Topical cooling with ice slush as an adjunct for myocardial protection during cardiac surgery has been shown to cause freezing injury of the phrenic nerves. This can cause diaphragmatic dysfunction and respiratory complications.

Twenty (n=20) male patients between the ages of 40 and 60 years were equally randomised to undergo elective coronary artery bypass grafting (CABG) with either cold cardioplegic arrest with topical ice slush cooling or cold cardioplegic arrest without the use of ice slush. The sniff nasal inspiratory force (SNIF) was used to compare inspiratory muscle strength.

There was no difference in the preoperative SNIF in the two randomised groups. In the immediate postoperative period, the ice slush group had worse SNIF (33.5±9.6cm H2O versus 47.8±12.2cm H2O; p=0.009). The pre-home discharge SNIF was still significantly lower for the ice slush group despite a noted improvement in SNIF recovery in both groups (38.3±10.6cm H2O versus 53.5±13.2cm H2O; p=0.011). Two patients in the ice slush group had left diaphragmatic dysfunction with none in the control group.

The use of topical ice slush is associated with freezing injury of the phrenic nerves. This will adversely affect the inspiratory muscle force which may lead to respiratory complications after surgery.