PEDIATRIC DEFIBRILLATION - CURRENT FLOW IS IMPROVED BY USING ADULT ELECTRODE PADDLES

Objective. Current flow, the major determinant of defibrillation succe ss, depends on delivered energy and transthoracic impedance. Previous experimental data suggest that transthoracic impedance is higher using ''pediatric'' electrode paddles compared to the larger ''adult'' elec trode paddles. There are few data from actual shocks to support the ex perimental studies. The purpose of this study was to measure transthor acic impedance during actual shock delivery and to determine the optim al electrode paddle size for pediatric defibrillation and cardioversio n. Methods. We prospectively evaluated all shocks of less than or equa l to 20 joules given to pediatric patients at the University of Iowa f rom 1988 to 1992. Data collected included energy selected by the opera tor, energy delivered by the defibrillator, peak current flow and tran sthoracic impedance. Data were analyzed by unpaired t test and linear regression. Results. Fifty-five shocks were delivered to 20 patients, age newborn to 8 years. Thirty-seven shocks were given with ''pediatri c'' electrode paddles (surface area 21 cm(2)) and 18 with ''adult'' el ectrode paddles (surface area 83 cm(2)). Selected energy correlated we ll with delivered energy (r = .98, P < .0001). Delivered energy using ''pediatric'' electrodes did not differ from that delivered with ''adu lt'' electrodes (8.0 +/- 0.9 joules vs 10.5 +/- 1.2 joules P > .1). Ho wever transthoracic impedance was significantly higher with ''pediatri c'' electrodes (78.1 +/- 4.4 ohms vs 54.6 +/- 2.7 ohms P < .0008), res ulting in lower peak current flow through ''pediatric'' electrode padd ies (6.2 +/- 0.5 amps vs 8.7 +/- 0.5 amps P < .002). There was no corr elation between joules/kg and peak current flow (r = .26, P > .05). Co nclusion. Use of ''pediatric'' electrode paddles results in higher tra nsthoracic impedance and thus lower peak current flow. In pediatric de fibrillation, larger ''adult'' electrode paddles should be used as soo n as chest size permits (approximately 10 kg). Lower transthoracic imp edance results in higher current flow that facilitates cardioversion a nd defibrillation.