FORWARD BLOOD-FLOW DURING CARDIOPULMONARY-RESUSCITATION IN PATIENTS WITH SEVERE ACCIDENTAL HYPOTHERMIA - AN ECHOCARDIOGRAPHIC STUDY

Background: The mechanism responsible for the forward blood flow assoc iated with external chest compression is still controversial. Evidence for both blood flow caused by direct cardiac compression and blood fl ow generated by a general increase in intrathoracic pressure has been found in experimental as well as clinical studies. No data are availab le concerning the mechanism causing forward blood flow in hypothermic patients undergoing cardiopulmonary resuscitation. Therefore, echocard iographic findings during external chest compression in seven hypother mic arrest victims are reported. Methods: All transesophageal echocard iographic studies performed at the Anaesthesia department between 1994 and 1997 were reviewed and seven hypothermic patients with transesoph ageal echocardiography performed during cardiopulmonary resuscitation were identified. Results: An open mitral valve or a circumferential re duction in aortic diameter during the compression phase was found in f our of seven patients, indicating that primarily an increase in intrat horacic pressure (thoracic pump mechanism) generated forward blood flo w. In three patients, mitral valve closure during external chest compr ession indicated that direct cardiac compression (cardiac pump mechani sm) contributed to forward blood flow. Two patients studied during act ive compression-decompression cardiopulmonary resuscitation demonstrat ed enhanced right Ventricular filling and aortic valve opening during active decompression of the thorax. Conclusions: In contrast to normot hermic arrest victims, an open mitral valve during external chest comp ression is a common finding during hypothermia, indicating that thorac ic pump mechanism is important for forward blood flow during cardiopul monary resuscitation in hypothermic arrest victims. Aortic valve openi ng in two hypothermic arrest victims suggests forward blood flow also during active decompression of the thorax with the Cardiopump(R).