Introduction

Pain is defined as “an unpleasant emotional sensation related to one's past experiences, with or without tissue damage originating from a particular part of the body” by the International Study Group on Pain¹ and is a major public health problem. Over 230 million surgical procedures are performed yearly, increasing gradually. Almost 80% of these patients express pain after surgery². Acute post-operative pain is defined as pain that gradually decreases in a patient who has undergone surgery due to a previous disease, surgical intervention, or the healing of tissue that develops due to both³.

The intensity of post-operative pain can be influenced by several factors, including the location and type of surgery, duration of the procedure, size and type of incision, patient's pain perception and coping mechanisms, pre-operative physical and mental health status, pre-operative pain management, and type of anesthesia administered, as well as the efficacy of pain management strategies employed before and after surgery. In addition, the presence of pre-operative pain and previous experiences with pain may also contribute to the overall level of post-operative pain experienced by the patient⁴. The frequency of adverse outcomes is influenced by factors such as the quality of post-operative management. Inadequate treatment of post-operative pain is a significant concern, particularly among specific patient populations such as pregnant women, children, the elderly, individuals with limited verbal communication abilities, and those with drug dependency⁵.

The advancement of knowledge concerning pain, including its mechanisms and physiopathology, has played a significant role in the emergence of numerous drugs and techniques aimed at minimizing pain. In addition, this has led to the recognition of pain as the fifth vital sign and its utilization to follow patients in the majority of health-care facilities. While pain can serve as a valuable indicator of tissue damage and facilitate immobility during the healing process, the stress response that arises in the post-operative period can have deleterious effects on all physiological systems⁶.

Preemptive analgesia refers to the strategy of utilizing pain management techniques before a surgical procedure to reduce the potential for the development of more severe and persistent pain, both during and following the operation. The pre-operative administration of antinociceptive therapy before the surgical incision is the most notable characteristic. Preemptive analgesia has the potential to prevent hypersensitization and exacerbation of post-operative pain by lowering changes that may arise during the transmission of afferent impulses⁷. Subsequent research has indicated that the cessation of the nociceptive afferent block induced by the pre-incision pain treatment approach can result in the reactivation of central sensitization in response to stimuli originating from the wound site. This implies that central sensitization can be initiated by factors other than surgical incisions⁸. Pre-operative pain of the patient, noxious inputs occurring during the operation, inflammatory process due to peripheral-central neuromodulators, and ectopic neural activity cause central sensitization and, thus, both exacerbation and long-term acute pain. The mechanism-oriented analgesia method, which aims to reduce the nociceptive effect caused by all pre-operative, intraoperative, and/or post-operative warnings rather than when the analgesic treatment is applied, is called preventive analgesia⁹.

The efficacy of preventive analgesia is attributed to its prolonged duration of action beyond initial expectations. The extended duration of the drug's efficacy can be attributed to its analgesic properties and its ability to impede the pathophysiological mechanisms involved in pain perception and transmission, specifically by halting the initiation of central sensitization. Multimodal analgesia, which aims to address various stages involved in the formation and processing of pain impulses, has been found to offer superior analgesic outcomes compared to interventions that solely target a single level¹⁰.

The objective of this prospective and randomized study was to alleviate post-operative pain associated with lumbar disc surgeries, particularly those related to surgical and muscular factors, in a timely manner. Pre-emptive analgesia was administered before the arrival of pain mediators in the brain through the spinal canal. The visual analog scale (VAS) score for leg pain is indicative of the surgical outcome's quality. Stated differently, it is anticipated that the VAS score for leg pain will improve following surgical intervention aimed at correcting the herniated disc. During the initial phase, it is crucial to ascertain the specific agent that effectively alleviates VAS-associated back pain. The findings of this study will provide guidance to surgical teams regarding the management of post-operative pain and the avoidance of unnecessary medication.

Materials and methods

A total of 120 patients who applied to our clinic between 2020 and 2022 and operated for single-level lumbar disc herniation were included in this prospective and randomized research. All procedures followed were in accordance with the ethical standards of the responsible committee on human experimentation (institutional and national) and with the Helsinki Declaration of 1975, as revised in 2008.

Patients with single-level lumbar disc herniation diagnosed through magnetic resource imaging were included in the study. On the other hand, individuals with multi-level disc herniation, spondylolisthesis, degenerative disc disease, rheumatic diseases, and immunosuppression were excluded from the study. The caudal epidural injection was performed for all patients 20 min before the surgical incision. The patients were systematically randomized and divided into three groups. The first group was given 10 ml of bupivacaine (0.5%, 50 mg) and 40 mg of methylprednisolone (in 2 ml of saline), and 8 ml of normal saline (NS) was added to complete 20 ml. The second group was administered 10 ml of SF and 10 ml of bupivacaine (0.5%, 50 mg). The third group was assigned as the control group, and 20 ml of NS was applied to the patients from the caudal epidural area. A single surgeon performed the operations as a single-level microscopic microsurgery. During the operation, the patient was withdrawn in case of neural injury or cerebrospinal fluid fistula complications.

During the pre-operative phase, patients were primarily administered diclofenac sodium, a non-steroidal anti-inflammatory drug (NSAID), for the purpose of pain relief. As the initial treatment was deemed ineffective, the administration of tramadol was continued for the patients. At the same time, those who required additional analgesics after the operation were given diclofenac sodium and tramadol intramuscularly. Tramadol was administered as an alternative in the absence of any observed impacts. The administration of medications before surgery and the requirement for supplementary medication after surgery was documented.

Pre-operative and post-operative pain at 0, 1, 2, 4, 6, 12, 18, and 24 h was interpreted thorugh a VAS. Whether the patients needed additional anesthesia, ambulation time, hospital stay, and side effects were recorded every hour. The VAS was readministered at post-operative 1^st and 6^th week.

Results

Within the research scope, 120 patients, 49.2% (n = 59) female and 50.8% (n = 61) male, were randomized in this prospective study. The ages of the patients ranged from 21 to 71, with a mean age of 50. Patients were divided into three groups according to the procedures applied. Group 1; 10 ml Bupivacaine (50 mg) + 2 ml methylprednisolone (40 mg) + 8 ml NS, Group 2; 10 ml bupivacaine (50 mg) + 10 ml NS and Group 3; 20 ml NS.

The distribution of demographic and clinical findings by treatment groups is denoted in table 1. When the table was examined, it was determined that there was a statistically significant difference between the groups regarding the rate of additional painkiller use, ambulation time, and hospital stay (p < 0.05).

The distribution of VAS back and leg pain severity before and after the operation according to the treatment groups is elaborated in table 2. When the table is examined, while there was no statistically significant difference in the pre-operative VAS back pain severity between the groups, it was determined that there was a difference between the groups in all measurements after the operation (p < 0.05). The statistical difference in all measurements resulted from the results between Group 1 and Group 3 and between Group 2 and Group 3. No difference in leg pain severity has been observed between the groups before the operation. Still, a statistical significance has been achieved between the groups at the 1^st h, 2^nd h, 4^th h, and 24^th h after the operation (p < 0.05).

The difference between the pain intensities of the patients at the 24^th h, 1^st week, and 6^th weeks after the operation compared to the pre-operative period according to the treatment groups is presented in table 3. When the table was examined, a statistically significant difference was found in all Group 1 and Group 2 measurements except the pre-operative and post-operative 6^th-week measurements (p < 0.05).

The results of the evaluation of the differences between the medical treatment groups that the patients received before the operation and the severity of back and leg pain before the operation according to the treatment groups are shown in table 4. When the table is examined, there was no statistically significant difference in pre-operative back pain severity between medical treatment in Group 3. All other measurements showed a statistically significant difference between the medical treatment groups (p < 0.05).

Discussion

The appropriate and sufficient management of post-operative pain in individuals who have undergone lumbar disc herniation surgery holds a significant position in the neurological recovery of patients. Inadequate management of acute post-operative pain in patients can result in delayed hospital discharge and prolonged recovery time for normal activities. Various pharmacological and analgesic modalities, including non-steroidal anti-inflammatory drugs (NSAIDs), opioids, central nerve blocks, and infiltration techniques, have been employed for the management of post-operative pain following lumbar disc herniation procedures. However, similar to numerous other surgical procedures, the establishment of a universal analgesic approach has proven to be elusive¹¹.

The utilization of infiltrative, peripheral, and central blocks for the management of acute post-operative pain ought to be regarded as the fundamental element of multimodal analgesia. These applications have the potential to be utilized in conjunction with general anesthesia to provide post-operative analgesia, or alternatively, they may be employed as a primary method. Analgesics such as paracetamol, metamizole, non-steroidal anti-inflammatory drugs (NSAIDs), opioids, and adjuvants are commonly employed in the management of pain. Various administration routes can be favored for these medications to offer analgesia after surgery. The administration of these medications is infrequent in isolation or in conjunction, contingent on the extent of post-operative discomfort resulting from the surgical procedure¹².

The caudal injection is a beneficial method for easing post-operative pain due to its ability to access both the dorsal and ventral epidural spaces. Furthermore, it appears safe for the management of post-surgical syndrome. The administration of bupivacaine and tramadol through a single caudal epidural injection as a preemptive analgesic technique has been found to be a secure, uncomplicated, and efficacious approach for the management of post-operative pain¹³. The caudal injection method is often advocated by neurosurgeons due to its high degree of dependability. It has been asserted that a reliable imaging technique is necessary to ensure the accurate positioning of the caudal needle, as the epidural space cannot be reached with a success rate of 25% in caudal injections. According to Klocke et al., the utilization of ultrasound guidance during caudal epidural steroid injection allows for clear visualization of anatomical structures, resulting in effective injection outcomes¹⁴.

Kaygusuz et al. conducted a preemptive study. They reported patient satisfaction as “very good–excellent” in the lornoxicam and tramadol groups but “poor–fairly well” in the placebo group¹⁵. Manchikanti et al. indicated that significant pain reduction (i 50%) was shown in 55-65% of patients with spinal stenosis after using of caudal epidural steroid injection (ESI)¹⁶. Botwin et al. reported a successful outcome in 65% of patients after 6 weeks, 62% after 6 months, and 54% after 12 months, and a reduction of at least 50% in visual analog pain scores after caudal epidural steroid injection¹⁷. On the contrary, caudal epidural steroid injection outcomes for chronic low back pain without stenosis are poor¹⁸. In our study, the distribution of VAS back and leg pain severity before and after the operation, the statistical difference has been obtained between the groups in all measurements in the post-operative period (p < 0.05). The statistical difference in all measurements resulted from the results between Group 1 (Bupivacaine + methylprednisolone) and Group 3 (control) and between Group 2 (Bupivacaine) and Group 3 (control). Still, there was statistical significance in the VAS leg scores between the groups after the 1^st h, 2^nd h, 4^th h, and 24^th h following the operation. The findings of this study indicate that bupivacaine is a more efficacious treatment option for post-operative low back pain compared to NS, whether administered as an independent therapy or in conjunction with methylprednisolone. The efficacy of the treatment in alleviating leg pain is noted to be limited to the initial 4-h period as compared to NS. The efficacy of lumbar disc surgery was noted to result in a reduction of leg pain during the post-operative phase.

Today, the clinical importance of post-operative pain management is increasing daily. Inadequately treated post-operative pain can lead to important clinical problems that may cause high morbidity, such as hypoxemia, atelectasis, pneumonia, deep vein thrombosis, pulmonary embolism, delayed recovery of bowel functions, myocardial ischemia, and urinary retention in the acute period¹⁹. The study revealed a statistically significant difference in the VAS back scores between pre-operative and post-operative back pain results in both Group 1 (Bupivacaine + methylprednisolone) and Group 2 (Bupivacaine). However, its efficacy diminishes beyond the 6^th-week post-operation, as statistical significance was not observed beyond this period.

On analysis of the additional analgesic requirements of the groups, it was noted that the entirety of the control group necessitated analgesic medication. The administration of additional analgesics proved unnecessary in the remaining two groups. The findings of this study indicate that preemptive analgesia has the potential to mitigate the necessity for additional medical intervention and potentially enhance its application.

By comparing ambulation times, it was observed that the mobilization time in the control group was determined to be 16.7 h. However, this duration can be reduced to 6 h, consequently protecting patients from potential complications associated with immobilization. Although no significant difference in side effects was detected among the groups, a marginal statistical difference was noted in the duration of hospitalization. It has been suggested that this intervention might reduce the occurrence of nosocomial infections and facilitate expedited rehabilitation of patients into the workforce.

Post-operative pain management should minimize or eliminate the patient's discomfort, facilitate recovery, avoid or effectively prevent side effects, and provide economical treatment. There is no ideal method of post-operative analgesia. There are differences between the advantages and disadvantages of each method, the area where it is effective, and the type of pain²⁰.

Conclusion

The fluoroscopy-guided caudal epidural injection is an effective and safe method to reduce post-operative pain and ameliorate functional capacity for the treatment of lumbar disc herniation. The use of bupivacaine, or in combination with methylprednisolone during caudal injection in the pre-operative period, leveraged clinical benefit in the management of post-operative pain.