No correlation between minimal electrical charge at the tip of the stimulating catheter and the efficacy of the peripheral nerve block catheter for brachial plexus block: a prospective blinded cohort study.

BACKGROUND: Stimulating catheters offer the possibility of delivering an electrical charge via the tip of the catheter. This may be advantageous as it allows verifying if the catheter tip is in close proximity to the target nerve, thereby increasing catheter performance. This prospective blinded cohort study was designed to investigate whether there is a correlation between the minimal electrical charge at the tip of the stimulating catheter, and the efficacy of the peripheral nerve block (PNB) catheter as determined by 24 h postoperative morphine consumption. METHODS: Forty adult patients with ASA physical health classification I-III scheduled for upper extremity surgery under combined continuous interscalene block and general anesthesia were studied. Six patients were excluded from analysis.After inserting a stimulating catheter as if it were a non-stimulating catheter for 2-5 cm through the needle, the minimal electrical charge necessary to obtain an appropriate motor response was determined. A loading dose of 20 mL ropivacaine 0.75% ropivacaine was then administered, and postoperative analgesia was provided by a continuous infusion of ropivacaine 0.2% 8 mL.h-1 via the brachial plexus catheter, and an intravenous morphine patient-controlled analgesia (PCA) device.Main outcome measures include the minimal electrical charge (MEC) at the tip of the stimulating catheter necessary to elicit an appropriate motor response, and the efficacy of the PNB catheter as determined by 24 h postoperative PCA morphine consumption. RESULTS: Mean (SD) [range] MEC at the tip of the stimulating catheter was 589 (1414) [30 - 5000] nC. Mean (SD) [range] 24 h morphine consumption was 8.9 (9.9) [0-29] mg. The correlation between the MEC and 24 h postoperative morphine consumption was Spearman's Rho rs = -0.26, 95% CI -0.56 to 0.09. CONCLUSION: We conclude that there is no proportional relation between MEC at the tip of the blindly inserted stimulating catheter and 24 h postoperative morphine consumption. TRIAL REGISTRATION: Trialregister.nl identifier: NTR2328.

Pharmacokinetics of 450 mg ropivacaine with and without epinephrine for combined femoral and sciatic nerve block in lower extremity surgery. A pilot study.

AIMS: No pharmacokinetic data exist on doses of ropivacaine larger than 300 mg for peripheral nerve block in man, although in clinical practice higher doses are frequently used. The purpose of the present study was to describe the pharmacokinetic profile in serum of 450 mg ropivacaine with and without epinephrine in patients undergoing anterior cruciate ligament reconstruction. METHODS: Twelve patients were randomly allocated to receive a single shot combined sciatic/femoral nerve block with 60 ml of either ropivacaine 0.75% alone (group R, n = 6) or ropivacaine 0.75% plus epinephrine 5 µg ml(-1) (group RE, n = 6). Venous blood samples for total and free ropivacaine serum concentrations were obtained during 48 h following block placement. Pharmacokinetic parameters were calculated using a non-compartmental approach. RESULTS: Results are given as mean (SD) for group R vs. group RE (95% CI of the difference). Total Cmax was 2.81 (0.94) µg ml(-1) vs. 2.16 (0.21) µg ml(-1) (95% CI -0.23, 1.53). tmax was 1.17 (0.30) h vs. 1.67 (0.94) h (95% CI -1.40, 0.40). The highest free ropivacaine concentration per patient was 0.16 (0.08) µg ml(-1) vs. 0.12 (0.04) µg ml(-1) (95% CI -0.04, 0.12). t(1/2) was 6.82 (2.26) h vs. 5.48 (1.69) h (95% CI -1.23, 3.91). AUC was 28.35 (5.92) µg ml(-1) h vs. 29.12 (7.34) µg ml(-1) h (95% CI -9.35, 7.81). CONCLUSIONS: Free serum concentrations of ropivacaine with and without epinephrine remained well below the assumed threshold of 0.56 µg ml(-1) for systemic toxicity. Changes in pharmacokinetics with epinephrine co-administration did not reach statistical significance.

Autologous platelet gel in total knee arthroplasty: a prospective randomized study.

PURPOSE: Total knee arthroplasty (TKA) is often associated with major postoperative blood loss, postoperative pain, and impaired wound healing. The application of autologous platelet gel (APG), prepared from the buffy coat of a unit of autologous blood, has been advocated to improve haemostasis after surgery, to decrease perioperative blood loss, diminish postoperative pain and to enhance the wound healing process. This randomized controlled pilot study was developed to assess the effects of APG after total knee arthroplasty on blood loss, wound healing, pain, range of motion, and hospital stay. METHOD: A prospective, randomized observer blind controlled trial was performed. Forty patients with only osteoarthritis of the knee were scheduled to have a TKA, and they were randomized into two groups. Patients in the treatment group were all treated with the application of autologous platelet gel after the prosthesis was implanted. Patients in the control group were treated with the same protocol but no APG was used. RESULTS: Preoperative and postoperative Hb levels showed no significant difference and allogenic blood transfusions were not given in either group. Haematomas were significantly larger in the control group than in the platelet gel group (P = 0.03). The pain score at rest was higher in the control group on the 3rd day (P = 0.04). Wound healing disturbances were seen in four patients in the control group and in no patients in the APG group (n.s.). Range of motion of the knee was similar postoperatively. Hospital stay was 6.2 days in the APG and 7.5 days in the control group (n.s.). CONCLUSION: In this prospective randomized pilot study on APG in total knee arthroplasty, differences in favour of the use of platelet gel were found, but these were subjective evaluations, marginal in effect, or did not reach statistical significance. The use of drains might have decreased the concentration of delivered platelets and may have diminished the effect. However, in this study, a statistically significant clinically important effect in favour of platelet gel application was not found. Further studies with larger numbers of patients, and without the use of drains, are warranted to investigate the possible benefits of autologous platelet gel in total knee arthroplasty.

A comparison of the lateral and posterior approach for brachial plexus block.

BACKGROUND: Brachial plexus block by the posterior approach described by Pippa is not widely used in contrast to the lateral approach of Winnie. We compared the clinical efficacy of both approaches in a randomized prospective study. METHODS: Eighty patients, American Society of Anesthesiologists physical status I or II, scheduled for surgery of the shoulder or upper arm were randomized in 2 groups: lateral (Winnie, n = 40) or posterior approach (Pippa, n = 40). A single injection of ropivacaine 7.5 mg/mL, 0.5 mL/kg, was made after obtaining a motor response in the distribution of the axillary nerve at a current below 0.5 mA (2 Hz, 0.1 millisecond). Onset and distribution of analgesia and motor block were assessed at 5, 10, 15, 20, 30, and 60 minutes after the local anesthetic injection. Complete block was defined as anesthesia in all dermatomes C3-C6 at 60 minutes after injection. RESULTS: The posterior approach provided complete block in 36 patients (90%) and the lateral approach in 33 patients (83%). Corresponding motor block was similar in both approaches, but the block procedure time was faster in the posterior approach (6.2 [5.2-7.2] minutes v 8.4 [7.1-10.2] minutes; P < .001). Surgical success rate (posterior 95% v lateral 93%) and side effects were similar in both approaches. One complication (thoracic epidural block) was seen using the lateral approach, whereas none occurred in the posterior approach. There was no difference in patient satisfaction scores of the 2 approaches, which were equally high in both groups (posterior 98% v lateral 95%). CONCLUSION: Both approaches are comparable regarding clinical efficacy for anesthesia of the shoulder and upper arm.

Successful defibrillation immediately after the intravascular injection of ropivacaine.

PURPOSE: To report successful resuscitation of ventricular fibrillation induced by accidental intravascular injection of ropivacaine. CLINICAL FEATURES: A 15-yr-old healthy girl weighing 59 kg was scheduled for transposition of the tibial tuberosity under combined sciatic/three-in-one block. No premedication was given. In the induction room, an iv infusion was started, along with electrocardiogram monitoring, non-invasive blood-pressure measurement and pulse-oximetry. The sciatic nerve was found with the use of a nerve stimulator at the first attempt by the classical approach of Labat. Aspiration for blood was negative and the injection of ropivacaine 0.75% without epinephrine started. Convulsions, followed within seconds by ventricular fibrillation occurred at the end of the injection of 18 mL ropivacaine 0.75%. Oxygen was administered by face mask ventilation and immediate defibrillation was successful on the second attempt (2 x 200 joules). Within two minutes convulsions stopped and normal cardiac rhythm returned. Propofol and sufentanil were injected and a laryngeal mask inserted to start general anesthesia for surgery. Postoperatively no evidence of sciatic block could be demonstrated. The patient did not remember the event and was discharged the following day with no residual effects. CONCLUSION: This case report shows that ventricular fibrillation after unintentional intravascular injection of ropivacaine can be treated successfully when one is prepared and cardiac life support measures are taken immediately.