Abstract
To the Editor:
We read with interest the article by Turgut et al, 1 who compared IV paracetamol, dexketoprofen trometamol, and topical lidocaine for pain relief in patients with scorpion stings. We applaud the authors for studying various pain relief modalities for scorpion stings, an important public health issue. However, we have certain concerns regarding the study methodology and authors’ conclusions.
Scorpion stings can undoubtedly be very painful. Providing analgesia for such patients is an important concern. The authors had a placebo group, in which no IV or topical analgesic was administered. It is not ethically right to deprive analgesia to patients with scorpion stings in whom pain is a major symptom. It is not clear what the need was for a placebo group considering the distress these patients may have been in due to pain in these scenarios. Inadequate pain relief may also lead to other deleterious effects, such as tachycardia and hypertension, and anxiety is a reliable early symptom of systemic envenomation, which can thus be confounded.2,3 The importance is further evident from the fact that 52% of patients in the placebo group needed rescue medication. Additionally, it is not clear why the patients in the placebo group had relatively low visual analog scale (VAS) scores (52±28). 1 Considering the patients in the placebo group had less pain to begin with, the groups were not comparable. We feel that to increase the validity of the results, it was essential to place a cutoff value of VAS (>60 mm or similar) for inclusion in the study rather than including everyone irrespective of their initial pain scores because the pain intensity may vary in individual cases depending on the specific pain threshold. Additionally, the pain intensity varies according to the biochemical and proteomic constituents of the injected venom, which are highly species-specific. 4
Rescue analgesia in the form of tramadol was administered in case of insufficient pain relief. However, it is not clear what the objective cutoff of this judgment was. Moreover, tramadol should be avoided in such patients as it inhibits norepinephrine uptake and can be counterproductive.5,6 As the authors themselves mentioned, opioids or their congeners should be avoided as they may lead to respiratory depression, which can worsen the patient’s condition, especially in case of systemic envenomation. Furthermore, tramadol can lead to nausea or vomiting and seizures even while using recommended doses, which can confound the picture of systemic envenomation in such cases. 6 Despite its challenges, the rationale for using tramadol for rescue analgesia is uncertain. Considering that many of the patients received rescue analgesia, it is surprising that none developed side effects due to tramadol.
Furthermore, the authors mentioned that there was no significant difference between the groups with regard to the need for rescue analgesia (P=0.2566). 1 As per the result, the rescue analgesia requirement was 27% in the dexketoprofen trometamol group, 33% in the paracetamol group, 44% in the topical lidocaine group, and 52% in the placebo group. 1 Although the reuse analgesia requirement of 27% in the dexketoprofen trometamol group, compared to 52% in the placebo group, is not statistically significant as per the result, it is clinically significant.
Another important concern is that lignocaine cream used in 1 group has an onset of effect at approximately 15 min and requires almost 40 min for optimal effect, and the duration is short-lived. 7 Hence, lignocaine cream may not have been optimally effective at the 30-min time point, and practically, it cannot be compared with other agents at different observation points. ELA-max 5 contains lignocaine 5% cream in a liposomal matrix; it has been approved by the Food and Drug Administration for temporary pain relief from minor cuts and abrasions and is mainly marketed for temporary relief of anorectal pain.3,8 This liposomal version provides a longer anesthesia duration than nonliposomal preparations. It is unclear whether the authors used liposomal or nonliposomal preparation, and the mode of application of placebo or lignocaine cream has not been defined. At 60 min, the effect was equivalent to that of the placebo, signifying the short duration of the effect.
Furthermore, although the authors used a cream that was similar to lignocaine ointment in color and odor, topical lignocaine at the onset of analgesia causes numbness, and this effect distinguishes it from any other placebo cream. So, it is practically difficult to blind the lignocaine group. The authors mentioned the possibility of a breach of blinding in their limitations section.
Peripheral nerve blocks are gaining increasing acceptance and popularity in the emergency department to provide pain relief from various animal bites and venomous snake bites.9,10 In our experience, ultrasound-guided selective sensory peripheral nerve blocks, such as superficial radial nerve blocks or superficial peroneal nerve blocks, can be achieved with a small amount (1–2 mL) of local anesthesia, without the loss of motor functions, and, in such small volumes, are devoid of systemic side effects. 11 If pain recurs, the block can be easily repeated because it is superficial. Because scorpion stings are mostly present on the extremities, regional anesthesia remains a viable and effective alternative in such cases. Hence, we would urge emergency physicians dealing with envenomation cases with severe localized pain to utilize regional techniques wherever feasible.