Beat-to-beat changes in stroke volume precede the general circulatory effects of mechanical ventilation: a case...

The haemodynamic as well as the ventilatory consequences of mechanical ventilation can be harmful in critically ill neonates. Newly developed ventilatory lung protective strategies are not always available immediately and in an acute situation the haemodynamic changes caused by mechanical ventilation can affect the oxygen delivery considerably. We report the case of a male neonate who was treated with conventional pressure-controlled mechanical ventilation because of respiratory distress and progressive respiratory acidosis resulting from meconium aspiration. Because of poor arterial oxygenation despite 100% inspired oxygen and increased ventilator settings, echocardiography was performed to exclude central haemodynamic reasons for low oxygen delivery.

Doppler echocardiography was used for the measurement of stroke volume and cardiac output. Pulse oximetry and aortic blood pressure were monitored continuously.

Echocardiography revealed no cardiac malformations or signs of persistent fetal circulation. When inspiratory pressures and duration were increased, beat-to-beat variation in stroke volume preceded decay in cardiac output. Stroke volume variations and oxygen saturation values guided ventilator settings until extracorporal membrane oxygenation could be arranged for. After recovery and discharge 4 weeks later the boy is progressing normally.

Because oxygen delivery is dependent on both blood flow and arterial oxygen content, measurement of cardiac output as well as left heart oxygen saturation is a useful guide to optimizing oxygen delivery. This case report demonstrates how Doppler echocardiographic monitoring of beat-to-beat changes in stroke volume can be used to detect early negative haemodynamic effects of increased mechanical ventilation settings before cardiac output is affected.