Fellowship Revision Notes Dec 2014 Page Acid-Base 2 Electrolytes 5 Cardiology 10 Dental, ENT, Ophthalmology 25 Dermatology 33 Rheumatology, Immunology 36 Endocrinology 41 Haematology and Oncology 47 Environmental 54 Gastrointestinal 65 Infectious Diseases 70 Management 76 Disaster and Retrieval 82 Neurology/Neurosurgery 88 O & G 97 Orthopaedics 107 Paediatrics 117 Psychiatry 130 Radiology 133 Renal 137 Urology 139 Respiratory 142 Resuscitation 151 Anaesthetics 157 Surgery 169 Toxicology 173 Trauma 197 Spinal 211 'All care, no responsibility' Feedback and corrections greatly appreciated Dr Laura Joyce, Advanced Trainee, Christchurch Hospital [email protected] shakEM by www.shakEM.co.nz is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License. www.shakEM.co.nz 1 Acid-Base Summary HCO3 = 24 PCO2 = 40 BE = -3 to +3 Metabolic Acidosis Exp pCO2 =(1.5 x HCO3) + 8 Alkalosis Exp pCO2 = (0.7 x HCO3) +20 Observed > expected = concurrent respiratory acidosis Observed < expected = concurrent respiratory alkalosis Respiratory Acidosis Acute: 1 for 10: HCO3 = (pCO2 - 40)/10 x 1 Chronic: 4 for 10: HCO3 = (pCO2 - 40)/10 x 4 Alkalosis Acute: 2 for 10: HCO3 = (pCO2 - 40)/10 x 2 Chronic: 5 for 10: HCO3 = (pCO2 - 40)/10 x 5 Observed > expected = concurrent metabolic alkalosis Observed < expected = concurrent metabolic acidosis Anion Gap AG = Na + K - HCO3 Normal = 12 Low albumin falsely elevates AG - for every drop by 10 in albumin, drop AG by 3 Incr AGMA + met alkalosis + resp alkalosis = sepsis/salicylates Major disturbance always in same direction as pH Delta Ratio AG - 12 24 - HCO3 <0.4 hyperchloraemic NAGMA 0.4 - 0.8 NAGMA + AGMA 0.8 - 2 AGMA > 2 AGMA + metabolic alkalosis or chronic respiratory acidosis A-a gradient PAO2 = (FiO2 x 713) - (PaCO2 x 1.25) A-a gradient = pAO2 – paO2 Normal A-a gradient = < (age/4) + 4 Hypoxic + Raised A-a gradient – V/Q mismatch, shunt, diffusion block (fibrosis) Hypoxic + Normal A-a gradient - hypoventilation or low FiO2 (eg altitude) Osmolar gap Calculated serum osm = (2 X Na) + Ur + Glu + ETOH Osmolar gap = measured - calculated Normal osmolality = 270-290 Normal osmolar gap = -4 to +10 Raised osmolar gap: Alcohols - ethanol, methanol, EG Ketones - DKA, AKA, acetone Sugars - mannitol Lactate Proteins, lipids, excessively high ions (Mg, Ca, phos) U:C ratio U:C >100 - pre-renal failure www.shakEM.co.nz 2 Corrected Na Corrected Na = Na + Glucose – 5 3 Corrected K+ 0.1 decr in pH - 0.5 incr in K Lactic acidosis Type A Decr O2 delivery: shock, hypoxia, severe anaemia, CO poisoning Incr O2 demand: seizure, pyrexia, exercise, shivering Type B1 Systemic disorders: leukaemia, lymphoma, thiamine def, pancreatitis, short bowel Decr metabolism: hepatic failure, renal failure, hypothermia, DM, sepsis Type B2 Drugs/toxins: EtOH, toxic alcohol, Fe, salicylates, isoniazid, cyanide, CO, metformin Type B3 Inborn errors of metabolism AGMA Ketones DKA, AKA, starvation Lactate Type 1 (shock), Type 2 (metabolic) Renal failure Toxins Alcohols, salicylates, iron, cyanide, valproate, metformin, paracetamol NAGMA Chloride gain Normal saline Bicarb loss GI: diarrhoea, fistulas GU: RTA, Addisons, acetazolamide Cl retained when HCO3 lost to maintain electroneutrality Most common causes - EDA: Extra Cl - high K, urinary Na <10 Diarrhoea - low K, urinary Na <10 Adrenal insufficiency - high K, low Na, urinary Na >10 Low AG Low albumin High unmeasured cations (Ca, Mg, Li) Falsely elevated Cl (bromide, iodide) Nitrites Myeloma Metabolic Alkalosis Most common causes: vomiting, diuretics, incr aldosterone Chloride loss (saline responsive, Urine Cl <10) kidney reabsorbs HCO3 > Cl to maintain electroneutrality aka contraction alkalosis (fluid loss - decr renal perfusion - incr aldosterone - loss H/reabsorp HCO3) GI: vomiting, NG suction GU: diuretics Skin loss: burns Potassium loss (saline resistant), Urine Cl >10, often hypertensive) Syndromes: Cushings, Conns, Bartters Eating disorders Excess liquorice Excess base (saline resistant, Urine Cl >10, normotensive) Antacids, milk-alkali, bicarb, citrate (dialysis, transfusion) Respiratory Acidosis 1. Decreased respiratory drive - decr RR CNS CVA, tumour, encephalitis, haemorrhage, spinal cord lesion above C4 Drugs Narcotics and sedatives, ETOH www.shakEM.co.nz 3 2. Decreased chest wall movement - decr TV Neurological NM disorders, Guillain-Barre, Myasthenia gravis, demyelinating, tetanus, spinal trauma Toxicity Muscle relaxants, Organophosphates, fentanyl, spider+snake venom Respiratory Trauma, surgery, chest wall deformity, tension pneumo, pleural effusion, airway obstruction Muscular Electrolyte abnormality, myopathy, muscular dystrophy Equipment Increased dead space, improper connection 3. Obstructive pulmonary disease - incr dead space COPD, asthma, pneumonia, very severe croup, angioedema, severe pulm oedema, inhaled FB, aspiration Respiratory Alkalosis Full compensation in pregnancy and at altitude 1. Stimulated respiratory drive CNS CVA, ICH, psychogenic, cerebral oedema, hepatic encephalopathy Hyper-metabolic Thyrotoxicosis, Pregnancy, early sepsis, DT, anxiety, pain, DKA and aspirin OD Environmental Hyperthermia, altitude related, exercise Drugs Aspirin OD, ammonia, progesterone, theophylline, CO, stimulants Iatrogenic Mechanical ventilation 2. Hypoxemia induced Pneumonia, PE, asthma, Congenital heart disease, Chronic altitude comp, early altitude, pulm oedema 3. Compensation for metabolic acidosis Use of Bicarbonate 1. Hydrofluoric acid toxicity 2. Correction of severe metabolic acidosis 3. Prolonged cardiac arrest (evidence unclear) 4. Cardiotoxicity secondary to fast Na channel blockade 5. Urinary alkalinisation in OD - enhanced elimination 6. Prevention of drug redistribution to CNS – incr unionized amount of drug - Salicylates 7. Severe hyperK 8. RTA www.shakEM.co.nz 4 Electrolytes Summary Hyponatraemia Mild >125 Mild GI Sx (anorexia, N+V) Moderate 120-124 Lethargy, confusion, muscle weakness Severe <120 Decr LOC, seizures; brainstem herniation, cerebral oedema, osmotic demyelination 1. Hypertonic: Osm >295 Glucose, mannitol 2. Isotonic: Osm 275-295 aka pseudohyponatraemia: incr lipids, incr protein (myeloma, Waldenstroms) 3. Hypotonic: Osm <275 Due to: solute depletion or solute dilution a. Hypovolaemic (most common): Loss of Na > H20 Renal (urine Na >20) Diuretics, osmotic diuresis Addisons Na losing nephropathy (RTA, CRF) Extrarenal (urine Na <20) Upper GI: vomiting Middle GI: pancreatitis, bowel obstruction Lower GI: diarrhoea Others: sweat, bleeding, burns Management: give N saline; correct at <0.5mmol/hr or <12mmol/day; aim to get Na >125 b. Euvolaemic: SIADH Hypothyroid Water intoxication: psychogenic, iatrogenic (TURP syndrome) Drugs: SSRI/TCA/MAOI, ecstasy, oxytocin, carbamazepine, NSAIDs, omeprazole Test urine osmolality: <100mosm/L = primary polydipsia; >100mosm/L = SIADH or endocrine Management: fluid restrict to 500-1500ml/day; consider ADH antagonist if SIADH c. Hypervolaemic: Incr H20 >> Na ARF CHF, cirrhosis, nephrotic syndrome Management: fluid and salt restrict; diuresis (loop); dialysis Hypertonic saline Indications: coma, seizure, new onset profound decr LOC; not indicated if asymp Give 25-100ml/hr (1-2ml/kg/hr) 3% saline via CVL Can give more rapidly (500ml or 4-6ml/kg bolus over 10mins) if seizing Endpoint: Sx resolved/Na incr by 8-20mmol/L/Na >125 Aim for correction of 1mmol/L/hr (max 10-14mmol/L/day) SE: central pontine myelinosis (osmotic demyelination) if too rapid correction of chronic (>48hr) SIADH Hypotonic (<275) hyponatraemia (<130) Inappropriately high urine osmolality (>100) Elevated urine Na >20 Clinically euvolaemic Normal cardiac, renal, adrenal, thyroid, liver function Correctable with water restriction www.shakEM.co.nz 5 Causes: Malignancy (ectopic ADH) - lung (small cell, mesothelioma), GI, GU, lymphoma, sarcoma, thymoma Pulmonary - pneumonia, COPD, lung abscess, TB CNS - infection, abscess, AIDs, trauma, stroke Drugs - cytotoxics, antidepressants, antipsychotics, desmopressin, oxytocin, vasopressin Hypernatraemia (Na >150) 1. Iatrogenic, incapacitated NaHCO3, hypertonic saline Formula (infants), neglect (elderly) 2. Pure water loss (H20 > Na) - hypovolaemic Renal = osmotic diuresis (glucose), diuretics Extra-renal = diarrhoea, blood loss, third spacing Rx: Normal saline resus then 1/2 normal saline Water deficit (L) = 1L per 3-5 incr Na = (0.6 x kg) x ((Na-140)/140) Give deficit + maintenance (1500ml/day in adults), with 50% over 24hrs, 50% over 48hrs Correct for ongoing losses Too rapid correction - cerebral oedema; correct at <0.5mmol/L/hr or 10-15mmol/L/day 3. Aldosterone excess - hypervolaemic Primary: Conns, Cushings Secondary: CCF, cirrhosis, nephrotic syndrome, dehydration Rx: frusemide + free water. Dialysis if renal failure 4. Diabetes insipidus - euvolaemic Rx: same as euvolaemic without fluid bolus. ADH or DDAVP Symptoms occur with Na >158 Osm 350 – 375 Restlessness, irritability, thirst, anorexia, N+V Osm 375 – 400 Tremor, ataxia Osm 400 – 430 Hyperreflexia, twitching, spasticity Osm >430 Seizures, death; subcortical and SAH Na 150 – suggests dehydration Na 170-190 – suggests DI Na >190 – suggests incr Na intake Children: if mod: paedialyte no more than 15ml/kg/hr use 0.45% saline + 2.5% dex and replace over 48hrs if severe: use 0.45% saline + 2.5% dex and replace over 72-96hrs Diabetes Insipidus Inability to concentrate urine - large amounts of severely diluted urine Failure of: - production of ADH (central DI: neoplasm, pituitary surgery, trauma, idiopathic) - response to ADH (nephrogenic DI: