What are the significant values in biochemistry?
As I mentioned back in Emergency Biochemistry in the Starting Material section, the significant values in biochemistry are all measured in millimoles per litre or mmolL-1, and they are listed in the table below. The reference range refers to values seen in about 95% of the population, and the critical low and critical high entails the extremes at which the body can tolerate before it shuts down.
What are the medical conditions that can result from extremely low or high analyte values?
Often, extreme lows or highs in the analyte values can land someone in the Emergency Department of a hospital. Almost all of the analytes that I mentioned above have a consequence which relates to injury of the brain as well as problems within the body. I’ll discuss each of the analytes separately and be discussing the consequences associated with critical high and low values.
Sodium (Na+) RR: 37-145mmolL-1
Sodium level extremes tend to almost exclusively affect the brain due to the process of osmosis, which forces water either in or out of cells along with the charged Na+ ions.
- Cerebral dehydration due to water being forced out of the brain
- Intracerebral haemorrhage (bleeding of the brain)
- Cerebral oedema (swelling) due to water being forced into the brain cells from the outside.
Potassium (K+) RR: 3.1-4.2mmolL-1 (heparin), 3.8-4.8mmolL-1 (clotting)
The problems tend to be centred around the heart, the gut and the kidneys: the heart and gut troubles can be linked to the brain, however, due to their innervation by the vagus nerve (cranial nerve X). Low potassium levels in the blood tend to be purely clinical in nature, however high potassium levels are often artefactual, so they need to be cross-checked first. More information about clinical vs. artefactual results can be found in Emergency Biochemistry.
- Cardiac (heart) arrhythmia, the heart beats but it does not maintain its normal lub-dub rhythm correctly.
- Cardiac arrest (ventricular fibrillation): the heart stops completely
- Kidney problems
- Metabolic alkalosis (high pH in the blood)
- Cardiac problems
- Gut paralysis
Bicarbonate (HCO3-) RR: 22-32mmolL-1
Bicarbonate tends to affect both the body and the brain, however low levels of bicarbonate tend to affect the brain more noticeably.
- Severe pulmonary (lung) disease
- Severe metabolic acidosis (low levels of pH in the blood)
- Impairment of nervous function
Glucose (C6H12O6) RR: 3.8-5.5mmolL-1 (fasting)
The variations in glucose levels, unlike the other analytes, has a specific name attached to the disease. The condition of uncontrolled glucose levels is known as diabetes mellitus, and it has two types: type 1, which is an autoimmune disease that rids the body of insulin-producing cells in the pancreas, and type 2, which is due to resistance of insulin. The lack of glucose of blood is detrimental to the brain because of the brain’s dependence on glucose for energy.
- Severe hyperglyercaemia (high levels of glucose in the blood)
- Diabetic ketoacidosis (release of ketones into the blood, which can be detected by a urine dip test)
- Severe hypoglycaemia (low levels of glucose in the blood)
- Cerebral starvation
Calcium (Ca2+) RR: 2.10-2.55mmolL-1
Calcium has a very narrow reference range: if the results end up outside of that range, it is immediately classified as an emergency. The excess or lack of calcium affects many different organs in the body.
- Cardiac arrhythmia
- Confusion due to lack of flowing blood in the brain
- Cardiac arrest due to paralysis in the vagus nerve (cranial nerve X)
- Tetanus due to nerve hyperexcitability
- Renal (kidney) failure
- Parathyroid adenoma post-surgery
Magnesium (Mg2+) RR: 0.7-0.9mmolL-1
Differences in magnesium levels are often associated with cytotoxic drugs: in other words, drugs that affect the cells of the body, causing them to release electrolytes. High levels of magnesium are rare but low magnesium is relatively common.
- Renal failure
- Infusion of cisplatin leading to renal (kidney) tubules leaking magnesium.