Optimal Single Dose Intrathecal Dexmedetomidine for Postoperative Analgesia

Study Overview
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Brief Summary
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Spinal anesthesia is a commonly used technique for lower limb surgeries offering better quality of postoperative analgesia, lower incidence of side effects, and shorter post-anesthesia care unit stay than general anesthesia. However, the relatively short duration of action of the currently available local anesthetics (LAs) make these advantages short-lived. The risk for local anesthetic toxicity (LAST) increases with the trials to use higher concentrations or volumes of intrathecal local anesthetics to increase the duration of analgesia. Dexmedetomidine has the potential to prolong the duration of perioperative analgesia without the need for using high doses of local anesthetics and hence with decreasing the potential risk of local anesthetic, but the increased likelihood adverse effects such as short term bradycardia and prolonged duration of motor block may offset these benefits.

Detailed Description
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The aim of this study is to determine the optimal single-dose of intrathecal dexmedetomidine that prolongs the analgesic duration with the least possible side effects. With the patients in the sitting position and the use of complete aseptic technique, 25G Whitacre spinal needles will be introduced through L2-L4 interspaces and after observing free flow of the CSF, a 3ml volume including bupivacaine 12.5mg in conjunction with dexmedetomidine (3 µg) will be injected in the first case, then the patient will be turned supine. The dose of intrathecal DEX given to the next patient will be guided by modified Dixon's up-and-down method using 1.5 mg as a step size, which assumed to be of clinical importance.

Official Title
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Optimal Single-dose Intrathecal Dexmedetomidine for Postoperative Analgesia After Lower Limb Surgery

Conditions
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Lower Limb Surgery

Intervention / Treatment
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* Drug: Intrathecal dexmedetomidine


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: American Society of Anesthesiologists physical class I to II. Patients scheduled for elective lower limb surgeries. Exclusion Criteria: Morbid obese patients. Severe or uncompensated cardiovascular disease. Significant renal disease. Significant hepatic disease. Pregnancy. Lactating . Heart block. Bradyarrhythmias. Receiving adrenergic receptor antagonist medications. Receiving calcium channel blockers. Patients with pacemakers. Patients with implanted cardioverter defibrillator. Allergy to the study medications. Psychological disease. Neurological disorders. Communication barrier. Mental disorders. Epilepsy. Drug or alcohol abuse. Contraindications to spinal anaesthesia. Receiving opioid analgesic medications within 24 h before the operation.

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 65 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Prevention
Intervention Model: Single Group Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Other: Intrathecal dexmedetomidine<br>Up-down sequential allocation The dose of intrathecal DEX given to the next patient will be guided by modified Dixon's up-and-down method using 1.5 mg as a step size, which assumed to be of clinical importance | Drug: Intrathecal dexmedetomidine<br>* The dose of intrathecal DEX given to the next patient will be guided by modified Dixon's up-and-down method using 1.5 mg as a step size, which assumed to be of clinical importance<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Duration of analgesia | The duration of analgesia, defined as the time from administering of intrathecal study solution (T0) to the time for the first rescue analgesic request | For 13 hours after surgery | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Postoperative pain score | Using visual analog scale | For 24 hours after surgery | 
| Onset of sensory blockade | Onset of sensory block time defined as the time elapsed from T0 to achieve the adequate sensory level for the planned surgery. | For 1 hour after initiaion of spinal anesthesia | 
| Onset of motor blockade | Onset of motor block time defined as the time elapsed from T0 to achieve the Bromage scale of 3 | For 2 hours after initiation of spinal anesthesia | 
| Highest dermatome level of sensory blockade | The highest dermatome level of sensory blockade and the time needed to achieve this level from the time of injection as well as time to two segment sensory regression after T0 will be recorded | For 4 hours after initiation of spinal anesthesia | 
| Time to motor regression | Time to motor regression to a Bromage scale of 2 | For 6 hours after initiation of spinal anesthesia | 
| Sedation score | Sedation scores will be assessed using a sedation scale (awake and alert= 0; quietly awake= 1; asleep but easily roused= 2; deep sleep= 3). | For 24 hours after initiation of spinal anesthesia | 
| Postoperative nausea and vomiting | The degree of nausea and vomiting. Nausea will be measured using a numerical rating system (none= 0; mild= 1; moderate= 2; severe= 3) | For 24 hours after initiation of spinal anesthesia | 
| Cumulative tramadol consumption |  | For 24 hours after surgery | 
| Intraoperative bradycardia |  | For 4 hours after initiation of spinal anesthesia | 
| Intraoperative use of ephedrine |  | For 4 hours after initiation of spinal anesthesia | 
| Intraoperative use of atropine |  | For 4 hours after initiation of spinal anesthesia | 
| Intraoperative use of supplemental fentanyl |  | For 4 hours after initiation of spinal anesthesia | 
| Intraoperative use of midazolam |  | For 4 hours after initiation of spinal anesthesia |