Mechanical Lung Assist Augments Forward Pulmonary Blood Flow in Primary Bidirectional Cavopulmonary Shunt Physiology in Neonatal Pigs
Osami Honjo, Sandra L. Merklinger, Abdullah A. Alghamdi, Setsuo Takatani, Glen S. Van Arsdell; 1The Labatt Family Heart Centre, The Hospital for Sick Children, Toronto, ON, Canada
Comment on this Abstract
Objective: Survival in patients with hypoplastic left heart syndrome might be improved by primary in-series palliation. Successful neonatal application of this approach would require lung circulatory assistance due to pulmonary vascular immaturity. We tested a novel miniature centrifugal pump as a means to augment forward bidirectional cavopulmonary shunt (BCPS) blood flow against higher neonatal pulmonary pressure and resistance in a neonatal pig model of primary 1+1/2 ventricle repair physiology (high pulmonary resistance model).
Methods: Six 3-week-old piglets (mean weight, 10.1 kg) underwent surgical creation of a BCPS. The final anatomy was that of a 1+1/2 ventricle repair with mechanical SVC blood flow assist. A 5 mL-prime miniature centrifugal pump was connected via cannulae placed in the SVC and main PA. Retrograde SVC flow caused by the pump and right ventricular pulsatility was limited by a band placed distal to the SVC cannula. Blood gas, hemodynamic and metabolic analysis were recorded at pump speeds of 1500, 2000, 2500 and 3000 RPM/min. Finally, as a means of testing conversion to an unassisted BCPS physiology, an 8Fr Mullins dilatation catheter was inserted into the SVC across the band whereby the artificially-created obstruction was dilated.
Results: Incremental increases in pump speed augmented SVC blood flow (p=0.03) and diminished SVC pressure (p=0.03) thereby normalizing cerebral perfusion pressure (p=0.02) (Table 1). Final pump flow achieved was equivalent to the baseline SVC flow (pre SVC flow: 436±96 ml/min vs. mechanical assist: 427±120 ml/min; mean±SD, p=NS). The animals were hemodynamically stable, well ventilated and oxygenated until euthanization at 3 hours following the procedure. Clinical demonstration of percutaneous conversion to unassisted SVC flow was shown with successful balloon dilation of the SVC band.
Conclusion: The study demonstrates that mechanical lung assist can normalize SVC flow, in a neonatal pig high pulmonary vascular resistance physiology, thereby maintaining ventilation, hemodynamic and metabolic stability, and adequate cerebral perfusion pressure. Coupled with percutaneous dilation of the SVC, this study raises the possibility of primary creation of BCPS with an aid of mechanical lung assist followed by percutaneous completion of unassisted BCPS circulation.
Hemodynamics and metabolism of primary BCPS with mechanical lung assist
| 1500RPM | 2000RPM | 2500RPM | 3000RPM | p Value (ANOVA) |
| SVC flow (mL/min) | 147+/-63* | 246+/-80 | 346+/-100 | 427+/-120* | *0.03 |
| SVC pressure (mmHg) | 14.0+/-1.8*¶ | 12.1+/-3.1 | 7.5+/-6.0¶ | 6.6+/-3.7* | *¶0.03 |
| Cerebral perfusion pressure (mmHg) | 29.0+/-4.5*¶ | 32.0+/-5.2 | 35.5+/-5.6¶ | 38.3+/-5.4* | *¶0.02 |
| pH | 7.38+/-0.03 | 7.39+/-0.03 | 7.39+/-0.04 | 7.41+/-0.06 | NS |
| PaCO2 (mmHg) | 40.6+/-0.8 | 41.1+/-1.7 | 40.0+/-2.1 | 40.3+/-3.1 | NS |
| PaO2 (mmHg) | 327.3+/-31.5 | 328+/-36.6 | 385+/-20.9 | 324+/-33.8 | NS |
| Lactate | 4.1+/-1.7* | 3.9+/-1.1 | 3.5+/-0.9 | 3.1+/-0.8* | *0.03 |
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