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- maintenance of adequate preload is fundamental in the postoperative management of cardiac surgical patients; 
- it has been stated that the optimal wedge pressure is in the range of 14-18 mm Hg, although this may not be necessary in many pts and may be insufficient in others; 
- in addition the CVP should be kept between 10-15 mm Hg; 
- in absence of absolute left ventricular (or right ventricular pressure) volume measurements, inadequate preload can only be assumed with low wedge pressure (or CVP for right ventricular preload) whereas high normal or high filling pressures may still reflect suboptimal preload