How to assess an ICU patient

How to assess an ICU patient
Photo by Hush Naidoo Jade Photography / Unsplash

When I first stepped onto the intensive care unit it was as a junior clinical fellow (FY3) and I had no idea how to go about assessing a critically unwell patient in any meaningful way, and what would have been really helpful would have been a brief 'how to' guide on the things to look for and what not to forget, so I thought I'd put one together.

This is not a comprehensive management tool for all things ICU - it is a scaffold on which to build your assessment to allow you (or your senior) to make sensible decisions.


The patient's airway can be one of three options:

  • Own and safe
  • Own and threatened
  • Intubated

The best airway is the patient's own airway, but if it's not safe because they're too obtunded to prevent aspiration or they have severe facial burns with impending laryngeal obstruction, then the better option might be a tube.

As we have mentioned on many previous occasions, there are only two reasons to intubate someone:

  • To protect their airway
  • To do the work of breathing for them

If a patient is intubated on the intensive care unit, then it is for one or both of these reasons.

The key is working out if those reasons are still legitimate, and therefore whether the person needs to remain intubated, or whether we can think about waking them up and extubating them.

For example:

  • Improving pneumonia requiring much less oxygen
  • Improving GCS after overdose or head injury
  • Post-op patient with adequate pain control on board

If they are to remain intubated, then check the position of the tube at the teeth, and on the chest xray, aiming for approximately 3cm above the carina.


A patient's breathing can be in one of four categories:

  • Unsupported on room air
  • Unsupported with supplemental oxygen (nasal cannula, facemask)
  • Non invasive support (CPAP or NIV)
  • Invasive ventilation (Endotracheal tube, tracheostomy)

If their breathing is unsupported, then their respiratory rate and work of breathing are a good measure of how hard they're working, and whether they need any more help.

If their breathing is supported, be that on a ventilator, non invasive ventilation or continuous positive airway pressure (any form of machine basically) then look at the tidal volumes they're achieving, how much pressure it's requiring and how much oxygen they need.

The key as always is the trend:

  • Are the parameters and settings better or worse than before? 
  • Does this patient need more support, or can we start to wean it down?

Often the ICU nurses will automatically wean ventilatory support as tolerated by the patient, and you'll walk in to find the settings vastly better than when you last looked at them, just keep communicating and regularly checking.


Is there enough blood, and is it being pumped to right places at the right pressure?

  • Blood pressure (mean arterial pressure ideally over 65 - 70 mmHg)
  • Heart rate
  • Temperature
  • Haemoglobin
  • Lactate
  • Urine output
  • Capillary refill time
  • Bedside ECHO if you know how

Is the patient in shock, and if so, which type of shock is it?

  • Is the patient's blood pressure supported (inotropes, vasopressors)?
  • Are they requiring more or less support than before?

Some patients have advanced cardiac output monitoring, such as PiCCO or LIDCO, or a pulmonary artery catheter. There is significant debate as to the utility of these monitoring tools, but one thing is for sure - the presence of advanced invasive cardiac output monitoring is a bad prognostic sign.


How conscious are they, and is that because they're unwell or because you've given them a whole bunch of drugs?

  • GCS
  • RASS scale
  • Blood glucose
  • Pupils
  • Muscle tone and power if they're awake

Usually patients on ventilators will have a sedation hold in the morning, and as the drugs wear off they start to wake up to at least some degree. This allows you to assess their cough and gag reflexes, as well as whether they are neurologically 'appropriate' to extubate.

If a patient is wide awake and looking at you, and nods when you ask 'would you like me to take the tube out?' they're probably safe to extubate - but run this past a senior first. 


  • What IV access have they got?
  • Are their limbs and pressure areas okay?
  • Any signs of DVT?
  • Are they particularly swollen?


Notoriously difficult to assess and hotly debated among the 'wet' and 'dry' intensivists who will tell you the others are heathenous degenerates.

  • Are they clearly very dry?
  • Are they clearly very overloaded?
  • Is their urine output sufficient?
  • Is their Hb strangely high or low?

If in doubt, assessing the response to a 250ml bolus or two is rarely a bad idea.

We probably vastly underestimate the insensible losses in the form of rapid breathing, sweating and oozing of bodily fluids, so patients may be clinically dry even when the fluid balance chart has an enormously positive number.


It's easy to assess the function of a tube if you simplify your approach

  • Is anything going in the top end? (NG feed, eating and drinking)
  • Is it coming back out the top end or is it being absorbed?
  • Is anything coming out the bottom end? 
  • Is the stuff coming out the bottom end the right colour and consistency?
  • Is it getting stuck in the middle? (bowel sounds, distension, pain, peritonitis)

All of gastro in five questions.


Is there an acceptable amount of each type of blood cell in the patient, and if not, why not?

  • Bleeding
  • Infection
  • Malignancy

Are all the organs that you are able to test working as they should?

  • Liver
  • Kidney
  • Bone marrow
  • Spleen?

I'm guessing now.


What evidence of infection is there, and what are we doing about it?

  • Temperature
  • Rashes, wounds, pus, drains, exudates and excretions
  • White cells, CRP, procalcitonin
  • What antibiotics are they on, how long for, and is this a good idea?
  • Do I need to take any pictures of where I think the infection might be? (Chest xray, Abdominal CT scan, MRI foot, US KUB etc)

Can you explain any of the patient's other problems (eg loose stool, red face, kidney injury) by their current antibiotic regimen?


Where has the patient come from and where are they going?

  • How bad were they when they came in?
  • Are they getting better or worse?
  • Does this look like a meaningful long term recovery?
  • If it all goes wrong at three in the morning, should we be putting this person through CPR and escalation of invasive treatment?

K+ and electrolytes

Check the latest ABG and blood results, and correct where necessary:

  • Potassium
  • Sodium
  • Magnesium
  • Phosphate
  • Calcium


  • What invasive lines does the patient have in situ?
  • Do they need to come out (infected or no longer needed)?
  • Do they need replacing (7-10 days depending on site and trust)?
  • Do they need any more?


  • What medications are they on?
  • Can any be stopped? (e.g. Day 15 of pabrinex)
  • Can any be switched to oral or NG?
  • Are they anticoagulated?
  • Do they have stress ulcer prophylaxis?
  • Do they need more pain relief?

Next of Kin

  • Are the family up to date?
  • Do they understand the plan, the trajectory and the prognosis?
  • Are they in agreement with ceilings of treatment?


  • Any other questions from patient, relatives, nurse or medical students?
  • Any referrals needed for help from other specialties?


  • What are today's aims with regards to each of the above?
  • Do the bedside nurse and nurse in charge know that this is the plan?

If you would like to read more of our ICU posts then click here