Effectiveness of local anesthesia with lidocaine in chronic opium abusers.

Context: It had been demonstrated that chronic opium abusers have lower pain thresholds compared with than non-abusers.

Aims: This study aimed to compare the required dose of lidocaine, a common local anesthetic drug, with regard to the onset of anesthesia in opium abusers with that in non-abusers undergoing similar suturing of minor hand lacerations.

Materials And Methods: In this study, 109 opium abusers and 91 non-abusers underwent similar suturing for hand lacerations known as digital block. We explained the patients that their case records would remain confidential and admitting to any history of opioid abuse could assist in alleviating any pain associated with the procedure.

Results: There was no statistically significant difference between the two groups with regard to age, gender, and cause of injury (P > 0.05). We found a significantly longer duration of onset of analgesia in nonopioid abusers (5.42 ± 1.93 min) than that in abusers (10.30 ± 1.79 min) (P < 0.001). In addition, the lidocaine dose administered to abusers (6.67 ± 1.21 ml) was higher (4.07 ± 1.26) as well as statistically significant (P < 0.001) than that in non-abusers.

Conclusion: The findings from this study suggest a longer duration of onset of anesthesia and requirement of a higher lidocaine dose in opium abusers compared with nonopioid abuser. Moreover, chronic opium abusers (4-5 years) experienced significantly higher time of onset of anesthesia compared with nonchronic abusers. This outcome may be useful in selecting a more suitable local anesthetic protocol in such patients.