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Peripheral regional analgesia with femoral catheter versus intravenous patient controlled analgesia after total knee arthroplasty: prospective randomized study

Introduction: The implantation of total knee prosthesis is considered to be one of the most painful surgical procedures in orthopedic surgery.Inadequate control of postoperative pain is associated with poor patient recovery, longer rehabilitation, extended hospital stay and higher cost of treatment. Uncontrolled pain leads to hormonal-metabolic stress response as well as to inflammatory response, which both have negative effects on other organ systems.The patients who undergo total knee arthroplasty are usually in the older age group with a decreased cardiac reserve and incipient impairments of other vital organ systems. This older age group has an increased sensitivity to medications. For postoperative analgesia, it is necessary to choose the method and analgesic with minimal side- effects. Hypothesis: The aim of this prospective, randomized study was to compare the effects of femoral analgesia (FA) with 0.25% levobupivacain and intravenous patient controlled analgesia (PCA) with morphine on postoperative pain assessed by visual-analog scale (VAS) score and their complications during the first 24 postoperative hours after the total knee arthroplasty (TKA). Secondary aim of the study included measuring/observing: morphine use, patient's satisfaction, active knee flexion on second postoperative day, operation duration and duration of hospital stay Methods: After the Ethics Committee of the University Hospital approved the study all patients gave written informed consent to participate. The 80 patients with ASA score of II or III were selected for TKA surgery. 9 patients were excluded, because femoral catheter fell out one hour after operation. The patients were randomized into two groups: group PCA (36 patients) and group FA (35 patients). Patients who had satisfied at least one of the following criteria were excluded from the study: previous vascular surgery in the region of femoral veins or arteries, confirmed coagulopathy, local infection, hepatic and renal insufficiency, dementia, body mass index (BMI) >30 kg/m2, allergy to local anesthetics, morphine and non-steroid anti inflamatory drugs, a previously diagnosed neurologic deficit and an ASA score>III. The femoral catheter was set before the spinal anesthesia with patients in the supine position, with a nerve stimulator (Stimuplex HNS 11, B.Braun, Germany) set to deliver a stimulus at a frequency of 2Hz and duration of 0.1 ms. The intensity of the current, initially set to 1.2 mA, was gradually decreased to 0.3 mA (<0.5 mA) while the stimulation of the femoral nerve was maintained. The puncture site was located 5 cm caudal to the inguinal ligament and one centimeter lateral to the femoral artery and then advanced in a lateral and posterior direction just distal to the inguinal ligament. The femoral nerve was identified by contractions of the quadriceps muscle, referred to as the “dancing” patella. The femoral nerve catheter was inserted from 5-10 cm beyond the tip of the needle in a cephalad direction. All orthopedics procedures were done in (under) spinal anesthesia with 0.5% levobupivacain. After the sensory recovery from spinal anesthesia and when the patients complained of pain (VAS higher than 3) group FA was given first a bolus dose of 8 ml 0.25%levobupivacain, then 5 mL per hour of 0.25% levobupivacain via a femoral catheter in addition to the intravenous dose of morphine: 5mg (patient weight <60kg) or 10 mg (patient weight >60 kg) if pain in the posterior part of the knee was higher than 3 points. Group PCA was given the patient controlled analgesia (PCA) pump, which contained morphine (concentration 1mg/ml ; “basal rate” 3 mg/h, bolus upon request 2 mg, with “lock out” interval of 8 minutes). Both groups received diclofenac 75 mg intravenous every 12 hours. The assessment of VAS was performed every 2 hours at rest and in motion. VAS score lower than or equal to 3 was considered good analgesia. Results: The only non-significant difference in postoperative VAS scores between the groups was observed 2 hours after operation. All other VAS scores in rest and motion differ significantly (P<0.001). The highest difference is 4 hours after the operation when group PCA had significantly higher VAS scores as compared to group FA (Table 1). Dynamics of VAS scores regarding measuring time and groups are shown in Fig 2 and 3. Changes in postoperative values of VAS scores (from 2h to 24h) during resting and motion were significant (P<0.001) in both groups respectively. There were no significant differences between group PCA and group FA regarding age, BMI, gender and ASA score distribution (Table 2) ; operation duration, duration of hospitalisation. Significant differences were noted only in the quantity of morphine used (higher values are in group PCA ; P<0.001) and in duration of tourniquet application (longer use in group FA ; P=0.013) (Table 3). Significantly more complications were recorded in group PCA (P<0.001): 28 (77, 8%) patients had gastrointestinal symptoms (nausea and vomiting), 21 (58.3%) had hemodynamic instability and 32 (88.9%) patients were moderately and highly sedated (response only to shouting or pain stimulus). There was no significant difference in heart rhythm disorders and in satisfaction with analgesia, although there were more satisfied patients in Group FA. Active motion (flexion over 60 degrees) occurred significantly more often in group FA, P<0.001 (Table 2). Discussion: Our results suggest that patients in group FA had significantly lower VAS score within the first 24 postoperative hours both at rest and in motion, less morphine use and less side effects or complications compared with group PCA. During the fourth postoperative hour the difference in VAS score between the groups had the greatest magnitude. The use of morphine in group FA was reduced by 60% within the first 24 postoperative hours. This study is subject to several methodological limitations. Firstly, the femoral catheter was inserted using a nerve stimulator, but without ultrasound control12, 13 because our anesthesiology unit does not have an ultrasound machine. Secondly, the assessment of pain and sensory analgesia was based on patients’ subjective assessment using VAS score. We did not use the “pin prick test” or other objective methods to estimate sensory analgesia. Analgesia was assessed only within the first 24 postoperative hours during each patient’s stay in the Intensive Care Unit. Conclusion: Femoral analgesia is an important part of multimodal balanced analgesia after TKA. It is a technique of choice for the postoperative analgesia after painful orthopedic surgery7. It contributes to a stronger analgesia and quicker postoperative rehabilitation15 with less side-effects16, less morphine use (“opiods sparing effect”)17 and more patient satisfaction.

Femoral analgesia; PCA; Total knee arthroplasty

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