How to deal with acute decompensation in pulmonary hypertension in case of right heart failure was discussed during the DGP congress in Munich.
Right ventricular (RH) failure is characterized by decreased cardiac output and/or increased right-sided filling pressures due to systolic and/or diastolic dysfunction of the right ventricle. RH failure is classified as severe if it leads to secondary dysfunction of other organs. The hearts of such patients are characteristically enlarged, the right ventricle is ballooned, and filling pressures, venous pressures, are visibly elevated on imaging. On the other hand, the left heart is underfilled, which ultimately damages all organs, but especially the liver, kidneys and intestines.
Patients admitted to the ICU with RH failure in the setting of decompensated pulmonary hypertension (PAH) have a high mortality. While this is well known, in fact there has only been one paper to date that has studied this in a cohort of 46 patients. Mortality after intensive care stay here was about 40% [1]. However, those patients who left the ICU again then continued to live for a longer period of time. “This means that in this case it was not the underlying disease itself or its worsening that was decisive for the intensive care admission, but as a rule other triggering factors,” explained Prof. Dr. Marius Hoeper, senior physician at the Department of Pneumology at Hannover Medical School. These factors typically include concomitant diseases, infections, or arrhythmias, particularly supraventricular tachyarrhythmias, atrial fibrillation, or atrial flutter, which often lead to cardiac decompensation in patients.
Recognizing RH failure – not so easy
The first step in helping a patient is to recognize their right heart failure. “And that’s not as trivial as it sounds,” Prof. Hoeper cautioned. Decompensated pulmonary hypertensive patients with chronic disease typically have little reverse failure but primarily forward failure, that is, cardiac pump failure. Recognizing this is challenging because patients are often clinically unremarkable. They are usually quiet, sleepy, and have a very typical pale grayish, peripherally cyanotic skin coloration. They are mostly hypotensive, systolic pressure is around 90/100, but still quite well compensated at that, and patients are moderately tachycardic. None of these are real warning signs. Diuresis naturally decreases, but this is hardly noticeable in the first 24 hours, especially if a catheter has been placed (tab. 1).
When these patients come to the ICU, the monitoring is no different than other patients admitted for hemodynamic instability. While an assessment of cardiac function is needed, Prof. Hoeper uses indirect means such as central venous or mixed venous oxygen saturation, central venous pressure, urine, and lactate for this in practice. “These are the parameters I always check on the ward when I want to know whether the patient is stable or not. That’s enough for me to judge whether everything is still in the green-yellow zone or whether there’s an emergency. If the central venous saturation is dropping, the urine flow is dropping at the same time, the lactate is rising and the CVD is high or rising, then there is basically danger ahead.”
This statement caused some irritation in the plenum, as the measurement of central venous pressure in the intensive care unit has been obsolete for some time because it is not a measure of volume status. But the expert explained, “We’re talking about patients with RH failure here, and we want to know two things: What is the filling situation and what is the cardiac pump function anteriorly, and we can just translate that quite well with mixed venous or central venous oxygen saturation.” Prof. Hoeper cited the following relationship for venous oxygen saturation in cardiac output for this purpose: The lower the cardiac output, the higher the oxygen depletion in the tissues and the lower the amount of oxygen that comes back. Therefore, invasive monitoring is not even necessary in many cases.
Reduce volume instead of increasing it
As far as treatment options are concerned, the expert warned emphatically: intubation should be avoided at all costs! “You can intubate patients with pulmonary hypertension if they are stable, for example before surgery, that’s not a problem. But to intubate a decompensated ventricular patient in an emergency situation usually means the patient will die. That’s virtually unavoidable.” The reason for this is the circulatory situation after intubation with sedation, loss of endogenous catecholamines, drop in blood pressure and increase in intrathoracic pressures due to ventilation, which all adds up to kill such a patient.
No less essential is the correct behavior during volume therapy. The rule is that patients in the ICU are elevated first. In addition, caregivers are quick to add additional fluids. However, according to Prof. Hoeper, this approach is wrong. With additional volume, the right-sided filling pressures are only further increased, with the result that the right ventricle, already ballooned, pushes even further toward the atrium. Instead, volume must also be withdrawn in hypotensive and in tachycardic patients. In such hearts, this is the only way to re-stabilize hemodynamics. Usually loop diuretics or even hemofiltration are sufficient for this purpose. Under this measure, even the hypotensive patients stabilize relatively reliably.
Other measures run in parallel: drug therapies for pulmonary hypertension often already exist and only need to be optimized in the ICU; prostacyclins i.v. or PDE-5 inhibitors are often used, plus circulatory support with inotropics or vasopressors if necessary.
Last resort lung transplantation
But what if all these measures do not work and the RH failure progresses? Then there are only two options. The more common of these is that the palliative therapy concept is initiated on the right side. In individual cases, however, one can also consider using what is probably the most effective therapeutic procedure available for right heart failure: extracorporeal membrane oxygenation (ECMO). However, this should only be done with a clearly defined goal, which is usually bridging to transplantation.
In venoarterial ECMO therapy, it is important to keep in mind that the problem of differential hypoxemia may occur in PAH patients, just as in pulmonary or fibrosis patients. In peripheral ECMO, there is venous and arterial access in the femoral vein and artery, respectively. The oxygenated blood in the aorta is pumped up from the bottom. The blood coming from the heart and the blood flow from ECMO meet at what is called the watershed. “The oxygenation of the blood through ECMO can be measured directly. But the problem is that we don’t know what the oxygenation is of the blood coming from the heart. If we’re not careful, cerebral hypoxemia can occur.” By monitoring the oxygen level in the right hand in such a case, treaters can see what’s coming into the head. “What can’t be monitored, however, is the ascending aorta, from which important vessels, the coronary arteries, branch off,” said Prof. Hoeper, explaining the risks of ECMO therapy. The process, although relatively young, is now established worldwide.
Early evaluation keeps options open
Large case series on ECMO bridging in PAH patients are not yet available. As of early 2018, there were 77 published patients who had been hybridized with ECMO with the goal of transplantation. Seventy-two of these (94%) achieved this goal, and hospital survival for these patients was 80%. Compared with one-year survival in elective lung transplantation, which is about 90%, this is worse. “But these,” says Prof. Hoeper, “are of course high-risk patients. And on the other hand, you have to say that virtually all of these patients would have died without the measures, so I think this 80% is more than acceptable.”
PAH is a chronic progressive and fatal disease. In particular, when patients decompensate during the course of their disease career, need to be admitted to the ICU, and have no treatable trigger, this is the end stage of the disease. When the possibility of transplantation exists, bridging is a useful procedure. However, this option is only available if the patient has been evaluated beforehand. This means that today, especially in patients with PAH, this has to be done very early. To keep the option open, “we now evaluate patients when they do not respond adequately to two oral tablets of PAH medication, even if they are otherwise still in relatively good health.” This is the only way to maintain the chance of still reaching transplantation and surviving as an emergency. This is practically impossible – especially since these patients often decompensate acutely – if no reasonable evaluation has taken place beforehand.
Source: 60th Congress of the German Society of Pneumology and Respiratory Medicine, Munich (D).
Literature:
- Sztrymf B, et al: Prognostic factors of acute heart failure in patients with pulmonary arterial hypertension. Eur Resp J 2010; 35(6): 1286-1293.
HAUSARZT PRAXIS 2019; 14(6): 43-44 (published 6/3/19, ahead of print).
InFo PNEUMOLOGY & ALLERGOLOGY 2019; 1(1): 35-36 (published 6/3/19, ahead of print).
