From the Guidelines
High-flow nasal cannula (HFNC) therapy can potentially compromise cardiac contractility in patients with shock, particularly in those with hypovolemic or cardiogenic shock, due to its positive pressure effect on intrathoracic pressure and subsequent reduction in venous return to the heart. HFNC delivers positive pressure to the airways, which can increase intrathoracic pressure and potentially reduce venous return to the heart, decreasing preload and cardiac output in volume-depleted patients 1. This is particularly concerning in hypovolemic or cardiogenic shock where cardiac function is already compromised. The positive pressure effect, while less than with non-invasive ventilation, can still impact hemodynamics in unstable patients.
When using HFNC in shock patients, careful hemodynamic monitoring is essential, including blood pressure, heart rate, perfusion markers, and potentially cardiac output measurements. Start with lower flow rates (20-30 L/min) and titrate cautiously while assessing for signs of hemodynamic deterioration. In distributive shock (like septic shock), HFNC may be better tolerated once adequate volume resuscitation has occurred. For patients with cardiogenic shock, the risk-benefit ratio should be carefully considered, as the respiratory support benefits may outweigh the potential negative hemodynamic effects in some cases. Fluid status optimization before initiating HFNC can help mitigate potential negative effects on cardiac contractility. According to the European Respiratory Society task force panel, HFNC can be used alongside conventional oxygen therapy (COT) and noninvasive ventilation (NIV) for the management of adults in acute settings with acute respiratory failure (ARF) 1.
Key considerations for using HFNC in shock patients include:
- Careful patient selection and monitoring
- Optimization of fluid status before initiating HFNC
- Starting with lower flow rates and titrating cautiously
- Close monitoring of hemodynamic parameters
- Consideration of the risk-benefit ratio in patients with cardiogenic shock.
From the Research
Heated Humidified High-Flow Nasal Cannula (HHHFNC) Therapy
- HHHFNC therapy is a mode of respiratory support that delivers heated and humidified oxygen through nasal cannula, and its use has been increasingly popular in the treatment of patients with respiratory failure across all age groups 2.
- The mechanisms of action of HHHFNC therapy include meeting inspiratory demands, increasing functional residual capacity, minimizing oxygen dilution, and washout of pharyngeal dead space 2.
Cardiac Contractility in Shock
- There is no direct evidence in the provided studies that suggests HHHFNC therapy can compromise cardiac contractility in shock.
- However, HHHFNC therapy has been shown to improve oxygenation and comfort in patients with respiratory failure, which may have indirect benefits for cardiac function 3, 4.
- The use of HHHFNC therapy in patients with acute heart failure has been reported, and it may be effective in improving oxygenation and reducing the need for intubation 5, 6.
Clinical Indications for HHHFNC Therapy
- The main adult indications for HHHFNC therapy include hypoxemic respiratory failure due to pneumonia, post-extubation, pre-oxygenation prior to intubation, acute pulmonary edema, and use in patients who are "do not resuscitate or intubate" 2.
- The main pediatric indication for HHHFNC therapy is in infants with bronchiolitis, but other indications are being studied, such as its use in asthma, croup, pneumonia, transport of a critically ill child, and post-extubation 6, 2.