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07. Acute Cor Pulmonale complicating acute respiratory distress syndrome
In this setting, two associated factors combine to raise right ventricular outflow impedance :
- underlying pulmonary disease, which usually causes permanent diffuse arteriolar obstructions(15) ;
- assisted ventilation (16), which results in microvascular, intermittent or permanent obstructions, by elevation of transpulmonary pressure (17, 18).
The frequency of this complication was 61% then, a value close to mortality of the syndrome. It is now known that these tidal volumes, and the high plateau pressure they induce, are excessive. Reduction in plateau pressure to below 30 cm H 2O significantly reduces the frequency of ACP to about 25% (9). he frequency of this complication was 61% then, a value close to mortality of the syndrome. It is now known that these tidal volumes, and the high plateau pressure they induce, are excessive. Reduction in plateau pressure to below 30 cm H 2O significantly reduces the frequency of ACP to about 25%(9).
Film 23 : In the same patient as in film 22, a few hours after reduction of tidal volume lowered the plateau pressure to 26 cmH2O, TEE shows the virtual disappearance of ACP. The systolic blood pressure is now 123 mmHg.
The onset of ACP during ARDS is generally more gradual than during PE and is observed after a certain time on assisted ventilation (9). In certain patients ACP :
- may occur on introduction of assisted ventilation,
- or can be triggered by untimely adjustment of respirator settings
In some patients, the later onset of ACP indicates a fibroproliferative phase, which can be arrested by corticosteroid therapy.
If ACP occurs during ARDS, the following measures should be implemented immediately :
- reduce plateau pressure to below 25 cm H 2O
- lower PEEP to below 8 cm H 2O
- reduce PaCO 2 to below 60-65 mmHg by use of a heater/humidifier in place of the filter (20), possibly by increasing respiratory frequency in certain patients. However, this maneuver is rarely effective and by generating an intrinsic PEEP often raises the plateau pressure, at the expense of right ventricular ejection (21). Remember that hypercapnia, which leads to systemic vasodilatation, has the reverse effect on the pulmonary circulation, resulting in arteriolar vasoconstriction (22).
- prone positioning if the ratio PaO 2/FIO 2 remains below 100 mmHg
- use TEE to check the absence of proximal PE
When ACP appears after more than one week of assisted ventilation in a patient whose lung compliance is deteriorating, and in whom hypercapnia is increasing, this combination is strongly suggestive of a fibroproliferative phase. We then always use corticosteroid therapy.
Lastly, inhaled NO can also afford rapid relief and reduce or eliminate signs of ACP.
In our experience, immediate implementation of these measures, which presupposes rapid echocardiographic diagnosis, has meant that ACP no longer results in excess mortality in ARDS. ACP can greatly reduce the likelihood of cure if specific and timely measures are not taken (19).
Contents
01. Reminder: ventricular independance
02. Principal echocardiographic views used to study detect ACP
03. Systolic overload
04. Diastolic overload
05. Effects of acute cor pulmonale on the left ventricle
06. Acute Cor Pulmonale complicating massive pulmonary embolism
07. Acute Cor Pulmonale complicating acute respiratory distress syndrome
08. Acute Cor Pulmonale in other clinical settings
09. References