Julia E. Pollock, MD
Patient-controlled Regional Analgesia (PCRA) at Home: Controlled Comparison between Bupivacaine and Ropivacaine Brachial Plexus Analgesia. Narinder Rawal MD, Ph.D; Renee Allvin CRNA, BSc; Kjell Axelsson MD, PhD; Jan Hallen MD; Gustav Ekback MD, PhD, Torbojorn Ohlsson CRN, MS, Anders Amillon MD. Anesthesiology 2002;96:1290-6.
Previously published studies have shown that 40-50% patients undergoing ambulatory surgery suffer from moderate to severe pain during the first 24-48 hours post-operatively. The aim of this double-blind study was to compare the efficacy of bupivacaine versus ropivacaine catheter brachial plexus analgesia for postoperative pain relief in patients undergoing outpatient hand surgery. A second goal was to determine the feasibility and safety of patient-controlled regional analgesia (PCRA) outside the hospital.
Methods
Sixty ASA I or II patients scheduled for a variety of ambulatory elective hand surgeries were consented for randomization in this study. During the pre-anesthesia visit, all patients were given an explanation of the visual analog scale (VAS) and verbal pain scoring, use of the "home pump" device (in this case a sterile, elastomeric, disposable balloon home pump from I-flow Corporation requiring the patient to open and close the clamp for it to function as a PCA device) and the importance of mailing the completed patient diary. Each patient was also familiarized with the use of PCRA. All surgeries were performed with an axillary brachial plexus blockade utilizing the paresthesia technique. Patients received 20 ml of 1.5% mepivacaine through the introducer cannula and then a contiplex catheter was threaded 2-3 cm beyond the tip of the introducer cannula and another 20 ml of local anesthetic was injected. After surgery, the catheter in the plexus was connected to the sterile home pump. Patients were kept in the PACU until the effects of the brachial plexus block had worn off, and patient's self-administered 1-2 doses of PCRA. Patients were randomized to receive either 0.125% bupivacaine or 0.125% ropivacaine for post-operative analgesia and were randomized to self-administer a bolus of 10 ml (12.5 mg) of the local anesthetic drug by opening the clamp on the PCRA device for 6 minutes. Each patient was given dextropropoxyphene tablets on discharge and instructed to take a 100-mg tablet if the PCRA was ineffective. Each patient received a patient diary. Every time patients used the home pump, they indicated their VAS before and about 20 min after treatment in the diary. The patients also graded their analgesia on a 5-grade scale. A research nurse who was blinded to the study protocol made a follow-up telephone call the day after surgery.
Results
All 60 patients recorded their pain scores before and after each treatment. Visual analog scale scores decreased after each treatment in both groups, but there were no significant differences between the two drugs. One patient in each group took rescue pain medications. In both groups, 87% of patients expressed their desire to have the same treatment again. There was a significant difference between the groups in regard to satisfaction with PCRA on the day of surgery: 81% of patients were satisfied or very satisfied with ropivacaine versus 52% with bupivacaine PCRA (p<0.05). On the day after surgery, the percentage of satisfied or very satisfied was similar with 79% and 83% for ropivacaine and bupivacaine respectively. The main reasons for dissatisfaction were persistent numbness of fingers and inability to extend fingers; some patients also complained of inadequate analgesia and motor weakness of arm and fingers.
Comments
This is the first controlled trial to evaluate the efficacy of axillary PCRA using two different local anesthestics after ambulatory surgery. The results show that the both local anesthetic drugs provide effective analgesia and the authors were unable to detect any significant differences in VAS between the two drugs. Significantly more patients were satisfied with ropivacaine on the day of surgery. According to the authors, previous studies have shown that epidurally administered ropivacaine is up to 40% less potent than epidural bupivacaine. However, at high concentrations for axillary plexus block for surgery, the two drugs appear to be equipotent. Despite the absence of a control group in this study, the authors are to be commended for demonstrating that analgesia by perineural infusion is feasible outside the hospital. They are also to be commended for the rigorous pre-anesthetic measures taken to reduce the risk of toxic complications in this group of outpatients. These measure included 1.) clear verbal and written instructions to patients and escort about PCRA technique, 2.)use of timer to encourage proper dosing, 3.) information provided regarding symptoms caused by local anesthetic overdosage, 4.) telephone and pager numbers of anesthesiologist at all times.
Continuous Infraclavicular Brachial Plexus Block for Postoperative Pain Control at Home: A Randomized, Double-blinded, Placebo-controlled Study. Brian Ilfeld MD, Timothy Morey MD, Kayser Enneking MD. Anesthesiology 2002; 96:1297-1304
Previous investigations of hospitalized patients suggest that local anesthetic infusions via perineural catheters decrease postoperative pain and narcotic requirements after a variety of procedures. Although at-home perineural infusions have been described in several series of patients, their efficacy has not been investigated in a randomized, double blind, placebo-controlled manner. The objectives of this study were to determine 1.) if local anesthetic infused via an infraclavicular brachial plexus perineural catheter decreases postoperative pain, oral narcotic requirements, narcotic-related side effects, and sleep disturbances, 2.) if a small, portable, battery-powered, infusion pump that allows PCRA is reliable and can be used successfully by outpatients, and 3.) if patients accept and understand the catheter and pump system well enough for postoperative analgesia at home to be successful.
Methods
For surgery all 30 patients received an infraclavicular block with 50 ml of mepivacaine 1.5%, sodium bicarbonate 5 mEq, epinephrine 125 ug and clonidine 100 ug. This injection was followed by placement of a 20-gauge multiport polyamide catheter. Patients were randomized to 0.2% ropivacaine or 0.9% saline at 8 ml/hr with a 2-ml patient-controlled bolus available every 20 min. Postoperatively, when patients met standard ambulatory home-discharge criteria, the catheter was tested for intravascular positioning with gentle aspirations followed by a 10-ml incremental bolus of study fluid into which 30 ug of fresh epinephrine had been added. Subsequently, a portable, programmable, battery-powered mechanical infusion pump was attached to the catheter with a reservoir containing 550 ml of study solution. Before discharge all patients were given oral methadone 5 mg.
Results
Patients receiving ropivacaine experienced significantly less postoperative pain compared with patients receiving normal saline during rest and limb movement (p<0.05). The ropivacaine group used significantly fewer narcotic tablets to remain comfortable and experienced fewer narcotic-related side effects and sleep disturbances than the placebo group. The average satisfaction with post-operative analgesia on a scale of 0-10 was ranked 9.2 by those who received ropivacaine and 5.8 by those who received placebo. All patients who received ropivacaine would repeat this analgesic method, only 8 out of 15 patients receiving placebo would repeat the technique. Roughly 50% of patients complained of leakage of clear fluid from under the occlusive dressing, and approximately 30% of patients had at least one nonscheduled contact with the on-call physician during the course of their infusion.
Comments
This is the first randomized, placebo controlled study to show that after moderately painful orthopedic surgery of the upper extremity, ropivacaine infusion using a portable, mechanical pump and an infraclavicular brachial plexus perineural catheter at home decreased pain, sleep disturbances, narcotic use and related side effects and improved overall satisfaction. The authors are to be commended for the rigorous study design. Patients were carefully screened and study requirements included understanding of the possible local anesthetic-related complications and the care of the catheter and pump. Patients also were required to have a caretaker who would remain with them through the first postoperative night and be available and capable to remove the catheter in the evening of postoperative day 2. It is interesting to note that despite extensive pre-study training 30% of patients had nonscheduled contact with the on-call physician.
A Comparison of Intrathecal Fentanyl and Sufentanil for Labor Analgesia. Kenneth Nelson MD, Traci Rauch MD, Victor Terebuh MD, Robert D'Angelo MD. Anesthesiology 2002 96:1070-3
Fentanyl and sufentanil are the most commonly used intrathecal opioids for labor analgesia. Despite a well-established ED50 for sufentanil, there is no direct comparison of the potencies and efficacies of fentanyl and sufentanil for labor analgesia. The purpose of the present study was 1.) to estimate an ED50 for intrathecal fentanyl and 2.) to compare the efficacy, duration of analgesia, and side effects from comparable doses of intrathecal fentanyl and sufentanil based on ratios estimated from the ED50s.
Methods
In previous work the authors had established an ED50 for 60 min of labor analgesia for intrathecal sufentanil using an up-down sequential allocation study design. For the current study, 75 ASA I and II nulliparous women requesting labor analgesia were enrolled. In part I of the study, 20 women received varying doses of fentanyl to establish an ED50 for 60 min of labor analgesia. In the second double-blind part of the study, 55 women were randomized to receive 2 times the ED50 of either intrathecal fentanyl (36 ug) or intrathecal sufentanil (8ug) via a combined spinal-epidural technique. Pain relief, side effects, block height, maternal hemodynamics, and fetal heart rate were assessed throughout the study. The duration of spinal analgesia was considered to be the time from injection of study drug to the time of the patient's first request for additional analgesia.
Results
In the first phase of the study, the ED50 for intrathecal fentanyl was determined to be 18.2 ug. Thus the authors conclude that the relative potency for intrathecal fentanyl to sufentanil in labor analgesia is 1:4.4 at the ED50 level. The duration of spinal analgesia was significantly longer with 8 ug of sufentanil than with 36 ug of fentanyl (104 mins vs 79 mins, p<0.05). Patient demographics and labor characteristics, oxytocin use, mode of delivery, and pain scores before and after spinal injection were similar between groups. Additionally, the incidence of maternal side effects such as pruritus, nausea, hypotension, sedation, etc. was similar between groups. The incidences of fetal bradycardia and Apgar scores were similar between groups with transient fetal heart rate decrease observed in one fentanyl patient and two sufentanil patients.
Comments
This is the first study to compare equipotent doses of intrathecal fentanyl and sufentanil for labor analgesia. This finding is similar to recent epidural studies suggesting that sufentanil is 4.5 times more potent than fentanyl. The conclusion is that intrathecal sufentanil lasts 25% longer for labor analgesia without increasing side effects. The authors of this study have done a beautiful job discussing study limitations and interpretation of this data. The most obvious limitation of comparing ED50s is that the definition of successful analgesia is not standardized. Also the authors discuss other limitations of the use of sufentanil including overdose potential with the more concentration formula, and the cost of the drug. They estimate that at their institution, where the acquisition cost of sufentanil is 29.5 times that of fentanyl ($7.08 vs $0.24 for a 2-ml generic ampule) and the delivery rate is 6,000 per year, with an epidural rate of 80%, the standard use of sufentanil would translate to an increased institutional cost of $32,000.00 per year.
Continuous Psoas Compartment Block for Postoperative Analgesia After Total Hip Arthroplasty: New Landmarks, Technical Guidelines, and Clinical Evaluation. Xavier Capdevila MD, PhD, Philippe Macaire MD, Christophe Dadure MD, Oliver Choquet MD, Philippe Biboulet MD, Yves Rychwaert MD, Francoise d'Athis MD. Anesth Analg 2002;94:1606-13
Concerned about the use of indwelling epidural catheters in orthopedic patients who are receiving post-operative anticoagulants, many practioners are evaluating the use of post-operative perineural catheters for analgesia in patients undergoing total joint replacement. Continuous psoas compartment blocks have been described and used for perioperative analgesia in patients with hip fractures. However several reports of major adverse events after psoas compartment blocks have caused many to question the utility of this technique for post-operative analgesia. The purpose of the present study was to reanalyze the classic landmarks for psoas compartment block and evaluate the feasibility and efficacy of continuous psoas compartment block (CPCB) after total hip replacement.
Methods
In the first part of this study, axial transverse computed tomographic sections of the lumbosacral region were performed on 35 adult patients. Determinations were made of the following 1.) The distance between a line passing through the middle of the spinous processes of L4 and L5 (midline) to a parallel line through the posterior superior iliac spine, 2.) The distance from a line passing through the middle of the spinous processes of L4 and L5 to a line passing through the lumbar plexus and 3.) The depth of the lumbar plexus.
In the second part of the study 80 non-randomized patients received continuous psoas compartment blocks following general anesthesia for total hip replacement. Nerve stimulating needles were utilized to insert catheters at the junction of the lateral third and medial two thirds of a line between the midline and a parallel line through the posterior superior iliac spine at the level of L4. The spinous process of L4 was estimated to be approximately 1 cm cephalad to the upper edge of the iliac crests. Once catheters were positioned, patients received a 0.4 mL/kg loading dose of 0.2% ropivacaine with a continuous infusion of 0.2% ropivacaine at 0.15mL/kg/hr for 48 hours. Pain control and adverse effects were recorded.
Results
In the CT study, there was a significant difference between men and women in depth of the lumbar plexus from the skin (85 vs 70 mm). There was a positive correlation between body mass index and the skin-lumbar plexus distances. In contrast, there was no difference regarding the ratio of the distance from a parallel line through the spinous processes-to a parallel line through the lumbar plexus and the distance from a parallel line through the spinous processes to a parallel line through the posterior superior iliac spine-median value 0.68.
In the second part of the study, at 1 hour sensory blockade of the femoral, obturator and lateral femoral cutaneous nerves was 95%, 90%, and 85% respectively. At 24 hours, the block rates were 88%, 88% and 85%. Patients reported low visual analog pain scales throughout the 48-hour study period.
Comments
Since there was no control group to compare analgesic requirements, the clinical portion of this study is difficult to evaluate. However, there appears to be great value in the CT analysis of the lumbosacral anatomy and everyone who has an interest in psoas compartment blocks should read this interesting work. The authors have confirmed a general clinical impression, that the classic landmarks described for needle insertion for the psoas compartment block are too far lateral. L4 appears to be the appropriate level to perform the block, since the L3 approach has resulted in ipsilateral renal subcapsular hematoma. The study found a significant difference in the depth of the lumbar plexus from the skin in men compared with women, and the depth of the lumbar plexus was correlated with weight or BMI. Also, the distance from the transverse process of L4 and the lumbar plexus was very consistent at 18mm. Finally, the consistency of the ratio of the distance from the spinous process to the lumbar plexus to the distance from the spinous process to the posterior superior iliac spine (0.67) in men and women despite weight or BMI values allows the puncture to be performed perpendicularly to the skin in all planes without fear of entering the epidural space.
