24.2 Critical Electrolyte Emergencies: Dyskalemias & Dysnatremias

ABFM Family Medicine Certification Study Guide Exam

Track your progress as you read

Finished sections get a check mark.

1 Chapter 1: Exam Structure, Blueprint & Clinical Decision-Making

1.1 Exam Blueprint, FMCLA vs. One-Day Exam & Board Scoring 1.2 Clinical Reasoning, Test-Taking Strategy & Ambiguity Management 1.3 Evidence-Based Medicine & Clinical Practice Guidelines in Primary Care

2 Chapter 2: Healthcare Systems, Practice Management & Quality

2.1 Practice Management, Billing, Coding & Documentation 2.2 Quality Improvement, Patient Safety & Diagnostic Stewardship 2.3 Interprofessional Team-Based Care & Care Coordination

3 Chapter 3: Ethics, Law, Biostatistics & Health Equity

3.1 Medical Ethics, Informed Consent & Surrogate Decision-Making 3.2 Biostatistics, Clinical Epidemiology & Diagnostic Test Interpretation 3.3 Social Determinants of Health, Health Equity & Cultural Humility 3.4 Physician Wellness, Burnout Prevention & Professionalism

4 Chapter 4: Lifestyle Counseling & Behavior Change

4.1 Alcohol Use Screening & Brief Intervention 4.2 Illicit Drug & Cannabis Counseling 4.3 Tobacco & Vaping Cessation Counseling

5 Chapter 5: Nutrition, Physical Activity & Chronic Disease Prevention

5.1 Dietary Counseling for Obesity & Chronic Disease Prevention 5.2 Exercise Prescription & Physical Activity Counseling 5.3 Genetic Risk Assessment & Family History Counseling

6 Chapter 6: Routine Adult Immunizations

6.1 ACIP Adult Respiratory Vaccines: Influenza, COVID-19, RSV & Pneumococcal 6.2 ACIP Adult Non-Respiratory Vaccines: Tdap, Shingrix, HPV & Hep B 6.3 Immunizations in Special Populations: Pregnancy, Asplenia & Immunocompromise

7 Chapter 7: Pediatric Health Maintenance & Surveillance

7.1 Newborn Examination & Early Postnatal Care 7.2 Well-Child Care, Developmental Surveillance & Milestones 7.3 Pediatric & Adolescent Screening: Vision, Hearing, Anemia & Lead 7.4 Pediatric Oral Health, Dental Screening & Fluoride

8 Chapter 8: Behavioral Health & Safety Screening

8.1 Primary Care Depression, Anxiety & Behavioral Health Screening 8.2 Domestic Violence, Intimate Partner Violence & Firearm Safety 8.3 Occupational Health & Recreational Safety Counseling

9 Chapter 9: Adult Preventive Screening: Cardiovascular & Metabolic

9.1 Cardiovascular Disease & Hypertension Screening 9.2 Type 2 Diabetes Screening & Prediabetes Risk Stratification 9.3 Abdominal Aortic Aneurysm & Osteoporosis Screening

10 Chapter 10: Adult Cancer Screening: Breast & Gynecologic

10.1 Breast Cancer Screening & Risk-Assessment 10.2 Cervical Cancer Screening & ASCCP Algorithms 10.3 Skin Cancer Clinical Assessment & Counseling

11 Chapter 11: Adult Cancer Screening: Colorectal, Lung & Prostate

11.1 Colorectal Cancer Screening Modalities & Intervals 11.2 Lung Cancer Screening with Low-Dose CT 11.3 Prostate Cancer Screening & Shared Decision-Making

12 Chapter 12: Sexual Health, Infectious Disease Screening & Contraception

12.1 Sexual Health Counseling & Risk-Reduction Strategies 12.2 STI Screening: Chlamydia, Gonorrhea, Syphilis & Trichomoniasis 12.3 Bloodborne Infectious Disease Screening: HIV & Hepatitis C

13 Chapter 13: Reproductive Life Planning, Lactation & Preoperative Care

13.1 Preconception Planning & Comprehensive Contraception Management 13.2 Lactation Support & Breastfeeding Counseling 13.3 Preoperative Medical Evaluation & Pre-Participation Sports Exam

14 Chapter 14: Emergent Cardiovascular Conditions

14.1 Acute Coronary Syndromes & Myocardial Infarction 14.2 Acute Chest Pain Risk Stratification & Triage 14.3 Acute or Critical Valvular Heart Emergencies

15 Chapter 15: Cardiac Arrhythmias, Heart Failure & Hypertensive Crises

15.1 Acute Atrial & Ventricular Arrhythmias 15.2 Acute Decompensated Heart Failure & Cardiogenic Shock 15.3 Hypertensive Emergency & Urgency Management

16 Chapter 16: Vascular & Thromboembolic Emergencies

16.1 Pulmonary Embolism & Deep Vein Thrombosis 16.2 Acute Aortic Syndromes & Peripheral Vascular Emergencies 16.3 Critical Limb Ischemia & Acute Arterial Occlusion

17 Chapter 17: Neurologic Emergencies: Stroke & Altered Consciousness

17.1 Acute Ischemic Stroke & Intracranial Hemorrhage 17.2 Syncope Evaluation & Status Epilepticus 17.3 Acute Delirium, Encephalopathy & Severe Confusion

18 Chapter 18: Neurologic Trauma & Acute Cranial Emergencies

18.1 Concussion, Moderate-to-Severe TBI & Intracranial Injury 18.2 Thunderclap & Acute Severe Secondary Headaches 18.3 Acute Ophthalmologic Emergencies

19 Chapter 19: Acute Abdominal, Pelvic & Gastrointestinal Emergencies

19.1 Acute Abdominal & Pelvic Pain Triage 19.2 Upper & Lower Gastrointestinal Bleeding 19.3 Acute Hepatic Failure, Cholangitis & Severe Jaundice

20 Chapter 20: Acute Pulmonary & Airway Emergencies

20.1 Acute Hypoxic Respiratory Failure & ARDS 20.2 Severe Community-Acquired Pneumonia & Empyema 20.3 Acute Severe Epistaxis & Airway Obstruction

21 Chapter 21: Acute Traumatic Injuries & Wound Care

21.1 Major Trauma Resuscitation & Initial Assessment 21.2 Burn Assessment, Inhalation Injury & Resuscitation 21.3 Laceration Management, Complex Wounds & Animal Bites

22 Chapter 22: Acute Orthopedic & Musculoskeletal Emergencies

22.1 Acute Ambulatory Fractures & Initial Splinting 22.2 Compartment Syndrome & Major Orthopedic Trauma 22.3 Septic Arthritis & Acute Microcrystalline Crises

23 Chapter 23: Severe Infections, Sepsis & Systemic Emergencies

23.1 Sepsis, Septic Shock & Initial Fluid Resuscitation 23.2 Necrotizing Soft Tissue Infections & Severe CNS Infections 23.3 Anaphylaxis Diagnosis, Epinephrine Dosing & Airway Protection

24 Chapter 24: Metabolic, Endocrine & Electrolyte Emergencies

24.1 Diabetic Ketoacidosis & Hyperosmolar Hyperglycemic State 24.2 Critical Electrolyte Emergencies: Dyskalemias & Dysnatremias 24.3 Severe Calcium Abnormalities & Acute Adrenal Crisis

25 Chapter 25: Hematologic, Urologic & Dental Emergencies

25.1 Severe Symptomatic Anemias & Coagulopathic Emergencies 25.2 Testicular Torsion, Priapism & Acute Urinary Retention 25.3 Urgent Odontogenic Infections & Dental Trauma

26 Chapter 26: Psychiatric, Behavioral & Obstetric/Gynecologic Emergencies

26.1 Suicidal Ideation, Acute Agitation & Behavioral Emergencies 26.2 Acute Physical & Sexual Assault Care 26.3 Life-Threatening Vaginal Bleeding & Ectopic Pregnancy 26.4 Environmental Heat Stroke & Severe Hypothermia

27 Chapter 27: Acute Head, Neck & Neurologic Symptoms

27.1 Primary Acute Headaches: Migraine, Tension & Cluster 27.2 Concussion & Minor Closed Head Injury Evaluation 27.3 Transient Ischemic Attack Evaluation & ABCD2 Risk Scoring

28 Chapter 28: Acute Cranial Nerves, Hearing & Sensory Symptoms

28.1 Peripheral Neuropathies: Bell's Palsy, Carpal Tunnel & Radiculopathy 28.2 Acute Tinnitus, Sudden Sensorineural Hearing Loss & Cerumen Impaction 28.3 Acute Dizziness, Benign Paroxysmal Positional Vertigo & Vestibular Neuritis

29 Chapter 29: Acute Upper Respiratory Tract Infections

29.1 Acute Viral Rhinosinusitis vs. Bacterial Rhinosinusitis 29.2 Acute Pharyngitis: Group A Streptococcus & Centor Criteria 29.3 Acute Otitis Media, Otitis Externa & Serous Effusion

30 Chapter 30: Acute Lower Respiratory Infections & Cough

30.1 Influenza, COVID-19 & Viral Respiratory Syndromes 30.2 Acute Bronchitis & Lower Respiratory Tract Infections 30.3 Ambulatory Community-Acquired Pneumonia

31 Chapter 31: Allergic, Nasal & Non-Infectious Pulmonary Conditions

31.1 Allergic Rhinitis & Acute Non-Anaphylactic Allergic Reactions 31.2 Acute Dyspnea in Ambulatory Care 31.3 Interstitial Lung Diseases & Sarcoidosis Presentation

32 Chapter 32: Acute Chest, Cardiac & Vascular Symptoms

32.1 Palpitations Evaluation & Arrhythmia Triage in Primary Care 32.2 Deep Vein Thrombosis & Superficial Thrombophlebitis 32.3 Ambulatory Hypotension & Orthostasis Evaluation

33 Chapter 33: Acute Upper Gastrointestinal Conditions

33.1 Peptic Ulcer Disease & Gastritis 33.2 Dysphagia, Esophagitis & Acute Esophageal Disorders 33.3 Acute Nausea, Vomiting & Foodborne Illness

34 Chapter 34: Acute Lower Gastrointestinal Conditions

34.1 Acute Infectious Diarrhea & Gastroenteritis 34.2 Acute Constipation & Functional Bowel Changes 34.3 Ano-Rectal Disorders: Hemorrhoids, Fissures, Abscesses & Pruritus Ani

35 Chapter 35: Inflammatory, Functional & Malabsorptive GI Disorders

35.1 Acute Flares of Inflammatory Bowel Disease 35.2 Irritable Bowel Syndrome: Diagnosis, Subtyping & Management 35.3 Celiac Disease & Malabsorption Syndromes

36 Chapter 36: Acute Abdominal, Hepatic & Biliary Disorders

36.1 Ambulatory Abdominal & Pelvic Pain Triage 36.2 Acute Cholecystitis, Biliary Colic & Pancreatitis 36.3 Acute Liver Injury & Viral Hepatitis

37 Chapter 37: Acute Abdominal Wall, Hernias & Dental Conditions

37.1 Abdominal Wall, Inguinal & Ventral Hernias 37.2 Acute Dental Pain, Odontogenic Abscess & Aphthous Ulcers 37.3 Acute Edema: Unilateral vs. Bilateral Diagnostic Evaluation

38 Chapter 38: Acute Infectious Dermatoses

38.1 Bacterial Skin Infections: Impetigo, Cellulitis & Cutaneous Abscesses 38.2 Fungal Skin Infections: Tinea Corporis, Cruris, Pedis & Onychomycosis 38.3 Viral Cutaneous Infections: Herpes Simplex, Zoster & Molluscum Contagiosum

39 Chapter 39: Inflammatory, Allergic & Autoimmune Dermatoses

39.1 Atopic Dermatitis, Contact Dermatitis & Eczematous Flares 39.2 Non-Infectious Rashes: Urticaria, Drug Eruptions & Erythema Multiforme 39.3 Cutaneous Malignancies & Premalignant Lesions: AK, BCC, SCC & Melanoma

40 Chapter 40: Acute Shoulder, Elbow & Upper Extremity Injuries

40.1 Rotator Cuff Pathology, Tendinopathy & Shoulder Impingement 40.2 Lateral & Medial Epicondylitis, Olecranon Bursitis & Elbow Sprains 40.3 Wrist & Hand Soft-Tissue Injuries: De Quervain, TFCC & Finger Sprains

41 Chapter 41: Acute Knee, Ankle & Lower Extremity Injuries

41.1 Meniscal Tears, Ligamentous Knee Injuries & Patellofemoral Pain 41.2 Ankle Sprains, Ottawa Ankle Rules & Achilles Tendinopathy 41.3 Plantar Fasciitis, Shin Splints & Overuse Syndromes

42 Chapter 42: Acute Ambulatory Fractures & Dislocations

42.1 Distal Radius, Scaphoid & Common Upper Extremity Fractures 42.2 Metatarsal, Clavicle & Common Lower Extremity Fractures 42.3 Joint Dislocation Management: Nursemaid's Elbow & Shoulder Subluxation

43 Chapter 43: Acute Axial Musculoskeletal Pain & Falls

43.1 Acute Low Back Pain: Red Flags, Strain & Disc Herniation 43.2 Acute Cervical Strain, Whiplash & Axial Neck Pain 43.3 Evaluation of Falls in Ambulatory & Older Patients

44 Chapter 44: Acute Inflammatory Arthropathies & Generalized Pain

44.1 Acute Inflammatory Arthritis & Spondyloarthropathies 44.2 Myalgias, Rhabdomyolysis & Post-Viral Pain Syndromes 44.3 Acute Non-Headache Pain Management Strategies

45 Chapter 45: Acute Renal, Urinary & Genitourinary Conditions

45.1 Uncomplicated UTI, Pyelonephritis & Acute Urethritis 45.2 Hematuria Workup & Glomerulonephritis 45.3 Nephrolithiasis & Acute Urinary Tract Obstruction

46 Chapter 46: Acute Male Genitourinary & Prostatic Conditions

46.1 Acute Prostatitis, Epididymitis & Orchitis 46.2 Acute Scrotal Pain: Torsion vs Appendage, BPH & Male Genital Emergencies 46.3 Acute Urinary Retention & Incontinence Evaluation

47 Chapter 47: Acute Women's Health & Early Pregnancy Care

47.1 Early Pregnancy Diagnosis, Dating & Initial Complications 47.2 Abnormal Uterine Bleeding & Acute Menstrual Disorders 47.3 Premenstrual Syndrome & Premenstrual Dysphoric Disorder

48 Chapter 48: Breast Disorders, STIs & Pediatric Elimination

48.1 Palpable Breast Mass, Mastitis & Nipple Discharge 48.2 Sexually Transmitted Infections: Diagnosis, Staging & CDC Guidelines 48.3 Pediatric Enuresis & Encopresis

49 Chapter 49: Systemic Signs, Metabolic Dysregulation & Miscellaneous Infections

49.1 Acute Fever, Sepsis Screening & FUO in Primary Care 49.2 Acute Hyperglycemia & Symptomatic Hypoglycemia 49.3 Electrolyte Abnormalities: Mild-to-Moderate Disturbances 49.4 Vector-Borne, Tick-Borne & Rickettsial Illnesses

50 Chapter 50: Chronic Cardiovascular Diseases: Hypertension & Ischemia

50.1 Essential Hypertension Management: 2025 AHA/ACC Guideline & JNC Strategies 50.2 Chronic Coronary Artery Disease & Post-MI Secondary Prevention 50.3 Chronic Heart Failure: HFrEF, HFpEF & Quadruple GDMT

51 Chapter 51: Chronic Vascular, Valvular & Dyslipidemic Diseases

51.1 Peripheral Arterial Disease & Claudication 51.2 Chronic Valvular Heart Disease & Murmur Evaluation 51.3 Lipid Disorders & ASCVD Risk-Based Statin Therapy

52 Chapter 52: Chronic Respiratory Diseases: Asthma & COPD

52.1 Chronic Asthma Management: GINA Stepwise SMART Therapy 52.2 Chronic Obstructive Pulmonary Disease: GOLD Recommendations 52.3 Solitary Pulmonary Nodule Evaluation & Fleischner Society Criteria

53 Chapter 53: Chronic Metabolic Diseases: Diabetes Mellitus

53.1 Type 2 Diabetes Management: ADA Pharmacotherapy Algorithms 53.2 Type 1 Diabetes: Basal-Bolus Insulin, CGMs & Diabetic Complications 53.3 Diabetic Microvascular & Macrovascular Disease Surveillance

54 Chapter 54: Obesity, Nutrition & Metabolic Bone Diseases

54.1 Medical & Behavioral Management of Obesity & Incretin Mimetics 54.2 Osteoporosis & Metabolic Bone Disease: DEXA, FRAX & Antiresorptives 54.3 Nutritional Deficiencies: Vitamin D, B12, Iron & Malnutrition

55 Chapter 55: Chronic Endocrine Disorders

55.1 Primary & Subclinical Hypothyroidism, Hyperthyroidism & Nodules 55.2 Adrenal Disorders: Addison's Disease & Cushing's Syndrome 55.3 Hypercalcemia, Hyperparathyroidism & Pituitary Disorders

56 Chapter 56: Chronic Kidney Disease & Venous Disorders

56.1 Chronic Kidney Disease: KDIGO Staging & Renoprotective Therapy 56.2 Chronic Venous Insufficiency, Stasis Dermatitis & Lymphedema 56.3 Chronic Electrolyte & Acid-Base Management in CKD

57 Chapter 57: Chronic Gastrointestinal & Hepatic Diseases

57.1 Gastroesophageal Reflux Disease, Barrett's Esophagus & Dyspepsia 57.2 Chronic Liver Disease: MASLD/NAFLD, Cirrhosis & Portal Hypertension 57.3 Viral Hepatitis B & C: Long-Term Monitoring & DAA Therapy

58 Chapter 58: Colorectal Surveillance & Chronic Pancreaticobiliary Care

58.1 Post-Polypectomy Colorectal Polyp Surveillance Guidelines 58.2 Chronic Pancreatitis & Exocrine Pancreatic Insufficiency 58.3 Chronic Nausea, Gastroparesis & Functional GI Disorders

59 Chapter 59: Chronic Musculoskeletal & Rheumatologic Disorders

59.1 Osteoarthritis: Hip, Knee & Hand Management 59.2 Spinal Conditions: Spinal Stenosis, Spondylolisthesis & Compression Fractures 59.3 Chronic Myopathies & Fibromyalgia Syndrome

60 Chapter 60: Chronic Neurologic & Neurodegenerative Disorders

60.1 Dementia: Alzheimer's, Vascular & Lewy Body Disease 60.2 Parkinson's Disease & Essential Tremor 60.3 Epilepsy: Chronic Antiseizure Medications & Post-Stroke Care

61 Chapter 61: Chronic Peripheral Nerves, Pain & Sensory Disorders

61.1 Diabetic & Chronic Peripheral Neuropathies 61.2 Chronic Pain Syndromes & Chronic Daily Headaches 61.3 Chronic Tinnitus, Presbycusis & Persistent Dizziness

62 Chapter 62: Chronic Psychiatric Disorders

62.1 Major Depressive Disorder & Generalized Anxiety Disorder 62.2 Bipolar Disorder: Maintenance Pharmacotherapy & Lithium Monitoring 62.3 Adult & Pediatric Attention-Deficit/Hyperactivity Disorder

63 Chapter 63: Chronic Behavioral Health & Neurodevelopmental Conditions

63.1 Chronic Behavioral Conditions: PTSD, OCD & Somatization 63.2 Autism Spectrum Disorder & Intellectual Disabilities 63.3 Eating Disorders: Anorexia Nervosa, Bulimia & Binge Eating

64 Chapter 64: Chronic Substance Use Disorders & Tobacco Cessation

64.1 Alcohol Use Disorder: Pharmacotherapy & Relapse Prevention 64.2 Opioid & Stimulant Use Disorders: MOUD & Harm Reduction 64.3 Longitudinal Tobacco Cessation Pharmacotherapy

65 Chapter 65: Chronic Dermatologic Conditions

65.1 Acne Vulgaris, Rosacea & Seborrheic Dermatitis 65.2 Chronic Plaque Psoriasis & Biologic Therapies 65.3 Chronic Eczema, Hidradenitis Suppurativa & Cutaneous Lupus

66 Chapter 66: Chronic Reproductive, Infectious & Geriatric Special Care

66.1 Chronic Menstrual Disorders, Infertility & Sexual Dysfunction 66.2 Menopause Management & Hormone Replacement Therapy 66.3 Chronic HIV Infection Management & Primary Care Integration 66.4 Gender-Affirming Primary Care & Hormone Therapy 66.5 Advance Care Planning, Palliative Care & End-of-Life Symptom Control

67 Chapter 67: Continuity Care: Sleep, Fatigue, Cancer, Pregnancy & the Adult Preventive Visit

67.1 Chronic Insomnia & Obstructive Sleep Apnea 67.2 Chronic Malaise, Fatigue & ME/CFS 67.3 Primary Care During Cancer Treatment & Survivorship 67.4 Routine Prenatal Care & Longitudinal Pregnancy Management 67.5 The Periodic Adult Health Examination & Medicare Annual Wellness Visit

24.2 Critical Electrolyte Emergencies: Dyskalemias & Dysnatremias

Key Takeaways Explain This Topic AI

Hyperkalemia (K+ >=6.5 mEq/L or any ECG abnormalities) mandates immediate myocardial membrane stabilization with IV Calcium Gluconate (10 mL of 10% over 2-3 min) or IV Calcium Chloride (preferred in cardiac arrest/shock via central line); calcium restores membrane excitability within 1-3 minutes but does NOT lower serum potassium.

Intracellular potassium shifting with IV regular insulin (10 units) plus D50W (25 g) and high-dose nebulized albuterol (10-20 mg) lowers serum potassium by 0.5-1.5 mEq/L within 15-30 minutes, but definitive removal requires loop diuretics, oral potassium binders (patiromer or sodium zirconium cyclosilicate), or emergent hemodialysis.

Severe hypokalemia (<2.5 mEq/L) is clinically refractory to potassium replacement until coexisting hypomagnesemia is corrected; intracellular magnesium is required to inhibit ROMK channels in the collecting duct and maintain Na+/K+-ATPase activity.

Acute severe symptomatic hyponatremia (seizures, coma, herniation) requires emergent administration of IV 3% Hypertonic Saline as a 100 mL bolus over 10 minutes (repeatable up to twice) to rapidly increase serum sodium by 4-6 mEq/L, but 24-hour correction must never exceed 8 mEq/L to prevent Osmotic Demyelination Syndrome.

Hypernatremia reflects a free water deficit that must be corrected gradually (maximum reduction rate of 10-12 mEq/L per 24 hours or 0.5 mEq/L/h) using hypotonic fluids (D5W or 0.45% NaCl) to prevent fatal cerebral edema and brain herniation.

Last updated: September 2026

Hyperkalemia: Pathophysiology & Electrocardiographic Progression

Potassium is the primary intracellular cation, with approximately 98% of total body potassium residing within the intracellular fluid space (intracellular concentration ~140-150 mEq/L vs extracellular concentration 3.5-5.0 mEq/L). The resting membrane potential of cardiac myocytes and excitable tissues is determined by the ratio of intracellular to extracellular potassium, as described by the Nernst equation. Elevating extracellular potassium depolarizes the resting membrane potential (making it less negative), which initially increases myocyte excitability. However, sustained depolarization leads to persistent inactivation of voltage-gated fast sodium channels, causing delayed intracardiac conduction velocity, prolonged repolarization, and eventual complete cardiac arrest.

Severity Classification
Mild Hyperkalemia : 5.1 to 5.9 mEq/L
Moderate Hyperkalemia : 6.0 to 6.4 mEq/L

Severe / Critical Hyperkalemia : >=6.5 mEq/L , OR any serum potassium level associated with electrocardiographic changes .

Caution

Pseudohyperkalemia Alert : Falsely elevated potassium results from in vitro mechanical lysis of erythrocytes during phlebotomy (excessive tourniquet time, fist pumping, fine needle aspiration, traumatic draw), or severe thrombocytosis (>500,000/uL) and marked leukocytosis (>50,000/uL). If the patient is asymptomatic, has a normal ECG, and has no clinical risk factors (e.g., normal renal function, no potassium-sparing medications), immediately confirm with a repeat non-hemolyzed blood gas or plasma electrolyte specimen drawn without a tourniquet.

Sequential Electrocardiographic Progression

The ECG changes in hyperkalemia follow a characteristic progression reflecting sequential impairment of cardiac conduction systems: ELECTROCARDIOGRAPHIC SEQUENCE IN HYPERKALEMIA

┌─────────────────────────┐ ┌─────────────────────────┐ ┌─────────────────────────┐
│ 1. TALL PEAKED T WAVES │ │ 2. P WAVE FLATTENING & │ │ 3. QRS WIDENING & │
│ (K+ 5.5 to 6.5 mEq/L)│ │ PR PROLONGATION │ │ BUNDLE BRANCH BLOCKS │
├─────────────────────────┤ ├─────────────────────────┤ ├─────────────────────────┤
│ • Earliest ECG sign │ │ • Flattening / loss of P│ │ • QRS widening >120 ms │
│ • Narrow base, tented, │ │ • Lengthening PR interval│ • Intraventricular delays │
│ symmetric, sharp apex │ │ • Sinoventricular rhythm│ │ • Progressive bradycardia│
│ • Prominent in V2-V4 │ │ • K+ 6.5 to 7.5 mEq/L │ │ • K+ 7.0 to 8.0 mEq/L │
└─────────────────────────┘ └─────────────────────────┘ └─────────────────────────┘
│
▼
┌───────────────────────────────────────────────────────────────────────────────────┐
│ 4. SINE WAVE PATTERN (K+ >8.0 mEq/L) │
│ • Widened QRS complex fuses smoothly with elevated, widened T wave │
│ • Smooth, biphasic undulating waveform; extreme pre-terminal emergency │
├───────────────────────────────────────────────────────────────────────────────────┤
│ 5. TERMINAL DYSRHYTHMIAS (Imminent Cardiac Arrest) │
│ • Ventricular Fibrillation, Pulseless Electrical Activity (PEA), Asystole │
│ • Requires immediate CPR and IV Calcium! │
└───────────────────────────────────────────────────────────────────────────────────┘

Tall, Peaked, Symmetric T Waves :

Earliest ECG manifestation (typically K+ 5.5-6.5 mEq/L); best seen in precordial leads V2 through V4.

Distinctive morphological features: narrow base, sharp symmetric apex, and prominent amplitude ("tented"). Differs from the broad-based, asymmetric hyperacute T waves seen in early acute myocardial infarction.

PR Prolongation & Flattening/Loss of P Waves :

As potassium rises to 6.5-7.5 mEq/L, atrial myocyte conduction slows.

Manifests as lengthening of the PR interval, progressive decrease in P-wave amplitude, and eventual total disappearance of visible P waves (sinoventricular rhythm).

QRS Complex Widening & Conduction Delays :

As potassium reaches 7.0-8.0 mEq/L, ventricular conduction velocity drops markedly.

Manifests as progressive widening of the QRS complex (>120 ms), development of non-specific intraventricular conduction delays, right or left bundle branch block morphologies, and progressive bradycardia.

The "Sine Wave" Pattern :

Extreme hyperkalemia (typically K+ >8.0 mEq/L) causes the widened QRS complex to merge smoothly with the elevated, widened T wave, creating a dramatic, biphasic undulating sine wave.

This is an extreme pre-terminal emergency heralding imminent ventricular fibrillation, pulseless electrical activity (PEA), or asystole.

The Emergency Hyperkalemia Treatment Triad

Emergency management of hyperkalemia must proceed through three sequential, non-interchangeable pathophysiologic phases: THE HYPERKALEMIA EMERGENCY TRIAD

PHASE 1: STABILIZE PHASE 2: SHIFT PHASE 3: ELIMINATE
┌─────────────────────┐ ┌─────────────────────┐ ┌─────────────────────┐
│ Calcium Gluconate │ │ Regular Insulin 10u │ │ Loop Diuretics │
│ 10% 10 mL IV │ │ + D50W 25 g IV │ │ (Furosemide 40-80mg)│
│ (or CaCl 10% in │ ───► │ Nebulized Albuterol │ ───► │ Lokelma / Patiromer │
│ shock/arrest) │ │ 10-20 mg │ │ Emergent Hemodial- │
│ Onset: 1-3 min │ │ IV NaHCO3 (if acid) │ │ ysis (definitive) │
│ Duration: 30-60 min │ │ Onset: 15-30 min │ │ Permanent removal │
└─────────────────────┘ └─────────────────────┘ └─────────────────────┘
Phase 1: Myocardial Membrane Stabilization (Immediate Action)

Indication : Any hyperkalemia with electrocardiographic abnormalities (peaked T waves, QRS widening, sine wave), or serum potassium >=6.5 mEq/L.

Intravenous Calcium Gluconate 10% :

Dose : 10 mL (1 g of calcium gluconate, containing 90 mg [4.6 mEq] elemental calcium) administered IV over 2 to 3 minutes.

Access : Preferred for peripheral venous access due to lower risk of severe chemical extravasation necrosis.

Repeat Dosing : May repeat dose in 5 to 10 minutes if ECG abnormalities persist or recur.

Intravenous Calcium Chloride 10% :

Dose : 10 mL (1 g of calcium chloride, containing 270 mg [13.6 mEq] elemental calcium— three times more elemental calcium than gluconate).

Indication : Preferred in cardiac arrest, profound hypotension, or shock; should be administered via central venous access whenever possible due to severe tissue necrosis and sloughing if extravasated.

Pharmacodynamics & Mechanism :

Onset: 1 to 3 minutes ; Duration: 30 to 60 minutes .

Mechanism : Antagonizes membrane excitability by shifting the threshold potential of myocytes to a less negative value, restoring the normal electrical separation between resting membrane potential and threshold. Calcium does NOT lower serum potassium levels by a single milliequivalent.

Phase 2: Intracellular Potassium Shifting (Temporary Reduction)

Regular Insulin PLUS Dextrose :

Dose : 10 units Regular Insulin IV PLUS 50 mL of 50% Dextrose (D50W, 25 g dextrose) infused over 5 minutes.

Clinical Caveat : If baseline blood glucose is >250 mg/dL , omit the dextrose bolus to prevent extreme hyperosmolality.

Mechanism : Insulin binds cell-surface receptors, stimulating the Na+/K+-ATPase pump to drive potassium into skeletal muscle and liver cells.

Pharmacodynamics : Onset 15 to 30 minutes; peak effect at 60 minutes; duration 4 to 6 hours. Lowers serum potassium by 0.5 to 1.2 mEq/L .

Safety Rule : Monitor capillary blood glucose hourly for at least 4 to 6 hours . Hypoglycemia occurs in up to 10-15% of patients, frequently delayed at 2-3 hours post-administration.

Inhaled Beta-2 Adrenergic Agonists (Albuterol) :

Dose : 10 to 20 mg nebulized in 4 mL normal saline over 15 minutes (note: this is 4 to 8 times the standard 2.5 mg bronchodilator dose ).

Mechanism : Beta-2 adrenergic stimulation increases intracellular cyclic AMP, activating the Na+/K+-ATPase pump.

Pharmacodynamics : Onset 15 to 30 minutes; duration 2 to 4 hours. Lowers potassium by 0.5 to 1.0 mEq/L . Has a synergistic, additive effect when combined with insulin.

Precautions : Ineffective in ~20% of patients on non-selective beta-blockers; may provoke tachycardia or myocardial ischemia in patients with active coronary artery disease.

Intravenous Sodium Bicarbonate :

Dose : 50 mEq (one 50 mL ampule of 8.4%) IV over 5 minutes.

Critical Guideline : Indicated ONLY in patients with concurrent severe metabolic acidosis (bicarbonate <15 mEq/L, pH <7.20) . Completely ineffective for shifting potassium in patients with normal acid-base status.

Phase 3: Total Body Potassium Elimination (Definitive Removal)

Loop Diuretics (Furosemide) :

Dose : 40 to 80 mg IV (or Bumetanide 1-2 mg IV) in patients with preserved renal function; blocks Na+/K+/2Cl- cotransporter in the loop of Henle, accelerating urinary potassium excretion.

Gastrointestinal Potassium Binders :

Sodium Zirconium Cyclosilicate (Lokelma) : 10 g orally three times daily with water for up to 48 hours, followed by 5-10 g daily. Selective inorganic cation exchanger that traps potassium in exchange for sodium and hydrogen throughout the entire gastrointestinal tract. Onset of action within 1 to 2 hours .

Patiromer (Veltassa) : 8.4 g orally once daily. Non-absorbed polymer that binds potassium in exchange for calcium primarily in the distal colon. Onset of action is 4 to 7 hours ; not suitable for hyperacute monotherapy.

The Black Box Warning on Kayexalate (Sodium Polystyrene Sulfonate - SPS) : SPS, especially when co-administered with sorbitol, carries a severe risk of intestinal necrosis, colonic perforation, and mesenteric ischemia . Its use has been largely superseded by modern binders.

Emergent Hemodialysis :

The gold standard and most definitive therapy for removing total body potassium (clears 25 to 50 mEq of potassium per hour of dialysis).

Mandatory in patients with end-stage renal disease (ESRD), oliguric acute kidney injury, extensive tissue necrosis (rhabdomyolysis, tumor lysis syndrome), or hyperkalemia refractory to medical shifting.

Hypokalemia: Clinical Manifestations, The Magnesium Nexus & Repletion
Severity Classification
Mild Hypokalemia : 3.0 to 3.4 mEq/L (often asymptomatic or mild fatigue)
Moderate Hypokalemia : 2.5 to 2.9 mEq/L (muscle weakness, cramps, constipation/ileus)

Severe Hypokalemia : <2.5 mEq/L (flaccid paralysis, hypoventilation/respiratory failure, tetany, rhabdomyolysis, life-threatening arrhythmias)

Electrocardiographic Findings

Decreasing extracellular potassium hyperpolarizes the resting membrane potential and prolongs ventricular action potential duration:

T-wave flattening and T-wave inversion;
ST-segment depression;
Prominent U waves (positive deflection following the T wave, best visualized in leads V2-V4);
Apparent QT interval prolongation (which actually represents a fused QU interval );

Severe dysrhythmias: premature ventricular contractions (PVCs), junctional rhythms, atrial fibrillation, ventricular tachycardia, and torsades de pointes (particularly in patients taking digoxin or antiarrhythmic drugs).

The Critical Magnesium Nexus: Why Hypokalemia Becomes Refractory

Hypokalemia is frequently accompanied by hypomagnesemia (common etiologies include loop/thiazide diuretics, chronic alcohol use, diarrhea, and proton pump inhibitors):

ROMK Channel Regulation : In the principal cells of the renal cortical collecting duct, intracellular magnesium acts as a natural, essential physiologic plug that inhibits the renal outer medullary potassium (ROMK) channels.

Unchecked Potassium Secretion : When intracellular magnesium is depleted, this inhibitory block is removed. ROMK channels remain persistently open, causing massive, uninhibited potassium secretion into the tubular lumen and wasting into the urine.

Pump Dysfunction : Hypomagnesemia impairs the enzymatic function of the Na+/K+-ATPase pump, impairing potassium uptake into cells.

Important

Board Exam Pearl : Refractory hypokalemia cannot be corrected until coexisting hypomagnesemia is identified and repleted. Always check serum magnesium in patients with hypokalemia; target magnesium >2.0 mg/dL by administering 2 g of IV Magnesium Sulfate over 30 to 60 minutes.

Potassium Repletion Protocols

Deficit Estimation : For every 1.0 mEq/L drop in serum potassium below 4.0 mEq/L, total body potassium deficit is approximately 100 to 200 mEq (deficits increase exponentially when serum K+ falls <2.5 mEq/L).

Oral Repletion (Preferred Route) :

Potassium Chloride (KCl) 20 to 40 mEq orally every 2 to 4 hours (maximum single oral dose 40 mEq to prevent gastrointestinal mucosal irritation).

Intravenous Repletion (Indications: K+ <2.5 mEq/L, ECG changes, or non-functioning GI tract) :

Peripheral IV Access : Maximum infusion rate is 10 mEq/h (up to 20 mEq/h in severe emergencies) at a maximum concentration of 40 mEq/L to prevent intense local pain, burning, and chemical phlebitis.

Central Venous Access : Infusion rates of 20 to 40 mEq/h can be administered under continuous cardiac telemetry monitoring in an intensive care setting.

Hyponatremia: Systematic Evaluation & Acute Emergency Protocols

Hyponatremia is defined as a serum sodium concentration <135 mEq/L ; severe hyponatremia is defined as <120 mEq/L . DIAGNOSTIC TRIAGE FOR HYPONATREMIA

MEASURE SERUM OSMOLALITY
│
┌────────────────────────────────┼────────────────────────────────┐
▼ ▼ ▼
HYPERTONIC (>295) ISOTONIC (275-295) HYPOTONIC (<275)
Hyperglycemia (DKA/HHS) • Pseudohypernatremia • True Hypotonicity
Mannitol infusion • Severe Hypertriglyceridemia Assess Clinical

(Osmotic transcellular shift) • Paraproteinemia (Myeloma) Volume Status:

│
┌─────────────────────────────────────────────────────────────────┼──────────────────────────────┐
▼ ▼ ▼
HYPOVOLEMIC EUVOLEMIC HYPERVOLEMIC
Urine Na <20: Dehydration, diarrhea, burns • SIADH (Urine Osm >100, • Urine Na <20: CHF,
Urine Na >20: Diuretics, Addison disease Urine Na >20-40) Cirrhosis, Nephrotic
Rx: Isotonic 0.9% Normal Saline • Hypothyroidism, 2° Adrenal • Urine Na >20: Renal Failure
Rx: Fluid Restriction, Vaptans Rx: Loop Diuretics, Fluid Restrict
1. Diagnostic Step 1: Serum Osmolality

Hypertonic Hyponatremia (>295 mOsm/kg) : Caused by osmotically active solutes in the extracellular space (glucose, mannitol) drawing free water out of cells. Calculate corrected sodium.

Isotonic Hyponatremia (275-295 mOsm/kg) : Pseudohyponatremia . Caused by severe hypertriglyceridemia (chylomicronemia) or extreme paraproteinemia (multiple myeloma) displacing aqueous volume. Modern direct ion-selective electrode testing confirms normal physiological sodium.

Hypotonic Hyponatremia (<275 mOsm/kg) : True hypotonic hyponatremia. Proceed to clinical volume assessment.

2. Diagnostic Step 2: Volume Status & Urine Chemistries

Hypovolemic : Decreased skin turgor, orthostasis, dry mucous membranes, flat neck veins.

Urine Sodium <20 mEq/L : Non-renal losses (vomiting, diarrhea, third-spacing, severe burns).

Urine Sodium >20 mEq/L : Renal losses (thiazide diuretics, mineralocorticoid deficiency / Addison disease, cerebral salt wasting).

Treatment : Volume restoration with Isotonic 0.9% Normal Saline .

Euvolemic : No edema, normal jugular venous pressure, normal blood pressure.

Syndrome of Inappropriate Antidiuretic Hormone (SIADH) : Inappropriately concentrated urine (Urine Osmolality >100 mOsm/kg, usually >300 mOsm/kg) with high urine sodium (Urine Na >20-40 mEq/L) in a clinically euvolemic patient with normal adrenal, thyroid, and renal function. Etiologies: small cell lung cancer, SSRIs, carbamazepine, pneumonia, CNS trauma. Treatment: Fluid restriction (500-1000 mL/day), oral salt tablets, loop diuretics, or vasopressin receptor antagonists (tolvaptan).

Other Euvolemic Causes : Severe hypothyroidism, secondary adrenal insufficiency, psychogenic polydipsia (Urine Osm <100 mOsm/kg), low solute intake (beer potomania, tea-and-toast diet).

Hypervolemic : Peripheral edema, ascites, jugular venous distention, pulmonary crackles.

Urine Sodium <20 mEq/L : Congestive heart failure, cirrhosis, nephrotic syndrome (decreased effective circulating volume triggers secondary hyperaldosteronism and non-osmotic ADH release).

Urine Sodium >20 mEq/L : Acute or chronic end-stage kidney disease.

Treatment : Sodium and fluid restriction, loop diuretics.

3. Emergency Management of Acute Severe Symptomatic Hyponatremia

Clinical Presentation : Severe neurologic symptoms resulting from cerebral edema and increased intracranial pressure: active seizures, coma, obtundation, respiratory depression, tentorial brain herniation.

The 3% Hypertonic Saline Emergency Regimen :

Administer 3% Hypertonic Saline (contains 513 mEq/L Na) as a 100 mL IV bolus over 10 minutes .

If severe symptoms persist, repeat the 100 mL bolus up to two additional times (total 300 mL) at 10- to 20-minute intervals.

Target Immediate Goal : Elevate serum sodium by 4 to 6 mEq/L acutely . A 4-6 mEq/L elevation reduces brain volume by ~10%, arresting seizures and preventing fatal brainstem herniation.

4. Osmotic Demyelination Syndrome (ODS) & Strict Correction Limits

Pathophysiology of ODS (Central Pontine Myelinolysis) :

In chronic hyponatremia (>48 hours), brain cells adapt to hypotonicity by extruding intracellular osmolytes (glutamate, taurine, myoinositol) to minimize brain swelling.

If serum sodium is raised too rapidly, extracellular tonicity exceeds intracellular tonicity before brain cells can re-synthesize or take up osmolytes.

This rapid osmotic gradient draws water violently out of brain cells, causing acute dehydration of glial cells, disruption of the blood-brain barrier, and oligodendrocyte apoptosis, leading to widespread demyelination—most severely in the central pons.

Clinical Presentation of ODS :

Characteristically manifests 2 to 6 days after over-rapid correction .

Symptoms: Dysarthria, dysphagia, horizontal gaze paralysis, spastic quadriparesis, and the catastrophic "locked-in syndrome" (awake, fully conscious, but completely paralyzed except for vertical eye movements).

The Absolute Correction Limits :

Standard Limit : Do NOT exceed an increase of 8 mEq/L in any 24-hour period (and <=14-16 mEq/L in 48 hours).

High-Risk Patients (advanced cirrhosis, severe malnutrition, chronic alcoholism, hypokalemia, baseline Na <105 mEq/L): Limit correction to 6 to 8 mEq/L in 24 hours .

Rescue Protocol for Accidental Over-Correction :

If serum sodium rises faster than target limits, immediately stop sodium infusion, initiate IV 5% Dextrose in Water (D5W) at 3 mL/kg/h , and administer Desmopressin (DDAVP) 1 to 2 mcg IV or SC every 6 to 8 hours to arrest water diuresis and re-lower serum sodium back into the safe range.

Hypernatremia: Free Water Deficit & Controlled Rehydration

Hypernatremia (serum sodium >145 mEq/L ; severe >160 mEq/L ) universally represents a deficit of free water relative to total body sodium.

Etiologies

Unreplaced Water Losses : Impaired thirst mechanism or lack of access to water (elderly, infants, intubated patients), fever, sweating, severe burns, osmotic diuresis (DKA, HHS, mannitol).

Diabetes Insipidus : Inability to concentrate urine due to lack of ADH (Central DI: pituitary surgery, trauma) or renal insensitivity to ADH (Nephrogenic DI: lithium toxicity, hypercalcemia). Hallmark: massive polyuria with inappropriately dilute urine (Urine Osm <300 mOsm/kg).

Exogenous Sodium Overload (rare): Hypertonic sodium bicarbonate infusions, 3% saline infusions, salt ingestion.

Free Water Deficit Calculation Formula
Free Water Deficit (L) = Total Body Water (TBW) x [(Measured Serum Na+ / 140) - 1]

Total Body Water (TBW) Constants :

Non-elderly males: 0.60 x Weight (kg)
Non-elderly females or elderly males: 0.50 x Weight (kg)
Elderly females: 0.45 x Weight (kg)
Controlled Rehydration Protocol

Fluid Selection : Oral or enteral water via nasogastric tube is preferred whenever feasible. If IV fluids are required, use 5% Dextrose in Water (D5W) or 0.45% NaCl .

Rate Limitation : Correct the free water deficit plus ongoing urinary and insensible losses slowly over 48 to 72 hours .

Crucial Rate Ceiling : Lower serum sodium at a maximum rate of 10 to 12 mEq/L per 24 hours (0.5 mEq/L per hour) .

Danger of Rapid Correction : Brain cells adapt to chronic hypernatremia by accumulating idiogenic intracellular osmolytes. Overly rapid rehydration shifts water into brain cells, precipitating life-threatening cerebral edema, seizures, permanent neurological damage, and death .