Elsevier

Resuscitation

Volume 71, Issue 3, December 2006, Pages 293-300
Resuscitation

Clinical paper
A randomised controlled trial of the effect of biphasic or monophasic waveform on the incidence and severity of cutaneous burns following external direct current cardioversion

https://doi.org/10.1016/j.resuscitation.2006.04.014Get rights and content

Summary

Objective

Cutaneous burns are a common cause of morbidity following direct current (DC) cardioversion. We designed a prospective randomised double-blinded controlled study to determine the effect of biphasic or monophasic waveform on the pain and inflammation occurring after elective cardioversion.

Materials and methods

One hundred and thirty nine patients undergoing elective DC cardioversion were randomised to receive monophasic (HP Codemaster XL; 100, 200, 300, 360, and 360 J) or biphasic (Welch Allyn-MRL PIC defibrillator; 70, 100, 150, 200, and 300 J) waveforms. Two hours after DC cardioversion, skin temperature, erythema index and sensory threshold to light and sharp touch was measured at the centre and edge of paddle sites. Visual analogue pain score (VAS) was recorded at 2 and 24 h.

Results

There was significantly less pain following biphasic cardioversion as assessed by VAS at both 2 h (p < 0.001; 95% confidence intervals of difference of medians (CI) 0.2–0.8 cm) and 24 h (p = 0.004; 95% CI 0.0–0.4 cm). There was significantly less erythema in patients receiving biphasic cardioversion at the edge of the sternal site (p = 0.046; 95% CI 0.41–4.5). There was no difference in any other variable at any site between biphasic and monophasic cardioversion.

Conclusion

The use of a biphasic waveform for DC cardioversion reduces the inflammation and pain of burns as measured by erythema index and visual analogue scale.

Introduction

We have shown previously that elective direct current (DC) cardioversion causes cutaneous burns as quantified by erythema index, skin temperature and hyperalgesia measured using Von Frey hairs.1 Pain is also common after this procedure, with 84% of patients experiencing some degree of pain and 23% experiencing moderate to severe pain at 2 and/or 24 h after the procedure. The severity of burns were found to correlate with the number and total energy of shocks delivered.1

Successful cardioversion requires the passage of a transthoracic current of sufficient magnitude to depolarise a critical mass of myocardium and restore sinus rhythm. Because of the high resistance across the thorax, a relatively high amount of energy is required to deliver sufficient current density. Protocols using a monophasic waveform discharge up to 360 J, equating to 30–50 A2 and approximately 3000 V.3 Although the time course of this shock is only 5–10 ms, the energy is sufficient to cause superficial burns to the skin. Damage may result from both thermal heating4 as a result of the high impedance at the electrode-skin interface, and electroporation of the cell membrane caused by high current density.5

Compared with monophasic waveforms, biphasic waveforms require less energy and current flow in DC defibrillation3, 6, 7, 8 and cardioversion9, 10, 11 to achieve equal or superior efficacy. Thus pain and inflammation after the procedure, which has been shown previously to correlate with the number and total energy of monophasic shocks delivered, might be expected to be less after biphasic cardioversion. However, although one study which incorporated a cross-over element to its design measured pain using a visual analogue scale (VAS)11 and another (which also incorporated a cross-over element to its design) used a subjective four point scale to document “dermal injury”, to our knowledge, there have been no previous detailed randomised studies of the effects of biphasic or monophasic waveform on pain and inflammation secondary to DC cardioversion. We therefore designed a prospective randomised double-blinded controlled study of patients undergoing elective DC cardioversion to compare the incidence and severity of burns using monophasic or biphasic waveforms.

Section snippets

Materials and methods

Following approval by the local Research Ethics Committee, informed written consent was obtained from 139 sequential adult patients (18 years of age or above) scheduled to undergo elective DC cardioversion. There were no exclusions other than refusal to participate in the study. Patients were randomised by a separate blinded investigator using random number generator software (www.randomizer.org) and sealed envelopes to receive either biphasic (70, 100, 150, 200, and 300 J) or monophasic (100,

Results

We prospectively obtained consent from 139 patients. Subsequently, 11 patients were withdrawn or withdrew after consent had been gained (see Table 1). We obtained complete results from 128 patients (93 male). Median age was 70 (22–87) years, weight 83.0 (42.0–139) kg, mean body mass index (BMI) 28.2 ± 4.50 kg m−2 and median TTI 81.5 (49.0–158) Ω. Prior to cardioversion, atrial fibrillation was present in 110 patients while atrial flutter was present in 18 patients. The numbers of shocks applied to

Discussion

This study found that patients who received a biphasic waveform for elective DC cardioversion of atrial arrhythmias experienced less pain as measured by visual analogue scale at two and 24 h after the procedure, compared with patients who received a monophasic waveform. There was also a reduction in erythema index at the edge of the sternal pad sites in those patients who received a biphasic waveform.

The number needed to treat indicates that on average, eight patients need to be treated with

Conclusions

The use of a biphasic waveform for DC cardioversion reduces the inflammation and pain of burns as measured by erythema index and visual analogue scale. On average, eight patients need to be treated with biphasic rather than monophasic cardioversion to reduce one patient's pain at 2 h from moderate or severe to mild or none.

Conflict of Interest Statement

We received a grant and the loan of the PIC biphasic defibrillator for the duration of the study from Welch-Allyn MRL inc. as above.

Acknowledgements

We thank Dr David A Zideman and Dr John A Prickett for their help and advice with this study.

This study was supported by unrestricted grants from Welch-Allyn MRL inc, Wessex Heartbeat (Southampton University Hospital NHS Trust) and the Association of Anaesthetists of Great Britain and Ireland.

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A Spanish translated version of the summary of this article appears as Appendix in the online version at doi:10.1016/j.resuscitation.2006.04.014.

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