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High-volume crystalloid cardioplegia. An improved method of myocardial preservation
Insights
High-volume crystalloid cardioplegia (HVCC) improved myocardial metabolic recovery post-cardiac surgery compared to normal-volume crystalloid cardioplegia (NVCC) and blood cardioplegia (BC). HVCC facilitated faster restoration of normal metabolic function, enabling early bypass discontinuation.
Area of Science:
- Cardiology
- Cardiovascular Surgery
- Biomedical Engineering
Background:
- Coronary artery bypass grafting (CABG) requires myocardial protection during surgery.
- Different cardioplegic techniques aim to preserve myocardial function.
- Evaluating the metabolic efficacy of cardioplegia is crucial for patient outcomes.
Purpose of the Study:
- To compare the metabolic efficacy of three cardioplegic techniques: normal-volume crystalloid cardioplegia (NVCC), high-volume crystalloid cardioplegia (HVCC), and blood cardioplegia (BC).
- To assess myocardial oxygen consumption, lactate, and potassium balance during and after cardioplegic arrest in patients undergoing CABG.
Main Methods:
- Controlled metabolic studies in 41 patients undergoing multiple CABG.
- Measurement of coronary blood flow, vascular resistance, oxygen difference, and myocardial metabolism (oxygen consumption, lactate, potassium) during and after cardioplegic arrest.
- Comparison of NVCC (1,946 ml), HVCC (4,961 ml), and BC (1,672 ml) infusion.
Main Results:
- Myocardial oxygen consumption was higher during BC (2.6 ml O2/min) and HVCC (increased utilization due to volume) compared to NVCC (1 ml O2/min).
- Potassium absorption was significantly greater with BC than crystalloid solutions.
- Only HVCC maintained pre-arrest myocardial oxygen extraction levels during reperfusion; NVCC and BC showed depressed extraction.
Conclusions:
- High-volume crystalloid cardioplegia (HVCC) demonstrates superior metabolic recovery compared to NVCC and BC.
- HVCC facilitates a rapid return to normal myocardial metabolic function, allowing for earlier discontinuation of cardiopulmonary bypass.
- These findings suggest HVCC may offer improved myocardial protection in CABG surgery.
Abstract:
Controlled metabolic studies were used to gauge the relative efficacy of three cardioplegic techniques in 41 patients undergoing multiple coronary artery bypass grafts. Normal-volume (1,946 +/- 155 ml) crystalloid cardioplegia (NVCC) (14 patients) was compared to high-volume (4,961 +/- 282 ml) crystalloid cardioplegia (HVCC) (14 patients) and to blood cardioplegia (BC) (1,672 +/- 127 ml) (13 patients). Measurements of coronary blood flow, coronary vascular resistance, coronary arteriovenous oxygen difference, myocardial oxygen consumption and extraction, and myocardial lactate and potassium extraction and release were all measured in the isolated, vented, paced, beating heart, before and for 20 minutes after a 1 hour arrest interval during which revascularization was completed. Additionally, during administration of the cardioplegic solution, infusion flow rate, myocardial oxygen consumption and extraction, and lactate and potassium release and uptake were noted. The results indicate that during cardioplegic administration, myocardial oxygen consumption is 1 ml O2/min with crystalloid infusion and 2.6 ml O2/min during BC infusion. The volume of crystalloid solution administered contributed to increased oxygen utilization during HVCC compared to NVCC, whereas BC promoted the highest oxygen utilization of the three groups. Potassium absorption was nearly three times greater during BC than during crystalloid administration. During myocardial reperfusion, oxygen extraction was maintained at prearrest levels only in the HVCC group. Following both NVCC and BC, oxygen extraction was depressed during the first 5 minutes of reperfusion, and the difference between the latter two groups and HVCC was significant (p less than 0.01). The rapid recovery in normal metabolic function seen with HVCC allows early discontinuation of cardiopulmonary bypass without myocardial metabolic depression.