High BP following cardiac surgery is usually due to:

High blood pressure following cardiac surgery is typically attributed to increased systemic vascular resistance (SVR). After surgery, various physiological and hemodynamic changes occur that can lead to an elevation in blood pressure. Increased SVR can occur due to multiple factors, including vasoconstriction, circulating catecholamines from surgical stress, or the response to pain or hypoxia.

As the vascular resistance increases, the heart must work against a higher pressure to eject blood. This can lead to elevated blood pressure readings.

The role of systemic vascular resistance is particularly critical in the post-operative period, as conditions like fluid shifts and medications given during surgery—such as vasopressors—can modify peripheral resistance significantly. Managing blood pressure in such a context often requires close monitoring and adjustments to medication or fluid management to ensure that the heart is not adversely affected by the increased resistance.

While factors such as low cardiac output or decreased contractility can lead to various hemodynamic changes, they do not typically cause high blood pressure; rather, they may lead to hypotension in the postoperative setting. Similarly, increased preload does not usually correlate with high blood pressure, as it can sometimes lead to reduced systemic resistance and potential fluid overload, rather than direct hypertension.