DIRECT CARDIAC MASSAGE WITHOUT MAJOR THORACOTOMY - FEASIBILITY AND SYSTEMIC BLOOD-FLOW

Background: Open-chest cardiac massage (OC-CM) provides higher blood p ressure and flow than closed-chest compression and may improve the pro bability of successful resuscitation from cardiac arrest. Its clinical use has been limited by its requirement for a major thoracotomy. The present pilot study tested the technical feasibility of performing eff ective direct cardiac massage without a major thoracic incision, by us ing a simple, manually-powered plunger-like device, inserted through a small thoracic incision, to cyclically compress the cardiac ventricle s. The method was termed minimally-invasive direct cardiac massage (MI D-CM). Systemic blood flow using MID-CM was compared to that with OC-C M, by both direct systemic hemodynamic measurements, cumulative metabo lic indicators of the ratio of whole body oxygen delivery and oxygen c onsumption, and a metabolic index of pulmonary blood flow. Methods: In 12 large swine, baseline systemic and pulmonary hemodynamic measureme nts were performed. Arterial and mixed venous blood gases and metaboli c indicators of systemic blood flow were measured. Ventricular fibrill ation was induced and after 4 min, animals underwent either bimanual O C-CM (N=6) or MID-CM (N=6). At 10, 20 and 30 min, hemodynamic and meta bolic measurements were repeated. Results: Systemic Blood Pressure: Ao rtic systolic and diastolic blood pressures were reduced from baseline levels with both OC-CM and MID-CM. No difference in pressure was note d between OC-CM and MID-CM groups. Pulmonary Artery Pressure: Pulmonar y artery systolic pressure was elevated from baseline during OC-CM and MID-CM. Pulmonary artery diastolic pressures remained constant throug hout the resuscitation period in both groups. No differences in pulmon ary systolic or diastolic pressure were noted between OC-CM and MID-CM groups. A trend towards higher pulmonary systolic pressures appeared with MID-CM. Thermodilution Blood Flow: Cardiac index fell from baseli ne levels with OC-CM and MID-CM. No difference in cardiac index was no ted between OC-CM and MID-CM groups. Metabolic Indices: Mixed venous O -2 saturation decreased from baseline levels during resuscitation in b oth experimental groups, with a further decrease at 30 min compared to 10- and 20-min levels. No difference was noted between OC-CM and MID- CM groups at any point. Arterial pH was reduced from baseline levels a t 30 min in both groups compared to baseline but no difference was not ed between groups. Arterio-venous PcO(2) difference increased above ba seline levels with both OC-CM and MID-CM. No difference was noted betw een groups. Lactate levels displayed a progressive increase up to 30 m in in both groups compared to baseline. No differences were noted betw een OC-CM and MID-CM groups for any time-period. Conclusions: Direct c ardiac massage without major thoracotomy is technically feasible. The level of systemic blood flow that can be achieved with MID-CM is hemod ynamically and metabolically equivalent to that obtained using convent ional bimanual OC-CM.