It's Topic Tuesday

Hi everyone! We hope your week has been off to a great start so far.

Today we will be going over a fairly niche topic: Deep Hypothermic Circulatory Arrest (DHCA), which is a technique often employed in cardiac surgery and even more specifically, in surgeries involving the aorta.

Deep Hypothermic Circulatory Arrest (DHCA) is a technique used primarily in cardiac procedures to temporarily stop blood circulation and significantly lower body temperature. This method allows surgeons to perform complex surgeries on the heart, aorta, and brain by providing a bloodless field and protecting the organs from ischemic damage. Here’s a description of the process, indications, and implications of DHCA:

Process of DHCA

1. Induction of Hypothermia:

• Preparation: The patient is prepared for surgery, and standard procedures such as anesthesia induction and intubation are performed.

• Cooling: The patient’s body temperature is gradually reduced using external cooling techniques (e.g., cooling blankets) and internal cooling methods, most commonly through cardiopulmonary bypass (CPB) with a heat exchanger. The goal is to lower the core body temperature to around 18-20°C (64.4-68°F). Cooling the body decreases metabolic rate and oxygen demand, which helps protect tissues during the period of circulatory arrest.

1. Circulatory Arrest:

• Stopping Blood Flow: Once the target temperature is reached, the heart-lung machine (cardiopulmonary bypass) is turned off, and blood circulation is stopped. At this point, the patient’s brain and other vital organs are not receiving blood flow.

• Surgical Procedure: The surgeon performs the required surgical intervention. During this time, the lack of blood flow and lowered metabolic rate due to hypothermia protect the organs, particularly the brain, from damage. The duration of circulatory arrest is typically kept within 30 to 45 minutes to minimize the risk of complications, although longer periods can sometimes be managed with additional protective strategies.

1. Rewarming and Reperfusion:

• Resuming Circulation: After the surgical procedure is completed, blood flow is gradually restored. The patient is slowly rewarmed using the cardiopulmonary bypass machine, bringing the body temperature back to normal.

• Monitoring: Vital signs and organ function are closely monitored throughout the rewarming process to detect any potential issues such as reperfusion injury or hemodynamic instability.

Indications for DHCA

DHCA is employed in various complex surgical procedures where temporary cessation of blood flow is necessary:

• Aortic Arch Surgery: Repairs of aneurysms or dissections in the aortic arch often require DHCA to allow surgeons to work in a bloodless field.

• Congenital Heart Defects: Certain pediatric heart surgeries utilize DHCA.

• Neurosurgery: In some cases of brain aneurysm or arteriovenous malformation (AVM) surgery, DHCA may be used to provide a bloodless field and protect the brain.

• Cardiopulmonary Procedures: DHCA can also be used in other cardiac surgeries where blood flow to the brain and other organs needs to be temporarily halted.

Risks and Complications

Despite its benefits, DHCA carries certain risks and potential complications:

• Neurological Complications: Prolonged circulatory arrest can lead to neurological deficits, including cognitive dysfunction, stroke, or transient ischemic attacks (TIAs).

• Rewarming Complications: Rapid or uneven rewarming can cause hemodynamic instability, reperfusion injury, or metabolic disturbances.

• Infection: As with any major surgical procedure, there is a risk of infection.

• Coagulopathy: Hypothermia can affect blood clotting mechanisms, leading to bleeding or thrombotic complications.

In conclusion, DHCA is a valuable technique in modern surgery, allowing for the successful completion of highly complex procedures that would otherwise be impossible.

And that is all we have for this week’s Topic Tuesday post. Thanks for tuning in! Stay healthy and we will see you next week.

Best,

Duc