Dexmedetomidine and Fentanyl Versus Midazolam and Remifentanil for Sedation in Patients Undergoing Ablation Procedures

Dexmedetomidine and Fentanyl Versus Midazolam and Remifentanil for Sedation in Patients Undergoing Ablation Procedures

A Pilot Study to Investigate the Efficacy and Safety of Dexmedetomidine and Fentanyl Versus Midazolam and Remifentanil for Sedation in Patients Undergoing Ablation Procedures for Treatment of a Tachyarrhythmia

To evaluate the safety and efficacy of dexmedetomidine and compare this to a current technique commonly used at TGH for sedation in patients undergoing ablation procedures for atrial fibrillation (AF) and atrial flutter. The investigators hypothesise that dexmedetomidine will be at least equivalent to, or more so, in terms of effectiveness and safety, when compared to midazolam and remifentanil for sedation during ablation procedures.

The role of ablation for chronic persistent AF has been debated amongst cardiologists for some time, and there is increasing evidence that ablation may be superior to medical management. As populations age, the rate of AF is likely to increase and therefore the numbers of ablations performed for this arrhythmia will also be expected to increase. Ablation procedures can vary in length from one to more than 6 hours in duration and require the patient to keep still so as not to influence the mapping procedure. Options for anaesthesia care include a general anaesthetic or sedation. Several studies have evaluated the safety of sedation for ablation, using combinations of fentanyl, midazolam and propofol. These demonstrate that the ablation procedures are well tolerated under deep sedation. Dexmedetomidine is an attractive potential agent for this role due to its favourable respiratory pharmacodynamics and good sedation profile. Dexmedetomidine is a short acting relatively specific alpha-2 receptor agonist (alpha 2: alpha 1 = 1300:1). It has been shown to have very little effect on respiratory parameters, even at high doses.In addition, it may offer some analgesic properties and therefore minimise the need for narcotic based agents. the investigators will compare dexmedetomidine infusion and fentanyl bolus with remifentanil infusion midazolam bolus.

This is a prospective, single blind, randomised controlled study looking at the feasibility of dexmedetomidine for sedation during ablation procedures at Toronto General Hospital.

Patients will be randomly allocated (computer generated) to receive either a dexmedetomidine infusion or a remifentanil infusion. The patient, interventional cardiologist and data analyser will be blinded to the drugs given. The anaesthesia care provider will not be blinded

The study drug dexmedetomidine (PrecedexTM) is supplied as dexmedetomidine HCL 200mcg/vial (100mcg/ml). This will be added to 98 ml 0.9% NaCl to achieve a concentration of 2mcg/ml and infused at 0.2-1mcg/kg/hour from the start of the case. The infusion rate will be commenced at 1mcg/kg/hour in those less than or equal to 65 years of age, and at 0.7mcg/kg/hr in those greater than 65 years of age, and then titrated based on the intraoperative sedation scores (to achieve a Sedation and Agitation scale (SAS) score of less than or equal to 4) and cardiovascular parameters (within 30% of baseline).

Remifentanil HCL will be infused at 0.01-0.2 mcg/kg/min titrated to sedation level (SAS less than or equal to 4) and cardiovascular parameters (within 30% of baseline)

The study drug dexmedetomidine (PrecedexTM) will be infused at 0.2-1mcg/kg/hour from the start of the case. The dexmedetomidine infusion will stop at completion of the procedure.

Remifentanil HCL will be infused at 0.01-0.2 mcg/kg/min titrated to sedation level (SAS less than or equal to 4) and cardiovascular parameters (within 30% of baseline). The infusion will be stopped at the end of the procedure.

a.Hypotension i. A decrease of 30% or more from baseline ii. Or absolute cut off values of SBP < 80mmHg DBP <40mmHg iii. Number of events and total dose of phenylephrine or ephedrine administered. b. Hypertension i. An increase in Systolic blood pressure 30% or more from baseline ii. Or an absolute cut off value of > 180mmHg iii. Total number of events c. Bradycardia i. A decrease of 30% or more from baseline ii. Or absolute cut off values of < 40bpm iii. Total number of events and total dose of glycopyrolate or atropine administered.

Respiratory events requiring intervention Respiratory rate < 6 breaths/min Airway obstruction requiring manual support Airway obstruction requiring guedel insertion Apnoea (cessation of respiration >10seconds) Hypoxia (saturations <90% for >20 seconds)

VAS score (visual analog score). VAS is a simple assessment tool consisting of a 10 cm line with 0 on one end, representing no pain, and 10 on the other, representing the worst pain ever experienced, which a patient indicates so the clinician knows the severity of his or her pain. Pain scores using a VAS scale ranging from zero to ten will be recorded every 30 minutes Total amount of additional fentanyl used intraoperatively

Sedation Agitation Scale (SAS) scale range from 1 to 7 will be recorded every 5 minutes. The SAS scale is outlined below with an optimal score of 4 for procedural sedation. Ref: Riker RR, Picard JT and Fraser GL. Prospective evaluation of the Sedation-Agitation Scale for adult critically ill patients. Critical Care Medicine 1999;27(7):1325-1329. Total amount of additional midazolam used intraoperatively

Assessed with the Iowa Satisfaction with Anaesthesia scale 24 hours post procedure b. Assessor blinded to technique c. To include direct questioning regarding the patients willingness to undergo the same procedure again using the same technique Iowa Satisfaction with Anaesthesia scale Ref: Dexter F, Aker J, Wright W. Development of a measure of patient satisfaction with monitored anaesthetic care: the Iowa Satisfaction with Anesthesia Scale. Anesthesiology 1997; 87: 865-73. Patient assessment I threw up or felt like throwing up I would have the same anaesthetic again I itched I felt relaxed I felt pain I felt safe I was too hot or cold I was satisfied with the anesthesia care I felt pain during the surgery I felt good I hurt

Total time spent in recovery until appropriate discharge criteria are met and patient is discharged to the ward

Inclusion Criteria: patients listed for an ablation procedure for treatment of atrial fibrillation or flutter at TGH requiring sedation provided by an anesthetist Valid consent Exclusion Criteria: Baseline HR <40 Baseline SBP < 80mmHg Baseline SBP > 180mmHg Second or third degree heart block unless pacemaker in situ Uncontrolled heart failure/severe LV dysfunction (Ejection fraction < 40%) Severe hepatic dysfunction (Transaminases greater than 2 times the upper limit of normal) Renal dysfunction: estimated GFR < 30ml/min, or requiring dialysis Allergy to any of the study drugs (dexmedetomidine, remifentanil, fentanyl, midazolam) Cognitive impairment precluding ability to tolerate sedation and comply with assessment methods Requirement for general anaesthetic for the procedure Pregnancy or breast feeding mothers Chronic use or addiction to opioids < 18 years of age

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