• Haemoglobin (Hb) (130-165 g/l) is a protein found in red blood cells that helps carry oxygen from the lungs to the cells. It can be high in dehydration or polycythaemia or low in bleeding or anaemia

• International Normalised Ratio (INR) (0.9- 1.2 Ratio) Measures how long blood takes to clot. When raised it takes blood longer to clot/form a thrombus. Used to determine the effectiveness of oral anti-coagulants e.g. warfarin

• Activated partial thromboplastin time (APTT) (0.85-1.15 Ratio) also measures how long it takes for blood to clot.

• Platelets (150-450) When your skin is injured or broken platelets clump together and form clots to stop the bleeding. Thrombocytopenia (low platelet count) ranges from mild to severe. Low platelet count can result in bleeding

• Troponin (<16 ng/ml) is a protein which is released when there is cardiac muscle damage

• D-dimer (<500 ng/ml) is a protein fragment that is released from the breakdown of a clot. If raised can indicate significant clot formation (DVT/PE) and can also help rule out a DVT/PE in patients with low risk

• Creatinine Kinase (CK) (10-150 U/l) is an enzyme found in the heart and skeletal muscle. Increased amounts are released into the bloodstream when there is muscle damage. Can indicate a myocardial infarction, trauma or even rhabdomyolysis.

Need to be maintained in a tight balance for normal body function

• Sodium (135-145 mmol/l) if elevated can be a sign of dehydration. Can cause lethargy, agitation or even life threatening coma >155. Low levels can be caused by large fluid loss (diarrhoea or vomiting) or fluid overload

• Potassium (3.5-5.0 or >4.0 mmol/l in cardiac patients) is essential for cardiac electrical signalling function. Can be high in renal failure or low with large fluid loss from diarrhoea or vomiting or polyuria. Abnormal levels may cause arrhythmias and lead to cardiac arrest if not treated

• Calcium (2.20- 2.60 mmol/l) is essential for functioning of nerves and muscles as well as healthy bones and teeth. It can be high in renal failure, hyperparathyroidism and malignancy. Low in malnutrition or hypoparathyroidism.

• Magnesium (0.7-1.0 mmol/l) helps to regulate muscle and nerve function. It is also a bronchodilator allowing for more air to flow in and out of the lungs

• Phosphate (0.80-1.40 mmol/l) is needed to help nerves function, muscles contract and build healthy bones and teeth

• White Blood Cells (WBC) (4.0-11.0) flow through the bloodstream to fight bacteria, viruses and other foreign invaders. Made in the bone marrow

• C-Reactive Protein (CRP) (<5) is a protein made in the liver that’s released into the bloodstream a few hours after tissue injury. It’s a marker of inflammation.

• Procalcitonin (PCT): When the immune system is activated by a pathogen PCT is produced in greater levels. Increased PCT levels are found in patients with bacterial infection. Reference range of Procalcitonin:

  • <0.50ng/mL represents a low risk of severe sepsis and/or septic shock

  • >2.00ng/mL represents a high risk of severe sepsis and/or septic shock

• Blood passes through the kidneys at a rate of 150 litres a day. They filter the blood by removing excess water and waste products which is then excreted as urine

• Urea (3.3- 6.7 mmol/l) is a waste product from the breakdown of food and body metabolism

• Creatinine (45-120 umol/l) is a waste product generated from muscle metabolism. It’s a more reliable indicator of kidney function as its less influenced by other factors such a diet or hydration

• Elevated Urea & Creatinine signify kidney impairment, this can be acute or chronic

Lactate is often used in the context of critical illness. It is used to evaluate tissue perfusion. However, it is important to be aware that there are other etiologies responsible for raised lactate. Lactate is a prognostic tool and studies have demonstrated a correlation between elevated lactate (>4mmols) and increased mortality. During the anaerobic process lactate is an end product of glycolysis.

You can learn more about the significance and management of raised lactate in this video from ResusMe:

https://youtu.be/TuvKcplVQLg

• Bilirubin (3-20 umol/l): Yellow pigment which is a waste product of red blood cell breakdown

• Alkaline Phosphatase (ALP) (30-130 IU/l) Enzyme found in the liver

• Aspartate Transaminase (AST) (10-50 IU/l ) Enzyme present in tissues

• Gamma- glutamyl Transferase (GGT) (5-55 IU/l) Enzyme mostly found in the liver

These are all measures of liver function. Elevated levels can indicate obstructive disease of the liver, liver cell damage, high alcohol intake, drug abuse or metastases.