What are perfusion and oxygen 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

Answer

Perfusion and oxygen demand

Patients with PH live with a relative oxygen deficit, not only because of increased demand from a hypertrophic ventricle but also because of decreased oxygen delivery resulting from compromised output. Like a hypertrophic LV, a hypertrophic RV is especially sensitive to decreased perfusion. Normally, the RV is perfused in both systole and diastole, but in a hypertrophic heart experiencing pressure overload, the smaller pressure gradient between the aortic root and the RV allows perfusion only when the pressure inside the RV is low—specifically, during diastole. This yields a perfusion situation similar to that in the LV. [8]

When perfusion pressure is low, a positive feedback loop can quickly develop whereby the reduced perfusion leads to decreases in function and cardiac output, further reducing perfusion pressure to the RV. Accordingly, optimizing perfusion pressure and limiting myocardial oxygen demand are key tenets of anesthesia for these patients.

A failing, dilated RV also results in a dilated tricuspid annulus, causing valvular regurgitation. This ultimately leads to further compromise of forward flow. Hypoperfusion of the kidneys leads to decreased urine output; however, it also results in increased renin-angiotensin activity, sodium and water retention, and release of vasopressin, thus worsening volume status and impairing contractile efficiency. [8]


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