Critical Care Medicine Flashcards
a) What are the symptoms, clinical signs and XR findings for APO?
b) What are the possible causes and 3 important initial investigations?
a) Rapid onset dyspnoea at rest, tachypnoea, tachycardia, and severe hypoxaemia. Crackles and wheeze due to alveolar flooding & airway compression. XR findings include peribronchial cuffing (peribronchial thickening/haziness-donut sign) causing the airway compression.
b) Cardiogenic vs non-cardiogenic causes of APO are difficult to distinguish.
1-Echo will identify systolic and diastolic ventricular dysfunction &/or valve issues.
2-ECG to observe ST elevation and evolving Q waves indicating acute MI.
3-BNP (Brain natriuretic peptide), when significantly high supports heart failure (HF) as the aetiology.
a) What are the basic considerations for APO treatment and what conditions can complicate it?
b) Describe the initial treatment measures to support gas exchange.
c) Describe when mechanical ventilation is indicated and it’s 3 main benefits.
a) Support of circulation, gas exchange, and lung mechanics. Must keep in mind infection, acidaemia, anaemia, and acute kidney dysfunction.
b) Generally aim for Sats >92%, Sats >98% may be detrimental. Positive Pressure Ventilation, this Non-invasic ventilation (NIV) can rest the respiratory muscles, improve oxygenation and cardiac function, and reduce need to intubation. c) Mechanical ventilation with PEEP can relieve WOB more completely as it 1-Decreases both pre-load and afterload, thus improving cardiac function, 2-Redistributes lung water from intraalveolar to the extraalveolar space (thus fluid interferes less with gas exchange), & 3-Increases lung volume to avoid atelectasis.
a) What considerations should be made for the kidney during APO?
a) For patients with refractory APO, metabolic acidosis (pH <7.15-7.25), hypoxaemia, &/or persistent hyperkalaemia, renal replacement therapy (RRT) should be considered. Particularly for hypotensive patients requiring ionotropic support (better than intermittant haemodialysis)
a) What are the 3 main medication options for reducing preload for patients in APO?
a) 1-Diuretics-Loop Diuretics e.g. Furosemide, Bumetanide. Also acts to venodilate which reduces preload. Initially 0.5mg/kg, up to 1mg/kg in patients with renal insufficiency, chronic diuretic use or hypervolaemia.
2-Nitrates-Nitroglycerin and Isosorbide dinitrate. mainly venodilators but dilate coronary vessels too. First line therapy Nitroglycerin spray 400mcg SL repeat every 5mins to max of 1200mcg. Closely monitor BP to avoid reduced coronary artery hypoperfusion.
3-Morphine-Transient venodilator that reduces preload while relieving dyspnoea and anxiety. This can in turn reduce catacholamine levels, tachycardia and ventricular afterload.
Morphine 1mg to 2.5mg IV single dose.
NB: Can also consider ACE-inhibitor for hypertensive patients. Titrate from low dose.
a) What are some other considerations for reducing pre-load in APO aside from the initial medications?
a) -Physical methods such as sitting the patient up with legs dangling on the side of the bed.
- Inotropic and Inodilator drugs e.g. sympathomimetic amines dopamine and dobutamine are potent inotropes.
- Digitalis Glycosides, now rarely used. May have a role with rapid ventricule response to AF or Flutter and LV dysfunction due to APO because thay do not have the negative ionotrpic effects of other drugs that inhibit AV nodal conduction
a) What are some special condierations when treating APO?
a) -Risk of Iatrogenic Cardiogenic Shock: Treatments may cause hypotension, coronary artery hypoperfusion, and shock. Generally hypertensive patients respond well to meds reducing pre-load, normotensive patients should have much lower doses instigated sequentially.
- ACS: This should be an immediate consideration as a possible cause of APO
- ECMO
a) What are some unusual causes of APO?
a) -Re-expansion pulmonary oedema after removal of pleural space air or fluid (hypotension or oliguria due to rapid-fluid shifts)
- High-altitude pulmonary oedema
- Pulmonary Oedema resulting from upper airway obstruction.
