Pathology development and precoma stage
Ketoacidotic coma does not develop suddenly. It is a logical consequence of the progressive worsening of metabolic disorders characteristic of the course of diabetes mellitus. When the body's compensatory mechanisms are exhausted, the patient enters the decompensation stage, known in clinical practice as precoma.
At this stage, the patient's consciousness is still preserved, but distinct signs of its alteration begin to appear. The body sends warning signals that can be divided into several groups:
- Skin and mucous membranes: become markedly dry. This is one of the initial visual markers of escalating disturbances.
- Gastrointestinal tract: erosive gastroenteritis develops, which is an important clinical sign of decompensation.
- Excretory system: a critical change in urination patterns occurs. Polyuria (excessive urine output) characteristic of diabetes is replaced by oliguria (a sharp decrease in urine volume).
Clinical features of full-blown coma
If the pathological process cannot be halted at the precoma stage, actual ketoacidotic coma develops. This critical condition is characterized by a complete lack of consciousness and profound depression of all reflexes.
The patient's neurological status undergoes major changes, with severe neurological disorders developing. Examination of the eyes reveals marked pupillary constriction (miosis), with a complete absence of the light reflex.
Vital functions of the body are threatened: circulatory and respiratory failure rapidly escalate. Renal function continues to decline: diuresis becomes extremely low and ultimately reaches the stage of anuria (complete cessation of urine entry into the bladder).
The most specific and easily recognizable symptom that allows suspecting this particular type of coma even before laboratory results are obtained is a sharp, pronounced smell of acetone in the exhaled air.
Laboratory changes
Laboratory tests play a key role in confirming the diagnosis. Blood and urine findings in coma ketoacidoticum have clear, specific criteria:
- Glucose level: marked hyperglycemia is observed. Blood sugar levels soar to 20–30 mmol/L.
- Ketone bodies: high ketonemia is recorded (blood ketone concentration reaches 10–17 mmol/L). Concurrently, ketonuria (excretion of ketone bodies in the urine) is invariably present in urinalysis.
- Plasma osmolarity: unlike some other types of diabetic comas, in the ketoacidotic variant, plasma osmolarity does not exceed 310–320 mosm/kg. This means the condition is characterized by iso-osmolarity or only slight hyperosmolarity.
Key markers of the condition
Summarizing the clinical and laboratory picture, it is important to emphasize the markers that make ketoacidotic coma recognizable.
First, respiration: the smell of acetone is the hallmark of this metabolic shift. Second, renal function dynamics: the transition from copious urination to its complete absence indicates a catastrophic escalation of circulatory failure. Third, the pupillary reflex: constricted pupils (miosis) unresponsive to light, against the background of a complete lack of consciousness, indicate profound central nervous system depression. Finally, the laboratory profile with high ketones and sugar at normal or slightly elevated osmolarity clinches the diagnosis.
Briefly: answers to topical questions
What type of pathological breathing is characteristic of full-blown ketoacidotic coma?
Full-blown ketoacidotic coma is characterized by Kussmaul breathing ("air hunger"). This is deep, noisy respiration with regular cycles consisting of an infrequent deep inspiration followed by a forced expiration. The pathology develops due to a drop in blood pH and a rise in CO₂. This type of breathing is accompanied by a specific smell of acetone (rotten apples) on the breath and is usually observed against the background of altered consciousness. Its appearance indicates an extremely grave condition of the patient.
How does the acid-base balance (blood pH) change in ketoacidotic coma?
In ketoacidotic coma, the acid-base balance changes with the development of decompensated metabolic acidosis, in which blood pH gradually decreases. The underlying mechanism is a massive release of ketone bodies into the blood (with β-hydroxybutyrate making the largest contribution) due to uncontrolled fatty acid oxidation. The accumulation of acidic products depletes buffer bases as they attempt to maintain balance. This condition is characterized by a combination of an acidotic shift with decreased levels of bicarbonate and other buffer bases.
How to remember the main signs of ketoacidotic coma? Use the mnemonic: C — Consciousness absent (reflexes depressed). U — Unresponsive pupils (miosis, no light reflex). H — History of chronic diabetes (cause is decompensation). O — Oliguria progressing to anuria (plus dry mucous membranes). I — Iso-osmolarity (osmolarity not exceeding 310–320 mosm/kg). ACETONE — Acetone breath, ketonemia (10–17 mmol/L), and ketonuria.
Class and exam questions
Which disease leads to the development of ketoacidotic coma?
This condition is the direct result of worsening metabolic disorders in decompensated diabetes mellitus. It is not related to diabetes insipidus, hypothyroidism, or Cushing's syndrome.
How does diuresis change during the transition from precoma to coma?
At the precoma stage, diabetes-associated polyuria is replaced by oliguria. With the development of full-blown coma, diuresis becomes extremely low, up to complete anuria.
What are the plasma osmolarity values in this type of coma?
Plasma osmolarity remains within normal limits or increases slightly. It does not exceed 310–320 mosm/kg, which is regarded as iso- or slight hyperosmolarity.
How do the patient's pupils react in a state of ketoacidotic coma?
Marked miosis (constricted pupils) is observed. At the same time, the light reflex is completely absent against the background of generalized reflex depression and loss of consciousness.
What else to study on this topic
- Pathogenesis of erosive gastroenteritis during decompensation of diabetes mellitus.
- Mechanisms of transition from polyuria to oliguria and anuria with escalating metabolic disorders.
- Causes of circulatory and respiratory failure in the full-blown coma stage.
- Biochemical basis of the acetone breath and high ketonemia.
- Differential diagnosis of diabetic comas based on plasma osmolarity indicators.
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