Changes in transthoracic impedance during sequential biphasic defibrillation.

INTRODUCTION: Sequential monophasic defibrillation reduces transthoracic impedance (TTI) and progressively increases current flow for any given energy level. The effect of sequential biphasic shocks on TTI is unknown. We therefore studied patients undergoing elective cardioversion using a biphasic waveform to establish whether this is a phenomenon seen in the clinical setting. METHODS: Adults undergoing elective DC cardioversion for atrial flutter or fibrillation received sequential transthoracic shocks using an escalating protocol (70J, 100J, 150J, 200J, and 300J) with a truncated exponential biphasic waveform. TTI was calculated through the defibrillator circuit and recorded electronically. Successful cardioversion terminated further defibrillation shocks. RESULTS: A total of 58 patients underwent elective cardioversion. Cardioversion was successful in 93.1% patients. First shock TTI was 92.2 [52.0-126.0]Omega (n=58) and decreased significantly with each sequential shock. Mean TTI in patients receiving five shocks (n=5) was 85.0Omega. CONCLUSION: Sequential biphasic defibrillation decreases TTI in a similar manner to that seen with monophasic waveforms. The effect is likely during defibrillation during cardiac arrest by the quick succession in which shocks are delivered and the lack of cutaneous blood flow which limits the inflammatory response. The ability of biphasic defibrillators to adjust their waveform according to TTI is likely to minimise any effect of these findings on defibrillation efficacy.

A survey of tracheostomy practice in a cardiothoracic intensive care unit.

OBJECTIVE: The purpose of this study was to assess current practice of performing tracheostomies in critically ill cardiac surgical patients, to establish complication rates, and to identify areas of this clinical practice that could be improved. DESIGN: Retrospective observational study. SETTING: A cardiothoracic intensive care unit in a teaching hospital. PARTICIPANTS: The most recent series of 100 tracheostomies performed in patients admitted to the intensive care unit. INTERVENTIONS: Percutaneous or surgical tracheostomy for respiratory management. MEASUREMENTS AND MAIN RESULTS: A total of 95 patients had 1 tracheostomy performed. One patient had a tracheostomy performed twice, and 1 patient had a tracheostomy performed 3 times; these repetitions were caused by recurrent respiratory failure. The median time from tracheal intubation to tracheostomy was 5 days (range, 1-23 days; interquartile range, 4-8 days), and median period between insertion and decannulation was 20 days (range, 2-77 days; interquartile range, 12-25 days). The most common reason for insertion was an anticipated long weaning time (55%) followed by insertion after failed extubation (32%). The Ciaglia percutaneous dilational technique was used for 89% of tracheostomies, whereas surgical techniques were used for 8%. The most common complication was either complete or partial obstruction of the tracheostomy tube (24%) followed by infection of the tracheostomy site in 18% (17/94) and bleeding at the time of insertion (11%). CONCLUSION: The percutaneous dilational technique of tracheostomy was used predominantly in this unit. The median time from tracheal intubation to tracheostomy was 5 days. The most common complications were bleeding at the time of insertion, obstruction of the tracheostomy tube, and stomal infection.

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.

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.

A randomized controlled trial of efficacy and ST change following use of the Welch-Allyn MRL PIC biphasic waveform versus damped sine monophasic waveform for external DC cardioversion.

OBJECTIVE: Biphasic waveforms have similar or greater efficacy at cardioverting atrial and ventricular arrhythmias at lower energy levels than monophasic waveforms, and cause less ST depression following defibrillation of ventricular fibrillation. No studies have investigated this effect on ST change with atrial arrhythmias. We studied the efficacy of the Welch Allyn-MRL PIC biphasic defibrillator. METHODS: One hundred and thirty-nine patients undergoing elective DC cardioversion for atrial arrhythmias were randomised to cardioversion by monophasic (Hewlett Packard Codemaster XL; 100, 200, 300, 360 and 360J) or biphasic (Welch Allyn-MRL PIC; 70, 100, 150, 200 and 300J) defibrillator. We analysed success of cardioversion after 0 and 30min, cumulative energy, number of shocks and energy at successful cardioversion. The ST change in the recorded electrocardiogram was measured at 15s after all shocks using electronic callipers. RESULTS: Immediately after cardioversion 59/68 (86.8%) of the monophasic group versus 56/60 (93.3%) of the biphasic group were in sinus rhythm. Of the monophasic group, 55/67 (82.1%) remained in sinus rhythm at 30min versus 53/58 (91.4%) of the biphasic group. These differences were not significant at 0min (P=0.35) or 30min (P=0.21). The biphasic group required significantly fewer shocks (P=0.006), less cumulative energy (P<0.0001) and required lower total energy for successful cardioversion (P<0.0001). Of the 102 patients with electrocardiogram recordings suitable for analysis, ST segment change was greater in the monophasic group (P=0.037). CONCLUSIONS: The Welch Allyn-MRL biphasic waveform for DC cardioversion results in fewer shocks, with less cumulative energy delivered and less post shock ST change than with a Hewlett Packard Codemaster XL damped sine wave monophasic waveform.

Post-shock myocardial stunning: a prospective randomised double-blind comparison of monophasic and biphasic waveforms.

INTRODUCTION: Compared with monophasic defibrillation, biphasic defibrillation is associated with less myocardial stunning and earlier activation of sodium channels. We therefore hypothesised that earlier sodium channel activation would result in earlier restoration of the first sinus beat following elective DC cardioversion. METHODS: Adults undergoing elective DC cardioversion were randomised to receive either monophasic or biphasic escalating transthoracic shocks. The ECG was recorded electronically during defibrillation and the time from delivery of the shock to restoration of the first sinus beat, measured from the beginning of the 'P' wave, was calculated. RESULTS: Seventy four patients were studied. Data were unavailable from 18 patients. There was no demographic difference between groups. Median time to the first sinus beat following monophasic defibrillation (n=25) was 3.66 s (95% CI 2.55-4.61 s) and following biphasic defibrillation (n=33) was 2.21s (95% CI 1.76-2.56 s; P

The effect of topical non-steroidal anti-inflammatory cream on the incidence and severity of cutaneous burns following external DC cardioversion.

INTRODUCTION: Cutaneous burns are a common cause of morbidity following direct current (DC) cardioversion. We designed a study to determine whether the application of non-steroidal anti-inflammatory cream prior to cardioversion reduces their incidence and severity. MATERIALS AND METHODS: Two hours before elective DC cardioversion, we randomised 55 patients to receive ibuprofen 5% cream or placebo cream over sternal and apical pad sites, with patients acting as their own controls. Two hours after cardioversion an independent blinded observer measured skin temperature, erythema index, and minimum sensory and pain detection thresholds at sternal and apical pad sites. Visual analogue pain score (VAS) for each site was recorded at 2 h and 24 h post-cardioversion. RESULTS: There was a statistically significant difference between pain measured by VAS, skin temperature and pain detection threshold measured at pad sites with pre-applied ibuprofen 5% cream and those with pre-applied aqueous cream, after elective DC cardioversion. CONCLUSION: Prophylactic application of topical ibuprofen 5% cream 2h prior to elective DC cardioversion reduces pain and inflammation. Consideration should be given to use of prophylactic application of topical ibuprofen as routine treatment for elective DC cardioversion.

The effect of prophylactic topical steroid cream on the incidence and severity of cutaneous burns following external DC cardioversion.

INTRODUCTION: Cutaneous burns are a common cause of morbidity following direct current (DC) cardioversion. We designed a prospective double-blinded controlled study to determine whether the application of steroid cream prior to cardioversion reduces their incidence and severity. MATERIALS AND METHODS: Two hours before elective DC cardioversion, we applied betamethasone 0.1% cream or placebo cream over sternal and apical pad sites in 56 patients, with patients acting as their own controls. Two hours after cardioversion, a separate blinded observer measured the visual analogue pain score (VAS), sensory and pain detection thresholds, skin temperature and erythema index at sternal and apical pad sites. RESULTS: The study had an 80% power to detect a 50% difference in VAS at 2 h, accepting an alpha error of 0.05. There was no difference between pain at 2 or 24 h, skin temperature, erythema index, sensory and pain detection thresholds at pad sites treated with steroid cream or control. CONCLUSION: Topical betamethasone 0.1% cream applied 2 h before elective DC cardioversion is no more effective than placebo at reducing the pain and inflammation from cardioversion burns.

The incidence and severity of cutaneous burns following external DC cardioversion.

INTRODUCTION: Cutaneous burns are a common cause of morbidity following direct current (DC) cardioversion, but the incidence and severity have never been quantified. MATERIALS AND METHODS: Two hours after elective DC cardioversion in 83 sequential patients, we measured skin temperature, erythema index, and minimum sensory and pain detection thresholds at paddle sites and control sites on the contralateral side. Visual analogue pain score (VAS) was recorded at 2 and 24h post-cardioversion. RESULTS: Values for areas over paddle sites were higher (P < 0.05) than control site for all variables measured at 2h. Eighty-four percent patients experienced some pain and 23% patients experienced moderate to severe pain as assessed by VAS. Burns were greater at the edge than the centre of sternal sites and greater at sternal than apical sites. There were positive correlations between transthoracic impedance (TTI) and total energy delivered (r(2) = 0.048; P = 0.04); total energy and pain at 2 h (r(2) = 0.38; P < 0.0001) and 24 h (r(2) = 0.23; P < 0.0001); and number of shocks and pain at 2 h (r(2) = 0.36; P < 0.0001) and 24 h (r(2) = 0.19; P < 0.0001). CONCLUSION: Elective DC cardioversion causes burns as measured by skin temperature, erythema index and sensory threshold to sharp touch. Pain experienced is related to the total energy and number of shocks delivered. To reduce burns, operators should apply optimal paddle force equally to both paddles, with the paddles applied so as to provide even contact along their edges. Burns may also be minimised by starting with lower energy shocks.