Post-spinal anaesthesia shivering is a frequent and distressing complication encountered in patients undergoing surgery under neuraxial blockade. The incidence of shivering following spinal anaesthesia has been reported to range between 40% and 70%, depending on patient characteristics and perioperative conditions [1]. Shivering not only causes discomfort but also leads to increased oxygen consumption, carbon dioxide production, lactic acidosis, raised intraocular and intracranial pressure, and interference with haemodynamic monitoring [2,3]. Hence, its prevention has important clinical implications.

The exact mechanism of post-spinal anaesthesia shivering is multifactorial. Spinal anaesthesia impairs thermoregulatory vasoconstriction below the level of the block, leading to increased heat loss and redistribution of core heat to the periphery [4]. Non-thermoregulatory factors, including unopposed sympathetic activity, pain, and reflex muscle activity, have also been implicated [5].

Various pharmacological agents such as meperidine, clonidine, ketamine, tramadol, and ondansetron have been used for the prevention and treatment of shivering, but none is devoid of limitations, including side effects like nausea, vomiting, respiratory depression, or delayed recovery [6,7].

Dexmedetomidine, a highly selective α₂-adrenergic receptor agonist, has emerged as a promising alternative due to its sedative, analgesic, anxiolytic, and sympatholytic properties [8]. It has been shown to reduce the shivering threshold and modulate central thermoregulatory control without significant respiratory depression [9]. However, the optimal dose of dexmedetomidine for preventing post-spinal shivering while minimizing haemodynamic instability remains unclear.

Therefore, the present randomized controlled trial was designed to compare the efficacy and safety of three different intravenous doses of dexmedetomidine (0.2, 0.3, and 0.5 µg/kg) in preventing shivering following spinal anaesthesia in patients undergoing lower abdominal, perineal, and lower limb surgeries.

MATERIALS AND METHODS

Study Design and Setting

 This prospective, randomized, controlled study was conducted after obtaining approval from the Institutional Ethical Committee and written informed consent from all participants. A total of 120 adult patients, aged 18–60 years and belonging to the American Society of Anaesthesiologists (ASA) physical status grades I or II, scheduled for lower abdominal, lower limb, or perineal surgeries under spinal anaesthesia, were included.

Inclusion Criteria

• Age between 18 and 60 years
• Male or female patients
• Glasgow Coma Scale score: 15/15
• Normal higher mental functions
• ASA physical status grade I or II
• Written informed and valid consent obtained
• Expected surgical duration between 1–3 hours

Exclusion Criteria

• Refusal to participate in the study
• Age <18 years or >60 years
• History of cardiac disease, chronic kidney disease, hepatic disease, or malignancy
• Contraindication to spinal anaesthesia
• Known allergy to local anaesthetics or dexmedetomidine
• Patient height <140 cm

Preoperative Evaluation

All patients underwent detailed history taking (including comorbidities, allergies, and addictions), general physical examination, and systemic examination of cardiovascular, respiratory, abdominal, and central nervous systems. Airway and spine evaluation were performed. Routine laboratory investigations included complete blood count, coagulation profile, liver and renal function tests, and random blood sugar. A 12-lead electrocardiogram was performed in all cases.

On the day of surgery, nil per oral (NPO) status was confirmed. Baseline body temperature was measured (36.5–37.5 ⁰C). In the operating theatre, temperature was kept constant at 18⁰C. Monitoring included ECG, non-invasive blood pressure (NIBP), and pulse oximetry (SpO₂). An intravenous line was secured using an 18-G or 20-G cannula, and patients were preloaded with 8–10 ml/kg Ringer’s lactate or normal saline before induction of anaesthesia.

Randomization and Grouping

Patients were randomly allocated into four groups (A, B, C, D) on an alternate basis:

• Group A: Spinal anaesthesia with 15 mg 0.5% hyperbaric bupivacaine followed by intravenous dexmedetomidine 0.2 µg/kg diluted to 10 ml in normal saline, infused over 10 minutes.
• Group B: Intravenous dexmedetomidine 0.3 µg/kg diluted to 10 ml in normal saline, infused over 10 minutes.
• Group C: Intravenous dexmedetomidine 0.5 µg/kg diluted to 10 ml in normal saline, infused over 10 minutes.
• Group D (Control group): Spinal anaesthesia with 15 mg 0.5% hyperbaric bupivacaine followed by 10 ml normal saline infusion over 10 minutes.

Spinal anaesthesia was administered under aseptic precautions in the sitting position at the L3–L4 interspace using a 25G Quincke needle. Free flow of CSF was confirmed before injecting bupivacaine.

Outcome Measures

Haemodynamic parameters, level of sensory block (assessed by the pinprick method), incidence and severity of shivering, sedation score, and complications (hypotension, bradycardia, nausea, vomiting) were recorded intraoperatively and during the immediate postoperative period (30 minutes).

• Sedation was assessed using the Modified Ramsay Sedation Scale (score 1–6).
• Shivering was graded according to Wrench’s scale (grade 0–4).

Management of Adverse Events

• Hypotension was treated with intravenous inj. Mephentermine.
• Bradycardia was treated with intravenous inj. Glycopyrrolate.
• Oxygen supplementation, warm fluids, warmer and patient covering were used as supportive measures against shivering.
• Persistent shivering was treated with intravenous inj. Dexamethasone or

inj. Tramadol as a second-line treatment with standard doses applicable.

RESULTS AND OBSERVATIONS

Table 1: COMPARISON OF AGE DISTRIBUTION IN STUDY GROUPS

In our study test was applied for comparison of age between the two study groups. In Group A the mean age was 35.13 +/- 11 years, in Group B the mean age was 38.33 +/- 12 years, in group C mean age was 38.20 +/- 11 years and in group D mean age was 39+/- 10 years. There was no statistical difference between the groups with respect to age as their p value (p = 0.525) was >0.05

Table 2: COMPARISON OF GENDER DISTRIBUTION IN STUDY GROUPS

In our study, the Chi square test was used to compare gender distribution between four study groups. The number of males and females in group A was 18 and 12, group B was 17 and 13, group C was 18 and 12, group D 19 and 11. There was a non-significant difference between gender distribution in all four groups (p=0.97)

Figure 1: Comparison of Shivering Grade

Figure 2: Comparison of Sedation Score in study groups

Table 3: COMPARISON OF SENSORY BLOCKADE ACHIEVED

This table compares the maximum sensory blockade achieved in all four groups. In this chi square test was used to compare the sensory blockade achieved in different groups. The maximum level achieved in group A, B, C was T4 while in 1 patient in group D achieved T2 level.

Table 4: COMPARISON OF MEAN SYSTOLIC BLOOD PRESSURE (SBP) IN STUDY GROUPS:

Figure 3: Comparison of Systolic Blood Pressure

Figure 4: Comparison of Diastolic Blood Pressure

Table 5: COMPARISON OF MEAN ARTERIAL PRESSURE

Table 6: COMPARISON OF COMPLICATIONS

Table 7: DETAILS OF RESCUE MEDICATIONS

DISCUSSION

Post-spinal anaesthesia shivering remains a significant challenge in the perioperative period. The present randomized controlled trial compared three different intravenous doses of dexmedetomidine (0.2, 0.3, and 0.5 µg/kg) with placebo for the prevention of shivering in patients undergoing surgeries under spinal anaesthesia. Our findings demonstrate that dexmedetomidine, at all three doses, significantly reduced the incidence and severity of shivering compared with control, with the highest efficacy noted at 0.5 µg/kg.

The incidence of shivering in the control group in our study was consistent with earlier reports, which documented shivering in 40–70% of patients after neuraxial blockade [1,2]. Dexmedetomidine’s efficacy in preventing shivering can be explained by its central α₂-adrenergic receptor agonism, which decreases central thermoregulatory thresholds for vasoconstriction and shivering [3]. Additionally, its sedative and anxiolytic effects may further contribute to better patient tolerance during hypothermic stress [4].

Our results align with the findings of Elvan et al. [5], who reported that dexmedetomidine significantly reduced postoperative shivering in patients undergoing abdominal hysterectomy. Similarly, Bajwa et al. [6] demonstrated that prophylactic dexmedetomidine infusion was effective in reducing the incidence of post-spinal shivering and also provided stable haemodynamics.

In terms of dosing, we observed that 0.5 µg/kg was most effective in preventing shivering with stable haemodynamics and optimal sedative effect but was associated with a transient bradycardia and hypotension in few patients, consistent with the dose-dependent sympatholytic action of dexmedetomidine [7]. The 0.3 µg/kg dose provided a favorable balance between  shivering control with minimal haemodynamic compromise, however recurrence of shivering intra and postoperatively was observed. This is in agreement with Usta et al. [8], who suggested that lower doses of dexmedetomidine can prevent shivering without major cardiovascular side effects.

Sedation scores in our study were higher in dexmedetomidine groups compared with control, which is consistent with its known sedative properties mediated via locus coeruleus suppression [9]. Importantly, no case of respiratory depression was observed, reaffirming dexmedetomidine’s safety profile compared with opioids like meperidine or tramadol [10].

Regarding haemodynamic effects, transient hypotension and bradycardia were noted, particularly at higher doses, but were manageable with standard interventions. Similar haemodynamic alterations have been described in earlier trials [11]. Thus, clinicians should carefully titrate doses, especially in patients with borderline cardiovascular reserve.

Overall, our findings suggest that dexmedetomidine is an effective pharmacologic option for the prevention of post-spinal shivering. Among the studied doses, 0.5 µg/kg may represent the optimal dose, balancing efficacy with haemodynamic safety. Future large-scale multicentric studies are needed to further validate these results and assess long-term outcomes.

CONCLUSION

Dexmedetomidine is an effective agent for the prevention of post-spinal anaesthesia shivering. In this randomized controlled trial, all three studied doses (0.2, 0.3, and 0.5 µg/kg) significantly reduced the incidence and severity of shivering compared with placebo. Among them, 0.5 µg/kg provided the best balance of efficacy and safety, with minimal haemodynamic compromise and adequate sedation, whereas the 0.3µg/kg and 0.2µg/kg dose, though effective, were associated with recurrence of shivering.

Thus, prophylactic administration of intravenous dexmedetomidine at 0.5 µg/kg appears to be an optimal strategy for preventing shivering following spinal anaesthesia in patients undergoing lower abdominal, lower limb, and perineal surgeries. Further large-scale studies are recommended to validate these findings and establish standardized dosing guidelines.

REFERENCES

1.      De Witte J, Sessler DI. Perioperative shivering: Physiology and pharmacology. Anesthesiology. 2002;96(2):467-484.

2.      Buggy DJ, Crossley AW. Thermoregulation, mild perioperative hypothermia and post-anaesthetic shivering. Br J Anaesth. 2000;84(5):615-628.

3.      Kurz A, Sessler DI, Christensen R, Clough D, Plattner O. Heat balance and distribution during the core-to-peripheral redistribution of body heat after anesthesia. Anesthesiology. 1995;82(3):662-673.

4.      Kamibayashi T, Maze M. Clinical uses of α₂-adrenergic agonists. Anesthesiology. 2000;93(5):1345-1349.

5.      Elvan EG, Oc B, Uzun S, Karabulut E, Coskun F, Aypar U. Dexmedetomidine and postoperative shivering in patients undergoing elective abdominal hysterectomy. Eur J Anaesthesiol. 2008;25(5):357-364.

6.      Bajwa SJ, Gupta S, Kaur J, Singh A, Parmar SS. Reduction in the incidence of shivering with perioperative dexmedetomidine: A randomized prospective study. J Anaesthesiol Clin Pharmacol. 2012;28(1):86-91.

7.      Belleville JP, Ward DS, Bloor BC, Maze M. Effects of intravenous dexmedetomidine in humans. II. Hemodynamic changes. Anesthesiology. 1992;77(6):1134-1142.

8.      Usta B, Gozdemir M, Demircioglu RI, Muslu B, Sert H, Yaldiz A. Dexmedetomidine for the prevention of shivering during spinal anesthesia. Clin Ther. 2011;33(6):1180-1187.

9.      Nelson LE, Lu J, Guo T, Saper CB, Franks NP, Maze M. The α₂-adrenoceptor agonist dexmedetomidine converges on an endogenous sleep-promoting pathway to exert its sedative effects. Anesthesiology. 2003;98(2):428-436.

10.   Piper SN, Fent MT, Maleck WH, Suttner SW, Boldt J. A comparison of meperidine, clonidine, and urapidil in the treatment of postanesthetic shivering. Anesth Analg. 2000;90(2):439-443.

11.   Hall JE, Uhrich TD, Barney JA, Arain SR, Ebert TJ. Sedative, amnestic, and analgesic properties of small-dose dexmedetomidine infusions. Anesth Analg. 2000;90(3):699-705.