Endocrine & Metabolic Emergencies
Diabetic ketoacidosis, hyperosmolar hyperglycemic state, adrenal crisis, and glycemic control.
Core Topics
9 topicsAcid-Base Disorders: Comprehensive Critical Care Approach
Stepwise 6-step interpretation algorithm, compensation formulas, albumin-corrected anion gap, delta ratio, and Stewart physicochemical (SID) principles.
Metabolic Acidosis: HAGMA, NAGMA, & Bicarbonate Evidence
Differential diagnosis (GOLD MARK vs HARDCARP), toxic alcohol osmolar gaps, Urine Anion Gap, and current sodium bicarbonate evidence including BICAR-ICU and BICARICU-2.
Diabetic Ketoacidosis (DKA)
Pathophysiology, SGLT2i euglycemic DKA, balanced fluid resuscitation, potassium-before-insulin safety rules, dextrose addition kinetics, and subcutaneous transition.
Hyperosmolar Hyperglycemic State (HHS)
ICU recognition and treatment of severe hyperglycemia, hyperosmolality and dehydration with careful fluid, potassium and insulin sequencing.
Adrenal Crisis
Time-critical recognition and empiric treatment of acute cortisol deficiency causing shock, electrolyte disturbance and hypoglycemia.
Endocrine Emergencies in Critical Care
Bedside recognition and organ-support priorities for thyroid storm, myxedema coma, adrenal crisis, pheochromocytoma crisis, and severe hypercalcemia.
Thyroid Storm
Clinical diagnosis and ICU treatment of decompensated thyrotoxicosis with adrenergic, cardiovascular, neurologic and thermoregulatory failure.
Myxedema Coma
Recognition and ICU treatment of decompensated profound hypothyroidism with altered mental status and multiorgan dysfunction.
Arginine Vasopressin Deficiency (Central DI) & Polyuria in the ICU
ICU evaluation of hypotonic polyuria and hypernatremia with safe fluid replacement, desmopressin use, and differentiation of AVP deficiency from osmotic and nephrogenic causes.
Clinical Problems & Bedside Triage
14 guidesAcute Hypercapnia & Ventilatory Failure
Triaging rising PaCO2: distinguishing acute uncompensated acidemia from chronic compensation, identifying central vs pump vs dead-space failure, and titrating noninvasive ventilation.
Refractory Shock Despite High-Dose Vasopressors
Advanced multimodal hemodynamic rescue: second-line vasopressors (vasopressin, angiotensin II), inotropic augmentation, stress-dose steroids, metabolic correction, and mechanical circulatory support evaluation.
New Tachycardia & Tachyarrhythmias
Algorithmic triage of acute heart rates > 100–150 bpm: stability screen (immediate cardioversion if unstable), narrow vs wide QRS differentiation, Brugada VT rules, and sinus tachycardia etiology search.
Acute Altered Mental Status & ICU Delirium
Systematic neurologic evaluation: immediate metabolic/toxic screening (glucose, hypoxia, hypercapnia), nonconvulsive status epilepticus exclusion, structural CT triage, and CAM-ICU delirium management.
Acute Severe Metabolic Acidosis
Physiologic acid-base evaluation: Anion Gap and Delta-Delta calculations, Winter's formula for respiratory compensation, distinguishing ketoacidosis/lactic acidosis/toxic alcohols from non-gap acidosis, and bicarbonate therapy indications.
Severe Metabolic Alkalosis
Bedside evaluation of severe alkalemia (pH > 7.55, HCO3 > 35 mEq/L): assessing chloride responsiveness (urine chloride), diuretic-induced contraction alkalosis, nasogastric suction loss, hypokalemia, and acetazolamide/CRRT rescue.
Severe Hyperkalemia & Cardiac Membrane Instability
Time-critical hyperkalemia protocol (K+ > 6.5 mEq/L or ECG changes): immediate membrane stabilization with IV Calcium, intracellular shifting with Insulin/Dextrose and beta-agonists, and definitive potassium elimination.
Severe Hyperosmolar Hyperglycemic Crisis
Profound dehydration and hyperosmolality with severe hyperglycemia: separate isolated HHS from mixed DKA/HHS, restore circulation, sequence potassium and insulin correctly, and avoid rapid osmotic shifts.
Suspected Adrenal Crisis in Shock
Refractory hypotension with adrenal-risk history, electrolyte disturbance or hypoglycemia.
Hyperthermia, Tachyarrhythmia and Thyrotoxic Organ Failure
Clinical thyroid storm: recognize decompensated thyrotoxicosis, stabilize failing organs, block hormone effect and synthesis/secretion in the correct sequence, and treat the precipitant.
Hypothermic Bradycardic Coma / Myxedema Decompensation
Severe hypothyroid decompensation with altered consciousness, hypoventilation, hypothermia, bradycardia, hyponatremia or shock requiring immediate ICU therapy before confirmatory testing is complete.
Polyuria with Rising Sodium / Suspected AVP Deficiency
High urine output with hypernatremia: distinguish AVP deficiency from osmotic diuresis, restore circulation first when depleted, replace free water, and use desmopressin with close sodium/urine monitoring.
DKA / Euglycemic DKA
Ketotic metabolic decompensation requiring fluid resuscitation, potassium-first insulin sequencing and continued insulin until ketoacidosis resolves—even when glucose is not markedly elevated.
Severe or Recurrent Hypoglycemia
Neuroglycopenia or recurrent low glucose requiring immediate glucose restoration, recurrence prevention and rapid investigation of drug, organ-failure, endocrine and nutritional causes.
Physiology Modules & Waveforms
12 conceptsRenal Acid-Base Regulation
Unlike the rapid, minutes-scale respiratory compensation for acid-base disturbances, renal compensation is slow — it takes one to several days to fully develop, because it depends on adjusting the rate of new bicarbonate generation and ammonium excretion rather than simply changing a rate of breathing. This is why an acute respiratory acidosis or alkalosis shows a smaller compensatory change in bicarbonate than the same disturbance present for several days (acute versus chronic compensation), and why renal failure (via impaired acid excretion) produces a metabolic acidosis of its own even without a primary respiratory problem.
Henderson-Hasselbalch Equation
Because pH depends on the ratio of HCO3 to PaCO2 rather than either value alone, the same pH can arise from many different combinations of the two — which is precisely why a blood gas can't be interpreted from pH alone. This ratio-based relationship is also why compensation works: a primary change in one component (metabolic or respiratory) can be partly offset by a directionally appropriate change in the other, moving pH back toward — but not all the way to — normal.
Anion Gap
Plasma must remain electrically neutral, so the total concentration of cations always equals the total concentration of anions — the 'gap' only exists because routine labs don't measure every ion. A rising anion gap during a metabolic acidosis means an unmeasured anion (lactate, ketoacids, or a toxic metabolite) is accumulating and displacing bicarbonate as it's consumed in buffering. A normal-anion-gap acidosis, by contrast, means bicarbonate is being lost directly and replaced by chloride, keeping the calculated gap unchanged.
Delta Gap
In a pure HAGMA, each unmeasured acid anion that accumulates consumes roughly one bicarbonate in buffering, so the rise in anion gap and the fall in bicarbonate should track together, producing a delta ratio near 1 (clinically, roughly 1–2). A ratio well below this range means bicarbonate has fallen more than the anion gap rose — some of the bicarbonate loss is unaccounted for by the gap acidosis alone, implying a concurrent normal-anion-gap process. A ratio well above this range means bicarbonate is higher than the gap would predict, implying a concurrent metabolic alkalosis is also present and partially offsetting the acidosis.
Osmolar Gap
The calculated osmolality only accounts for sodium, glucose, and urea — the routinely measured osmotically active solutes. Any other osmotically active substance present in significant concentration (most importantly the toxic alcohols: methanol, ethylene glycol, and isopropyl alcohol, as well as ethanol itself) raises the measured osmolality without being reflected in the calculation, producing a gap. Because these alcohols are metabolized over time into their toxic acid metabolites, the osmolar gap is often most elevated early, before a high anion gap has fully developed — the two findings can appear at different points in the same poisoning.
Acid-Base Compensation
Respiratory compensation is fast (minutes to hours) because it only requires a change in minute ventilation; renal compensation is slow (one to several days) because it requires actually changing rates of bicarbonate reabsorption and generation. Compensation is never complete — it moves pH back toward normal but does not fully normalize it — and each type of primary disturbance has a predictable, quantifiable compensatory response (e.g. Winter's formula for a metabolic acidosis), which is what allows a clinician to check whether the observed compensation is appropriate or whether a second, independent disturbance is also present.
Winter's Formula
A falling bicarbonate normally triggers a proportional increase in ventilation (via central and peripheral chemoreceptors sensing the resulting acidemia), lowering PaCO2 and partially restoring the HCO3/PaCO2 ratio toward normal. Winter's formula captures the empirically observed slope of this response. If the measured PaCO2 falls within the predicted range, compensation is appropriate and only one primary process is likely present; if it falls outside that range, a second, independent respiratory disorder must also be present.
Mixed Acid-Base Disorders
Because compensation and a second primary disorder can move pH, PaCO2, and bicarbonate in similar directions, a mixed disorder can't reliably be detected from pH alone — it requires systematically checking whether the observed PaCO2 matches the expected compensation (via Winter's formula or an equivalent rule) and, for a high-anion-gap acidosis, whether the delta gap suggests an additional process. Critically ill patients very commonly have more than one acid-base process at once — for example, a septic patient can simultaneously have a lactic acidosis (metabolic acidosis), a compensatory or sepsis-driven tachypnea (respiratory alkalosis), and diuretic use (metabolic alkalosis) — so mixed disorders should be actively sought, not assumed to be the exception.
Diabetic Ketoacidosis: Insulin Deficiency, Ketogenesis, and Potassium Paradox
Insulin deficiency combined with high glucagon uninhibits hormone-sensitive lipase in adipose tissue, releasing massive quantities of free fatty acids (FFAs) into the circulation. In hepatocytes, carnitine palmitoyltransferase-1 (CPT-1) channels FFAs into mitochondrial beta-oxidation, producing acetoacetate and beta-hydroxybutyrate. These ketoacids dissociate into hydrogen ions and ketoacid anions, consuming serum bicarbonate and creating a severe High Anion Gap Metabolic Acidosis (HAGMA). Concurrently, severe hyperglycemia exceeds the renal tubular absorptive threshold (180 mg/dL), driving profound osmotic diuresis with massive urinary loss of water, sodium, potassium, and magnesium. The Potassium Paradox: Acidosis, insulinopenia, and hyperosmolarity shift potassium OUT of cells into the bloodstream, making initial serum potassium appear normal or high despite catastrophic total-body potassium deficits (300–600 mEq). Starting insulin drives potassium rapidly back into cells, causing lethal hypokalemia unless potassium is repleted concurrently.
Primary Acid-Base Disorders: 4 Pathologies & Compensatory Limits
The body utilizes chemical buffers (bicarbonate, hemoglobin, intracellular proteins), respiratory minute ventilation adjustment (acting within minutes to hours), and renal tubular proton secretion/bicarbonate reabsorption (acting over 2–5 days) to defend physiological pH (7.35–7.45). Compensatory rules: 1. Metabolic Acidosis: For every 1 mEq/L fall in HCO3-, PaCO2 drops by ~1.2 mmHg (Winter's Formula: Expected PaCO2 = 1.5 × [HCO3-] + 8 ± 2). 2. Metabolic Alkalosis: For every 1 mEq/L rise in HCO3-, PaCO2 rises by ~0.7 mmHg (Expected PaCO2 = 0.7 × [HCO3-] + 21 ± 2). 3. Acute Respiratory Acidosis: For every 10 mmHg rise in PaCO2, HCO3- rises by 1 mEq/L (cellular buffering). Chronic: HCO3- rises by 3.5–4 mEq/L (renal retention). 4. Acute Respiratory Alkalosis: For every 10 mmHg fall in PaCO2, HCO3- falls by 2 mEq/L. Chronic: HCO3- falls by 4–5 mEq/L.
Lactate Kinetics & Cellular Dysoxia in Shock
Type A Hyperlactatemia is caused by tissue hypoperfusion and anaerobic metabolism. In the absence of oxygen, mitochondrial pyruvate dehydrogenase (PDH) is inhibited and NADH accumulates, shifting pyruvate to lactate via lactate dehydrogenase (LDH) with an elevated lactate-to-pyruvate ratio (>20:1). Type B Hyperlactatemia occurs with preserved tissue oxygenation: - Type B1: Underlying disease (liver failure, malignancy, thiamine deficiency). - Type B2: Drugs and toxins (epinephrine, linezolid, metformin, beta-2 agonists via Na+/K+-ATPase stimulation). - Type B3: Inborn errors of metabolism. In sepsis, endogenous and exogenous adrenergic stimulation accelerates aerobic glycolysis via beta-2 receptors faster than PDH can process pyruvate, generating lactate despite adequate tissue PO2.
Central DI vs Osmotic Diuresis Differentiation
In Central Diabetes Insipidus (e.g. post-transsphenoidal pituitary surgery, severe TBI, brain death), absolute deficiency of pituitary ADH prevents aquaporin-2 insertion in the collecting duct. The kidney cannot concentrate urine: urine is maximally dilute (Uosm < 100–200 mOsm/kg, specific gravity < 1.005), leading to rapid hypernatremic dehydration if free water is not replaced. In Osmotic Diuresis (e.g. DKA/HHS with glycosuria, post-mannitol administration, or urea excretion during post-AKI recovery), unreabsorbed high-concentration luminal solutes create an osmotic gradient that drags water and electrolytes along the tubule. Urine osmolality is isotonic or moderately concentrated (Uosm > 300 mOsm/kg), and total daily solute excretion is markedly elevated.
Clinical Reasoning Cases
10 casesSevere Diabetic Ketoacidosis Resuscitation
Fluid resuscitation, potassium kinetics, insulin therapy, and safe transition
Refractory Septic Shock: Multi-Vasoactive Strategy
Escalating vasopressor requirements after initial resuscitation and source control
Triple Mixed Acid-Base Disorder in Sepsis & Cirrhosis
High-anion-gap metabolic acidosis with concurrent respiratory and metabolic alkalosis
Acute Adrenal Crisis After Glucocorticoid Withdrawal
Hemodynamic collapse after abrupt cessation of chronic prednisone
Severe Metabolic Alkalosis After Massive Transfusion
Mechanism-based management of severe alkalemia, electrolyte abnormalities, and volume overload
Hyperosmolar Hyperglycemic State
Recognition, fluid resuscitation, insulin, and controlled osmolar correction
Toxic Alcohol Ingestion
Recognition and emergency treatment of suspected methanol or ethylene glycol poisoning
Severe Metabolic Acidosis & Peri-Intubation Collapse
Physiologically difficult airway management when compensatory ventilation is life-sustaining