Deep Hypothermic Circulatory Arrest (DHCA)

Introduction

Deep Hypothermic Circulatory Arrest (DHCA) is a medical technique used during highly complex cardiovascular surgeries, particularly aortic arch and congenital heart defect repairs. It involves cooling the patient's body to very low temperatures (usually 18–20°C) to reduce metabolic demands and allow surgeons to temporarily stop blood circulation without causing irreversible organ damage.

Physiological Basis

1. Hypothermia and Metabolism: Lower temperatures slow cellular metabolism and reduce oxygen consumption, protecting organs, especially the brain, from ischemic injury.
2. Circulatory Arrest: Blood flow is completely halted during surgery, preventing major blood loss and allowing precise surgical intervention.

Indications

DHCA is primarily used in: - Aortic arch surgery (e.g., aortic dissection, aneurysm repair). - Congenital heart defect corrections. - Complex cerebrovascular procedures requiring temporary blood flow cessation. - Selective cases of cardiac tumor excisions.

Procedure Overview

1. Cooling Phase: The patient’s temperature is gradually reduced using cardiopulmonary bypass (CPB) until the target hypothermic state is reached.
2. Circulatory Arrest: Once cooled, the circulation is halted, providing a bloodless surgical field.
3. Surgical Intervention: The procedure is performed within a strict time window (typically ≤30-40 minutes to minimize complications).
4. Rewarming Phase: The patient’s body is slowly warmed up, and circulation is restored via CPB.

Risks and Complications

• Neurological complications: Stroke, cognitive dysfunction, seizures.
• Coagulopathy: Blood clotting abnormalities due to hypothermia.
• Organ dysfunction: Temporary or lasting effects due to prolonged circulatory arrest.
• Rewarming shock: Rapid temperature increases can cause hemodynamic instability.

Neuroprotection Strategies

• Shorter arrest duration: Minimizing circulatory arrest time.
• Selective antegrade cerebral perfusion (SACP): Providing some blood flow to the brain during DHCA.
• Pharmacological neuroprotectants: Using drugs to reduce ischemic damage.

Conclusion

DHCA is a life-saving technique in complex cardiac and vascular surgeries. Although it carries risks, advanced neuroprotection strategies and improved surgical techniques have enhanced its safety and effectiveness.

Source recommendations

1. American Heart Association Guidelines for Cardiovascular Surgery

1. https://professional.heart.org/en/guidelines-and-statements
2. https://www.ahajournals.org/doi/10.1161/CIR.0000000000001038
3. https://www.heart.org/en/health-topics/consumer-healthcare/what-is-cardiovascular-disease/heart-surgery-resources
4. https://www.ahajournals.org/doi/10.1161/CIR.0000000000001285
5. https://www.heart.org/en/health-topics/heart-attack/treatment-of-a-heart-attack/cardiac-procedures-and-surgeries

2. European Society of Cardiology Guidelines on Aortic Diseases

1. https://www.escardio.org/Guidelines/Clinical-Practice-Guidelines/Peripheral-Arterial-and-Aortic-Diseases
2. https://academic.oup.com/eurheartj/article/35/41/2873/407693
3. https://www.ahajournals.org/doi/10.1161/CIR.0000000000001106
4. https://academic.oup.com/eurheartj/article/45/36/3538/7738955
5. https://pubmed.ncbi.nlm.nih.gov/39210722/

3. European Association for Cardio-Thoracic Surgery Guidelines

1. https://www.eacts.org/clinical-practice-guidelines/
2. https://academic.oup.com/eurheartj/article/43/7/561/6358470
3. https://www.eacts.org/
4. https://academic.oup.com/eurheartj/article/45/36/3314/7738779
5. https://pubmed.ncbi.nlm.nih.gov/39210723/