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Postoperative Patient-Controlled Local Anesthetic Administration at Home

1998; Lippincott Williams & Wilkins; Volume: 86; Issue: 1 Linguagem: Inglês

10.1213/00000539-199801000-00017

1526-7598

Narinder Rawal, Kjell Axelsson, Jan Hylander, Renée Allvin, Anders Amilon, Gunnar Lidegran, Jan Hällén,

Pediatric Pain Management Techniques

For most day-surgery patients, postoperative pain can be managed adequately at home with conventional oral analgesics, such as paracetamol, nonsteroidal antiinflammatory drugs (NSAIDs), and weak opioids (codeine, dextropropoxyphene). However, for moderate to severe pain, this treatment may be inadequate [1-4]. Our recent study of 1035 patients undergoing a variety of day-surgical procedures [5] showed that approximately 30% of patients experienced moderate to severe pain at home. Severe pain was experienced by many patients who underwent the following surgeries: orthopedic (knee, shoulder, iliac bone graft, maxillofacial, halux valgus), breast augmentation, inguinal hernia, and varicose veins. We describe a technique using an elastometric balloon pump, which allows the patient to self-administer local anesthetic analgesia at home. This study was undertaken to evaluate the safety and applicability of the technique in a wide range of surgical procedures. Methods Ethics committee approval was obtained for this preliminary prospective study of 70 patients undergoing a variety of day-surgical procedures (Table 1). Informed consent was obtained from each patient at the time of preoperative evaluation. The technique involves the placement of a multihole, thin (22-gauge) epidural catheter (B. Braun, Melsungen, Germany) subcutaneously into the surgical wound, subacromially, intraarticularly, or in the axillary brachial plexus sheath (Table 1). The catheter was tunneled 4-5 cm subcutaneously by the surgeon and firmly secured on the skin by using sterile tape (Proxi-Strip[registered sign]; Johnson & Johnson, New Brunswick, NJ). Axillary brachial plexus catheters were placed and secured in position by anesthesiologists. The catheters were introduced 3-5 cm within the sheath and secured to the skin by using transparent dressing and tape.Table 1: Use of Patient-Controlled Regional Analgesia After Various Surgical OperationsThese catheters were used for surgery and postoperative analgesia. They could be secured in less than 5 min. Using aseptic technique, the catheters were connected to a 50- or 100-mL elastometric (balloon) pump (Figure 1) with the appropriate concentration and volume of local anesthetic drug (Home pump[registered sign]; I-Flow Corporation, Lake Forest, CA). The balloon pump was filled with a volume of local anesthetic to provide 10 doses for postoperative pain management. The Home pump[registered sign] is designed and approved to deliver intravenous antibiotics and cytostatic drugs and costs approximately $15-$20. Postoperatively, when the patient feels pain, the local anesthetic infusion is started by opening the clamp (Figure 2a). The patient stops the infusion by closing the clamp after the prescribed time (usually 6 min) or earlier if pain relief is adequate (Figure 2b). When the patient no longer requires analgesia, he or she removes the tape, pulls out the catheter, and discards the pump. In most cases, the patient self-administers the first dose in the postanesthesia care unit (PACU).Figure 1: Use of the pump (arrow) in the patient's home.Figure 2: Self-administration of the local anesthetic solution by a patient. On opening the clamp (a), the solution starts running into the catheter. After the prescribed time (usually 6 min), the patient closes the clamp (confirmed by a clicking sound) to stop the infusion (b). The patient is encouraged to use a timer as a reminder to close the clamp.Bupivacaine 0.125% was used in brachial plexus catheters; in all other catheters, a 0.25% concentration was used. The 0.125% solution was used to reduce or avoid the risk of possible injury due to excessive motor block. The maximal volume of local anesthetic allowed for each administration was 2.5 mL for maxillofacial surgery, 5-10 mL for surgical wounds, and 10 mL for the remaining procedures. An appropriate pump (50 or 100 mL) filled with local anesthetic to provide 10 doses at home was given to the patient before discharge. The patient was instructed to avoid using the pump more than once every hour. Before using the technique at home, it was evaluated in 35 inpatients. These patients were given instructions, which were later provided in similar form to the home patients. The written instructions to the patients included information about: a) symptoms of local anesthetic overdosage; b) protection of the catheter and pump system during washing, showering, etc.; c) catheter removal before discarding the pump; and d) how to contact nurses and anesthesiologists. Additionally, the patient was given a form on which to record the following: pain intensity on a verbal scale (severe, moderate, mild, none) after each treatment, the clock time of each administration, the total number of times a local anesthetic was self-administered, use of "rescue" analgesic tablets (NSAIDs, acetaminophen/codeine, or acetaminophen/dextropropoxyphene), technical problems with the pump, and overall satisfaction/dissatisfaction (excellent, adequate, poor) with analgesia. Onset of analgesia was assessed from first administration of local anesthetic in the PACU and from patient comments. The duration of analgesia was evaluated from the clock time at each administration. The patient was given a stamped, self-addressed envelope in which to return the completed questionnaire within 2-3 days after surgery. A nurse made a follow-up call the day after surgery and inquired about the patient's general condition, pump function, satisfaction/dissatisfaction with analgesia, and suggestions for improving technique. Results Seventy patients received analgesia by self-administration of local anesthetic solution on demand. All patients (100%) returned the completed questionnaire. The results are based on data from inpatients, PACU, and patient comments from the questionnaire. None of the patients had any problems using the pump. The onset of analgesia was usually within 5 min but was longer (up to 15 min) in patients with brachial plexus and subacromial catheters. The duration of analgesia after each administration of local anesthetic varied from 2 to 8 h. Most patients required two to four administrations. Six patients did not use the pump at home because the first dose of local anesthetic in the hospital provided prolonged pain relief; these patients were not included in the data analysis. Pain relief was considered good to excellent by 57 (89%) patients, adequate by 4 (6%) patients, and poor by 3 (5%) patients. However, 4 patients complained that the total amount of medication was insufficient (all had received a 50-mL pump). Except for the above-mentioned 3 patients with poor analgesia and 4 patients who received an insufficient dose of local anesthetic, none required analgesic tablets. Follow-up calls confirmed that the technique was generally perceived as simple and effective. No technical problems were encountered. None of the patients reported any symptoms of local anesthetic toxicity. One patient commented that the act of removing the catheter was unpleasant. One patient with opioid dependency required unusually large doses (three doses of 20 mL 0.25% bupivacaine subacromially during a period of 1.5 h). Although this patient was asymptomatic, a bupivacaine level was drawn approximately 2 h after the first dose and was found to be 1.15 micro mol/L, which is well below toxic levels. Discussion Effective management of pain may make the difference between surgery being performed on an inpatient or day-care basis. Although NSAIDs, paracetamol, and weak opioids, such as codeine and dextroproxyphene, are adequate for mild to moderate pain, these drugs may be ineffective in patients with moderate to severe pain. Local anesthetic infiltration in a wound or close to peripheral nerves is not common; in several studies, it has been demonstrated as a highly effective analgesic technique [6-10]. Infiltration with local anesthetics modulates pain at the peripheral level by inhibiting the transmission of nociceptive impulses from the site of injury. The technique is generally considered to be simple, safe, and inexpensive. The main limitation to its widespread use is the need for repeated administration because of the short analgesic effect (usually two to six hours) of a single dose. Intermittent injections or continuous infusions through indwelling catheters in the wound area have been described for inpatients [6-10,11]. Our preliminary data show that this technique can also be used at home. This study demonstrates the safety, efficacy, and applicability of the technique in a wide range of surgical procedures. Although nearly all patients had adequate to excellent pain relief, the efficacy of this technique was not compared with that of oral analgesics. The major concern with this pump system is that the entire volume of local anesthetic will be delivered if the patient fails to close the clamp. To avoid this complication, the following steps were taken: a) oral and written information was given to the patient and the escort, b) the use of a timer was encouraged, c) the patient was informed that a clicking sound is heard when the clamp is closed, and d) the patient was instructed to close the clamp and contact an anesthesiologist if there was numbness of the tongue or tinnitus. The "worst-case scenario" is that all 50 mL of 0.125% or 0.25% bupivacaine is delivered (100 mL is used only for shoulder surgery), and although technically possible, this should not lead to any serious problems because the local anesthetic is delivered to peripheral tissue, the drug is delivered over a period of 1 h, and the total dose of bupivacaine is large but not excessive. The doses we used are far smaller than some reported in the literature. Single infiltration by 50 mL 0.25% bupivacaine after cholecystectomy [12,13] and repeated administration of 10 mL 0.25% bupivacaine every 4 hours for 48 hours [7,14] have been reported. Doses up to 40 mL 0.25% bupivacaine every 4 hours for 48 hours have been administered subcutaneously to treat pain after abdominal aortic surgery, and no signs of systemic toxicity were observed in any of these studies [16]. However, it may not be valid to compare the intermittent administration of large doses of local anesthetics and accidental administration of 50-100 mL of 0.125% or 0.25% bupivacaine within one hour. Other concerns may be the risk of delayed wound healing and infection. The latter may be particularly important for intraarticular technique. The literature does not support these concerns. Indeed, local anesthetic drugs have bacteriostatic and antimicrobial effects [17-19]. The surgeon tunnels the catheter under the skin so that it exits 3-5 cm from the wound. This procedure reduces the risk of infection and catheter dislodgment. The closed pump system described herein avoids repeated injections and handling of the catheter, thereby further reducing the risk of infection. A bacterial filter is included in the pump system (Figure 2), and an additional bacterial filter was used in this study. Nevertheless, the risk of infection at home needs to be studied in more detail. Although there were no complications in any of our 70 patients, we emphasize that our results are preliminary. Controlled trials are necessary to compare this technique with traditional methods and to evaluate the optimal concentration and volume of local anesthetic. The role of opioids and nonopioids, such as NSAIDs and clonidine, as adjuvants to local anesthetic drugs also needs to be studied.