الفهرس 
Anatomy of the Brachial PlexusOnly 14 pages are availabe for public view
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Abstract
Regional blocks especially the brachial plexus block has revolutionized the management of hand injuries in that the patients can be taken immediately for surgery without fear of ’full stomach’ as in general anesthesia. Further the role of the anesthesiologist is not over by providing analgesia intra-operatively but also extends well into the postoperative period. This is accomplished by brachial plexus block (Movafegh et al., 2006).
An axillary block is the most commonly performed variety of brachial plexus block. The landmarks are easy to identify and it is associated with fewer complications than other approaches to the brachial plexus (Tindinwebwa, 1995).
Local anesthetics of short, intermediate and long duration of action are well known and have been used in brachial plexus blockade. Lidocaine offers the advantage of having a rapid onset yet of short duration of action. Thus, different additives have been used to prolong its action (Chavan et al., 2011).
Clonidine is a useful adjuvant for brachial plexus blockade, particularly when admixed with intermediate-acting local anesthetics for axillary block AXB. Prolongation of anesthesia and analgesia with brachial plexus clonidine is most likely peripherally mediated and, like its side effect profile, dose-dependent (McCartney et al., 2007).
Ultra-low doses of opioid antagonists could selectively block the excitatory effects of opioids. Therefore, it is likely that an ultra-low dose of naloxone, added to local anesthetic solution, prolongs nerve sensory and motor blockades. A small dose of naloxone may enhance release of endogenous opioid peptides by blocking presynaptic autoinhibition of enkephalin release (Crain and Shen, 2000).
In order to compare the efficacy of naloxone to that of clonidine when each is added to lidocaine-fentanyl mixture in axillary block, 60 adult patients were included in this prospective study and were randomly allocated into 3 groups; 20 patients each. Group F: received 34ml lidocaine 1% +100µg fentanyl (2ml) + 1ml normal saline, Group FN: received 34 ml lidocaine 1%+100µg fentanyl (2ml) +100ng naloxone (1ml) and Group FC: received 34 ml lidocaine 1%+100µg fentanyl (2ml) +150 µg clonidine (1ml). They were scheduled for elective short (≤60 min) forearm or hand surgery under axillary brachial plexus block. The groups were matched for age, sex, American Society of Anaesthesiologists (ASA) score according to the inclusion criteria.
Duration and onset of sensory and motor blockade were recorded in the three groups. We also assessed the sedation score and compared the results in the three groups. Hemodynamic data were monitored all through the study and were recorded together with the incidence of any side effects or complications.
The results showed that group C (who received clonidine) had statistically significant longer durations of sensory blockade when compared to the other two groups (Group F: mean125.070±9.300 mins, Group N: mean142.668± 9.202 mins, Group FC: mean 241.275±13.922 mins , P <0.001 ), followed by group FN (who received naloxone) with statistically significant difference compared to the control group (P<0.001).
Similarly group C had statistically significant longer durations of motor blockade when compared to the other two groups (Group F: mean148.300 ±9.310mins, Group FN: mean 165.668±8.102 mins, Group FC: mean 266.224 ±10.224mins, P<0.001), followed by group FN (who received naloxone) with statistically significant difference compared to the control group (P value <0.05).
No statistically significant differences were found between the three goups regarding the onset of anesthesia (P>0.05).
Sedation scores were significantly higher in patients who received clonidine compared to the other two groups who recorded nearly the same scores (Group F mean 1.776± 0.716, Group FN: mean 1.734 ±0.371, Group FC: mean 2.525 ±0.512, P <0.001).
Mean blood pressure was significantly lower in group FC patients when compared to groups F and FN (Group F: mean 75.758±4.409 mmHg, Group FN: mean 74.320±3.450 mmHg, Group FC: mean 64.486±2.961 mmHg, P<0.001). Heart rates were also lower in patients who received clonidine, with statistically significant differences compared to the other two groups (Group F: mean 83.462±11.248 b/min, Group FN: mean 83.055±10.798 b/min, Group FC: mean 68.251±8.219 b/min, P <0.001).
Regarding the incidence of side effects, they were nearly the same in all groups and included: dizziness, hypotension, nausea, vomiting and pruritis.
Clonidine in current study has proved to be more efficacious in lengthening the duration of anesthesia and analgesia than naloxone when each is added to lidocaine-fentanyl mixture in Axillary block. No serious adverse effects or drawbacks were recorded with the dose we used (150µg).