A comparative study between hypothermic and normothermic cardiopulmonary bypass in open heart surgery in dogs--effects on systemic hemodynamics

Challenges of cardiopulmonary bypass-a review of the veterinary literature

Cardiopulmonary bypass (CPB) has been used in veterinary medicine in experimental surgery and to address congenital and acquired diseases. We review the veterinary literature and expose common challenges of CPB in dogs and cats. Specifically, we describe the most specific elements of this technique in veterinary patients. The variety in animal size has made it difficult to standardize cannulation techniques, oxygenators, and priming volumes and solutions. The fact that one of the most common cardiovascular disorders, mitral valve disease, occurs predominantly in small dogs has limited the use of bypass in these patients because of the need for small, low prime oxygenators and pumps that have been unavailable until recently. Coagulation, hemostasis, and blood product availability have also represented important factors in the way CPB has developed over the years. The cost and the challenges in operating the bypass machine have represented substantial limitations in its broader use.

Comparison of Right Atrium Incision and Right Ventricular Outflow Incision for Surgical Repair of Membranous Ventricular Septal Defect Using Cardiopulmonary Bypass in Dogs

OBJECTIVE

To compare right atrium incision (RAI) and right ventricular outflow incisions (RVI) for surgical repair of membranous ventricular septal defect (VSD) facilitated by cardiopulmonary bypass (CPB).

STUDY DESIGN

Retrospective study.

ANIMALS

Dogs (n=10) with VSD.

METHODS

Medical records of dogs that had VSD repair were reviewed. Membranous VSD without any malformation and abnormality was confirmed on several clinical examinations and by angiocardiography. RAI (5 dogs) and RVI (5 dogs) was used for VSD access and repair facilitated by CPB. Procedure comparison was by surgical duration, postoperative recovery period, and occurrence of postoperative arrhythmia.

RESULTS

Duration of surgery was similar for RAI and RVI; however, postoperative recovery time was significantly reduced with RAI. Significant moderate operative damage occurred with right atrium incision.

CONCLUSIONS

Right atrium incision was more effective than RVI for repair of membranous VSD using CPB.

CLINICAL RELEVANCE

RAI should be considered in preference to RVI for repair of membranous VSD using CPB.

Comparison of extracapillary and endocapillary blood flow oxygenators for open heart surgery in dogs: efficiency of gas exchange and platelet conservation

The goal of the current study was to compare the efficiency of gas exchange and platelet conservation of a new extracapillary blood flow oxygenator versus an endocapillary blood flow oxygenator during open heart surgery with extracorporeal circulation in dogs. Dilation and remodeling of the right ventricular outflow tract of dogs was performed using a patch graft technique to simulate pulmonary stenosis. Sequential pre- and post-operative blood analysis revealed that gas exchange efficiency and platelet conservation was significantly greater with the extracapillary blood flow oxygenator than with the endocapillary blood flow oxygenator. However, the priming volume of the extracapillary blood flow oxygenator was significantly greater, leading to hemodilution. We conclude that while the extracapillary blood flow oxygenator provided benefits in terms of gas exchange and platelet conservation, development of a smaller extracapillary blood flow type oxygenator to reduce hemodilution effects would be beneficial.

A long term comparison between Denacol EX-313-treated bovine jugular vein graft and ultrafine polyester fiber graft for reconstruction of tight ventricular outflow tract in dogs

A Denacol EX-313 (Denacol)-treated bovine venous graft and an ultrafine polyester fiber (UFPF) graft were transplanted as patch graft into the right ventricular outflow tract under extracorporeal circulation in six dogs each experimentally. Hemodynamics in right heart and histological findings around the graft were compared between both groups over a period of one year after grafting. Pressure measurements and angiocardiography were performed through a cardiac catheter. Right ventricular pressure, pulmonary artery pessure, and right ventricle to pulmonary artery gradient were within normal limits in both groups at 1, 2, 3, 4, 6, and 12 months or more after grafting. No difference were seen between the values for the Denacol and the UFPF group. Histologically, the medial surface at the site of grafting was covered with vascular endothelial cells at one month after grafting in both groups. The density of the vascular endothelial cells increased with time after grafting, showing no clear difference between the two groups. Subendothelial layers comprised of collagen fibers, elastic fibers, and inflammatory cells decreased with time in both groups, but there was less cell infiltration in the Denacol group than in the UFPF group at all time points after grafting. In addition, the central cut thickness value of the graft tended to be thinner in the Denacol group than in the UFPF group at all observation time points after grafting. In the Denacol group, very slight metaplasia of cartilage was noted in a portion of the graft margin at six months or more after grafting, but no other abnormalities were observed. These results suggest that the Denacol-treated bovine venous graft has better grafting characteristics than the UFPF graft with easier intra-operative handlings and less tissue reactions after grafting.

Experimental study of materials for patch graft on right ventricular outflow tract under extracorporeal circulation in dogs--comparison between Denacol EX-313-treated bovine jugular vein graft and expanded polytetrafluoroethylene (EPTFE) graft

A comparison between a bovine jugular vein treated with a hydrophilic polyepoxy compound cross-linker (Denacol), and expanded polytetrafluoroethylene (EPTFE), an artificial material, as a patch graft for the reconstruction of the right ventricular outflow tract under extracorporeal circulation in dogs, as if they had pulmonic stenosis, was made. Hemodynamic and histological examinations were conducted two weeks after the transplantation. Hemodynamic problems were not observed in either the Denacol or EPTFE groups. Macroscopically, organization of new tissue on the graft surface was more marked in the EPTFE group than in the Denacol group, and newly-formed tissue was seen surrounding the border of the graft and burying it in the EPTFE group. In the Denacol group, microscopic findings revealed the presence of inflammatory cells and fibroblasts, and an invasion of the graft by collagen fibers and elastic fibers. In the EPTFE group, there was minimal cellular infiltration of the graft and a thick layer consisting of collagen fibers and fibroblasts was observed around the graft. These results indicated that two weeks after transplantation the graft was better assimilated and organized with blood vasculature in the patch graft in the Denacol group than in the EPTFE group.