European Journal of Cardiovascular Medicine

Arthroscopy of the knee joint, including anterior cruciate ligament reconstruction, is a commonly performed outpatient procedure. Effective postoperative pain management is essential to facilitate early mobilization, rehabilitation, and timely discharge. Traditionally, postoperative pain has been managed using oral analgesics, including opioids administered on an as-needed basis. However, this approach often results in inadequate pain control, which may delay discharge, hinder participation in rehabilitation programs, prolong recovery, worsen clinical outcomes, and increase healthcare utilization.

Intra-articular administration of analgesics is a well-established technique for postoperative pain management following arthroscopic knee surgery. Intra-articular instillation of local anaesthetics provides targeted analgesia with minimal systemic effects and has been widely adopted by orthopaedic surgeons. To enhance the duration and quality of analgesia, several adjuvants have been evaluated in combination with intra-articular local anaesthetics, including morphine [1], clonidine [2], fentanyl [3], and tramadol [4,5].

Dexmedetomidine is a highly selective α2-adrenergic agonist with a markedly greater α2:α1 receptor selectivity ratio compared with clonidine. It is widely used for sedation and anxiolysis in intensive care settings and is the S-enantiomer of medetomidine. Unlike opioids and sedative agents such as propofol and benzodiazepines, dexmedetomidine provides sedation and analgesia without causing respiratory depression [6]. Its sedative effect closely resembles natural sleep and is associated with less amnesia [7]. Dexmedetomidine exerts analgesic effects at both spinal and supraspinal levels [8], thereby reducing opioid requirements while maintaining effective pain control.

Intravenously administered dexmedetomidine demonstrates linear pharmacokinetics, with a rapid distribution half-life and a terminal elimination half-life of approximately two hours. It is highly protein bound [9], primarily metabolized in the liver via glucuronidation and cytochrome P450 pathways, and predominantly excreted in the urine.

To date, comparative data evaluating intra-articular dexmedetomidine as an adjuvant to ropivacaine in patients undergoing arthroscopic knee surgery under spinal anaesthesia are limited. Therefore, this prospective, randomized, controlled study was designed to compare the analgesic efficacy and hemodynamic stability of intra-articular dexmedetomidine and tramadol as adjuvants to ropivacaine during the early postoperative period following arthroscopic knee surgery.

After obtaining approval from the Institutional Ethical Committee (Ref. No. 0018/Ethics/R.Cell-16) of King George’s Medical University (KGMU), Lucknow, written informed consent was obtained from all participants. This prospective, randomized, double-blind, controlled study was conducted in 60 patients of either sex, aged 18–60 years, with ASA physical status I or II, scheduled for elective arthroscopic knee surgery. Patients with ±20% of ideal body weight and height were included. Patients were excluded if they had severe systemic disease, known allergy to study drugs, long-term analgesic use, intake of analgesics or non-steroidal anti-inflammatory drugs within 24 hours before surgery, seizure disorder, traumatic knee injury, or refusal to participate. All patients were preoperatively familiarized with a 10-cm visual analogue scale (VAS) [Table 1], where 0 represented no pain and 10 the worst imaginable pain. Sedation and anxiety were assessed using the Ramsay Sedation Score [Table 2]. Standard monitoring included electrocardiography, non-invasive blood pressure, and pulse oximetry. Using a computer-generated randomization sequence, patients were allocated into three groups (n = 20 each). Group I received intra-articular ropivacaine 0.2% (19 mL) with dexmedetomidine (1 µg/kg); Group II received intra-articular ropivacaine 0.2% (19 mL) with tramadol (1 mL); and Group III received intra-articular ropivacaine 0.2% (19 mL) with normal saline (1 mL). The study drugs were prepared by an independent anaesthesiologist and were blinded to the surgeon, anaesthesiologist, and patient. All patients underwent standard pre-anaesthetic evaluation, fasted for 8 hours, and received oral ranitidine 150 mg and alprazolam 0.25 mg the night before surgery. Low-dose spinal anaesthesia was administered with 1.5 mL of 0.5% hyperbaric bupivacaine at the L3–L4 interspace using a 25-G Quincke spinal needle under aseptic conditions. The study drug was injected intra-articular through the arthroscopic port at the end of surgery, with the tourniquet maintained for 10 minutes to prevent drug leakage. Postoperative pain was assessed using VAS at 0, 2, 4, 6, 12, and 24 hours. Sedation was evaluated using the Ramsay Sedation Score. Rescue analgesia was administered when VAS ≥4, using intramuscular diclofenac sodium 75 mg, followed by tramadol 100 mg if pain persisted. Time to first rescue analgesia and total analgesic consumption during the first 24 hours were recorded. Adverse effects, including bradycardia, hypotension, nausea, vomiting, excessive sedation, and respiratory depression, were monitored and managed accordingly. Statistical Analysis Sample size estimation was based on postoperative pain scores as the primary outcome variable. Based on data from a pilot study and assuming a standard deviation of 1 cm, a minimum of 17 patients per group was required to achieve 80% power to detect a difference of 1 cm on the visual analogue scale (VAS) at a two-sided significance level of 5%. To account for possible dropouts, 20 patients were enrolled in each group. Statistical analysis was performed using the Statistical Package for the Social Sciences (SPSS), version 15.0. Continuous variables were expressed as mean ± standard deviation (SD), while categorical variables were presented as number and percentage. Intergroup and intragroup comparisons of continuous parametric data, including heart rate and systolic and diastolic blood pressure, were analysed using analysis of variance (ANOVA). The Chi-square test was used to compare categorical variables, including demographic characteristics and outcome measures. VAS scores, which were not normally distributed, were analysed using the Kruskal–Wallis H test to assess differences among the three study groups. A p value of less than 0.05 was considered statistically significant.

This study was conducted in the Department of Anaesthesiology, King George’s Medical University, Lucknow, and included 60 adult patients who met the inclusion criteria and provided informed consent. Patients were randomly allocated into three equal groups of 20 each: Group I received intra-articular dexmedetomidine, Group II received intra-articular tramadol, and the control group received intra-articular normal saline.

Demographic Characteristics

The overall age of patients ranged from 18 to 56 years. The mean age was higher in the dexmedetomidine group compared with the tramadol and control groups; however, this difference was not statistically significant. The majority of patients in all groups were between 21 and 40 years of age. Male patients predominated across all groups, and the gender distribution was comparable, with no statistically significant intergroup difference. [Table 3]

Pain Scores

Baseline VAS scores at rest and on movement were comparable among the three groups. During the postoperative period, significant differences in VAS scores were observed at specific time points. At 4, 6, and 24 hours postoperatively, VAS scores were significantly lower in the dexmedetomidine group compared with the tramadol and control groups. The control group consistently demonstrated higher pain scores at these time points. No statistically significant differences were observed at 0, 2, or 12 hours postoperatively. [Table 4]

Haemodynamic Parameters

Heart rate, systolic blood pressure, and diastolic blood pressure remained within clinically acceptable limits in all groups throughout the study period. Significant intergroup differences in heart rate were observed at 4, 6, and 24 hours postoperatively, with higher values noted predominantly in the tramadol and control groups. Systolic blood pressure differed significantly among groups at 6 and 12 hours, while diastolic blood pressure showed a statistically significant difference only at 24 hours. These variations were transient and did not require therapeutic intervention [ Table 5,6,7].

Rescue Analgesia

The requirement for rescue analgesia was significantly lower in the dexmedetomidine group compared with the tramadol and control groups. Time to first rescue analgesia was longest in patients receiving dexmedetomidine, followed by the tramadol group, and shortest in the control group. This difference was statistically significant. Total analgesic consumption during the first 24 hours was also significantly reduced in the dexmedetomidine group [Table 8].

Sedation and Adverse Effects

Most patients exhibited Ramsay Sedation Scores greater than 2, with no significant intergroup differences. No episodes of bradycardia, hypotension, excessive sedation, or respiratory depression were observed. Nausea and vomiting occurred in one patient in the tramadol group; however, the incidence of adverse effects was comparable among groups and not statistically significant. [Table 9]

Table 1:

Table 2: RAMSAY SEDATION SCORE:

Table 3: Intergroup Comparison of Demographic Variables

Table 4: Intergroup Comparison of VAS Score at Rest and at Action (Kruskal Wallis test)

Table 5: Comparison of Heart Rate at different time intervals

Table 6: Comparison of Systolic Blood pressure at different time intervals

Table 7: Comparison of Diastolic Blood pressure at different time intervals

Table 8: Intergroup Comparison of Outcome characteristics

Table 9: Intergroup Comparison of Adverse Effects

Arthroscopic knee surgery is commonly performed as a day-care procedure; however, inadequate postoperative pain control may hinder early mobilization, rehabilitation, and timely discharge. Various analgesic strategies—including systemic analgesics, regional techniques, and intra-articular drug administration—have been employed to manage postoperative pain following knee arthroscopy. Each of these approaches has inherent limitations, such as the need for specialized equipment, increased monitoring, or the risk of adverse effects that may prolong hospital stay or necessitate readmission. Consequently, intra-articular analgesia has gained popularity due to its simplicity, targeted action, and favourable safety profile.

Previous studies have demonstrated effective postoperative analgesia with intra-articular administration of α2-adrenoceptor agonists such as clonidine and its derivatives. Dexmedetomidine, a highly selective α2-adrenoceptor agonist with substantially greater receptor selectivity than clonidine, produces analgesia through supraspinal, spinal, and peripheral mechanisms. When administered intra-articular, its analgesic effect appears to be predominantly local, although a contribution from systemic absorption cannot be excluded. The proposed mechanisms include inhibition of nociceptive transmission through C and Aδ fibres and stimulation of peripheral release of enkephalin-like substances, resulting in prolonged analgesia.

In the present study, intra-articular dexmedetomidine used as an adjuvant to ropivacaine provided superior postoperative analgesia compared with tramadol and local anaesthetic alone. This was evidenced by lower VAS scores, delayed requirement of first rescue analgesia, and reduced total analgesic consumption. These findings are consistent with earlier studies demonstrating prolonged analgesia with dexmedetomidine added to ropivacaine. The longer duration of analgesia observed in this study may also be attributed to the additive effect of low-dose spinal anaesthesia.

Studies evaluating intra-articular tramadol have reported improved analgesia compared with local anaesthetic alone, particularly during the early postoperative period. In agreement with these findings, the present study demonstrated better pain control with ropivacaine–tramadol compared with ropivacaine alone, although the effect was less pronounced and of shorter duration than that observed with dexmedetomidine.

Haemodynamic parameters remained stable throughout the study period, and no clinically significant adverse effects were observed. This supports the safety of intra-articular dexmedetomidine when used in appropriate doses as an adjuvant to local anaesthetics.

This prospective, randomized, controlled study demonstrates that intra-articular dexmedetomidine, when used as an adjuvant to ropivacaine, provides superior early postoperative analgesia compared with tramadol in patients undergoing arthroscopic knee surgery under low-dose spinal anaesthesia. Dexmedetomidine was associated with lower pain scores, prolonged duration of analgesia, reduced rescue analgesic requirements, and stable haemodynamic profiles, without an increase in clinically significant adverse effects. Intra-articular tramadol also improved postoperative analgesia compared with local anaesthetic alone, but its analgesic efficacy was inferior to that of dexmedetomidine, particularly beyond the early postoperative period. Based on these findings, intra-articular dexmedetomidine appears to be a safe and effective adjuvant to ropivacaine for postoperative pain management following arthroscopic knee surgery. Larger studies are warranted to further evaluate its safety profile and to explore the influence of patient-related factors and age-related physiological changes on haemodynamic responses during low-dose spinal anaesthesia. Financial support and sponsorship Nil Conflicts of interest There are no conflicts of interest.

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