What is a case example of a surgical candidate with undiagnosed 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

This is a disaster averted. In this patient with undiagnosed PH presenting for elective surgery, an extensive preoperative evaluation is a must. His functional symptoms raise concerns about moderate-to-severe disease. In fact, the patient's hypotension and associated tachycardia, against the background of uncharacterized CAD, could cause a myocardial oxygen deficit and subsequent inferior-wall ischemia as seen on ECG. A right-heart catheterization would have been useful for assessing the severity of his disease, and a recent echocardiogram would have been helpful for evaluating cardiac function (especially RV function).

In many cases, TKA is done with a subarachnoid block. However, spinal anesthesia does carry a risk of profound decrease in preload/perfusion and can trigger RV failure. It is acceptable to plan for general anesthesia. However, in view of this patient's suspected PH and known cardiac history, further invasive monitoring is warranted; at a minimum, an arterial line should be considered. If the surgery had been urgent, intraoperative echocardiography or placement of a pulmonary artery (Swan-Ganz) catheter could be considered. Additionally, it would be beneficial to have dobutamine and phenylephrine infusions available and to use milrinone early in the setting of beta blockade.

It has been shown that deflation of a tourniquet, especially after prolonged inflation, causes a small decrease in blood pressure related to the increase in venous capacitance; it also causes an increase in CO2 and acid metabolites returning into the circulation from the ischemic limb. This, in turn, can trigger a steep increase in PVR, as well as decreased RV perfusion and contractility. This state, if neglected, can quickly escalate into acute pulmonary hypertensive crisis and cardiovascular collapse. In addition, nitrous oxide has been proved to increase PVR in patients with PH and thus should be avoided in all patients with suspected or proven PH who are undergoing general anesthesia. [23]

Fortunately, the crisis was averted in this case, but it would have been advantageous to have had a more extensive workup and a better intraoperative monitoring strategy, as well as to have avoided intraoperative use of nitrous oxide.


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