Does Ice Slush Placed Inside Pericardial Well During Mitral Valve Replacement Cause Injury to Phrenic Nerve

Objective of the study was to determine frequency of phrenic nerve injury during mitral valve replacement, with application of Ice Slush, and compare it with international data. This study was performed at Punjab Institute of Cardiology Pakistan from January 2010 to December 2015. A total of 1105 patients with only primary rheumatic mitral valve disease were prospectively observed. A total of 931 patients were enrolled into the study. After sternotomy & cardiopulmonary bypass (CPB) at 28-32°C, antegrade blood cardioplegia with potassium, Ice slush was applied all the time during repair or replacement of the mitral valve. A pre-designed proforma was used, that recorded phrenic nerve injury. Statistical Package for Social Sciences (SPSS) for Windows version 21 was used for the analysis of data. Out of 931 patients who underwent mitral valve repair or replacement, 466 (50.1%) were males. Time spent on CPB ranged from 40 to 120 min; in 58.1% patients the time remained less than 80 minutes. As far as the ascending aortic cross clamp time was concerned, 83.1% patients had less than 40 minutes of cross clamp time. Post-operative chest X-ray remained normal in 97.5% patients whereas it showed atelectasis in 2.3% and elevated left hemidiaphragm in 0.2% of the patients. The total in-hospital mortality was 3.2% during study period. No patient was found to have phrenic nerve injury, unilateral or bilateral, during the study period.Topical cooling of heart, during mitral valve replacement, with Ice slush per se is not responsible for Phrenic nerve injury.