Cardioversion and the use of sedation

Reduced Motion External Defibrillation (RMD): Reduced Subject Motion with Equivalent Defibrillation Efficiency validated in Swine

BACKGROUND

External defibrillators are used for arrhythmia cardioversion and for defibrillating during cardiac arrest. During defibrillation, short-duration Biphasic pulses cause intense motion due to rapid chest-wall muscle contraction. A reduced-motion external defibrillator (RMD) was constructed by integrating a commercial defibrillator with a Tetanizing-waveform generator. A long-duration low-amplitude Tetanizing-waveform slowly stimulated the chest musculature prior to the Biphasic pulse, reducing muscle contraction during the shock.

OBJECTIVE

Evaluate RMD defibrillation in swine for subject-motion during defibrillation pulses and for defibrillation effectiveness. RMD defibrillation can reduce the duration of arrhythmia ablation-therapy or simplify cardioversion procedures.

METHODS

The Tetanizing unit delivered a triangular 1-kHz pulse of 0.25-2.0sec duration and 10-100Volt peak amplitude, subsequently triggering the conventional defibrillator to output standard 1-200J energy Biphasic pulses at the next R-wave. Forward-limb motion was evaluated by measuring Peak Acceleration and Limb Work during RMD (Tetanizing+Biphasic) or Biphasic-pulse-only waveforms at 10^-3sec sampling-rate. Seven swine were arrested electrically and subsequently defibrillated. Biphasic-pulse-only and RMD defibrillations were repeated 25-35 times/swine, varying Tetanizing parameters and the Biphasic-pulse energy. Defibrillation thresholds (DFTs) were established by measuring the minimum energy required to restore sinus-rhythm with Biphasic-pulse-only or RMD defibrillations.

RESULTS

Two forward-limb acceleration-peaks occurred during both the Tetanizing-waveform and Biphasic-pulse, indicating rapid and slower nociceptic (pain-sensation) nerve-fiber activation. Optimal RMD Tetanizing-parameters (25-35V, 0.25-0.75sec duration), relative to Biphasic-pulse-only defibrillations, resulted in 74+10% smaller Peak Accelerations and 85+10% reduced Limb Work. DFT energies were identical, comparing RMD to Biphasic-pulse-only defibrillations.

CONCLUSION

Relative to conventional defibrillations, RMD defibrillations maintain rhythm-restoration efficiency with drastically reduced subject-motion.

General anaesthesia for external electrical cardioversion of atrial fibrillation: experience of an exclusively cardiological procedural management

AIMS

External electrical cardioversion (EC) usually requires brief general anaesthesia involving anaesthetists. The aim of this study was to evaluate the feasibility and safety of inducing anaesthesia for EC of atrial fibrillation (AF) exclusively by the cardiologic team with anaesthetists on-hand.

METHODS AND RESULTS

A retrospective analysis of 624 elective EC, over a 6-year period, was made. No patients were excluded due to the severity of pathology or comorbidities. The protocol of the intravenous anaesthesia was 5 mg bolus of midazolam and subsequent increasing doses of propofol starting from 20 mg to achieve the desired sedation level. After delivering DC shock, a direct observation period followed in order to assess the post-sedation recovery and to detect the procedure-related complications. Electrical cardioversion was effective in 98.9% of the cases. General anaesthesia was effective in 100% of cases with a dosage of propofol, ranging between 20 mg to a maximum of 80 mg, after 5 mg of midazolam was administered. All patients generally showed a fast recovery waking up in a few minutes. The anaesthesiology team was never called for assistance. All the procedures were carried out by the cardiologic team as planned. No thrombo-embolic and allergic complications were observed. Arrhythmic complications were uncommon and essentially bradyarrhythmias.

CONCLUSION

A general anaesthesia for outpatient EC of AF can be safely handled by a cardiologist having adequate experience with anaesthetical agents. Moreover, the association of midazolam and a very small dosage of propofol, given their synergic action, is effective and safe in inducing anaesthesia. Arrhythmic complications are rare and limited to bradyarrhythmias.

Safety and Acceptability of Implantation of Internal Cardioverter-Defibrillators Under Local Anesthetic and Conscious Sedation

BACKGROUND

Implantation and testing of implantable defibrillators (ICDs) using local anesthetic and conscious sedation is widely practiced; however, some centers still use general anesthesia. We assessed safety and patient acceptability for implantation of defibrillators using local anesthetic and conscious sedation.

METHODS

The records of 500 consecutive device implants from two UK cardiac centers implanted under local anesthetic and conscious sedation from January 1996 to December 2004 were reviewed. Procedure time, left ventricular ejection fraction (LVEF) sedative dosage (midazolam), analgesic dosage (fentanyl or diamorphine), requirement for drug reversal, and respiratory support were recorded. Patient acceptability of the procedure was also assessed.

RESULTS

Of 500 implants examined, 387 were ICDs, 88 were biventricular ICDs, and 25 were generator changes. Patients with biventricular-ICDs had significantly longer (mean +/- SD) procedure times 129.7 +/- 7.6 minutes versus 63.3 +/- 32.3 minutes; P < 0.0001 and lower LVEF 24.4 +/- 8.4% versus 35.7 +/- 15.4%; P < 0.0001. There were no differences in the doses (mean +/- SD) of midazolam 8.9 +/- 3.5 mg versus 8.0 +/- 3.1 mg; P = NS, diamorphine 4.3 +/- 2.0 mg versus 3.8 +/- 1.7 mg; P = NS or fentanyl 94.4 +/- 53.7 mcg versus 92.2 +/- 48.6 mcg; P = NS, between the two groups. There were no deaths or tracheal intubations in either group. Acceptability was available for 373 of 500 (75%) patients, 41 of 373 (11%) described "discomfort," but from these 41 patients only 14 of 373 (3.8%) declined a second procedure under the same conditions.

CONCLUSIONS

Implantation of defibrillators under local anesthetic and sedation is safe and acceptable to patients. General anesthesia is no longer routinely required for implantation of defibrillators.

Sedation with midazolam for electrical cardioversion

BACKGROUND

Electrical cardioversion (ECV) usually requires the assistance of the anesthesiology team. To avoid this dependence, previous studies have considered the use of sedation with benzodiazepines administered by cardiologists. We describe our experience with intravenous Midazolam during cardioversion.

METHODS

We performed 280 ECV in 202 patients sedated with intravenous Midazolam, without anesthesiology supervision. In scheduled cardioversions, we tested two protocols of Midazolam administration: a bolus of 3 mg, followed by 2 mg each minute until necessary, and a loading dose of 0.09-0.1 mg/kg. In cardioversions performed during electrophysiology studies or defibrillator implant, Midazolam was administered by small repeated doses during the entire procedure.

RESULTS

Midazolam was effective to obtain adequate sedation in 99% of cases. All patients had amnesia with regards of the cardioversion. A loading dose of Midazolam allowed a shortening of the procedural time without serious adverse events. Intubation or the assistance of an anesthetist was never necessary.

CONCLUSION

Sedation with Midazolam for ECV is effective and well tolerated, with some cautions discussed. A loading dose of Midazolam is well tolerated and further reduces the procedural time.

Four years experience of a nurse-led elective cardioversion service within a district general hospital setting

AIMS

External direct current cardioversion is an effective method of restoring sinus rhythm (SR) in patients with persistent atrial arrhythmias. Increasing demand for hospital beds, together with a reduction in junior doctors' hours, has adversely affected cardioversion provision. A regular nurse-led cardioversion service conducted in a dedicated hospital day-unit was introduced to resolve these constraints. There are limited data on the safety or efficacy of such a service.

METHODS AND RESULTS

All cardioversions between October 2000 and October 2004 were performed by an appropriately trained specialist nurse, under general anaesthesia. Patients attended a pre-assessment clinic. Energy requirements for initial and subsequent defibrillations were guided by a local protocol in accordance with the guidelines from American Heart Association, American College of Cardiology, and the European Society of Cardiology. Rectilinear biphasic defibrillation was introduced in January 2004 with an appropriate protocol amendment. In the absence of complications, the aim was to discharge patients the same day. A total of 578 cardioversions (475 monophasic; 103 biphasic) were performed on 464 patients [72.1% male, mean (+/- SD) age 67.8 +/- 9.4 years] with atrial fibrillation (AF) (89.7%) and atrial flutter (10.3%). SR was restored in 84.0 and 100% of patients with AF and atrial flutter, respectively, which increased to 90.2 and 100% following the introduction of biphasic defibrillation. Biphasic shocks cardioverted AF with less energy (163 +/- 22 vs. 289 +/- 81 J) and less cumulative energy (230 +/- 139 vs. 455+/-255 J) than monophasic (P < 0.001 for both), despite no difference in the duration of AF (P = 0.26) or patient age (P = 0.78). Two patients required hospital admission due to transient bradycardia; both were discharged within 72 h, without the need for permanent pacing. A total of 99.6% of patients was discharged home the same day; there were no deaths.

CONCLUSION

The provision of a nurse-led elective cardioversion service is feasible and effective, without compromising safety.

Nurse-led elective cardioversion: an evidence-based practice review

By posing a clinical practice question, this article aims to document and explore the published evidence base supporting nurse-led cardioversion. A literature review was undertaken to determine the best evidence for practice. Five articles and two conference abstracts describing practice were found to be pertinent to the question. Description of the methodology used was a weakness of all the articles studied, with only one article purported to be framed as a research study. The remainder describe a planned change in nursing practice to encompass the delivery of a service previously, organizationally viewed as, physician led. Evaluations of practice were descriptive and supported by audit data in most articles, however, appropriate evidential comparisons were not offered. These articles were critically appraised in relation to safety and efficacy. Whilst the evidence may be seen to be limited and weak, it does add credence to the notion that a nurse with a suitable experiential background and knowledge base can make a significant contribution to the care of this group of patients. It is clearly evident that further developments in practice should be framed within a research context to support and strengthen the evidence base. Four prominent themes emerged from the review, 'change milieu', 'reshaping boundaries', 'nurse-led', 'efficacy of practice', which are modelled into a conceptual framework. Nursing roles are expanding within the cardiological setting, affording practitioners unprecedented practice opportunities within a supportive organizational framework, however, these roles must be subject to appropriate evaluation in order to continue informing a robust evidence base.