Author + information
- Received October 10, 1991
- Revision received December 26, 1991
- Accepted January 15, 1992
- Published online July 1, 1992.
- Richard E. Kerber, MD∗,a,
- Sara Vance, RNa,
- Stephan J. Schomer, MDa,
- D.James Mariano, MDa and
- Francis Charbonnier, PhD∗
- ↵∗Address for correspondence: Richard E. Kerber, MD, Department of Internal Medicine, University of Iowa Hospital, Iowa City, Iowa 52242.
The purpose of this study was to determine the effect of sternotomy on transthoracic impedance, a major determinant of current flow and defibrillation success. Transthoracic impedance was determined by using a validated test-pulse technique that does not require actual shocks. Seventeen patients undergoing median sternotomy were studied prospectively. Transthoracic impedance was determined before operation, 3 to 5 days after operation and (in eight patients) ≥1 month after operation.
When measured using paddle electrodes placed in the standard apex-right parasternal defibrillating position, transthoracic impedance declined after sternotomy in all patients, from 77 ± 18 to 59 ± 17 Ω (p < 0.01); smaller declines were demonstrated by using other electrode positions. Transthoracic impedance remained below the preoperative level in the eight patients who underwent a second set of measurements at least 1 month after operation. Six normal subjects not undergoing sternotomy underwent serial transthoracic impedance measurements at least 5 days apart; mean transthoracic impedance did not change.
It is concluded that transthoracic impedance declines after sternotomy. At any operator-selected energy level a higher current flow will result after sternotomy; this may facilitate postoperative defibrillation.
☆ This study was supported in part by Grant HL-14388 from the National Institutes of Health, Bethesda, Maryland and in part by a grant from the Hewlett-Packard Corporation.
- Received October 10, 1991.
- Revision received December 26, 1991.
- Accepted January 15, 1992.