New Devices and Application Strategies in Patient-Controlled Analgesia

New Devices and Application Strategies in Patient-Controlled Analgesia

NEW DEVICES AND APPLICATION STRATEGIES IN PATIENT-CONTROLLED ANALGESIA

O. Nutu¹, L.Chiriac², M.Gheorghe³,M.Popescu4

¹Hopital Foch Paris, ²Army’s Clinical Center for Cardiovascular Disease,

³University Titu Maiorescu Bucharest, 4EliasHospital Bucharest

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The Romanian Review Precision Mechanics, Optics & Mecatronics, 2008 (18), No. 34

New Devices and Application Strategies in Patient-Controlled Analgesia

Abstract – Patient-controlled analgesia (PCA) has develop into the gold standard for acute pain managing since it was first introduced, and its qualities have been discussed in a large amount of publications. This analysis summarizes the more recent developments, such as new application devices and strategies, including intranasal, spinal, and regional PCA.

Key Words – analgesia, patient-controlled, analgesics, opioids, local anesthetics

Introduction

This update will primarily discuss the most recent progresses in postoperative pain and underline the variability of drug use patterns in PCA. It will give attention on articles published since 2001.

Results

Most advantageous application modes for PCA were discussed from the very beginning. Over the years, it became evident that continuous, that is, demand-independent background infusions usually did not improve the quality of analgesia but increased overall opioid consumption with the risk of higher incidences of respiratory depression – a result which was recently reconfirmed in a study with nalbuphine PCA.

Greatest demand doses seem to exist for each opioid with respect to immediate onset of action, efficacy, and control of side effects. Variable dose PCA, as recommended by Owen et al., where patients have the choice between three demand buttons delivering 0.5–1.5 mg of morphine, are obviously only seldom used.

The concept of pharmacokinetically based PCA (PKPCA), where patients can adjust target controlled opioid plasma concentrations seems to be advocated only by some high-tech enthusiasts.

Tamsen’s Prominject was the first device to adjust background infusion rates according to the frequency of earlier demands, but clinical efficacy could not significantly be enhanced. This concept has recently caused new interest with the introduction of “rapidly learning” PCA devices, taking into account demand history and electronically registered pain scores.

Shieh et al. demonstrated for 25 extracorporeal shock-wave lithotripsy patients that a fuzzy logic PCA algorithm with alfentanil improved pain relief during conscious sedation and reduced opioid consumption. Infusion rate and bolus size were adjusted according to a look-up table that accepted the button-pressing history over the last lockout intervals. Study group patients had a mean delivery/demand ratio of 82%, compared with 60% in conventional PCA.

Useful in clinical practice is the modification of a Graseby 3300 PCA pump, as outlined by Murray et al. The authors changed the original handset so that the system could be activated by mouth with a light puff of air, which was very helpful in rheumatoid arthritis patients who lacked thenecessary motor skills for pressing the hand button.

This concept has previously been reportedalso for successful PCA in a quadriplegic patient.

Elastomeric devices were more or less continuouslyintroduced since PCA received worldwideattention. Cost considerations were notalways in favor of disposable mechanically (in comparison with electronically) controlledpumps, but the simple systems seem to havefound their place, particularly in ambulatorycare using local anesthetics. Banks andPavy reported good postoperative pain reliefafter cesarean section with a pethidine-primeddisposable epidural infuser. The nursing stafffound the device easy to prime and understand, the only drawback being the occasional incidence of equipment failure, and patients expressed a high level of satisfaction.

Capdevila et al. performed a direct comparison of electronic and elastomeric PCA pumps in 76 ambulatory patients after orthopedic surgery who used ropivacaine for pain control; they found less technical problems with the disposable devices and therefore higher patient’s acceptance.

The PCA principle was never restricted only to intravenous opioids and postoperative pain. Intranasal administration of lipophilic opioids has been shown to be an effective method of administration, which is devoid of major side effects. Extending earlier experience with alfentanil, butorphanol, fentanyl, oxycodone, pethidine, or sufentanil, Ward et al. recently investigated patient-controlled intranasal analgesia (PCINA) with diamorphine (heroin) in comparison with the intravenous route in 52 patients undergoing lower limb joint replacement surgery. PCINA patients had significantly higher VAS scores than those in the intravenous group, both at rest and on movement. However, significantly fewer patients in the intranasal group suffered episodes of vomiting.

Dale et al. came to comparable conclusions from asystematic review of intranasal analgesia; they believed that nasal administration of opioids had promising features, but was still in its infancy. Improvements of nasal sprayer devices and opioid formulations might improve clinical outcome.

PCEA was discussed at the first PCA workshop1 and has since the continuously been extended into an increasing number of indications. The most recent publications deal with labor analgesia (Petry et al. could not find a marked advantage in adding a basal rate infusion to PCEA using bupivacaine, sufentanil and epinephrine

Velickovic and Leicht described successful ropivacaine and fentanyl PCEA in a parturient with chronic inflammatory demyelinating polyneuropathy. Patientcontrolled intrathecal analgesia, on the other hand, is a relatively new technique.

Pavy demonstratedits successful use in two parturients where previous back surgery made epidural analgesia impractical; 22 gauge spinal catheters were used for the application of either bupivacaine and fentanyl or fentanyl, morphine, and clonidine, which confirmed earlier positive experience with fentanyl or bupivacaine in orthopedic patients.A large number of publications indicate special interest in the use of local anesthetics for peripheral nerve block. Patient-controlled regional analgesia (PCRA) has been reported for a variety of postoperative pain situations. For interscalene brachial plexus analgesia after open shoulder surgery, a mixture of bupivacaine, sufentanil, and clonidine was most effective as a combination of continuous infusion with PCA boluses. Rawal et al. found encouraging results with ambulatory brachial plexus PCRA after hand surgery.

Patients, using disposable elastomeric “home-pumps,” expressed high acceptance, with hardly any differences between 0.125% bupivacaine or 0.125% ropivacaine. None of the patients showed signs or symptoms of local anesthetic toxicity or catheter infection. According to the authors, patient selection, follow-up telephone call, and 24-hour access to Anesthesiology services are prerequisites for PCRA at home. Ilfeld et al. came to comparable conclusions with 0.2% ropivacaine using an infraclavicular brachial plexus perineural catheter and a portable infusion pump for outpatients undergoing moderately painful, upper extremity orthopedic surgery.

Borgeat et al. compared interscalene PCRA with 0.2% ropivacaine and 0.15% bupivacaine after major open shoulder surgery. For similar pain control, ropivacaine was associated with better preservationof strength in the hand and less paresthesia in the fingers. Pain scores were similar in the two groups at all times, and patient satisfaction was comparable. Successful use of PCRA was also published for postoperative pain relief after lower extremity surgery. In 45 patients after total knee arthroplasty, 0.125% bupivacaine with clonidine was administered via a femoral nerve sheath catheter either as a continuous infusionat 10 ml/h, as a continuous infusion at 5 ml/hplus PCRA boluses or as PCRA boluses only.

Reasonably low pain scores and supplemental analgesia, as well as side effects and acceptancewere comparable, but bupivacaine consumptionwas significantly less in the PCRA onlygroup. Comparable results were found in a later study with the addition of low dose sufentanil to the anesthetic mixture65 and in a larger trial with 140 patients published by Eledjam et al., using 0.2% ropivacaine. Low dose epinephrine did not alter the duration of 0.2% ropivacaine PCRA in a femoral 3-in-1 block.67 Continuous subgluteus sciatic nerve blocks in 50 patients recovering from orthopedic foot and ankle surgery were investigated by di Benedetto et al., who used either a 10 mL/h continuous infusion with 0.2% ropivacaine or a 5 mL/h basal rate with 5 mL bolus every 60 minutes. The quality of pain relief and patient acceptance was good in both groups, and none experienced complications.

Nine patients in the continuous group versus 7 PCRA patients required rescue morphine because of pain in the femoral dermatomes. Ropivacaine consumption was significantly less with PCRA. Continuous popliteal sciatic nerve block using ropivacaine PCRA provided good pain control and high acceptance in ambulatory patients having moderately painful, lower extremity orthopedic surgery, with a notable reduction of rescue analgesics and improved quality of sleep.

Shabat et al. demonstrated the usefulness of PCRA for intraarticular opioid application. A terminal 48-yearold woman with a pathological femoral neck fracture who was unsuitable for operative treatment because of her bad general status, received 0.25% bupivacaine as a continuous infusion and top-up doses of 4 mg intra-articular morphine. Pain scores, maximal before beginning of this treatment, were markedly reduced, and returned to maximum after the intra-articular catheter was removed. PCRA for wound infiltration with 0.25% bupivacaine, on the other hand, was not effective in decreasing postoperative pain or opioid requirements in a group of 50 patients undergoing major intra-abdominal surgery.

Conclusion

The concept of patient-controlled analgesia was one of the most important developmentsin pain management, not simply because it providedbetter analgesia to patients but also becauseit improved our understanding of pain and suffering, and because it forced medicalcare providers to no longer close their eyes.There might be more effective strategies foracute and chronic pain relief than intravenousopioids, but even this insight was strongly supported by the “incredible” results which continue to be produced in ever increasing numbers.

References

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The Romanian Review Precision Mechanics, Optics & Mecatronics, 2008 (18), No. 34