The Hypoxic Patient

Question 1

You are the medical FY1 on call. You are called to review a patient on the ward. Mr R is a 39 year old, admitted 2 days ago with an acute asthma exacerbation. He is currently being treated with regular nebs and steroids.

• His observations are: HR 118, BP 125/82, RR 30, Sats 91% on 2L and Temp 37.1.
• He is audibly wheezy from the end of the bed, can speak a few words and is leaning forward to rest on his hands.

a) What severity of asthma exacerbation is this? (think PUFF and PORSCHE)
b) Why are his saturations low?

Answer 1

a) Life-threatening: due to hypoxia (91% on 2L)

PUFF: (any one of these for severe)

• PEF 33-50% best/predicted,
• Unable to talk in complete sentences,
• Fast breathing (RR 25+),
• Fast heart rate (HR 110+)

PORSCHE: (any one of these for life-threatening)
- PEF < 33% best/predicted, 
- Oxygen low (SpO2 <92% / PaO2 <8 kPa), 
- Reduced consciousness
- Silent chest
- Cyanosis,
- Hypotension
- Exhaustion (if T2RF/ need ventilation = life-threatening)
(Also: arrhythmia) 

b) Bronchoconstriction, causing reduced oxygen delivery to the alveoli and reduced diffusion into the blood

Question 2

How should you assess a patient with an acute asthma exacerbation?

Answer 2

A - E assessment

Airway.
- patent?

Breathing.

• 100% oxygen 15L/min via non-rebreathe mask
• SpO2 (attach probe if not already) and RR
• Assess trachea and chest expansion (?pneumothorax)
• Percussion and auscultation (?wheeze, crackles, consolidation)
• Do an ABG (for anyone critically unwell, with SpO2 < 92% or at risk of hypercapnia)
• Record PEFR (>75%: mild, 50-75%: moderate, 33-50%: severe, <33%: life-threatening)

Circulation.

• Colour, temperature, CRT, signs of shock
• Feel pulse, record a BP
• Mucous membranes - dry?

Disability.
- AVPU/GCS

Exposure.

Question 3

Management of acute asthma.

a) O SHIME
b) What patients needs ICU input?

Answer 3

Oxygen.

• initially 100% oxygen at 15L/min via non-rebreathe mask
• aim for 94 - 98% (may need to titrate, e.g. Venturi)
• ABG if < 92% / risk of hypercapnia/ severe asthma

Salbutamol.
- via spacer: 4 puffs initially, then 2 puffs every 2 minutes up to a maximum 10); or,
~ 5-10 mg/hour via oxygen-driven nebulisers if severe/life-threatening

Steroids.

• Prednisolone oral 40 mg; or,
• Hydrocortisone 100mg IV

Ipratropium.
- nebulised (with salbutamol nebs)

Magnesium sulphate

• IV infusion 1.2 - 2.0g over 20 mins
• in acute severe asthma, not responding to bronchodilator therapy
• beware hypotension!

Escalate to ICU - criteria:
- Anyone with life-threatening/near-fatal asthma who is failing to respond to therapy, i.e. :
• deteriorating PEF
• hypercapnia, or persisting/worsening hypoxia
• acidosis or fall in pH
• exhaustion, feeble respiration
• drowsiness, confusion, altered conscious state
• respiratory arrest

Question 4

Indications for a CXR in acute asthma

Answer 4

– Suspected pneumomediastinum or pneumothorax
– suspected consolidation
– life-threatening asthma
– failure to respond to treatment satisfactorily
– requirement for ventilation

Question 5

Why is an ECG useful in the context of hypoxia?

Answer 5

• Pulmonary embolism: sinus tachy, RBBB, Q1/S3/T3
• ACS
• Right heart strain (?pneumothorax, cor pulmonale)

Question 6

You are bleeped by a nurse about a 75 year old patient who is saturating at 80%.

a) What can you ask the nurse to do?
b) What should you do on assessing the patient?

Answer 6

a) Ask the nurse if they can:
- administer 15L/min via a non-rebreathe
- take a new set of obs
- put in a cannula, etc.

b) A-E assessment

Question 7

Common causes of hypoxia.

a) Acute
b) Chronic
c) Type 1 vs Type 2 RF

Answer 7

a) - Airway: obstruction, reduced GCS
- Breathing: pneumonia, PE, pneumothorax, acute asthma/COPD
- Circulation: MI, acute heart failure (pulmonary oedema)

b) - Pulmonary: COPD, OHVS/OSA, pulmonary fibrosis
interstitial lung disease, bronchiectasis/CF
- Cardiac: heart failure

c) - Type 1 (hypoxic): pneumonia, PE, pulmonary oedema, asthma/COPD
- Type 2 (hypercapnic): tiring COPD/asthma, NMD, OHS