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

Abstract

AIMSNo 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. METHODSTwelve 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 mg 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. RESULTSResults are given as mean (SD) for group R vs. group RE (95% CI of the difference). Total Cmax was 2.81 (0.94) mg ml -1 vs. 2.16 (0.21) mg 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) mg ml -1 vs. 0.12 (0.04) mg ml -1 (95% CI -0.04, 0.12). t1/2 was 6.82 (2.26) h vs. 5.48 (1.69) h (95% CI -1.23, 3.91). AUC was 28.35 (5.92) mg ml -1 h vs. 29.12 (7.34) mg ml -1 h (95% CI -9.35, 7.81). CONCLUSIONSFree serum concentrations of ropivacaine with and without epinephrine remained well below the assumed threshold of 0.56 mg ml -1 for systemic toxicity. Changes in pharmacokinetics with epinephrine co-administration did not reach statistical significance. WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT• For peripheral nerve blocks, larger doses of local anaesthetic than recommended are frequently used. In the absence of pharmacokinetic data, using higher than recommended doses may pose a medico-legal problem in cases of local anaesthetic systemic toxicity. WHAT THIS STUDY ADDS• This is the only study describing the pharmacokinetic profile in serum of 450 mg ropivacaine with and without epinephrine for combined sciatic/femoral nerve block. Free serum concentrations of ropivacaine in both groups remained well below the assumed threshold of 0.56 mg ml -1 for systemic toxicity.

Pharmacokinetics of 400 mg Locally Infiltrated Ropivacaine After Total Knee Arthroplasty Without Perioperative Tourniquet Use

“…17 This T max of 240 to 360 minutes seen with LIA is much later than the T max associated with peripheral nerve blocks. In a study using 450 mg ropivacaine with epinephrine 5 μg/mL for combined sciatic/femoral nerve block, the mean T max was 100 minutes, 18 and others have reported a mean T max of 80 minutes for lumbar plexus block and 38 minutes for combined lumbar plexus/sciatic nerve block using ropivacaine with epinephrine 2.5 μg/mL. 19 T max is largely determined by absorption from the site of injection and elimination; because differences in the elimination of ropivacaine between LIA and peripheral nerve blocks are unlikely, the most likely explanation for the difference in T max is that absorption with LIA is considerably slower than with peripheral nerve block.…”

Quadratus Lumborum Block

“…Although the duration of analgesic effect was not enhanced, the peak arterial levobupivacaine concentrations were lowered with epinephrine after TAPB 17 and combined femoral and sciatic nerve blocks. 18 Applying this technique can decrease C max and extend T max of QLB. Further study is needed for evaluating the value of epinephrine for QLB.…”

Chronological Changes in Ropivacaine Concentration and Analgesic Effects Between Transversus Abdominis Plane Block and Rectus Sheath Block

“…Epinephrine might reduce the risk to some extent, because it reduces absorption of injected local anesthetics, decreases Cmax and extends Tmax. 18,22,23 Both TAPB and RSB are effective against somatic pain. 2-5 However, the duration of the block differed between the 2 groups.…”