DISCUSSION
The mechanism of pain in acute renal colic involves changes in intraluminal pressure, renal blood flow, and glomerular filtration rate caused by increased NO and prostaglandin release as a result of urinary system obstruction by stones 17. The sympathetic preganglionic nerves that form the renal innervation originate from the spinal segments T8 and L1. The ureter has an abundant source of autonomic nerves originating from the celiac, aortorenal, and mesenteric ganglions in addition to superior and inferior hypogastric (pelvic) plexus. The sympathetic response to the ureter arises from the preganglionic fibers of the lumbar segments T11, T12, and L1. Distention of the renal capsule and the collecting system causes stimulation of renal pain fibers that carry signals through the sympathetic nerves, thus resulting in the visceral-type referred pain in the flank, groin, or scrotal (labial) regions 18.
The time to reach effective analgesia is an important clinical indicator in determining the quality of the care offered for emergency patients19. This time varies depending on the condition that caused the pain, but it should ideally be not more than 20-25 min20. In a recently published systematic review, it has been observed that the VAS scores at minute 30 post-procedure are considered in many studies on NSAIDs or opioids focusing on pain management in acute renal colic in the literature 21. However, in the present study, the VAS scores not only at minute 30 but also at other times throughout the procedure were significantly lower in the ESP group. It was significant importance that the patients expressed their pain diminished immediately after the ESP block procedure. The pain scores at minute 5 already demonstrate that the pain reduced by 70% compared to the admittance pain scores.
There are still some considerations that need clarification although the NSAIDs are the first choice analgesics for acute renal colic due to their efficacy and levels of adverse effects. Renal dysfunction, gastrointestinal bleeding, and thrombosis dysfunction are the well-known adverse effects of NSAIDs. There are also differences that have been reported in terms of need for additional analgesic and adverse effects based on administration methods. Compared to opioids, NSAIDs have been demonstrated to have less need for additional analgesic when administered intravenously and less rates of vomiting when administered only intramuscularly 22-24. On the other hand, despite the existing complications described for ESP block in the literature, there were not any complications or adverse effects during the course of the present study.
Since it is applied in various procedures such as FAST procedure in emergency departments, there is an increased familiarity with ultrasonography, and it sheds light on other procedures that can be applied under the guidance of ultrasonography. Ultrasound-guided application of regional anesthetic techniques at emergency departments gains popularity in pain management. Opioid consumption is getting less popular especially as a highly efficient, easily-applicable and safe component of multi-model analgesic. ESP block has been successfully employed at emergency departments in pain management of various clinical situations such as rib fractures, burns, herpes zoster, acute pancreatitis 9. With the ESP block, the local anesthetic solution crosses the superior costotransverse ligament and spreads into the paravertebral space. Blockade of the ventral rami of the spinal nerves is the primary mechanism of the analgesic effect25. The most important reason of this common use of ESP block is because it is a highly safe plane block. Especially the vertebrae transverse process, which is the target point of the injection during the block, constitutes a safety point for the practitioner. This is therefore highly advantageous in outpatient procedures.
The present study has some limitations. The first of these limitations is although an ESP block takes relatively more time than intravenous analgesia with NSAIDs, in our institution, we perform ultrasound-guided ESP block in less than 5 min. Additional time, staff, and equipment may create a limitation in terms of time and cost-effectiveness. Therefore, further studies may be required to determine the cost-effectiveness of the study. The second limitation is that patient pain scores were followed up only for 60 min in the ED. Moreover the long-term outcomes of patients (sleep, physical function, depression, pain catastrophizing, etc.) were not evaluated according to our study protocol. If long-term results were evaluated, different results could have been obtained. Finally, possible biases could not have been prevented since the present study was designed as a study with no blindness for patients and practitioners.