Last week's reading was on pulmonary hypertension.
( Roham TZ et al. Managing strategies for patient with pulmonary hyertension in the ICU. Critical Care Medicine 2008)
This paper highlights that pulmonary hypertension and concomitant right ventricular failure present a particularly difficult diagnostic and therapeutic challenge in haemodynamically unstable patients in the ICU.
The categories of underlying aetiology can be sub-divided into those that causes:
1) pulmonary arterial hypertension;
2) associated with significant venous or capillary disease;
3) secondary to left heart disease;
4) Due to lung disease or hypoxaemia
5) due to thrombotic / embolic diseases
There are few important learning messages from this paper:
1) Fluid resuscitation must be carefully initiated because intravascular depletion (hence low pre-load) or over-load can worsen haemodynamics.
2) Mechanical ventilation - especially at high tidal volume and high PEEP can worsen pulmonary hypertension and hence haemodynamics (Target PEEP 5 - 8).
3) Effective treatment relies on ability to accurately identify the underlying cause - from history, thorough examination, and appropriate investigations (ECHO; the gold-standard cardiac catheterisatio; ECG, CXR etc) and address the primary cause.
4) Although studies of inotropes and vasodilators in pulmonary hypertension (especially in ICU) are limited, the use of dobutamine, inhaled nitric oxide, and IV prostacycline have the greatest support in the literature). As for other treatments, relies on good understanding of their pharmacokinetics / dynamics and co-morbidities of the patient being treated.
5) The use of vasopressors should be carefully titrated to their lowest effective dose due to higher risk of side-effects without extra treatment benefits. Such important side-effects include tachycardia, increasing cardiac oxygen demand, profound hypotension, and arrhythmias.
