Why is a patient experiencing volume overload in cardiogenic shock with a clear lung examination?

From the Guidelines

In cardiogenic shock with clear lung examination, volume loading may be necessary despite the cardiac origin of shock, as indicated by the most recent guidelines from 2022 1. This approach is supported by the fact that cardiogenic shock is defined as a state of low systolic blood pressure (<90 mmHg) despite adequate volume status, with signs of hypoperfusion 1. The key is to identify patients who may benefit from volume loading, such as those with signs of hypovolemia or inadequate preload, which can occur in right ventricular failure, ventricular septal rupture, or with excessive diuresis or vasodilation. Initial fluid challenge should be conservative, typically 250-500 mL of isotonic crystalloid (normal saline or lactated Ringer's) administered over 15-30 minutes, with careful reassessment after each bolus, as recommended by the European Heart Journal in 2015 1. The goal is to optimize preload to improve cardiac output without causing pulmonary congestion, which is crucial in preventing fluid overload and its associated morbidity and mortality. Some key points to consider when volume loading in cardiogenic shock include:

• Hemodynamic monitoring is essential during volume loading, ideally using parameters like central venous pressure, pulmonary capillary wedge pressure, or dynamic measures like stroke volume variation if available 1.
• The physiological basis for this approach is the Frank-Starling mechanism, where increased preload improves myocardial fiber stretch and contractility up to an optimal point 1.
• Frequent reassessment of lung examination, oxygen saturation, and hemodynamic parameters is crucial to prevent fluid overload and its associated complications.
• Team-based cardiogenic shock management provides the opportunity for various clinicians to provide their perspective and input to the patient’s management, which can improve outcomes 1.

From the Research

Cardiogenic Shock and Volume Load

• Cardiogenic shock is a physiologic state in which cardiac pump function is inadequate to perfuse the tissues 2.
• The use of inotropic agents, such as milrinone and dobutamine, is common in patients with cardiogenic shock to increase cardiac contractility and improve tissue perfusion 3, 4, 5, 6.
• However, the evidence on the use of these agents is limited, and there is no clear consensus on which one is more effective or safer 3, 4, 5, 6.

Volume Load in Cardiogenic Shock

• Patients with cardiogenic shock may require volume loading to optimize cardiac preload and improve cardiac output 2.
• However, the decision to administer volume loading should be made cautiously, as excessive volume loading can worsen cardiac function and lead to pulmonary edema 2.
• The presence of a clear lung examination does not necessarily preclude the need for volume loading, as cardiogenic shock can occur in the absence of pulmonary congestion 2.

Inotropic Agents and Arrhythmias

• Both milrinone and dobutamine can cause arrhythmias, including ventricular and supraventricular tachyarrhythmias 4, 6.
• Dobutamine may be more likely to cause arrhythmias due to its beta-1 and beta-2 agonist effects, while milrinone may be more likely to cause hypotension due to its phosphodiesterase-3 inhibitory effects 4, 6.
• The management of arrhythmias caused by these agents requires a tailored approach, emphasizing clinical vigilance and individualized patient care 6.