Since renal colic pain caused by urinary stones is severe and sudden, an appropriate treatment is of great necessity. Narcotics have been considered as main treatment of renal colic for years; they relieve pain with central effects on narcotic receptors. Although narcotics have adequate effects, there is possibility of their being misused, excessive drowsiness, and other central nervous system and gastrointestinal complications .
Recently, the benefits of non-steroidal anti-inflammatory drugs (NSAIDS) in renal colic have been reported suggesting them to be more effective compared to narcotic analgesics [8, 9].
Renal colic pain is caused by endopelvic pressure and ureteral obstruction. Increase in renal blood flow following obstruction increases urine and endopelvic and ureter pressure. Prostaglandins cause increase in renal blood follow and smooth muscle spasm .
Nonsteroidal anti-inflammatory drugs, inhibiting cyclooxygenase enzyme, relieve colic pain. Their pain relief mechanism however differentiates them from narcotic analgesics. NSAIDs can relieve pain locally and centrally inhibiting prostaglandin synthesis .
In spite of the beneficial effects of nonsteroidal anti-inflammatory drugs on pain, NSAIDs can reduce renal blood flow and ureter pressure in acute ureteral obstruction .
Therefore, because in our country (Iran), intravenous nonsteroidal anti-inflammatory drugs are not available, we thought of an alternative intravenous drug, i.e. lidocaine, whose analgesic effects on various pains (postoperative, cancer and etc.) have been proven .
Being an amino amide local anesthetic, Lidocaine blocks the voltage dependant sodium channels and impulses in axons . Lidocaine is a relatively safe medication, if used in low doses. Allergy to this drug however would increase the risk of cardiac arrhythmia and dyspnea in rare cases. Most side effects are related to its cumulative effects including: perioral numbness, dizziness, confusion, feeling hangover, and impaired speech .
Lidocaine is an effective and cheap drug with few side effects including dizziness, nausea and constipation. Prevalence of these complications however is less with lidocaine compared to narcotics and other analgesics .
On the other hand, side effects of lidocaine are predictable with a wide range of confidence. Due to the low half life, toxicity symptoms of lidocaine are transient and rapidly reversible. Based on the results of Rebecca Ferrini’s study on 100 patients, in most patients having received narcotics infusion of intravenous lidocaine was effective when the pain was central or visceral, and even when narcotics were not effective or accompanied unwanted and unacceptable complications, intravenous lidocaine could be useful .
In the study of Nicky Forov et al. on a pregnant woman with resistant renal colic, subcutaneous paravertebral nerve block was performed using lidocaine, in this study patient’s pain relieved considerably . In our other case series study, from 8 patients suffering from renal colic resistant to treatment (morphine and NSAIDS), intravenous lidocaine relieved the pain in 7 patients significantly with no considerable complications .
Other case studies have also been reported regarding using lidocaine in relieving pain in cancerous and renal colic patients. In a similar study carried out by Rebecca Ferrini et al. A single dose of lidocain was administered for reducing pain resistant to morphine in a patient suffering from primary neuroectodermal tumor. The patient had received other complementary medicines, in addition to morphine, such as: gabapentin, baclofen, amitriptyline, clonidine and clonazepam. Patient’s pain however considerably relieved after using a single dose of lidocaine (1.5 mg/kg) .
The only study which can be compared with ours regarding considerable pain reduction in short time is a study carried out by Mansuri Igochi et al. in which local injection of lidocaine in the most painful point was used in patients suffering from renal colic (control group received scopolamine). Considering response to treatment, lidocaine was more effective than scopolamine .
Fortunately, in our study no serious or life threatening complications were observed in patients of lidocaine group, therefore our study is similar to the study of Rebecca Ferrini et al.
Lidocaine causes change in sympathetic smooth muscle tone through reducing the transmission of afferent sensory pathways. Intravenous lidocaine causes considerable reduction in pain and can be a suitable alternative for cases in which narcotics are ineffective or associated with undesirable complications .