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

Background: The haemodynamic as well as the ventilatory consequences of mec hanical ventilation can be harmful in critically ill neonates. Newly develo ped ventilatory lung protective strategies are not always available immedia tely and in an acute situation the haemodynamic changes caused by mechanica l ventilation can affect the oxygen delivery considerably. We report the ca se of a male neonate who was treated with conventional pressure-controlled mechanical ventilation because of respiratory distress and progressive resp iratory acidosis resulting from meconium aspiration. Because of poor arteri al oxygenation despite 100% inspired oxygen and increased ventilator settin gs, echocardiography was performed to exclude central haemodynamic reasons for low oxygen delivery. Method: Doppler echocardiography was used for the measurement of stroke vol ume and cardiac output. Pulse oximetry and aortic blood pressure were monit ored continuously. Results: Echocardiography revealed no cardiac malformations or signs of per sistent fetal circulation. When inspiratory pressures and duration were inc reased, beat-to-beat variation in stroke volume preceded decay in cardiac o utput. Stroke volume variations and oxygen saturation values guided ventila tor settings until extracorporal membrane oxygenation could be arranged for . After recovery and discharge 4 weeks later the boy is progressing normall y. Conclusion: Because oxygen delivery is dependent on both blood flow and art erial oxygen content, measurement of cardiac output as well as left heart o xygen saturation is a useful guide to optimizing oxygen delivery. This case report demonstrates how Doppler echocardiographic monitoring of beat-to-be at changes in stroke volume can be used to detect early negative haemodynam ic effects of increased mechanical ventilation settings before cardiac outp ut is affected.