Etiology and classification
Comatose states represent the consequence of critical shifts in the body's homeostasis. In the vast majority of cases, they are triggered by severe internal organ pathology.
In clinical practice, six main types of loss of consciousness are most commonly encountered:
- Uremic.
- Hepatic.
- Diabetic (ketoacidotic).
- Hypoglycemic.
- Coma in traumatic brain injury (TBI).
- Alcoholic.
Metabolic comas (renal and hepatic)
Uremic Coma The pathogenesis of this condition is inextricably linked with terminal renal failure, leading to massive retention of nitrogenous waste products in the body.
- Dynamics: symptoms develop gradually.
- Background: most commonly manifests at the terminal stage of chronic kidney disease (CKD), somewhat less frequently precipitated by acute kidney injury (AKI).
- Symptom Complex: accompanied by anemia, elevated blood potassium levels (hyperkalemia), and acidosis.
- Prevention: timely transition of the patient to hemodialysis.
Hepatic Coma The primary cause is severe hepatic parenchyma damage.
- Dynamics: unlike renal pathology, it can develop in a very short timeframe.
- Prodromal Period: precursors include mental status changes and atypical patient behavior.
- Diagnostic Trap: physicians frequently make the mistake of attributing these early abnormalities to a person's character traits or situational nervousness.
Complications of Diabetes Mellitus
Diabetic (Ketoacidotic) Coma This condition is characterized by a fairly rapid onset, and initially the patient may report a quite satisfactory general condition. Patients often conceal the presence of precursors, which include:
- pronounced thirst;
- excretion of an abnormally large volume of urine (polyuria);
- marked dry skin.
Hypoglycemic Coma Develops in the context of diabetes mellitus as a result of ongoing insulin therapy (in case of drug overdose or dietary non-compliance).
- Features of Development: despite being preceded by a feeling of hunger, loss of consciousness often occurs suddenly (frequently on the street or in public transport).
- Differential Sign: the most important distinction from hyperglycemic coma is pronounced skin moisture.
- Safety: patients need to carry special identifiers ("Diabetic Patient Card" or documentation with the insulin dosage).
Traumatic and Alcoholic Comas
Coma in Traumatic Brain Injury (TBI) Diagnosis is based on history-taking (information on the fact of trauma) and physical examination (presence of hematomas, bleeding from ENT organs).
- Neurological Status: a characteristic sign is pupillary asymmetry (anisocoria), as well as sluggish reaction to light or its complete absence.
- Vital Functions: respiration is variable (most often slow or irregular), pulse is unstable — initial tachycardia is eventually replaced by bradycardia.
Alcoholic Coma The diagnosis is confirmed by the presence of an alcohol odor on the breath and a blood ethanol concentration of 0.3–0.7 mg%.
- Important Clinical Rule: the presence of an alcohol odor does not rule out concurrent TBI. The physician must conduct a thorough examination to exclude traumatic brain injury.
Briefly: answers to topical questions
What is the algorithm for emergency medical care in hypoglycemic coma?
Emergency medical care in hypoglycemic coma consists of the emergency intravenous administration of hypertonic glucose solution. Due to the rapid development of the condition outside the hospital setting (on the street, in transport), diagnostic difficulties may arise. To verify the diagnosis, it is important for the patient to have an identifier ("diabetic patient card" or medical documentation indicating the insulin dose). Laboratory signs: decreased blood glucose levels, absence of glucose and acetone in the urine at its normal specific gravity. A key differential sign is pronounced skin moisture.
What pathological breathing types are observed in diabetic ketoacidotic coma?
In diabetic ketoacidotic coma, Kussmaul breathing (also known as "air hunger") is observed. It occurs as compensation for acute metabolic acidosis (decrease in blood pH) and aims to reduce carbon dioxide levels through hyperventilation.
Characteristic features of this breathing type:
- Kussmaul breathing — regular cycles characterized by a slow, deep, and noisy inspiration followed by an enhanced expiration.
In ketoacidotic coma, this pathological breathing is specifically accompanied by the smell of acetone (rotting apples) on the breath, which is associated with the formation of ketone bodies during fat breakdown. The appearance of such a symptom indicates an extremely severe condition of the patient.
What clinical stages are distinguished in the development of hepatic encephalopathy and coma?
Four main clinical stages are distinguished in the development of hepatic encephalopathy and coma:
- Stage I (prodromal period) — transient mood changes (depression or euphoria/agitation), behavioral disorders, and sleep inversion.
- Stage II (profound neuropsychiatric disorders) — inappropriate behavior, lethargy, and specific flapping tremor of the fingers (asterixis).
- Stage III (precoma) — stupor, dysarthria, increasing asterixis, pathological reflexes, and respiratory disorders (Cheyne-Stokes or Kussmaul type). A specific hepatic breath odor appears (fetor hepaticus).
- Stage IV (actual hepatic coma) — complete loss of consciousness and areflexia (terminal state).
Due to which toxic substances does hepatic coma develop?
Hepatic coma develops as a result of the accumulation of toxic substances in the systemic circulation, their penetration through the blood-brain barrier, and CNS dysfunction.
An important pathogenetic link is the accumulation of excess ammonia. Ammonium compounds are also specified: ammonium carbonate, ammonium carbamate, and ammonium hydroxide. Damage mechanisms include inhibition of Na+, K+-ATPase, formation of toxic metabolites, and damage to benzodiazepine receptors.
In addition, in hepatic coma, protein breakdown products in the large intestine increase in the blood: putrescine, cadaverine, phenol, indole, and skatole derivatives. Their accumulation is associated with a decrease in the detoxifying function of the liver during necrosis or functional insufficiency of hepatocytes.
To distinguish diabetic comas by skin condition, remember: in hypoglycemia, the patient is "wet" (pronounced moisture), while in ketoacidosis, they are "dry" (dry skin).
Class and exam questions
How to quickly distinguish hypoglycemic coma from diabetic (ketoacidotic) coma?
A key clinical sign is the state of the skin: in hypoglycemia, the skin is pronouncedly moist, whereas in ketoacidosis, marked skin dryness is observed.
What prodromal signs are characteristic of hepatic coma?
In the prodromal period, mental and behavioral changes occur in the patient, which physicians often mistakenly attribute to ordinary nervousness or character traits.
What is the main danger when diagnosing alcohol-induced coma?
The smell of ethanol on the breath can mask the symptoms of concurrent traumatic brain injury, therefore a thorough examination is always required to rule out brain damage.
What else to study on this topic
- Pathogenesis of nitrogenous waste accumulation in end-stage chronic kidney disease (CKD).
- Mechanisms of hyperkalemia and metabolic acidosis development.
- Neurological examination of a patient with suspected traumatic brain injury (TBI).
- Impact of diet and insulin dosing on the risk of hypoglycemia.
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