20 min of tourniquet inflation and for the 20 min of washout after cuff deflation. While the tourniquet was inflated, the leak for the lower limb (mean 29 (SD 8) %) was significantly greater (P < 0.004) than the leak for the upper limb (15 (5) %). Moreover, in each of 10 volunteers, the leak was always greater for the lower than the upper limb. During the first 3 min after tourniquet deflation the loss of radioactivity was 58 (8) % of the maximal amount for the upper limb and 39 (8) % for the lower limb (P < 0.001). As the leak under the tourniquet was significantly greater for the lower than the upper limb, we conclude that IVRA for the lower limb can be associated more frequently with a shorter duration of successful anaesthesia and/or failure.

IMPROVEMENT IN I.V. REGIONAL ANAESTHESIA BY RE-EXSANGUINATION BEFORE SURGERY

A modification of an i.v. regional anaesthesia (IVRA) technique is described in which the arm is re-exsanguinated before surgery (re-IVRA). IVRA and re-IVRA were compared for quality of operative field, sensory and motor block, quality of analgesia and blood concentrations of prilocaine, lignocaine and mepivacaine in a double-blind study in 120 patients undergoing hand surgery. Re-IVRA provided a significantly better surgical field without affecting sensory or motor block. Re-exsanguination improved tolerance of the tourniquet. Plasma concentrations in the re-IVRA group showed some increases, but these were not in the toxic range.

EFFECT OF SODIUM BICARBONATE ON THE KINETICS OF BUPIVACAINE IN I.V. REGIONAL ANAESTHESIA IN DOGS

Changes in pH studied in vitro affected considerably the distribution of bupivacaine between the erythrocyte and incubation medium: in an acidic medium, the uptake of bupivacaine by erythrocytes was decreased. The acidosis induced in vivo in dogs' limbs during i.v. regional anaesthesia (IVRA) with bupivacaine was corrected by injecting sodium bicarbonate into the occluded limb. The concentration of bupivacaine in the cephalic vein was measured in dogs under. IVRA. After removal of the tourniquet, the drug concentration-time relationship showed a biexponential pattern of decline. Injection of sodium bicarbonate into the limb 10 min before the release of the tourniquet suppressed the rate at which the concentration of bupivacaine decreased during the second phase. This slower rate of drug release from the tissues may prolong residual analgesia.