CCP Cardioplegia Delivery Methods 3 — Questions and Answers
Question 1: The St. Thomas' Hospital cardioplegia solution is classified as:
- Intracellular-type crystalloid cardioplegia
- Extracellular-type crystalloid cardioplegia (Correct answer)
- Warm blood cardioplegia
- Histidine-tryptophan-ketoglutarate (HTK) solution
Correct answer: Extracellular-type crystalloid cardioplegia
St. Thomas' solution is an extracellular-type crystalloid cardioplegia with sodium and calcium concentrations approximating extracellular fluid.
Question 2: Histidine-tryptophan-ketoglutarate (HTK/Custodiol) cardioplegia is primarily indicated for:
- Frequent re-dosing every 15 minutes
- Single-dose myocardial protection with extended ischemic tolerance (Correct answer)
- Continuous warm delivery
- Pediatric open-heart surgery exclusively
Correct answer: Single-dose myocardial protection with extended ischemic tolerance
HTK solution provides extended single-dose myocardial protection, commonly used for heart transplantation and complex procedures requiring longer ischemic times.
Question 3: During antegrade cardioplegia delivery via aortic root, what pressure range is typically targeted to ensure adequate coronary perfusion without causing distension?
- 10–20 mmHg
- 50–80 mmHg (Correct answer)
- 150–200 mmHg
- Greater than 200 mmHg
Correct answer: 50–80 mmHg
Antegrade aortic root cardioplegia is typically delivered at 50–80 mmHg to achieve adequate coronary distribution without pressure-related myocardial damage.
Question 4: Which potassium concentration range is most commonly used to induce initial cardiac arrest in hyperkalemic cardioplegia?
- 2–4 mEq/L
- 8–12 mEq/L
- 20–40 mEq/L (Correct answer)
- 60–80 mEq/L
Correct answer: 20–40 mEq/L
Initial cardioplegia doses typically contain 20–40 mEq/L potassium to rapidly depolarize the myocardium and achieve cardiac arrest.
Question 5: Which myocardial temperature target is associated with optimal protection during cold crystalloid cardioplegia?
- 37°C
- 28°C
- 15°C (Correct answer)
- 0°C
Correct answer: 15°C
Cold crystalloid cardioplegia aims to cool the myocardium to approximately 15°C, markedly reducing metabolic oxygen demand during ischemia.
Question 6: What is the significance of adding magnesium to cardioplegia solution?
- Magnesium raises the resting membrane potential
- Magnesium acts as a calcium antagonist and reduces reperfusion injury (Correct answer)
- Magnesium increases heart rate upon reperfusion
- Magnesium primarily serves as a pH buffer
Correct answer: Magnesium acts as a calcium antagonist and reduces reperfusion injury
Magnesium competes with calcium at cellular channels, reducing calcium overload during ischemia and reperfusion, thus limiting myocardial injury.
Question 7: Why is topical myocardial cooling used in conjunction with cardioplegia delivery?
- To increase cardiac output after cross-clamp removal
- To provide additional surface cooling and offset rewarming from surrounding structures (Correct answer)
- To replace the need for cardioplegic solution
- To maintain electrical activity of the heart
Correct answer: To provide additional surface cooling and offset rewarming from surrounding structures
Topical cooling with iced saline counteracts rewarming from mediastinal structures and blood, maintaining myocardial hypothermia between cardioplegia doses.
CCP Cardioplegia Delivery Methods 3
The St.
Thomas' Hospital cardioplegia solution is classified as: