Elsevier

Clinical Therapeutics

Volume 39, Issue 1, January 2017, Pages 89-97.e1
Clinical Therapeutics

Dexmedetomidine Added to Local Anesthetic Mixture of Lidocaine and Ropivacaine Enhances Onset and Prolongs Duration of a Popliteal Approach to Sciatic Nerve Blockade

https://doi.org/10.1016/j.clinthera.2016.11.011Get rights and content

Abstract

Purpose

A literature review of multiple clinical studies on mixing additives to improve pharmacologic limitation of local anesthetics during peripheral nerve blockade revealed inconsistency in success rates and various adverse effects. Animal research on dexmedetomidine as an adjuvant on the other hand has promising results, with evidence of minimum unwanted results. This randomized, double-blinded, contrastable observational study examined the efficacy of adding dexmedetomidine to a mixture of lidocaine plus ropivacaine during popliteal sciatic nerve blockade (PSNB).

Methods

Sixty patients undergoing varicose saphenous vein resection using ultrasonography-guided PSNB along with femoral and obturator nerve blocks as surgical anesthesia were enrolled. All received standardized femoral and obturator nerve blocks, and the PSNB group was randomized to receive either 0.5 mL (50 µg) of dexmedetomidine (DL group) or 0.5 mL of saline (SL group) together with 2% lidocaine (9.5 mL) plus 0.75% ropovacaine (10 mL). Sensory onset and duration of lateral sural cutaneous nerve, sural nerve, superficial peroneal nerve, deep peroneal nerve, lateral plantar nerve, and medial plantar nerve were recorded. Motor onset and duration of tibial nerve and common peroneal nerve were also examined.

Findings

Sensory onset of sural nerve, superficial peroneal nerve, lateral plantar nerve, and medial plantar nerve was significantly quicker in the DL group than in the SL group (P < 0.05). Sensory onset of lateral sural cutaneous nerve and deep peroneal nerve was not statistically different between the groups (P > 0.05). Motor onset of tibial nerve and common peroneal nerve was faster in the DL group than in in the SL group (P < 0.05). Duration of both sensory and motor blockade was significantly longer in the DL group than in the SL group (P < 0.05).

Implications

Perineural dexmedetomidine added to lidocaine and ropivacaine enhanced efficacy of popliteal approach to sciatic nerve blockade with faster onset and longer duration.

Introduction

Pain medicine parameters for lower-extremity surgery using sciatic, femoral, and obturator nerve blockade have proven effective1, 2 and provide added value for patients with severe cardiovascular and/or respiratory disease(s).3, 4 However, pharmacology and duration of current long-acting local anesthetics (LAs) used during regional anesthesia can limit blockade effectiveness. Adding various adjuvant(s) to LAs during regional anesthesia to enhance peripheral nerve blockade (PNB) has been previously investigated and found to have varying degrees of efficacy.5, 6

Dexmedetomidine7, 8 is a selective α2-adrenoceptor agonist with sympatholytic, sedative, amnestic, and analgesic properties. In recent years, as an adjuvant to LAs during PNB, it has been investigated and found effective in both clinical studies9 and animal models.10, 11 Esmaoglu et al12 found advantages in the quality of the block (shortened onset time and extended duration) in their axillary brachial plexus that was formed with dexmedetomidine as an adjuvant to levobupivacaine. Brummett et al11 reported that adding dexmedetomidine to ropivacaine caused an approximately 75% increase in the duration of analgesia in rats. However, these investigations have often been confined to single terminal nerve branches (ulnar nerve13) or upper extremity brachial plexus blockade.12 This randomized, double-blinded, contrastable observational study was designed to examine the effects of dexmedetomidine as an adjuvant to LAs (mixture of lidocaine and ropivacaine) on sensory and motor onset and duration of popliteal sciatic nerve blockade (PSNB).

Section snippets

Patient Demographic Characteristics

Informed consent was obtained from 60 patients enrolled in a clinical trial receiving regional anesthesia for unilateral varicose saphenous vein resection and high ligation. All received ultrasonography-guided femoral, obturator nerve block and groin skin infiltration. In addition, patients were randomized to receive PSNB with 0.5 mL (50 µg12, 13, 14) of dexmedetomidine (DL group) (lot No. 13071034, Jiangsu Hengrui Medicine Co Ltd, Lianyungang, China); or 0.5 mL of saline (SL group) mixed with

Results

All patients enrolled in this investigation completed the study. Both groups (DL and SL) had comparable demographic characteristics with equal numbers of males and females, similar ages ranging from 30 to 80 years, and comparable patient height and weight characteristics (P > 0.05) (Table I).

PSNB sensory onset times for sural nerve (P = 0.031), superficial peroneal nerve (P < 0.001), lateral plantar nerve (P < 0.001), and medial plantar nerve (P = 0.004) were shorter in the DL group than those

Discussion

Because sciatic nerve is the largest peripheral nerve (wrapped by multilayer fascia) within the human body, it is anticipated that sciatic nerve blockade would require longer onset time for the LA to penetrate or diffuse toward target sodium channels compared with smaller-gauge nerves.20, 21 This concept can create clinical concern about timing efficacy of regional anesthesia during PSNB.22

Another more significant concern with regional anesthesia is clinical limitation of PNB duration. Duration

Conclusion

Significant improvement in regional anesthesia efficacy during ultrasonography-guided PSNB using 50 µg of dexmedetomidine (perineural injection) in combination with 0.75% ropivacaine and 2% lidocaine has been found. Achieving quicker onset and longer duration of PSNB can deliver both clinical and economic benefits in optimal patient care. However, future studies on perineural dexmedetomidine dose response, efficacy, and safety profile while various PNBs are performed are needed.

Funding Sources

This project was supported by grant LY13HO90008 from the Natural Science Foundation of Zhejiang Province, China, and grant Y20140326 from the Wenzhou Science and Technology Bureau, Zhejiang Province, China.

Conflicts of Interest

The authors have indicated that they have no conflicts of interest regarding the content of this article.

Acknowledgments

X. Hu contributed to the literature search, study design, conduct of the study, data collection, analyses, and writing of the manuscript. J. Li contributed to the study design and the writing of the manuscript. R. Zhou and Q. Wang contributed to the conduct of the study and data collection. F. Xia contributed to the conduct of the study and Figure creation. T. Halaszynski contributed to the writing of the manuscript. X. Xu contributed to the literature search, study design, data interpretation

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