Jan Kugelberg

Treatment of accidental hypothermia.

A case of severe, chronic hypothermia (body-temperature 21.4°C) was successfully treated by means of extracorporeal circulation containing heat-exchanger and oxygenator. Thoracotomy was avoided. As far as we know, this is the first patient to survive such a low temperature without any residual disability.

Hemoconcentration by ultrafiltration during open-heart surgery.

Ultrafiltration was used during extracorporeal circulation (ECC) with heart-lung machine in 17 critically ill cardiac patients. In ultrafiltration (hemofiltration), water and small molecules (e.g. urea, creatinine and electrolytes), are separated from the blood by hydrostatic pressure generated on the blood side of a semipermeable membrane. The patients had severe water overload for three reasons, viz. congestive heart failure (10), renal failure (6) or iatrogenic extreme hemodilution (1). On average 2090 (800-5700) ml water was filtered off, increasing the hematocrit from 25 to 33%. Three indications for ultrafiltration during ECC and two modes of such treatment are exemplified in three case reports. No negative effect of the treatment was observed. Ultrafiltration during ECC thus may help to improve the postoperative course in patients with severe water overload due to congestive heart failure, renal failure or iatrogenic extreme hemodilution.

Late cardiac tamponade following open-heart surgery: Diagnosis and Treatment

Late cardiac tamponade is a rare but serious complication following open-heart surgery. It occurred in 9 (0.8%) of 1 094 consecutive patients 6 to 13 (median 8) days after operation. Six patients had undergone valve replacement and three coronary bypass surgery. All were on anticoagulant medication postoperatively (median TT index 7%). Early symptoms of cardiac tamponade were nausea and general malaise (present in all 9 cases), whereas classical signs of tamponade such as arterial hypotension and distended neck veins appeared late. The cardiac silhouette was radiographically enlarged in all cases, but this finding was seldom diagnostic. Computed tomography gave the surest diagnosis and permitted quantitative assessment of the fluid in the pericardium. Pericardial needle puncture was effective in temporarily relieving the tamponade, but insertion of a tube by the subxiphoid approach gave definitive drainage.

Electrical induction of ventricular fibrillation in the human heart. A study of excitability levels with alternating current of different frequencies

An experimental study was made on induction thresholds for ventricular fibrillation with alternating currents at frequencies ranging between 6 and 1 600 c/s. The tests were performed on experimental dogs and on patients in association with open-heart surgery. The most vulnerable range was found to be between 12 and 60 c/s. A close similarity was demonstrated between canine and human hearts. The induction of ventricular fibrillation during open-heart surgery is discussed. Ventricular fibrillation, caused by electricity, is either accidental or deliberately induced for medical purposes. The myocardial threshold of excitability towards alternating currents is dependent on two parameters, current and frequency. The vulnerability of the heart towards current has been thoroughly investigated by several authors (Walter, 1969; Dalziel & Lee, 1969; Nickel & Spang, 1965; Kugelberg, 1975). A frequency of 50-60 c/s was utilized in all these determinations, as this is the one of choice in networks for distribution of electric power all over the world. Thus, accidental ventricular fibrillation is most likely to occur with currents of this frequency, and inductions for medical purposes, i.e. during open-heart operations, are achieved in the easiest way with simple transformers delivering the same frequency.

The Interelectrode Electrical Resistance at Defibrillation

A determination of electrical resistance over the living, human myocardium was performed during defibrillation. Measurements were made between electrodes directly applied on the naked heart as well as on the chest for external use. Internal defibrillations showed a resistance of 32.7 ohms, which is approximately half the value of earlier assumptions. This knowledge is important for the construction of good defibrillators.

Acute immobilization of the disc in the Björk-Shiley aortic tilting disc valve prosthesis. A report of 3 cases.

Acute non-thrombotic immobilization of the disc in the Björk-Shiley aortic valve prosthesis occurred as a result of extrinsic factors in three patients. Unravelled suture or long suture ends were the cause in two cases. Tissue detached from the aortic intima migrated into the valve and locked the disc in closed position in one case. The mechanisms of extrinsic disc immobilization and its prevention and treatment are discussed.

Accidental Ventricular Fibrillation of the Human Heart: A Study of Excitability Levels with Alternating Current

With the use of electronic equipment in medical work an electrical hazard can not be completely avoided. The danger for the patient lies in an accidental ventrical fibrillation induced by a current passing through the body. Thresholds of vulnerability for such currents were determined in dogs as well as on the human heart during cardiopulmonary bypass. Various electrode positions were tested and the minimum current of induction was measured. The lowest current producing fibrillation of the human heart was 100 muA. At the electrode surface the density of the electrical field then was 6-14 muA/mm2. In our routine procedure during open-heart surgery, the mean value for induction was found to be 600 muA.

Local Myocardial Hypothermia an Alternative to Coronary Perfusion in Aortic Valve Surgery

A series of experiments on healthy dogs is described. Coronary perfusion during aortic occlusion was compared with local, myocardial hypothermia according to Bretschneider. The evaluation of postoperative performance of the heart was made by ventricular function studies. Local hypothermia was superior to coronary perfusion in preserving the heart muscle during 60 minutes of aortic occlusion.

Multicentre Investigation of Myocardial Protection with Cold Cardioplegia: A Computerized Study of 144 Patients Undergoing Isolated Aortic Valve Replacement

In order to analyze factors of importance for the efficiency of myocardial protection during open-heart surgery, a study was made of 144 patients undergoing isolated aortic valve replacement with various cardioplegic techniques. The cardioplegia was of Bretschneider type in 54 cases, St Thomas in 31 and Ringer-potassium type in 11 cases. Single or multi-dose blood cardioplegia was used in 11 cases and continuous blood cardioplegia in 30 cases. Local cardiac hypothermia was additionally employed in all patients. The efficiency of myocardial protection was assessed mainly from the incidence of postoperative conduction disturbances, myocardial enzyme release and need for inotropic support. All patients survived the operation. In 20% surgery was followed by transient or persistent disturbance of conduction, in 9% by abnormally increased CK-MB release and in 5% by requirement for inotropic support. Preoperative risk factors such as high age or severe left ventricular (LV) hypertrophy or dysfunction had little influence on the results. Patients in whom aortic stenosis (AS) was dominant in the complex with aortic insufficiency (AS + AI) showed 20-hour postoperative CK-MB enzyme activity twice as high as those with pure aortic insufficiency. The most important factors in myocardial protection were the duration of aortic occlusion and the myocardial temperature during cardioplegia. When the aortic occlusion lasted more than 80 min there was a 32% incidence of conduction disturbances and 20-hour CK-MB activity thrice as high as after shorter occlusion. Patients with mean myocardial temperature below 18 degrees C during cardioplegia invariably had low enzyme activities, which indicated good myocardial protection. The best overall results were obtained in patients operated on during hypothermia at 25-27 degrees C, with single or multi-dose blood cardioplegia and with efficient local cooling of the heart.

Myocardial Protection During Heart Surgery: An Experimental Evaluation of Normothermic and Hypothermic Cardioplegia

Heart surgery with hypothermic cardioplegia during normothermic bypass is sometimes complicated by rewarming of the myocardium caused by collateral flow of arterial blood. This problem is particularly evident in surgery of congenital malformations. The present work is a comparative study in dogs on 3 methods of avoiding the rewarming problem. In the first group, the heart was kept cold and the warm blood was drained off from the left atrium. In the second group, total body hypothermia to the level desired was used and in the third group, normothermic cardioplegia was induced (Cardioplegin) in normothermic animals. In the two latter groups, the undesired temperature gradient between heart and body was eliminated. Evaluation of the differences was made by means of ventricular function determinations. Local, hypothermic cardioplegia showed the best postoperative function (69%) followed by the total body cooling which was fully acceptable (41%). Normothermic cardioplegia after the same duration of arrest showed a too low myocardial performance (20%).