Effect of Dexmedetomidine on Pain Due to Propofol Injection

Propofol is commonly used IV anesthetic, it has been formulated in a concentration of 10 mg/ml in a fat emulsion consisting of 10% soybean oil (long-chain triglycerides). When used for anesthetic induction, propofol causes pain on injection in 28%-90% of patients. pain probably results from a direct irritant effect. Several methods have been used to reduce this pain. Lidocaine pretreatment has been commonly proposed to decrease propofol induced pain, but its failure rate is between 13-32%. Dexmedetomidine is highly selective alfa-2 adrenoreceptor agonist. Alpha-2 receptors are located on blood vessels where they inhibit norepinephrine release. Investigators, therefore, speculated that dexmedetomidine could attenuate the pain due to injection of propofol. Investigators conducted a study to determine the efficacy of dexmedetomidine in decreasing pain due to injection of propofol.

Propofol solution is fat emulsion consisting of soyabean oil. When used for anesthetic induction, propofol causes pain or discomfort on injection. Many factors appear to affect the incidence of pain, which includes site of injection, size of vein, speed of injection, buffering effect of blood, temperature and composition of propofol solution and concomitant use of drugs such as local anaesthetics and opiates.

Pain on injection of propofol can be immediate or delayed. Immediate pain probably results from a direct irritant effect whereas delayed pain probably results from an indirect effect via the kinin cascade. Delayed pain has latency of between 10 and 20 s. The pain produced is usually described as tingling, cold, or numbing, at its worst, a severe burning pain proximal to the site of injection. This sensation tends to occur within 10-20 s of injection and lasts only for the duration of injection. Despite this discomfort, the incidence of phlebitis is less than 1%.

Several methods have been used to reduce this pain with limited success. Lidocaine pretreatment is commonly used to decrease propofol induced pain, but its failure rate is between 13-32%.

Dexmedetomidine is an selective alfa-2 adrenoreceptor agonist with supraspinal, spinal, and peripheral actions. Alpha-2 receptors are located on blood vessels where they inhibit norepinephrine release. Investigators, therefore, speculated that dexmedetomidine could attenuate the pain due to injection of propofol.

• Pain
• Intravenous Propofol Injection

• Drug: I.V injection of 10 ml normal saline
  Patients were randomly assigned in to three groups of 50 each using a computer-generated table of random numbers. Patients Group NS were injected intravenously with 10 ml of normal saline before injection of propofol.
  Other Name: Group NS
• Drug: I.V injection with 0.25mic/kg of dexmedetomidine
  Patients were randomly assigned in to three groups of 50 each using a computer-generated table of random numbers. Patients Group D25 were injected intravenously with 0.25mic/kg of dexmedetomidine diluted with normal saline into 10ml before injection of propofol.
  Other Name: dexmedetomidine
• Drug: I.V injection of 0.50mic/kg of dexmedetomidine
  Patients were randomly assigned in to three groups of 50 each using a computer-generated table of random numbers. Patients Group D50 were injected intravenously with 0.50mic/kg of dexmedetomidine diluted with normal saline into 10ml before injection of propofol.
  Other Name: Dexmedetomidine

• Placebo Comparator: Group NS
  Patients were randomly assigned in to three groups of 50 each using a computer-generated table of random numbers. Patients Group NS were injected intravenously with 10 ml of normal saline before injection of propofol.
  Intervention: Drug: I.V injection of 10 ml normal saline
• Active Comparator: Group D25
  Patients were randomly assigned in to three groups of 50 each using a computer-generated table of random numbers. Patients Group D25 were injected intravenously with 0.25mic/kg of dexmedetomidine diluted with normal saline into 10ml before injection of propofol.
  Intervention: Drug: I.V injection with 0.25mic/kg of dexmedetomidine
• Active Comparator: Group D50
  Patients were randomly assigned in to three groups of 50 each using a computer-generated table of random numbers. Patients Group D50 were injected intravenously with 0.50mic/kg of dexmedetomidine diluted with normal saline into 10ml before injection of propofol.
  Intervention: Drug: I.V injection of 0.50mic/kg of dexmedetomidine

Inclusion Criteria:

• ASA I & II
• Both gender
• Age 18-60
• Elective surgery

Exclusion Criteria:

• Patients taking sedatives or analgesics in the past 24 hours
• History of allergic reactions to anesthetic drugs,
• Atrio-ventricular conduction defects
• Cardiovascular disease and
• Pregnant