A comparison of heat exchangers for blood cardioplegia

During open heart surgery, myocardial protection provided by oxygenated blood-based cardioplegia is superior to that provided by non-oxygenated crystalloid cardioplegia. However, the widespread use of blood cardioplegia has been limited by the cost and complexity of the associated cooling and delivery systems. The performance of a simple system--a polyethylene coil immersed in ice--has been compared with three systems incorporating specialized, water-jacketed heat exchangers: Buckberg Shiley, Shiley BCD and Bentley HE-100. Blood was diluted to a haematocrit of 22% and delivered to each cooling system at flow rates of 200-500 mL/min and temperatures of 25 degrees C and 30 degrees C. Cooling water at 0-1 degree C was supplied to the heat exchangers at flow rates of 2, 4, and 6 L/min. Performance was measured by comparing the blood outflow temperatures at the same inflow temperature under a variety of test conditions which simulated those occurring in clinical practice. All cooling systems, except the Buckberg Shiley, were able consistently to cool blood cardioplegia adequately (below 10 degrees C), but the ice coil was the most effective. The heat exchanger systems are 3-4 times more expensive than the ice coil and require an external source of cold water. Thus the ice coil system has the advantages of simplicity, efficiency, and economy.     

Topical Cardiac Cooling by Recirculation: Comparison of a Closed System Using a Cooling Pad with an Open System Using a Topical Spray

Topical cardiac cooling plays an important part in maintaining myocardial hypothermia during cardiac operations under hypothermic cardioplegic arrest. We have compared two systems of topical cooling in which the cooling fluid is recirculated. In one system the cold fluid circulates through a sealed plastic cooling pad wrapped around the heart; in the other it is sprayed over the surface of the heart.In dogs undergoing 60 minutes of hypothermic cardioplegic arrest, the cooling pad was ineffective: it did not adequately cool the anterior left ventricular wall or the interventricular septum. Under the same conditions, the spray system produced myocardial temperatures 6° to 12°C lower than the cooling pad system. In limited clinical tests, the cooling pad was unable to sustain overall myocardial hypothermia and there was difficulty in maintaining contact between the heart and the pad during coronary operations. Since the topical spray can maintain profound global myocardial hypothermia regardless of the position of the heart, we conclude that it is superior to the cooling pad system.     

Ultrasound examination of the hand

Twenty-five surgically confirmed soft-tissue lesions of the hand were examined prospectively by real-time ultrasound. Use of sonography enabled a reliable diagnosis of the cystic or solid nature of soft-tissue lesions, an accurate estimation of the volume, and precise three-dimensional localization of the abnormality. Sonography also facilitated the location of foreign bodies. Assessment of anatomic relationships of these lesions to tendons and surrounding structures by real-time sonography during palpation, flexion, and/or extension also aided in the surgical approach.     

Comparison between irrigation and conventional treatment for empyema and pneumonectomy space infection.

A new method of treating pleural empyema or pneumonectomy space infection by irrigation was evaluated in 11 patients. The infected cavities were filled with an antibiotic or antiseptic solution for three hours, and allowed to drain for one hour. This cycle was repeated every four hours for seven to 10 days. When cultures of the infected cavity became sterile the irrigation tube was removed and the wound sealed. Using this method, infection was eradicated after an average of 11 days in five of six patients with pleural empyema and in all five patients treated for an infected pneumonectomy space, including one with a bronchopleural fistula. The results of treating 58 similar cases of intrapleural sepsis over a 10-year period by the standard methods of aspiration, open drainage, decortication, or thoracoplasty were compared with the results of irrigation. In general, cyclical irrigation resulted in a shorter hospital stay and a shorter period of wound drainage than other methods.     

I. Development of an In Vitro Model of Myocardial Cooling: A Study of the Effect of Cardiac Size on Cooling Rate

A physical model for the study of local cardiac hypothermia was developed using excised animal hearts. The validity of the model was established by showing close similarity between cooling curves of dog hearts in vivo and in the model. The model was then used to compare the cooling rates of three groups of excised hearts using cold saline irrigation. Groups 1, 2, and 3 had mean left ventricular weights of 166, 379, and 1,429 gm, respectively, and mean left ventricular wall thicknesses of 1.5, 2.0, and 3.1 cm, respectively. For the same 10°C temperature fall, Group 1 took 25 ± 2.8 minutes, Group 2 took 54 ± 9.2 minutes, and Group 3 took 117 ± 21 minutes. To avoid slow cooling and consequent ischemic damage in the hypertrophic ventricle, it may be desirable to initiate cooling using coronary perfusion with cold blood or cold cardioplegic solutions.