Cardioplegia delivery systems can cause problems. These can be classified into
Problems of preparation of cardioplegiaEdit
Failure to add a sufficient amount of Potassium is the most common error when preparing cardioplegic solutions. This can be avoided by using commercial bags or ampoule's. Calculation errors must be stringently avoided. In case of a doubt the sample (at the aortic end !!) must be sent for analysis and a result can be quickly obtained.
Problems in the delivery systemEdit
Roller occlusion must be proper or else cardioplegia delivery may not occur even if the rollers are running. The heating cooling unit may fail and cardioplegia may not be delivered at the right temperature. A simple test is to feel the cardioplegia line during delivery. It should be at the temperature during delivery and also a mist must form if giving cold cardioplegia and if using metallic direct cardioplegia cannulae the handle must cool. Monitoring of septal temperature with a myocardial temperature probe is a direct measure of the cooling capability of the hypothermic cardioplegia. The main problem with this is dislodgement giving erroneous readings.
Problems in the delivery system to the heartEdit
Management of a heart that does not arrest on clamping and delivering cardioplegiaEdit
Look at the aorta
- Low K
- Clamp incompletely applied: sometimes the aorta is clamped in a plaque site and not occluded. In these situations the heart assumes activity very soon. Palpate always the aorta to clamp it between plaques, better in pure CABG is to work off-pump and perform arterial revasculariisation.
==Aorta Flaccid== *Aortic regurgitation *Roller malocclusion *Roller malcalibration
Many times cardioplegia is given antegradely in severe aortic stenosis with mild regurgitation. If a left ventricular vent through the pulmonary veins is functioning, may be an aortic insufficiency is misdiagnosed and the cardioplegia goes into the left ventricle. Stop the vent and palpate the heart. Eventually, give ostial or retrograde cardioplegia.