KC Endo Flashcards
*What are 4 risk factors for metformin-induced lactic acidosis?
Impaired renal function
Heart failure
Coexisting metabolic acidosis
IV contrast media
Concurrent liver disease
Active alcohol abuse
Prior hx of lactic acidosis during metformin therapy
Decreased tissue perfusion / hemodynamic instability
*What are 4 harms of giving sodium bicarbonate?
Paradoxical CNS acidosis
Hypokalemia
Volume overload
Hyperosmolality
Overshoot alkalosis
*What are 3 indications of giving sodium bicarbonate?
ASA OD
TCA OD
Acidemia primarily driven by bicarb loss or impaired acid secretion (renal failure)
*Why do we need to measure albumin when looking at an anion gap (3 marks)
Correction for albumin is important because significant depression of the serum albumin level will reduce the anion gap, potentially masking the presence of an important unmeasured anion
*What are two causes of a low anion gap?
Increased unmeasured cation (lithium toxicity)
Decreased unmeasured anion (low albumin)
Spurious ion measurements
or
Lithium toxicity
Hypergammaglobulinemia seen in multiple myeloma.
Bromide toxicity may cause spurious hyperchloremia, and hypertriglyceridemia may cause spurious hyponatremia, which can also cause a low or negative anion gap.
unmeasured anions such as albumin, sulfate, phosphate, and citrate (so hypoalbuminemia)
*pH 7.27, CO2 78, HCO3 35.
i. What is the primary acid base disturbance?
ii. Is it acute or chronic?
iii. List 4 disorders that can cause this disturbance.
i. Resp acidosis
ii. Chronic
- Airway obstruction
- Pulmonary disease (pneumonia, asthma, pulmonary edema, aspiration pneumonitis)
- Central nervous system depression (recreational drugs, ICH)
- Neuromuscular disorders (myasthenia gravis, Guillain-Barre syndrome)
- Thoracic trauma (pneumothorax, flair chest)
*pH 7.15, CO2 20, HCO3 5
i. What is the primary disturbance?
ii. List 5 TOXIC causes
i. Met acidosis
- Methanol
- Ethylene glycol
- Toluene
- Paraldehyde
- Aspirin
- Carbon monoxide
- Methemoglobinemia
- Cyanide
- Metformin
- Reverse transcriptase inhibitors - Paracetamol
- Iron
- Isoniazid
*58M CAD chronic back pain, DM on asa, metoprolol, oxycontin, metformin found with decreased LOC. pH 7.29 pCO2 73 pO2 65
a. What is the primary cause of his altered mental status?
b. What are 3 causes of his acid base abnormality
c. What is the most important intervention
d. What is one contraindication to NIPPV
e. What would you expect his bicarbonate to be?
f. What would you expect it to be if this was chronic?
a. CO2 retention
b. hypoventilation from oxy, or from ICH, or pna impairing gas exchange
c. needs to be ventilated (NIPPV)
d.
- need for emergency intubation
- decreased level of consciousness
- lack of respiratory drive
- increased secretions
- hemodynamic instability
- conditions that would prevent an adequate mask seal (eg facial trauma)
e.
73-40=33
330.1 = 3.3
24+3.3 = 27
f.
73-40 = 33
33 0.35 = 12
24+12 = 36
List 5 causes of respiratory acidosis
Won’t breathe - recreational drugs, intracranial catastrophe (ICH, stroke, SAH)
Can’t breathe - neuromuscular disorder (myastheniaTravis, Guillain-Barre), ALS, airway obstruction
Can’t breathe enough - narrowing of the airways/trapping from COPD/asthma, obesity, pulmonary disease (pneumonia, edema), pneumothorax
Describe the two physiologic buffer systems in acid base disturbances
Renal buffers generally determine HCO3-
- H+/K+ exchange in the kidneys
- The kidney regulates HCO3- excretion, reabsorption, and formation (takes 4-5 days)
- Retention of H+ (i.e. in alkalemia) cannot occur unless potassium stores are sufficient to allow urinary K+ extraction
Respiratory processes generally determine PaCO2
- Adjusted through minute ventilation
List 5 causes of respiratory alkalosis
Hyperventilation
- Anxietyor psychogenic
- Central - CNS tumors or bleeds, increased ICP
- Tox - salicylates, thyroxine, caffeine
- Pulmonary/hypoxia - high altitude, anemia, V/Q mismatch, PE, pneumonia, edema, asthma
- Endocrine - hyperthyroid, hepatic encephalopathy
- Pregnancy - should be alkaloid at baseline; normal pH suggests hypoventilation
Pain, pregnancy
Why does a respiratory alkalosis present with symptoms of hypocalcemia
Sx: lip and extremity parasthesias, muscle cramps, lightheadedness, syncope
Higher pH (alkalosis), calcium binds more strongly to albumin, decreases free calcium
List 7 causes of elevated AG metabolic acidosis
Keto acids (diabetic, starvation, alcohol)
Lactic acids
- Type A: inadequate oxygen (shock, mesenteric ischemia, muscle hyperactivity/seizure, hypoxia)
- Type B: adequate oxygen (liver failure, malignancy, thiamine deficiency, drug toxicity)
Uremia
Tox: IMPACTS - Iron/isoniazid (due to seizures), metformin, phenformin/paraldehyde, ASA/acetaminophen/alcohols, cyanide/CO, Toluene, salicylates
List 7 causes of non AG metabolic acidosis
Overall due to an imbalance of chloride and bicarb
- GI: diarrhea, colostomy or ileostomy, enteric fistulas, Kayexalate, TPN
- Renal: RTA, interstitial renal disease, hyperparathyroidism
- Normal saline infusion: urologic procedures, ureterosigmoidostomy
- Ingestions: acetazolamide, calcium chloride, magnesium sulfate
- Other: hypoaldosteronism, hyperkalemia, toluene
Mnemonic - HARD UP: hyperalimentation (TPN), acetazolamide, renal tubular acidosis, diarrhea, uretosigmoid fistula, pancreatic fistula
remember - gain chloride means H breaks off weak acids, bicarb loss, TPN is accumulation of organic acids (dont count), diamox is bicarb loss
List 5 causes of metabolic alkalosis
Due to gain of bicarb of loss of acid
Volume contraction - vomit (lose H)
diuretics (contraction alkalosis)
Endocrine - hyperaldosteronism, hypercortisolemia, hypoalbuminemia,
milk-alkali syndrome,
hypercalcemia, massive transfusion (generates citrate)
more calcium intake means more bicarb gets resorbed
More aldosterone get rid of more H ions
loop diuretics get rid of Cl
MTP - citrate gets turned into bicarb
Contraction alkalosis - when you try to keep volume, the kidneys keep water, salt and bicarb
Hypoalbuminemia - volume contraction
Describe the expected metabolic compensation in acute and chronic respiratory acidosis and alkalosis
See photo compensation
(1-2-HCOS-4-5)
Describe the expected respiratory compensation in metabolic acidosis and alkalosis
See photo compensation 2
Whether an appropriate respiratory compensation to a metabolic acidosis has occurred can be approximated by comparing the Paco2 to the last two digits of the serum pH. Ex. a patient with a pH of 7.20 should have a PaCO2 of 20mmHg
How do you calculate the anion gap
Na-(Cl+HCO3)
What is a normal anion gap
~8-12
How do you correct anion gap for albumin
Albumin corrected anion gap = anion gap +2.5*(normal albumin-measured albumin)
Albumin is an anion. AG will be lowered in the presence of hypoalbuminemia, thereby masking an elevated AG - a normal AG may actually represent a metabolic acidosis
What is the strong ion difference
(Na+K-Cl) <40 suggests an acidosis is present
What is the delta gap? How do you calculate it and what does it represent
Delta gap = (AG-12)-(24-HCO3-)
Determines if the anion gap is accounted for by the change in Bicarb
An elevated anion gap and a delta gap >6 indicates a metabolic alkalosis + a metabolic alkalosis. There is another process that is increasing bicarbonate levelsex. DKA with severe vomiting
An elevated anion gap and a delta gap <-6 indicates a metabolic acidosis (elevated AG) + a metabolic acidosis (normal AG). Ex. lactic acidosis with severe diarrhea
What is Winter’s equation? What does it represent
PaCO2 = (1.5*serum HCO3-) + (8 )
Used to calculate the expected arterial PCO2 for the serum bicarbonate level. Tells us if there is a mixed picture. If the PCO2 is higher than expected the patient may be fatiguing and need ventilator support
What is base excess
Defined as the amount of acid (H+) required to restore a Litre of blood to its normal pH and a PaCO2of 40 mmHg.
Estimates the metabolic component of the acid-base balance
A positive base excess means excess base, i.e. a metabolic alkalosis
A negative base excess means reduced base, i.e. a metabolic acidosis
What electrolyte abnormality is expected in chronic respiratory acidosis
Hypochloremia; Cl is excreted by the kidneys to maintain HCO3
What electrolyte abnormality is expected in chronic respiratory alkalosis
Hyperchloremia, Cl is kept by the kidneys to excrete HCO3
Hypokalemia, K+ is excreted by the kidneys to keep H+
*3 reasons why cancer patients get hypercalcemia
- Ectopic secretions of parathyroid hormone
- Multiple myeloma
- Cancer metastatic to bone
*5 treatments for hypercalcemia
- Oral rehydration
- IV normal saline infusion
- Bisphosphonate
- Calcitonin
- Glucocorticoids
- Phosphates
- Mab
- Hemodialysis
*2 ECG changes for hypercalcemia
Short QT interval
ST segment elevation
In severe cases:
- Sinus bradycardia
- Bundle branch block
- High degree AV block
- J waves
*Most common cause of hyperCa in hospitalized patients?
cancer metastatic to bone
*2 causes of hyperCA in each category:
• MALIGNANT DISEASE
• ENDOCRINE
• GRANULOMATOUS DISEASE
• PHARMACOLOGIC AGENTS
• MISCELLANEOUS
• MALIGNANT DISEASE
• Ectopic secretions of parathyroid hormone, multiple myeloma, cancer metastatic to bone
• Most common: Breast, lung, hematologic, kidney, prostate
• ENDOCRINE
• Hyperparathyroidism, multiple endocrine cancers, hyperthyroidism, pheochromocytoma, adrenal insufficiency
• GRANULOMATOUS DISEASE
• Sarcoidosis, tuberculosis, histoplasmosis, berylliosis, coccidioidomycosis
• PHARMACOLOGIC AGENTS
• Vitamins A and D, thiazide diuretics, estrogens, milk-alkali syndrome
• MISCELLANEOUS
• Dehydration, prolonged immobilization, iatrogenic, rhabdomyolysis, familial, laboratory error
*Hypomagnesemia: cause of each category
Dietary
Gastrointestinal
Renal
Endocrine or metabolic
Drug induced
Dietary: chronic EtOH and malnutrition
Gastrointestinal: chronic diarrhea or inflammatory bowel conditions
Renal: mostly related to diuretics, pure renal wasting is rare
Endocrine or metabolic: hypokalemia, hypocalcemia, hyponatremia,
Drug induced: loop or thiazide diuretics, long term PPI
*2 uses for IV Mg in ED
Torsades / long QTC
Eclampsia / pre-eclampsia
Asthma
Hypokalemia/hypomag
*2 side effects of rapid IV magnesium in ED
• Hyporeflexia
• Brady
• Hypotension
• Flushing
• Resp arrest/apnea
*EKG findings of hyperkalemia
- Peaked T wave
- Flattened P wave
- Prolonged PR
- Absent P wave
- Wide QRS
- Sine wave
- “Slow” ventricular tachycardia
- Wide-complex bradycardia
*6 medications you can give to treat hyperK
- Calcium gluconate/chloride
- Ventolin
- Insulin/dextrose
- Kayexalate
- Bicarbonate
- Lasix (if making urine)
- Dialysis (if anuric)
*Recent thyroidectomy with perioral numbness and tingling. Most likely diagnosis
Hypocalcemia
*2 EKG findings of hypocalcemia
o Arrythmias
o Long QT
*Treatment of hypocalcemia
Mild symptoms can be treated with oral calcium supplementation, such as calcium carbonate.
Hypocalcemic tetany: 100-300 mg elemental calcium (~3 g calcium gluconate) IV over 5-10 minutes, followed by continuous IV infusion at 0.5 mg/kg/hr (may be increased to 2 mg/kg/hr)
*Two special tests and descriptions for hypocalcemia
o Chvostek sign: When examiner taps the facial nerve, facial or eye muscle twitching occurs
o Trousseau sign: When examiner inflates blood pressure cuff to 20 mmHg above systolic blood pressure for 3 minutes, carpal spasms will occur
*Max correction in 24h for hyponatremia
Previous guidelines have endorsed the safety of raising the serum sodium by up to 10 to 12 mEq within the first 24 hours. However, in patients believed to have been hyponatremic for more than 48 hours, severe hyponatremia should be corrected by no more than 0.5 mmol/hr or 8 mEq in the first 24 hours.
*Causes of hyponatremia with high serum osmolality
? pseudohyponatremia
Hyperglycemia
Positive osmotic gap ( sorbitol, mannitol, lab error)
*Causes of SIADH
Lung Masses
Cancer (especially small cell)
Pneumonia
Tuberculosis
Abscess
Central Nervous System Disorders
Infection (meningitis, brain abscess)
Mass (subdural, postoperative, cerebrovascular accident)
Psychosis (with psychogenic polydipsia)
Drugs
Thiazide diuretics
Narcotics
Oral hypoglycemic agents
Barbiturates
Antineoplastics
*69F with advanced small cell lung cancer presents with confusion. Hemodynamically stable with normal cardiac exam. He is not clinically dehydrated. Sodium of 112 on his routine blood work. What other tests would you like to order for this patient in order to further characterize the nature of his hyponatremia?
Urine lytes
Serum osmolality
*What is the specific treatment for seizures from hyponatremia?
3% hypertonic saline 100 mL IV over 10 minutes (though she should get it for her confusion anyway)
*Why is it probably not a great idea to give a bolus of normal saline?
It would worsen the hyponatremia given that the extra water would be retained through the SIADH but the extra sodium would be excreted
*What is the pathophysiology for her confusion and twitchiness?
Cerebral edema from increased fluid shift in the cells, including cerebral cells
*How to correct mild hyponatremia from SIADH
Fluid restriction
*What is the delayed neurologic consequence if hyponatremia is corrected too rapidly?
osmotic demyelinating syndrome (ODS)
*What common BP medication should patients with hypercalcemia not take?
HCTZ (thiazides promote calcium reabsorption at kidneys)
*List hematological causes of high potassium
Cell death: Rhabdomyolysis, tumor lysis syndrome, massive hemolysis or transfusion, crush injury, burn
*What’s the difference between calcium chloride and calcium gluconate? What are 2 benefits to caCl in addition to 1 drawback?
- Contains 3 times as much calcium molecules in the same volume
- (but needs to be infused centrally),
- less volume needs to be given and therefore faster and easier;
- CaCl is a salt therefore dissociates right away and doesn’t need enzymatic cleavage by the liver
*What medications cause high potassium
Beta-blockers, acute digitalis overdose, succinylcholine, angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, nonsteroidal anti-inflammatory drugs (NSAIDs), spironolactone, amiloride, potassium supplementation
*How does Adrenal insufficiency cause hyperkalemia
Low aldosterone signals to kidneys to spit out sodium and fluid and to retain potassium