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Hemodynamic determinants of subdiaphragmatic venous return during closed-chest CPR in a canine cardiac arrest model
J T Niemann1, J P Rosborough, P C Pelikan
1Department of Emergency Medicine, UCLA School of Medicine.
Objective:
To assess the hemodynamic determinates of peripheral subdiaphragmatic venous-to-right-heart return during closed-chest CPR.
Model:
Seven anesthetized dogs subjected to electrically induced ventricular fibrillation for five minutes.
Interventions:
Conventional closed-chest CPR and closed-chest CPR with continuous abdominal binding at a chest compression rate of 60 per minute, a compression-to-relaxation ratio of 50:50, and a ventilation-to-compression ratio of 1:5.
Methods:
Solid-state catheters were positioned in the ascending aorta, right atrium (RA), and inferior vena cava (IVC). Cannulating electromagnetic flow probes were inserted into the IVC and a carotid artery. Analog-to-digital conversion was performed electronically. Five minutes after ventricular fibrillation was induced, interventions were performed in an alternating sequence. Systolic, diastolic, and mean pressures and flows were measured and compared.
Statistical Methods:
Two-tailed, unpaired t test applied to equal sample size, linear regression analysis, and multiple regression analysis.
Results:
Abdominal binding during CPR significantly increased (P less than .05) all measured systolic and diastolic CPR intravascular pressures compared with CPR without abdominal binding but did not affect IVC-to-right-heart venous return. During conventional CPR without abdominal binding, venous return was dependent on the diastolic IVC pressure (r = .86, P = .014), mean IVC pressure (r = .80, P = .03), and carotid blood flow (r = .99, P = .001) but not on the IVC-to-RA pressure gradient. With abdominal binding, venous return was not correlated with any study hemodynamic variable, including the peripheral venous-to-RA pressure gradient.
Conclusion:
Venous return from the subdiaphragmatic venous bed during CPR is dependent on venous pressure, not on the peripheral venous-to-right-heart pressure gradient. Abdominal binding during CPR does not affect venous return. Venous return during CPR diastole is highly dependent on central venous capacitance (left heart outflow during CPR systole).