What are ventilation and metabolic considerations in the perioperative management of pulmonary hypertension (PH)?

Updated: Sep 11, 2019
  • Author: Swapnil Khoche, MBBS, DNB, FCARCSI; Chief Editor: Sheela Pai Cole, MD  more...
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Answer

Ventilation and metabolic considerations

Patients with PH are exquisitely sensitive to the effects of both general anesthesia and PPV. It is well known that PPV increases intrathoracic pressure, thereby reducing venous return and decreasing RV preload. This effect can also be seen with the addition of excessive positive end-expiratory pressure (PEEP). [16]

However, increases in intrathoracic pressure also increase pulmonary artery transmural pressure, thus increasing RV systolic transmural pressure, RV wall stress, and RV afterload. This dual effect (ie, reducing preload and increasing afterload) can lead to a drastic reduction in the ability of the RV to pump blood through the pulmonary circulation. [17]  PVR is lowest at functional residual capacity, with lower volumes resulting in atelectasis and hypoxia and higher volumes resulting in compression of alveolar vessels. [4]

On the other hand, it is also important to avoid oversedating and creating hypoxia and hypercarbia during spontaneous ventilation, either of which can raise PVR above the patient's baseline. Pain and acidosis can lead to acute increases in pulmonary pressures as well, particularly in a patient in active labor or a septic patient with a severe acidosis. Everything possible should be done to minimize these exacerbating factors. Recognizing and treating volume overload is vital; unmonitored fluid challenges can be disastrous. Furthermore, certain medications and agents (eg, N2O) can vasoconstrict the pulmonary circulation and should be avoided.


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