Common investigations 

Again a massive topic and unfortunately due to copyright reasons we aren't able to show you worked examples in this section. 

However we can cover a standard structure for how to review ECG's, Chest X Rays and blood gases that you can apply to clinical practice to help you spot any abnormalities. These are in no way detailed.  There are however lots of pre-existing resources that I would highly recommend you to review and they will be in the reference section. 

ECG's 

• Demographics, date / time of ECG 

  • Make sure it's for the correct patient 

  • Also consider the quality of the ECG - this can affect interpretation

  • If there are previous ECG's take the time to compare them

• Rate 

  • Bradycardia or tachycardia present? 

• Rythym 

  • Regular 

  • Irregular 

• PR Interval

  • Normal is less than 200ms. 

  • Prolonged in heart block 

• QRS / ST segment

  • Lots of potential anomalies so take the time to look carefully 

  • Look for Q waves - often suggestive of previous MI 

  • Check R waves - progression? 

• ST Segment 

  • Elevation 

  • Depression  

• QTC 

  • Remember normal values differ for male vs female 

  • If prolonged consider causes and review drug chart for contributing factors 

Things to consider particularly if arrhythmias? 

• Electrolyte anomalies - think potassium / magnesium in particular 

• Hormonal imbalances eg hyperthyroidism 

• Dehydration 

• Have we given anything? 

Chest X Rays 

• Demographics, date / time of CXR 

• The film quality 

  • Is it rotated? 

  • Adequate inspiration?

  • Is it AP or PA 

  • Adequate exposure? 

• And back to ABCDE 

  • A - Look at the trachea - is it central 

  • B - Look at the lung fields properly and compare both sides 

    • Are they clear 

    • Is there consolidation 

    • Is there evidence of fluid - this can be an effusion, pulmonary oedema with signs of congestion 

    • Any evidence of pneumothorax

  • C - Look at the heart 

    • Is it enlarged? 

    • Is the mediastinum normal or widened? 

  • D - Diaphragm 

    • Is it visible 

    • Is it flattened or tented

    • Any evidence of air 

  • E - everything else inlcuding bones and soft tissue 

    • Looking for rib fractures

    • Evidence of surgical emphysema 

    • Are any lines / drains / tubes in the appropriate site 

Blood gases 

• Demographics, Date and time 

  • Review  trends.

• Is it venous or arterial 

  •  Check PaO2 and Sats and correlate Sats with the patient clinically if you aren't sure 

• Check the pH 

  • Acidosis or alkalosis 

• Review CO2 

  • If it's low - are they compensating for a metabolic acidosis 

  • If its high - are they tiring? Is this T2RF? Do they have a respiratory acidosis 

• Review metabolic status - Bicarbonate and base excess

• Lactate 

  • If this is continuing to rise escalate to seniors 

• Blood glucose

• anion gap 

  • Often overlooked and so so useful in acidotic patients for narrowing down the underlying aetiology 

    • Normal anion gap acidosis - ABCD 

      • A - Addisons 

      • B - Bicarb loss - Renal tubular acidosis, excessive diarrhoea 

      • C - Chloride 

      • D - Drugs - acetazolamide, 

    • Raised anion gap acidosis - MUDPILES 

      • M - Methanol 

      • U - uraemia - check U&E's / K+ 

      • D - DKA 

      • P - proylene glycol / paracetamol

      • I - Isonazid 

      • L - Lactic acidosis

      • E - ethylene glycol 

      • S - Salicylates 

• Are they compensating - if yes is it full or partial compensation or is it uncompensated. 

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Disclaimer:

This is a not for profit education resource designed for new resident doctors. All information serves as a guide to help doctors approach day to day life as an F1. It is not intended as a guide to patient care and should never be used as such or in place of advice of treating clinicians or published clinical guidelines. All cases are fictional and any resemblance is purely coincidental. Additionally all images are AI generated unless otherwise stated.