The comparative pathology of open chest vs. mechanical closed chest cardiopulmonary resuscitation in dogs

We compared the pathologic changes following open-chest cardiopulmonary resuscitation (OCCPR) vs. closed chest cardiopulmonary resuscitation (CCCPR) in 28 healthy mongrel dogs subjected to experimentally induced ventricular fibrillation (VF). VF was induced in 29 dogs. No treatment was given for 3 min, then mechanical CCCPR was given for the next 12 min. External defibrillation (80 joules) was then attempted twice. One dog was resuscitated. The remaining 28 dogs were divided into 2 groups of 14 each. Group A received continued CCCPR and group B received OCCPR. All dogs received advanced cardiac life support and were followed until resuscitated or dead. All dogs were autopsied and gross pathology scores and histopathology scores were determined for each animal, and for each of 19 separate tissues within each animal. The mean gross pathology scores for the following tissues were significantly greater for dogs that received OCCPR vs. those that received CCCPR: skin (3.4 vs. 1.2; P < 0.001), subcutaneous tissue (3.7 vs. 0.6; P < 0.001), chest wall muscle (3.7 vs. 0.5; P < 0.001), and pleura (1.9 vs. 0.1; P < 0.001). The mean total gross pathology score was also greater in dogs that received OCCPR vs. those that received CCCPR (17.2 vs. 7.7; P < 0.001). The mean histopathology scores for the following tissues were significantly greater for dogs that received OCCPR vs. those that received CCCPR: skin (2.5 vs. 0.0; P < 0.001), subcutaneous tissue (2.2 vs. 0.1; P < 0.001), muscle (2.3 vs. 0.1; P < 0.001), pleura (1.6 vs. 0.0; P < 0.001), pericardium (1.4 vs. 0.2; P < 0.01), epicardium (2.5 vs. 0.2; P < 0.001), mycocardium (2.5 vs. 0.3; P < 0.0001), and endocardium (1.9 vs. 0.5; P < 0.01). The mean total histopathology score was also greater in dogs that received OCCPR vs. those that received CCCPR (20.1 vs. 7.4; P < 0.001). The histopathology score for brain tissue was greater for the CCCPR group than for the OCCPR group (1.9 vs. 0.4; P < 0.05). This study showed that OCCPR in dogs following VF caused more severe pathologic changes than CCCPR. These changes were attributed to thoracotomy-induced chest wall injury and to internal defibrilation induced myocardial injury. However, OCCPR caused less severe microscopic brain lesions than CCCPR.