Comprehensive Study Notes on Pathophysiology and Management of Diabetic Ketoacidosis

Introduction to Diabetic Ketoacidosis (DKA)

• Context and Significance:     * Diabetic ketoacidosis (DKA) is recognized as the most frequent complication of diabetes.     * In approximately $50\%$ of cases, DKA is the initial clinical presentation that reveals the presence of diabetes.     * In pediatric populations (children), DKA is a medical emergency that remains potentially fatal, with a mortality rate ranging between $0.4\%$ and $2\%$

Definition of Diabetic Ketoacidosis

• Diagnostic Criteria: The diagnosis of DKA is defined by the following biochemical thresholds:     * Hyperglycemia: A blood glucose level greater than $2.5\,g/L$.     * Ketosis: A ketonemia level greater than $5\,mmol/L$ or a ketonuria level of more than $++$ on a urinary test strip (bandelette urinaire).     * Acidosis: An arterial blood $pH < 7.3$ or plasma bicarbonate ($HCO_3^{-}$) levels lower than $15\,mEq/L$.

Clinical Forms of Presentation

• 1. Inaugural Form (Initial Diagnosis):     * This form reveals the underlying Type 1 Diabetes (DT1).     * Patient History: Often includes a Polyuro-polydipsic syndrome (excessive thirst and urination) or enuresis (bed-wetting) identified during the interview.     * Progression: Patients typically report asthenia (weakness) and weight loss (amaigrissement) occurring over a period of 1 to 3 months, with symptoms worsening significantly in the period just before presentation.
• 2. Secondary Form:     * Occurs in patients where diabetes is already known and being treated.     * Causes of DKA in these cases:         * Cessation (arrêt) or under-dosage of insulin therapy.         * A defect in patient education regarding their condition and management.

Physiological Role of Insulin

• Primary Functions of Insulin:     * Transports glucose to the muscles and adipose (fat) tissue.     * Activates hepatic and muscular glycogenogenesis (creation of glycogen).     * Inhibits hepatic and muscular glycogenolysis (breakdown of glycogen).     * Inhibits tissue lipase (preventing fat breakdown).     * Activates lipogenesis (creation of fat).
• Hormonal Balance: Insulin acts in opposition to counter-regulatory hormones: Catecholamines, Glucagon, Cortisol, and GH (Growth Hormone).
• Basal Insulin-Secretion Mechanism:     * In a healthy individual, basal insulin maintains a balance: $+\text{Insulin} \rightarrow \text{Inhibition of Lipolysis and Ketogenesis}$.     * The Regulatory Loop: A drop in insulin secretion triggers lipolysis and ketogenesis. The resulting ketone bodies then stimulate insulin secretion, which in turn brakes lipolysis and ketogenesis to maintain homeostasis.     * The Diabetic State: A patient who is insulin-deprived (insulino-prive) escapes this retro-control loop, leading to uncontrolled catabolism.
• Fasting Physiology:     * A drop in insulinemia during fasting initiates the catabolic pathway, allowing the body to use its reserves.     * The cardiac muscle utilizes fatty acids (from adipose tissue) and ketone bodies produced by hepatic metabolism.     * The brain primarily requires glucose. Hepatic glycogen reserves can only satisfy half of the daily glucose consumption of the brain; the remainder is provided by hepatic neoglucogenesis.

Pathophysiology: Hyperglycemia and Dehydration

• Mechanism of Hyperglycemia:     * Caused by the absence of insulin-sensitive glucose transport to adipose and muscle tissues.     * Driven by hepatic glycogenolysis and, importantly, neoglucogenesis, which can produce several hundred grams of glucose per day.
• Consequences of Hyperglycemia:     * Extracellular Hyper-osmolarity: This causes a shift of water and potassium ($K^{+}$) from the intracellular compartment to the extracellular compartment.     * Glycosuria: High glucose levels exceed the renal threshold, leading to osmotic diuresis (polyuria rich in ions).     * Hypovolemia: Resulting from fluid loss, leading to a drop in glomerular flow and filtration.     * Functional Renal Failure (IRA): This elevation in the renal threshold for glucose further aggravates hyperglycemia.
• Dehydration Summary:     * Intracellular Dehydration (DIC): Caused by hyper-osmolarity drawing water out of cells.     * Extracellular Dehydration (DEC): Caused by profound osmotic diuresis.     * Clinical Results: Can lead to Coma, Hypotension (Hypo/TA), and Acute Renal Failure (IRA).

Pathophysiology: Ketogenesis and Acidosis

• Mechanism of Ketogenesis:     * Insulin is the only hormone that inhibits adipocyte lipase (anti-lipolytic hormone).     * Insulin deficiency leads to increased lipolysis at the hepatic level and the transformation of fatty acids (AG) into ketone bodies:         * Acetoacetic acid (Acide acétyl-acétique).         * Beta-hydroxybutyric acid (Acide bêta hydroxy butyrique).         * Acetone (formed via decarboxylation).
• Note on Beta-hydroxybutyric Acid: This is the most abundant ketone body in the blood. It is formed from acetoacetate through a reversible hydrogenation process catalyzed by the enzyme D-3-hydroxybutyrate dehydrogenase.
• Consequences of Metabolic Acidosis:     * Respiratory depression.     * Decreased myocardial contractility.     * Reduced vascular tone.     * Decreased sensitivity to endogenous catecholamines.     * Vascular collapse.

Role of Counter-Regulatory Hormones

• These hormones play a synergistic and critical role in DKA; however, their lipolytic action only manifests when there is an absolute or relative insulin deficiency.
• 1. Glucagon: The primary counter-regulatory hormone; it determines the metabolic orientation of the liver.
• 2. Cortisol: Stimulates lipolysis. Its hyperglycemic action is due to the increase in amino acids which serve as precursors for neoglucogenesis.
• 3. Catecholamines: These have both hyperglycemic and lipolytic actions (the latter via $\beta$ effect) and stimulate ketogenesis.
• 4. Growth Hormone (GH): Its role in DKA appears to be secondary.

Diagnostic Procedures

• 1. Clinical Diagnosis:     * Dehydration signs.     * Kussmaul Respiration: Deep, labored breathing (dyspnea).     * Consciousness Disorders: Ranging from obnubilation (clouded consciousness) to a full coma.     * Scent: Acetone breath (fruity odor).     * Digestive Signs: Nausea, vomiting, and abdominal pain; these signs can be so severe they mimic a surgical emergency (pseudo-surgical table).     * Fever: May be present if an underlying infection is the trigger.
• 2. Biological Diagnosis:     * Standard Glycemia: Hyperglycemia $> 2.5\,g/L$ ($1\,g = 5.5\,mmol$).     * Ketone Confirmation: Positive ketonemia (specifically measuring $\beta$-hydroxybutyrate) or ketonuria $> ++$.     * Acid-Base Balance: pH $< 7.3$ or $HCO_3^{-} < 15\,mEq/L$.     * Ionogram Findings:         * Natremia (Sodium): Variable. Corrected Natremia ($Na_c$) must be calculated using the formula: $Na_c = Na_m + [Gly\,(mmol/L) - 5]$.         * Kaliemia (Potassium): May appear normal or low; however, total body potassium is depleted. An ECG is mandatory to assess for cardiac effects of potassium imbalances.

Criteria for Severity

• Biochemical Severity Levels:     * Mild: $pH < 7.30$ or $HCO_3^{-} < 15\,mEq/L$.     * Moderate: $pH < 7.20$ or $HCO_3^{-} < 10\,mEq/L$.     * Severe: $pH < 7.10$ or $HCO_3^{-} < 5\,mEq/L$.
• Clinical Severity Criteria:     * Young age or pregnancy.     * Severe dehydration.     * Coma (Glasgow Scale $< 12$) upon admission.     * Hemodynamic disturbances.
• Advanced Biological Markers of Severity:     * Major hyperglycemia leading to extreme hyperosmolarity.     * Acidosis with $pH < 7.1$.     * Hypocapnia with $Pco_2 < 15\,mmHg$.     * Elevated urea $> 11\,mmol/L$.
• Note: The presence of these criteria necessitates immediate discussion for hospitalization in an intensive care unit (ICU).

Factors Triggering DKA

• Absolute Insulin Deficiency:     * Initial presentation of Type 1 Diabetes (DT1).     * Cessation of insulin treatment.     * Therapeutic errors.     * Insulin pump failure.
• Relative Insulin Deficiency (Intercurrent Causes):     * Infections.     * Trauma or surgery.     * Myocardial Infarction (IDM) or Stroke (AVC).     * Mesenteric infarction.     * Medications: Corticosteroids, adrenergic agonists.     * Endocrine Issues: Hyperthyroidism, hypercortisolism, pheochromocytome.     * Pregnancy: Especially during the last trimester.     * Intoxications: Acute intoxication, Cocaine, Amphetamines.

Differential Diagnosis

• Hyperosmolar Hyperglycemic State (HHS):     * Also called non-ketotic hyperosmolar coma.     * Typically occurs in young Type 2 diabetics and is rare in Type 1.     * HHS Biochemical Criteria:         * Glycemia $> 33.3\,mmol/L$ ($6\,g/L$).         * $pH > 7.30$.         * $HCO_3^{-} > 15\,mmol/L$.         * Low ketonuria; normal or slightly elevated ketonemia.         * Effective serum osmolarity $> 320\,mosm/Kg$.         * Presentation: Stupor or coma.     * Overlapping States: Some patients may present with features of both HHS and DKA (e.g., severe dehydration and moderate acidosis), and Type 1 diabetics may show HHS signs if they consume high volumes of sugary drinks to quench thirst before diagnosis.

Treatment Protocol

• Primary Goals: Restore hemodynamics (rehydration), correct hyperglycemia/ketonemia/acidosis (insulin), correct ion imbalances, and treat triggering factors.
• Rehydration Strategy:     * Adult volume deficit is typically $6$ to $9$ liters.     * Rehydration target: Compensate volume over $24$ to $36$ hours, with $50\%$ occurring in the first $8$ to $12$ hours.     * Initial fluid: Isotonic saline ($0.9\%\,NaCl$) at $1$ to $1.5\,L/h$ ($15\text{--}20\,ml/kg/h$).     * Transition: Once glycemia drops below $2\,g/L$ ($11\,mmol/L$), add $5\%$ glucose perfusion at a rate of $2$ to $4\,L/24h$ to allow continued high-rate insulin perfusion until ketonemia is resolved.
• Insulin Therapy:     * Begin after the first ionogram result and after the first hour of rehydration.     * Continuous intravenous infusion at $0.1\,U/kg/h$.     * Monitor glycemia: The speed of correction should be $3$ to $5\,mmol/L/h$, aiming for a level of $11\,mmol/L$.
• Correction of Electrolytes (Potassium):     * If $K^{+} < 3.3\,mmol/L$: Administer $20$ to $30\,mEq/h$.     * If $K^{+}$ is between $3.3$ and $5.3\,mmol/L$: Add $20$ to $30\,mEq$ of Potassium per liter of rehydration solution.

Complications and Management

• 1. Complications related to Acidosis and Dehydration:     * Consciousness disorders (coma).     * Hemodynamic shock (EDC).
• 2. Treatment-Induced Complications:     * Hypoglycemia: Avoided through continuous IV monitoring and avoiding rapid glucose normalization.     * Hypo or Hyperkaliemia: Requires ECG monitoring and careful supplementation.     * Acute Cerebral Edema (OCA): A critical, potentially fatal risk.
• 3. Management of Cerebral Edema:     * Monitor for alarm signs.     * Elevate the head of the bed.     * Administer Mannitol at $1$ to $2\,g/kg$, repeated every $6$ hours if necessary.     * Restrict hydration to $1/3$.     * Perform cerebral imaging once the patient is stabilized.

Final Summary

• Insulin-dependent diabetes (DID or DT1) is among the most frequent endocrine diseases.
• DKA is caused by profound insulin deficiency and is primarily associated with Type 1 Diabetes.
• DKA can reveal diabetes for the first time; therefore, a capillary glucose test is mandatory for any patient in a coma.
• Most DKA cases are preventable by avoiding triggering factors.
• Critical metabolic risks in the first 24 hours of treatment include hypokaliemia, hypoglycemia, and the dangerous acute cerebral edema (OCA).
• Disclaimer: This support was created based on course photos from Dr. KECHIDA; errors can be reported on Telegram to @achkinez.