Dear editor
According to recent studies, in opioid abusers, compared with non-addicts, spinal anesthesia with local anesthetics has been accompanied with shorter duration of action and lower level of sensory block.1-4 Thus, it seems that chronic opiate abuse can produce tolerance, or probably, cross-tolerance to analgesic effects of local anesthetics. As yet, no clear explanation has been presented for this tolerance.
Local anesthetics produce their analgesic effects through connection to voltage-gated sodium channels.5 Opiate analgesia is attributed to µ receptors.6 Apparently, there is no similarity between opiate or local anesthetic receptors. This can explain addicts’ tolerance to local anesthetics. Opiates cause respiratory depression.7 Therefore, they cause mild respiratory acidosis in opioid abusers. Plasma acidosis can lead to diffusion of H+ to cerebrospinal fluid. Acidosis reduces the lipophilicity, and hence, efficiency of local anesthetics.
Based on the abovementioned issues, perhaps occurrence of unexpected phenomenon, such as reduction of sodium channels, following chronic addiction to opiates results in tolerance to intrathecal local anesthesia. Moreover, secondary acidosis in cerebrospinal fluid following chronic addiction to opiate may be the cause of reduction in the efficacy of intrathecal local anesthesia. Therefore, we recommend these topics for future studies.
REFERENCES
- 1.Dabbagh A, Dahi-Taleghani M, Elyasi H, Vosoughian M, Malek B, Rajaei S, et al. Duration of spinal anesthesia with bupivacaine in chronic opium abusers undergoing lower extremity orthopedic surgery. Arch Iran Med. 2007;10(3):316–20. [PubMed] [Google Scholar]
- 2.Hashemian AM, Omraninava A, Kakhki AD, Sharifi MD, Ahmadi K, Masoumi B, et al. Effectiveness of local anesthesia with lidocaine in chronic opium abusers. J Emerg Trauma Shock. 2014;7(4):301–4. doi: 10.4103/0974-2700.142765. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 3.Karbasy SH, Derakhshan P. Effects of opium addiction on level of sensory block in spinal anesthesia with bupivacaine for lower abdomen and limb surgery: a case-control study. Anesth Pain Med. 2014;4(5):e21571. doi: 10.5812/aapm.21571. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 4.Vosoughian M, Dabbagh A, Rajaei S, Maftuh H. The duration of spinal anesthesia with 5% lidocaine in chronic opium abusers compared with nonabusers. Anesth Analg. 2007;105(2):531–3. doi: 10.1213/01.ane.0000268496.46141.4f. [DOI] [PubMed] [Google Scholar]
- 5.Wood JN, Boorman JP, Okuse K, Baker MD. Voltage-gated sodium channels and pain pathways. J Neurobiol. 2004;61(1):55–71. doi: 10.1002/neu.20094. [DOI] [PubMed] [Google Scholar]
- 6.Gomes I, Jordan B, Gupta A, Trapaidze N, Nagy V, Devi LA. Heterodimerization of µ and d Opioid Receptors: A Role in Opiate Synergy. J Neurosci. 2000;20(22):RC110. doi: 10.1523/JNEUROSCI.20-22-j0007.2000. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 7.Shook JE, Watkins WD, Camporesi EM. Differential roles of opioid receptors in respiration, respiratory disease, and opiate-induced respiratory depression. Am Rev Respir Dis. 1990;142(4):895–909. doi: 10.1164/ajrccm/142.4.895. [DOI] [PubMed] [Google Scholar]