Plasma concentrations of ropivacaine given with or without epinephrine for brachial plexus block

A Comparative Analysis of Pain Control Methods after Ankle Fracture Surgery with a Peripheral Nerve Block: A Single-Center Randomized Controlled Prospective Study

Background and Objectives: Patients experience severe pain after surgical correction of ankle fractures. Although their exact mechanism is unknown, dexamethasone and epinephrine increase the analgesic effect of anesthetics in peripheral nerve blocks. This study aimed to compare the postoperative pain control efficacy of peripheral nerve blocks with ropivacaine combined with dexamethasone/epinephrine and peripheral nerve blocks with only ropivacaine and added patient-controlled analgesia in patients with ankle fractures. Materials and Methods: This randomized, controlled prospective study included patients aged 18-70 years surgically treated for ankle fractures between December 2021 and September 2022. The patients were divided into group A (n = 30), wherein pain was controlled using patient-controlled analgesia after lower extremity peripheral nerve block, and group B (n = 30), wherein dexamethasone/epinephrine was combined with the anesthetic solution during peripheral nerve block. In both groups, ropivacaine was used as the anesthetic solution for peripheral nerve block, and this peripheral nerve block was performed just before ankle surgery for the purpose of anesthesia for surgery. Pain (visual analog scale), patient satisfaction, and side effects were assessed and compared between the two groups. Results: The patients' demographic data were similar between groups. Pain scores were significantly lower in group B than in group A postoperatively. Satisfaction scores were significantly higher in group B (p = 0.003). There were no anesthesia-related complications in either group. Conclusions: Dexamethasone and epinephrine as adjuvant anesthetic solutions can effectively control pain when performing surgery using peripheral nerve blocks for patients with ankle fractures.

Comparison of plasma concentrations of levobupivacaine with and without epinephrine for thoracic paravertebral block: A randomised trial

BACKGROUND

Thoracic paravertebral block (TPVB) is effective for analgesia for unilateral thoracic surgery. However, since the paravertebral space is highly vascular, injection of local anaesthetics into the paravertebral space may induce systemic local anaesthetic toxicity. We examined the effect of addition of epinephrine to paravertebral levobupivacaine on its plasma concentration.

METHODS

In a randomised single blind trial, twenty-four male patients who were scheduled to undergo elective unilateral pulmonary lobectomy or segmentectomy under general anaesthesia combined with TPVB were enrolled in this study. They were randomly divided into two groups: one group received a single bolus thoracic paravertebral injection of 1 mg/kg of 0.25% levobupivacaine with 5 μg/mL epinephrine and the other group received a single bolus thoracic paravertebral injection of 1 mg/kg of 0.25% levobupivacaine alone. Arterial blood samples were obtained for plasma levobupivacaine assay after injection. The peak plasma concentration (Cmax) and the time to peak plasma concentration (Tmax), for levobupivacaine were calculated.

RESULTS

There were no significant differences in patients' characteristics between the two groups. The mean arterial Cmax values of levobupivacaine were 0.48 ± 0.11 μg/mL with epinephrine and 0.71 ± 0.31 μg/mL without epinephrine (P = 0.041). The mean arterial Tmax values of levobupivacaine were 46.0 ± 35.6 min with epinephrine and 12.0 ± 7.2 min without epinephrine (P = 0.005).

CONCLUSION

The addition of 5-μg/mL epinephrine to a single bolus thoracic paravertebral injection of 1-mg/kg levobupivacaine significantly decreased Cmax and delayed Tmax of levobupivacaine. The addition of epinephrine to levobupivacaine may be a useful strategy to reduce systemic levobupivacaine toxicity.

CLINICAL TRIAL REGISTRATION NUMBER

UMIN 000021942.

Dexamethasone and Clonidine, but not Epinephrine, Prolong Duration of Ropivacaine Brachial Plexus Blocks, Cross-Sectional Analysis in Outpatient Surgery Setting

Objective

The primary aim of this study is to determine the effect of adding dexamethasone, clonidine or both with and without epinephrine to ropivacaine and bupivacaine brachial plexus blocks.

Design

Observational study of prospectively collected data.

Setting

Single academic outpatient surgery center.

Methods

We evaluated 5,515 patient entries who received brachial plexus block (BPB). Multiple, rescue, unsuccessful, and distal nerve blocks of the upper extremity were excluded. The duration was calculated from the time the block was performed until the resolution of the block by patient report. Block durations were compared using Analysis of Variance.

Results

After exclusions, 3,706 nerve blocks were analyzed. The median concentration of ropivacaine used was 0.5%. Both clonidine and dexamethasone significantly increased block duration by 1.1 and 3.0 hours, respectively. Combining clonidine and dexamethasone with ropivacaine increased block duration by 6.2 hours (p<0.001) when compared to ropivacaine alone. Dexamethasone and Clonidine increased block duration by 5.2 hours (p<0.001) when compared to clonidine alone and by 3.2 hours (p<0.001) compared to dexamethasone alone. The addition of epinephrine to any of the adjuvants made no statistically significant difference to the duration of action except when it was added to dexamethasone.

Summary

For brachial plexus blocks, epinephrine did not affect the duration of analgesia when added to ropivacaine. Epinephrine did not enhance the observed increase of block duration induced by clonidine or the combination of clonidine and dexamethasone. The most block duration enhancement was observed when combination of clonidine and dexamethasone were added to ropivacaine.

Adjuvants to local anesthetics: Current understanding and future trends

Although beneficial in acute and chronic pain management, the use of local anaesthetics is limited by its duration of action and the dose dependent adverse effects on the cardiac and central nervous system. Adjuvants or additives are often used with local anaesthetics for its synergistic effect by prolonging the duration of sensory-motor block and limiting the cumulative dose requirement of local anaesthetics. The armamentarium of local anesthetic adjuvants have evolved over time from classical opioids to a wide array of drugs spanning several groups and varying mechanisms of action. A large array of opioids ranging from morphine, fentanyl and sufentanyl to hydromorphone, buprenorphine and tramadol has been used with varying success. However, their use has been limited by their adverse effect like respiratory depression, nausea, vomiting and pruritus, especially with its neuraxial use. Epinephrine potentiates the local anesthetics by its antinociceptive properties mediated by alpha-2 adrenoreceptor activation along with its vasoconstrictive properties limiting the systemic absorption of local anesthetics. Alpha 2 adrenoreceptor antagonists like clonidine and dexmedetomidine are one of the most widely used class of local anesthetic adjuvants. Other drugs like steroids (dexamethasone), anti-inflammatory agents (parecoxib and lornoxicam), midazolam, ketamine, magnesium sulfate and neostigmine have also been used with mixed success. The concern regarding the safety profile of these adjuvants is due to its potential neurotoxicity and neurological complications which necessitate further research in this direction. Current research is directed towards a search for agents and techniques which would prolong local anaesthetic action without its deleterious effects. This includes novel approaches like use of charged molecules to produce local anaesthetic action (tonicaine and n butyl tetracaine), new age delivery mechanisms for prolonged bioavailability (liposomal, microspheres and cyclodextrin systems) and further studies with other drugs (adenosine, neuromuscular blockers, dextrans).

Epinephrine Affects Pharmacokinetics of Ropivacaine Infiltrated Into Palate

Pulpal anesthesia success rates for ropivacaine following maxillary infiltration anesthesia seem to be low. We investigated the hypothesis that the addition of epinephrine would affect the pharmacokinetics of ropivacaine by retaining ropivacaine in the mucosa of the injected area through the time-dependent distribution of ropivacaine in the rat maxilla and serum following maxillary infiltration anesthesia using (3)H-labeled ropivacaine. We then examined the vasoactivity of ropivacaine with or without epinephrine on local peripheral blood flow. The addition of epinephrine to ropivacaine increased ropivacaine concentrations in the palatal mucosa and adjacent maxilla by more than 3 times that of plain ropivacaine at 20 minutes. By observing the autoradiogram of (3)H-ropivacaine, plain ropivacaine in the maxilla was remarkably reduced 20 minutes after injection. However, it was definitely retained in the palatal mucosa, hard palate, adjacent maxilla, and maxillary nerve after the administration with epinephrine. Ropivacaine with epinephrine significantly decreased labial blood flow. This study suggests that 10 μg/mL epinephrine added to 0.5% ropivacaine could improve anesthetic efficacy and duration for maxillary infiltration anesthesia over plain ropivacaine.

The efficacy of simultaneous bilateral axillary brachial plexus block under the guidance of neurostimulator or ultrasound: a prospective study

PURPOSE

This study was designed to investigate the risk of local anesthetic toxicity and efficacy of simultaneous bilateral axillary brachial plexus block performed under the guidance of ultrasound or a neurostimulator.

METHODS

One hundred and twenty patients who were anesthetized with bilateral axillary plexus block simultaneously between February 2012 and March 2014 were enrolled in the study. The patients were anesthetized under the guidance of a neurostimulator (group N, n = 60) or ultrasound (group U, n = 60). The block performance time, procedure-related pain, adverse events, total and free plasma concentrations of ropivacaine, and other data were recorded. The comparison was analyzed statistically.

RESULTS

The block performance time, and onset of the sensory and motor block, of group N was longer than that of group U (p < 0.001). The procedure-related pain of group N was more serious than that of group U (p < 0.05). The patient satisfaction rate of group U was higher than that of group N (p < 0.05). The total plasma concentrations of ropivacaine in group N were comparable to those of group U, except for the value at 50 min after injection (p < 0.05). The free plasma concentrations of ropivacaine of group N at 5 min were significantly higher than that of group U (p < 0.001). No apparent serious adverse events were observed perioperatively in both groups.

CONCLUSIONS

Simultaneous bilateral axillary brachial plexus block guided by neurostimulator or ultrasound in bilateral distal upper extremity surgery seems to have a low risk of local anesthetic toxicity and to be effective. The ultrasound-guided block is superior in terms of providing the same degree of anesthesia with shorter duration, less pain, and faster onset of sensory and motor blockades, which is important in clinical practice.

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.

Effects of increasing the dose of ropivacaine on vertical infraclavicular block using neurostimulation

BACKGROUND

Use of an infraclavicular block is appropriate for surgery of the upper limb. However, it does not consistently block the entire brachial plexus. The aim of this study was to investigate whether increasing the dose of ropivacaine could enhance the success rate, onset time, and efficacy of the sensory and motor block during the use of a vertical infraclavicular block using neurostimulation in upper limb surgery.

METHODS

TWO HUNDREDS AND TEN PATIENTS WERE PROSPECTIVELY RANDOMIZED INTO THREE GROUPS: Group 1 (30 ml of 0.5% ropivacaine; n = 70), Group 2 (40 ml of 0.5% ropivacaine; n = 70), and Group 3 (40 ml of 0.75% ropivacaine; n = 70). Patients in each group received a vertical infraclavicular block using neurostimulation and obtained a distal motor response of the ulnar or median nerve. Recorded outcome measures included block success rate, onset time, sensory and motor blocks, and adverse events.

RESULTS

No differences were found in the block success rate among the three groups (92.8%, 97.1%, and 94.2% for Groups 1, 2, and, 3, respectively; P = 0.346). There were no significant differences in onset time (P = 0.225) among groups, nor was there enhancement in the sensory block, but the motor block was enhanced. Local anesthetic toxicity was observed in five female patients from group 3 (P = 0.006).

CONCLUSIONS

Although the efficacy of the motor block was significantly improved, success rate, onset time, and efficacy of sensory block were not enhanced significantly among groups despite differences in volume and volume/concentration of the local anesthetic.

Paravertebral blocks

PVB remains an underused block. It is easy to perform reliable and effective blocks for a wide variety of applications both for acute or chronic pain. As evidence continues to be published showing the advantages of PVB versus traditional methods of pain control, it is hoped that PVB will become part of the standard repertoire of blocks used in teaching hospitals and in private practice.

Ultrasound-guided supraclavicular brachial plexus block in pediatric patients -A report of four cases-

Supraclavicular brachial plexus blocks are not common in pediatric patients due to the risk of pneumothorax. Ultrasonography is an important tool for identifying nerves during regional anesthesia. Directly visualizing the target nerves and monitoring the distribution of the local anesthetic are potentially significant. In addition, ultrasound monitoring helps avoid complications, such as inadvertent intravascular injection or pneumothorax. This paper reports four cases of pediatric patients who received ultrasound-guided supraclavicular brachial plexus block for upper limb surgery.

Regional Anaesthesia for Bilateral Upper Limb Surgery: A Review of Challenges and Solutions

Regional anaesthesia for bilateral upper limb surgery can be challenging, yet surgeons are becoming increasingly interested in performing bilateral procedures at the same operation. Anaesthetists have traditionally avoided bilateral brachial plexus block due to concerns about local anaesthetic toxicity, phrenic nerve block and pneumothorax. We discuss these three concerns and review whether advances in ultrasound guidance and nerve catheter techniques should make us reconsider our options. A search of Medline and EMBASE from 1966 to January 2009 was conducted using multiple search terms to identify techniques of providing anaesthesia or analgesia for bilateral upper limb surgery and potential side-effects. Ultrasound imaging and nerve catheter techniques have led to a reduction in dose requirements for effective blocks without side-effects. Effective regional anaesthesia can be performed for bilateral surgery while remaining within recommended safe dose limits. Spacing blocks apart in time can further reduce potential toxicity issues, such that peak absorption rates for each block do not coincide. Since phrenic nerve block remains an issue even with low doses of local anaesthesia, bilateral interscalene blocks are still not recommended. Peripheral nerve blocks have excellent safety profiles and are ideal for ultrasound guidance. Regional anaesthesia can be a suitable option for bilateral upper limb surgery.

Upper extremity regional anesthesia: essentials of our current understanding, 2008

Brachial plexus blockade is the cornerstone of the peripheral nerve regional anesthesia practice of most anesthesiologists. As part of the American Society of Regional Anesthesia and Pain Medicine's commitment to providing intensive evidence-based education related to regional anesthesia and analgesia, this article is a complete update of our 2002 comprehensive review of upper extremity anesthesia. The text of the review focuses on (1) pertinent anatomy, (2) approaches to the brachial plexus and techniques that optimize block quality, (4) local anesthetic and adjuvant pharmacology, (5) complications, (6) perioperative issues, and (6) challenges for future research.

The pharmacokinetics of ropivacaine after four different techniques of brachial plexus blockade

Arterial plasma concentrations of ropivacaine were measured after brachial plexus blockade using four different approaches: lateral interscalene (Winnie), posterior interscalene (Pippa), axillary and vertical infraclavicular. Four groups of 10 patients were given a single 3.75 mg.kg(-1) injection of ropivacaine 7.5 mgxml(-1). The pharmacokinetics of ropivacaine were evaluated for 1 h after local anaesthetic injection. The supraclavicular techniques (lateral and posterior) were associated with earlier and higher peak plasma concentrations of local anaesthetic than the infraclavicular techniques (axillary and vertical infraclavicular): mean (SD) values = 3.30 (0.65) microgxml(-1) vs 2.55 (0.62) microgxml(-1) (p = 0.001) in 13.4 (6.9) min vs 25.0 (10.8) min (p = 0.0002). More ropivacaine is taken up by the systemic circulation in the first hour after the supraclavicular approaches; the mean (SD) area under the concentration-time curve was larger: 2.63 (0.51) microgxml(-1).h vs 2.10 (0.49) microgxml(-1).h (p = 0.002). These results show that the technique used for brachial plexus blockade significantly influences the systemic uptake of ropivacaine.

Seminars: Local and regional anesthesia for thyroid surgery

BACKGROUND

Thyroid surgery is performed by a large number of surgeons with varying experience in thyroidectomy. The standard technique involves the use of general anesthesia, which provides patient comfort and virtually unlimited time to conduct the operation. Historically, thyroid surgery was conducted under local anesthesia by surgeons with significant expertise in the treatment of thyroid diseases. Over the past decade, there has been a renewed interest in the art of performing thyroidectomy under local/regional anesthesia in some specialized high volume endocrine surgery centers.

METHODS

Here we review the indications and contraindications and technical considerations for performing thyroidectomy under local or regional anesthesia.

RESULTS AND CONCLUSION

Local and regional anesthesia is safe and well tolerated for the majority of thyroid surgery.

The pharmacokinetics of ropivacaine in hepatic and renal insufficiency

In patients with chronic end-stage liver disease, the peak plasma concentrations of ropivacaine after a single intravenous ropivacaine dose are similar to those in healthy subjects. However, patients with end-stage liver disease have about a 60% lower mean ropivacaine clearance than healthy subjects and are thus expected to have over two-fold higher steady-state ropivacaine plasma concentrations during a continuous ropivacaine infusion. The peak plasma concentrations of ropivacaine after an axillary plexus block in uraemic patients are considerably higher than those in non-uraemic patients. However, uraemic patients have significantly higher alpha-1-acid glycoprotein plasma concentrations than non-uraemic patients, and the peak plasma concentrations of free ropivacaine (related to toxicity) are similar in both groups. The pharmacokinetics of intravenously administered ropivacaine in patients with renal insufficiency and the possibility of clinically significant (S)-2',6'-pipecoloxylidide metabolite accumulation during continuous or repeated ropivacaine administration in these patients remain to be clarified.

Plasma Ropivacaine Levels Following Scalp Block for Awake Craniotomy

The plasma levels of ropivacaine HCl with 5 mcg/mL epinephrine were measured in 10 patients following scalp blockade for awake craniotomy. A mean dose of 260 mg (3.6 mg/kg) resulted in peak plasma concentrations of 1.5 +/- 0.6 mcg/mL, with a median time to peak plasma concentration of 15 minutes. The pattern of rise of plasma level was similar in all patients and rapid compared with other regional blocks (epidural, intercostal, and axillary brachial plexus block). Despite this rapid rise of plasma level, no signs of cardiovascular or central nervous system toxicity were observed. In this group of patients undergoing awake craniotomy for excision of lesions in the eloquent areas of the cerebral cortex, ropivacaine HCl with epinephrine appeared to be a safe and effective local anesthetic agent in the dosages used.

Benefit-Risk Assessment of Ropivacaine in the Management of Postoperative Pain

Ropivacaine is a long-acting amide-type local anaesthetic, released for clinical use in 1996. In comparison with bupivacaine, ropivacaine is equally effective for subcutaneous infiltration, epidural and peripheral nerve block for surgery, obstetric procedures and postoperative analgesia. Nevertheless, ropivacaine differs from bupivacaine in several aspects: firstly, it is marketed as a pure S(-)-enantiomer and not as a racemate, and secondly, its lipid solubility is markedly lower. These features have been suggested to significantly improve the safety profile of ropivacaine, and indeed, numerous studies have shown that ropivacaine has less cardiovascular and CNS toxicity than racemic bupivacaine in healthy volunteers. Extensive clinical data have demonstrated that epidural 0.2% ropivacaine is nearly identical to 0.2% bupivacaine with regard to onset, quality and duration of sensory blockade for initiation and maintenance of labour analgesia. Ropivacaine also provides effective pain relief after abdominal or orthopaedic surgery, especially when given in conjunction with opioids or other adjuvants. Nevertheless, epidurally administered ropivacaine causes significantly less motor blockade at low concentrations. Whether the greater degree of blockade of nerve fibres involved in pain transmission (Adelta- and C-fibres) than of those controlling motor function (Aalpha- and Abeta-fibres) is due to a lower relative potency compared with bupivacaine or whether other physicochemical properties or stereoselectivity are involved, is still a matter of intense debate. Recommended epidural doses for postoperative or labour pain are 20-40 mg as bolus with 20-30 mg as top-up dose, with an interval of >or=30 minutes. Alternatively, 0.2% ropivacaine can be given as continuous epidural infusion at a rate of 6-14 mL/h (lumbar route) or 4-10 mL/h (thoracic route). Preoperative or postoperative subcutaneous wound infiltration, during cholecystectomy or inguinal hernia repair, with ropivacaine 100-175 mg has been shown to be more effective than placebo and as effective as bupivacaine in reducing wound pain, whereby the vasoconstrictive potency of ropivacaine may be involved. Similar results were found in peripheral blockades on upper and lower limbs. Ropivacaine shows an identical efficacy and potency to that of bupivacaine, with similar analgesic duration over hours using single shot or continuous catheter techniques. In summary, ropivacaine, a newer long-acting local anaesthetic, has an efficacy generally similar to that of the same dose of bupivacaine with regard to postoperative pain relief, but causes less motor blockade and stronger vasoconstriction at low concentrations. Despite a significantly better safety profile of the pure S(-)-isomer of ropivacaine, the increased cost of ropivacaine may presently limit its clinical utility in postoperative pain therapy.

Cardiac arrest after interscalene brachial plexus block with ropivacaine and lidocaine

Serious adverse reactions to ropivacaine and lidocaine are rare. In this report, we describe a case of sudden cardiac arrest after an interscalene brachial plexus block with a mixture of 150 mg of ropivacaine and 360 mg of lidocaine in a previously healthy, 34-year-old, 97-kg man. Severe hypotension occurred after successful resuscitation, necessitating an infusion of epinephrine. The patient developed pulmonary oedema, and was mechanically ventilated for 22 h. He eventually made a good recovery. We conclude that although ropivacaine and lidocaine are often considered relatively safe local anesthetics, serious cardiovascular complications can occur after the use of these drugs.

Concept for postoperative analgesia after pedicled TRAM flaps: continuous wound instillation with 0.2% ropivacaine via multilumen catheters. A report of two cases

Pedicled TRAM flap surgery is a complex procedure characterised by an extensive wound site. We present two patients with efficient postoperative pain relief by continuous wound instillation of ropivacaine 0.2% via two multilumen catheters. The catheters were placed subcutaneously before the wound closure through the umbilicus into the abdominal wound, and under the autologous flap into the breast. Each multilumen catheter provides even distribution for local anaesthetics over 12.5 cm. At the end of surgery, patients received a single shot dose of local anaesthetic via the pain catheters. After surgery the continuous infusion of ropivacaine 0.2% was commenced at a rate of 10 ml/h per catheter. Pain scores at rest and on coughing were low on the first postoperative day, and later zero. No medication for breakthrough pain was required throughout the recovery period, and the patients experienced no adverse events linked to the analgesia scene. Patient satisfaction was excellent, and quality of recovery score was superior.

The effect of the addition of epinephrine on early systemic absorption of epidural ropivacaine in humans

The addition of epinephrine to ropivacaine has not been recommended because ropivacaine has intrinsic vasoconstrictor properties. However, few pharmacokinetic data are available on the addition of epinephrine to epidural ropivacaine in humans. In this prospective, double-blinded study, we randomized patients having elective abdominal hysterectomy to receive epidural ropivacaine 1.5 mg/kg, diluted in 15 mL, either with (epinephrine group, n = 12) or without (plain group, n = 12) epinephrine 5 microg/mL and then measured arterial and venous plasma concentrations of ropivacaine at intervals up to 180 min. We found that arterial and venous plasma ropivacaine concentrations were smaller in the epinephrine group compared with the plain group in the first 60 min after the drug administration (P < 0.01). Mean (+/- SD) maximum total plasma ropivacaine concentration was smaller in the epinephrine group (arterial, 0.92 +/- 0.32 microg/mL; venous, 0.82 +/- 0.33 microg/mL) compared with the plain group (1.31 +/- 0.39 microg/mL and 1.31 +/- 0.50 microg/mL, respectively; P = 0.01). Time to maximum total plasma ropivacaine concentration was not significantly different between groups (mean +/- SD; arterial, 16 +/- 2 min; venous, 23 +/- 2 min in the epinephrine group versus 9 +/- 2 min and 12 +/- 3 min, respectively, in the plain group; P = 0.08). Arterial plasma ropivacaine concentrations were larger than venous concentrations during the first hour (P < 0.01); the arterio-venous difference decreased exponentially, and the rate and magnitude of this decrease was unaffected by epinephrine. We conclude that the addition of epinephrine 5 microg/mL to ropivacaine reduced the early systemic plasma concentrations of ropivacaine after epidural injection and may be useful for decreasing the risk of toxicity from systemic absorption of epidural ropivacaine.

IMPLICATIONS

The addition of epinephrine 5 microg/mL to epidural ropivacaine reduced the systemic arterial and venous plasma concentrations of ropivacaine in the first hour and the maximum plasma concentration of ropivacaine. Epinephrine may be a useful additive for reducing the risk of systemic toxicity when large doses of ropivacaine are given epidurally.

Perioperative interscalene blockade: an overview of its history and current clinical use

Use of single-dose and continuous interscalene brachial plexus block (ISB) are gaining widespread popularity. When compared with general anesthesia, ISB has been reported to provide superior postoperative analgesia with fewer side effects, and it is associated with greater patient satisfaction. Anatomical landmarks are readily identifiable, which contributes to the ease of performing this block. In the future, we anticipate increased use of continuous interscalene catheters or injection of biodegradable local anesthetic impregnated microspheres to provide prolonged perioperative outpatient analgesia.

Treatment of distal colitis with local anaesthetic agents

The results of clinical and experimental studies on topical treatment of distal colitis with local anaesthetic agents are summarized. The original observation was an adrenergic hyperinnervation of the inflamed mucosa (hyperinnervation hypothesis). In order to silence local nervous reflexes, the mucosa was treated topically with 2% lidocaine gel. The clinical results are promising and no side effects have been observed. The relapse rate is relatively high and related to the duration of treatment. In studies of experimental colitis a potential antagonism between harmful adrenergic nerves (vasoconstrictor substances and proinflammatory cytokines) and mucosa-protective visceral afferents (antiinflammatory cytokines) in the pathogenesis of colitis is intriguing. Other studies have emphasized the importance of neutrophils for causing damage to the colon epithelium (neutrophil hypothesis) and local anaesthetics have potent effects on several steps of the inflammatory response in addition to the nervous blockade.

The pharmacokinetics and pharmacodynamics of bupivacaine-loaded microspheres on a brachial plexus block model in sheep

We evaluated bupivacaine-loaded microspheres (B-Ms) using a brachial plexus block model in sheep. In the first step, pharmacokinetic characterization of 75 mg bupivacaine hydrochloride (B-HCl) (IV infusion and brachial plexus block) was performed (n = 12). In the second step, a brachial plexus block dose response study of B-HCl was performed with 37.5 mg, 75 mg, 150 mg, 300 mg, and 750 mg. As a comparison, evaluations were performed using a 750-mg bupivacaine base (B). In the third step, evaluations of brachial plexus block were performed with B-Ms (750 mg of B as B-Ms) using two formulations, 60/40 and 50/50 (w/w %); drug-free microspheres were also evaluated. Toxicity evaluations were also performed after IV administration of B-HCl (750 mg and 300 mg), B-Ms (750 mg), and drug-free microspheres (30 mL over 1 min). As the B-HCl dose increased, the time of onset of block decreased and the duration of complete motor blockade increased at the expense of an increase in bupivacaine plasma concentrations. The time of maximum concentration appeared to be independent of the B-HCl dose. In brachial plexus block, a 37.5-mg dose of B-HCl did not induce motor blockade whereas a dose of 750 mg of B-HCl was clinically toxic. In the case of IV administration, doses of 300 mg of B-HCl were as toxic as 750 mg of B-HCl. Compared with the 75 mg of B-HCl administration for brachial plexus block, administration of 750 mg of B as B-Ms increased the duration of complete motor blockade without significant difference in maximum concentration. No significant clinical difference between the two formulations of B-Ms was demonstrated. The IV administration of B-Ms was safe. We conclude that the controlled release of bupivacaine from microspheres prolonged the brachial plexus block without obvious toxicity.

IMPLICATIONS

Administration of 750 mg of bupivacaine as loaded-microspheres resulted in prolongation of brachial plexus block in sheep. The peak plasma concentration was not significantly larger than that obtained with 75 mg of plain bupivacaine. The motor blockade was increased more than six times compared with 75 mg plain bupivacaine.

A comparison of 1% prilocaine with 0.5% ropivacaine for outpatient-based surgery under axillary brachial plexus block

We compared the use of 1% prilocaine with 0.5% ropivacaine for axillary brachial plexus anesthesia in a double-blinded manner in day-stay patients to determine the better of the two local anesthetics in terms of onset time and duration of motor block. Sixty patients scheduled for outpatient upper-limb surgery were allocated randomly to receive either prilocaine (28 patients) or ropivacaine (32 patients) at a volume of 0.7 mL/kg. The brachial plexus was located with a plexus needle and nerve stimulator. By 20 min after injection of prilocaine or ropivacaine, there was no difference in analgesic effect. By this time, it was apparent whether or not a block was going to be adequate for surgery. Pain returned after a mean of 278 min (SD 111 min; range, 160-630 min) with prilocaine as compared with 636 min (SD 284 min; range, 210-1440 min) with ropivacaine. Analgesia use was similar in both groups. Duration of motor block with prilocaine was a mean of 254 min (SD 62 min; range, 130-385 min), as compared with 642 min (SD 199 min; range, 350-1080 min) with ropivacaine. We conclude that there is no clinically important difference between 1% prilocaine and 0.5% ropivacaine in time to onset of axillary brachial plexus block when they are injected in equal volumes. There is a significantly longer duration of action with ropivacaine, which may make it less suitable for day-stay upper-limb surgery because of the handicap from reduced muscle power.

IMPLICATIONS

This study compares two local anesthetics to determine which is most suitable for day-stay upper-limb surgery under axillary brachial plexus block. Prilocaine 1% is more suitable than ropivacaine 0.5% because of a more prolonged duration of action of ropivacaine, although this could be useful in other circumstances.

Double-blind comparison of ropivacaine 7.5 mg ml(-1) with bupivacaine 5 mg ml(-1) for sciatic nerve block

Two groups of 12 patients had a sciatic nerve block performed with 20 ml of either ropivacaine 7.5 mg ml(-1) or bupivacaine 5 mg ml(-1). There was no statistically significant difference in the mean time to onset of complete anaesthesia of the foot or to first request for post-operative analgesia. The quality of the block was the same in each group. Although there was no statistically significant difference in the mean time to peak plasma concentrations the mean peak concentration of ropivacaine was significantly higher than that of bupivacaine. There were no signs of systemic local anaesthetic toxicity in any patient in either group.

Ropivacaine: an update of its use in regional anaesthesia

Ropivacaine is a long-acting, enantiomerically pure (S-enantiomer) amide local anaesthetic with a high pKa and low lipid solubility which blocks nerve fibres involved in pain transmission (Adelta and C fibres) to a greater degree than those controlling motor function (Abeta fibres). The drug was less cardiotoxic than equal concentrations of racemic bupivacaine but more so than lidocaine (lignocaine) in vitro and had a significantly higher threshold for CNS toxicity than racemic bupivacaine in healthy volunteers (mean maximum tolerated unbound arterial plasma concentrations were 0.56 and 0.3 mg/L, respectively). Extensive clinical data have shown that epidural ropivacaine 0.2% is effective for the initiation and maintenance of labour analgesia, and provides pain relief after abdominal or orthopaedic surgery especially when given in conjunction with opioids (coadministration with opioids may also allow for lower concentrations of ropivacaine to be used). The drug had efficacy generally similar to that of the same dose of bupivacaine with regard to pain relief but caused less motor blockade at low concentrations. Lumbar epidural administration of 20 to 30ml ropivacaine 0.5% provided anaesthesia of a similar quality to that achieved with bupivacaine 0.5% in women undergoing caesarean section, but the duration of motor blockade was shorter with ropivacaine. For lumbar epidural anaesthesia for lower limb or genitourinary surgery, comparative data suggest that higher concentrations of ropivacaine (0.75 or 1.0%) may be needed to provide the same sensory and motor blockade as bupivacaine 0.5 and 0.75%. In patients about to undergo upper limb surgery, 30 to 40ml ropivacaine 0.5% produced brachial plexus anaesthesia broadly similar to that achieved with equivalent volumes of bupivacaine 0.5%, although the time to onset of sensory block tended to be faster and the duration of motor block shorter with ropivacaine. Ropivacaine had an adverse event profile similar to that of bupivacaine in clinical trials. Several cases of CNS toxicity have been reported after inadvertent intravascular administration of ropivacaine, but only 1 case of cardiovascular toxicity has been reported to date. The outcome of these inadvertent intravascular administrations was favourable.

CONCLUSION

Ropivacaine is a well tolerated regional anaesthetic with an efficacy broadly similar to that of bupivacaine. However, it may be a preferred option because of its reduced CNS and cardiotoxic potential and its lower propensity for motor block.

Clonidine prolongs the effect of ropivacaine for axillary brachial plexus blockade

PURPOSE

To evaluate the effect of adding clonidine to ropivacaine, for axillary brachial plexus blockade, on the onset and duration of sensory and motor block and duration of analgesia.

METHODS

In a prospective randomised double blind placebo controlled study axillary brachial plexus blockade was performed in 50 patients using 40 ml ropivacaine 0.75%. Group (A) had 150 microg clonidine and Group (B) 1 ml normal saline added to the local anesthetic. Sensory function was tested using pinprick (sharp sensation, blunt sensation or no sensation) and temperature with an ice cube compared with the opposite arm, (cold/not cold). Motor function was assessed using a modified Bromage scale. Postoperative analgesia was standardised. Onset and duration of sensory and motor blockade, duration of analgesia, postoperative pain score, and analgesic requirement were compared.

RESULTS

The clonidine patients showed an increase in duration of sensory loss from 489 min to 628 min with a mean difference of 138 min (95% confidence interval of 90 to 187 min), motor blockade from 552 min to 721 min with a mean difference of 170 min (95% confidence interval of 117 to 222 min), and analgesia from 587 min to 828 min with mean difference of 241 min (95% confidence interval of 188 to 294 min). There was no difference in onset time. No side effects were noted.

CONCLUSION

The addition of 150 microg of clonidine to ropivacaine, for brachial plexus blockade, prolongs motor and sensory block and analgesia, without an increased incidence of side effects.

The pharmacokinetics of caudal ropivacaine 0.2% in children. A study of infants aged less than 1 year and toddlers aged 1-5 years undergoing inguinal hernia repair

This study evaluates the pharmacokinetics of ropivacaine in children after caudal epidural injection. Twenty male children undergoing inguinal hernia repair were enrolled after ethics committee approval and informed parental consent, and were grouped according to age (10 'infants' aged less than 1 year and 10 'toddlers' aged 1-5 years). After induction of general anaesthesia, caudal epidural injection using ropivacaine 0.2% 1 ml.kg-1 was performed. Plasma concentrations of ropivacaine in the first 2 h after injection were determined by reversed-phase high-pressure liquid chromatography. Caudal blockade with ropivacaine 2 mg.ml-1 resulted in mean (SD) peak plasma concentrations of 0.73 [0.27] microg.ml-1 in infants and 0.49 [0.21] microg.ml-1 in toddlers (p < 0.01). Maximum plasma concentrations occurred after a median [range] period of 60 [15-90] min and 52.5 [30-120] min in infants and toddlers, respectively. Two infants (weighing 3.8 and 5.0 kg) showed the highest individual maximum plasma concentrations: 1.31 and 1.11 microg.ml-1. No clinical signs of local anaesthetic toxicity were observed. The results of the present investigation suggest that, from a pharmacokinetic point of view, caudal blockade using ropivacaine 0. 2% 1 ml.kg-1 can be regarded as a safe technique in children, i.e. in infants as well as in toddlers.

Pharmacokinetics of ropivacaine during extradural anesthesia for total hip replacement

STUDY OBJECTIVE

To determine plasma concentrations of ropivacaine during epidural anesthesia with ropivacaine 10 mg/mL in patients undergoing elective total hip replacement.

DESIGN

Phase III prospective study.

SETTING

Orthopedic surgical unit of the University Hospital in Kiel, Germany

PATIENTS

11 ASA physical status I, II, and III patients undergoing elective total hip replacement after premedication with a benzodiazepine.

INTERVENTIONS

Peripheral venous plasma samples were collected prior to and 10, 15, 20, 30, 45, 60, 90, and 120 minutes following the epidural dose.

MEASUREMENTS AND MAIN RESULTS

After solid phase extraction, plasma concentrations of ropivacaine were measured by high-performance liquid chromatography (HPLC). Free unbound concentrations were determined after ultracentrifugation. In 9 of 11 patients excellent epidural anesthesia was achieved with an initial dose of 144 +/- 13 mg (120 to 150 mg) of ropivacaine corresponding to a dose of 1.9 +/- 0.4 mg/kg body weight. We suspected inadvertent intravascular catheter malposition in one case. Peak plasma concentrations occurred after 20 minutes (10 to 30 min) with a mean of 1.38 +/- 0.42 micrograms/mL (range 0.95 to 2.26 micrograms/mL). Maximum unbound free plasma concentrations of ropivacaine were 0.05 +/- 0.03 microgram/mL (range 0.02 to 0.13 microgram/mL).

CONCLUSION

Ropivacaine 10 mg/mL proved to be suitable for epidural anesthesia for total hip replacement. The plasma concentrations after 120 to 200 mg of its epidural application were not associated with signs of local anesthetic toxicity in patients pretreated with benzodiazepines, even in one case of suspected inadvertent intravascular application.

The effects of clonidine on ropivacaine 0.75% in axillary perivascular brachial plexus block

INTRODUCTION

The new long-acting local anesthetic ropivacaine is a chemical congener of bupivacaine and mepivacaine. The admixture of clonidine to local anesthetics in peripheral nerve block has been reported to result in a prolonged block. The aim of the present study was to evaluate the effects of clonidine added to ropivacaine on onset, duration and quality of brachial plexus block.

METHODS

Patients were randomly allocated into two groups. In group I brachial plexus was performed using 40 ml of ropivacaine 0.75% plus 1 ml of NaCL 0.9%, and in group II brachial plexus was performed using 40 ml of ropivacaine 0.75% plus 1 ml (0.150 mg) of clonidine. Onset of sensory and motor block of radial, ulnar, median and musculocutaneous nerve were recorded. Motor block was evaluated by quantification of muscle force, according to a rating scale from 6 (normal contraction force) to 0 (complete paralysis). Sensory block was evaluated by testing response to a pinprick in the associated innervation areas. Finally, the duration of the sensory block was registered. Data were expressed in mean+/-SD. For statistical analysis a Student t-test was used. A P-value of < or = 0.05 was considered as statistically significant.

RESULTS

The duration of blockade was without significant difference between the groups. Group I: 718+/-90 min; Group II: 727+/-117 min. There was no intergroup difference in sensory and motor onset or in quality of blockade.

CONCLUSION

The addition of clonidine to ropivacaine 0.75% does not lead to any advantage of block of the brachial plexus when compared with pure ropivacaine 0.75%.

High-performance liquid chromatographic determination of ropivacaine, 3-hydroxy-ropivacaine, 4-hydroxy-ropivacaine and 2',6'-pipecoloxylidide in plasma

A sensitive HPLC method has been developed for the determination of ropivacaine, 3-hydroxy-ropivacaine, 4-hydroxy-ropivacaine and 2',6'-pipecoloxylidide in plasma. The procedure involved extraction from plasma with a mixture of n-heptane-ethyl acetate and a back-extraction into an acidified aqueous solution. The chromatography was achieved using a LiChrospher RPB C8 column with a mobile phase consisting of a mixture of acetonitrile and pH 2.1, 0.01 M potassium dihydrogenphosphate, the latter phase containing 0.005 M 1-heptanesulfonic acid for ropivacaine metabolites analysis. The extraction yields of ropivacaine, 3-hydroxy-ropivacaine, 4-hydroxy-ropivacaine and 2',6'-pipecoloxylidide were 94.7%, 79.4%, 79.4% and 77.7%, respectively. The limits of detection of ropivacaine, 3-hydroxy-ropivacaine, 4-hydroxy-ropivacaine and 2',6'-pipecoloxylidide in plasma samples were 0.9 ng/ml, 3 ng/ml, 5 ng/ml and 1 ng/ml, respectively.