Left hemidiaphragm elevation is frequently noted following cardiac surgery employing topical
hypothermia. We speculate that contact of the left phrenic nerve with
ice causes nerve injury, resulting in left hemidiaphragm
paresis or
paralysis and left lower lobe
atelectasis. Left diaphragm elevation was noted on postoperative chest x-ray examination of 36 of 60 (60 percent) consecutive patients in whom topical cooling of the heart with a cold slush
solution was administered prior to use of a cardiac insulation pad (CIP, Shiley Laboratories, Irvine, California). Following the use of the CIP in a similar group of 60 consecutive patients, only five (8 percent) showed evidence of diaphragmatic elevation. The difference in the incidence of diaphragmatic elevation between these two groups is statistically significant (p less than 0.001). A comparison of postoperative left lower lobe
atelectasis prior to the use of the CIP was also statistically significant (p less than 0.001). There was no significant difference in the aortic cross-clamp time or the volume of intraaortic
cardioplegia used in these two groups. The use of topical cardiac
hypothermia has been shown to protect the myocardium. Phrenic nerve injury secondary to the use of
ice in this method has been documented. The use of a cold
solution without
ice chips or slush, or the insertion of a CIP prior to the use of topical cardiac
hypothermia (when
ice chips or slush are used) decreases the exposure of the phrenic nerve to
cold injury and decreases the incidence of
paresis of the left diaphragm and resultant
atelectasis.