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31 Cards in this Set
- Front
- Back
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Alveolar Gas Equation
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** [ Simple equation ] :
7 x FiO2 (%) - CO2 x 10 / 8 = ( pAtm - pH2O) x FiO2 = ( 760 - 47 ) x FiO2 pAtm = atmospheric pressure pH2O = partial pressure of water vapour FiO2 = fraction inspired Oxygen |
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Arterial-alveolar ( Aa) Gradient
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= pAlvO2 - pArtO2
pAlvO2 = Calculated pArtO2 = Measured Normal = < Age/4 |
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Role of A-a gradient in Clinical decision making?
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Should be limited to situations where A-a gradient is MARKEDLY ABNORMAL
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Define the Anion Gap and the normal range.
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The concentration of unmeasured anions.
Anion = negative charge Measured anions = - Organic anions ( lactate ; ketoacids ) - Serum proteins - phosphate - Sulfate NORMAL RANGE = 12 (varies per source) |
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Define the importance of albumin in the Anion Gap calculation.
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AG = Na - HCO3 - CL + (40 - Albumin / 4)
- Albumin makes up most of anion gap - As albumin drops, the "normal range drops" - A low Albumin makes calculated anion gap "falsely low" " For every 10 g/L below the normal level of albumin, Add 2.5 to the anion gap ..." |
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Mnemonic for High Anion Gap Metabolic Acidosis.
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"CAT MUDPILES"
C arbon monoxide / Cyanide A lcohol / Alcoholic ketoacidosis T oluene M etformin / Methanol U raemia Diabetic Ketoacidosis Paracetamol / Paraldehyde / Propylene glycol Isoniazid / Iron Lactic Acidosis Ethylene glycol Salicylates |
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What are the formulas for compensation for a metabolic acidosis? (Expected PCO2)
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Respiratory Compensation:
** 1.5 x HCO3 + 8 +/- 2 Lowest possible CO2 = 12 ** For every 1 mmol/L reduction in HCO3 , PCO2 should decrease by 1.3 mmHg |
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What is the formula for corrected K+ with pH changes.
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** For every reduction in pH of 0.1 mmol/L
K+ deceases by 0.5 mmol/L Predicted K+ = (K+m) - [ ( 7.4 - pH ) x 5 ] Decreased pH = decreased K+ Increased H + = decreased K+ ** H+ and K+ compete for intracellular transport. |
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In regards to Lactic Acidosis, which of the following is Type A.
A. Isoniazid B. G6-PD deficiency C. Anaemia D. Diabetes |
C.
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List the conditions of a Type A Lactic acidosis.
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Tissue Hypoxia and Elevated lactate production:
1. Shock 2. Cardiac arrest 3. Hypoxia 4. Anaemia 5. Severe exercise |
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List the conditions of a Type B Lactic acidosis.
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Normal tissue oxygenation - impaired lactate utilisation.
1. B1 = Systemic disorders [ Sepsis ; Diabetes ; Renal Insufficiency ; Leukaemia ] 2. B2 = Substances [ Metformin ; Salicylates ; Methanol ; Iron ; Isoniazid ; Carbon monoxide ; Cyanide ; methaemoglobinaemia ] 3. B3 = Hereditary metabolic disorders [ G6-PD ] |
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Mnemonic for Non-anion gap metabolic acidosis.
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"HARDUPS"
Hyperalimentation Acetazolamide / Addison's ( Hypoaldosteronism ) Renal tubular acidosis ( RTA I , II , IV ) * Diarrhoea Uretero-pelivc shunt Post-hypocapnia (low CO2 ) * Saline (iatrogenic ) / Spironolactone |
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What are the primary electrolyte / metabolic losses / excesses associated with a normal anion gap metabolic acidosis?
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1. Loss of HCO3
2. Excess H+ intake 3. Decreased H + losses * Chloride is usually maintained. * RTA usually hyperchloraemic acidosis |
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What is the equation for corrected bicarbonate?
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Corrected Bicarbonate =
Anion Gap - 12 + HCO3 Corrected HCO3 > 30: underlying metabolic ALKALOSIS Corrected HCO3 < 23 = underlying metabolic acidosis |
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An Anion is positive or negatively charged?
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Anion = negative charge (-)
Cation = positive charge (+) |
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What is the mnemonic for a Metabolic Alkalosis?
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"CLEVER PD"
Contraction Licorice Endocrine ( Cushings / Conns) * Vomiting / NG suction Excess alkali Refeeding alkalosis Post hypercapnia * Diuretics * = Saline / Chloride responsive. |
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What are the compensatory equations for a metabolic alkalosis?
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* Last 2 digits of pH between 7.1 and 7.6
* 0.9 x HCO3 + 9 [Highest CO2 = 55 ] * For every 1 mmol/L increase in HCO3 , PCO2 should increase by 0.6 mmHg |
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What are the Main electrolyte / metabolic gains / losses with a metabolic alkalosis?
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1. Gain of HCO3
2. Loss of acid / Chloride |
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What are the Chloride responsive causes of metabolic alkalosis?
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1. Vomiting / Upper GI losses
2. Diuretics 3. Chloride wasting diseases [ CF ; Chloride enteropathy] Urine chloride < 10 Managed by replacing with NaCl |
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What are the Chloride "unresponsive" causes of metabolic alkalosis?
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1. Hyperaldosteronism [ Cushings ]
2. Renal artery stenosis 3. Renin secreting tumours 4. Exogenous mineralocorticoids [ Licorice ; fludrocortisone ] 5. Syndromes [ Gitelman's ; Bartter's ] Urine Chloride > 10 Manage the underlying cause |
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What is the mnemonic for an Acute Respiratory
Acidosis ? |
None
"Anything that causes HYPOVENTILATION" 1. CNS - Head trauma / CVA / Sedation (drugs) / Metabolic 2. Airway Obstruction - Foreign Body ; Laryngospasm ; Croup 3. Pulmonary - Pneumonia / Pulmonary oedema / Pleural effusion - COPD / Pulmonary fibrosis - pneumothorax - haemothorax 4. Neuromuscular - Myasthenia / Polio - Guillain Barre Syndrome (GBS) - Muscle relaxants / Venoms / Organophosphates |
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What are the compensatory equations for an acute respiratory acidosis?
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* CO2 : HCO3 ratio
Acute = 10:1 Chronic = 10:4 * For every 10mmHg increase in PCO2, HCO3 should increases by : 1mmol/L for acute 4 mmol/L for chronic |
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What are the conditions that causes a Respiratory Alkalosis?
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"Anything that causes Hyperventilation"
1. Sepsis 2. Salicylates 3. Hypoxia 4. CNS disease [ CVA ; Infection ; Tumour ] 5. Mechanical ventilators 6. Progesterone (Pregnancy) 7. Anxiety |
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What are the compensatory equations for Respiratory alkalosis?
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* CO2 : HCO3 ratio
Acute = 10: 2 Chronic = 10:4 * For every 10 mmHg decrease in PCO2, HCO3 should decrease by : 2 = acute 5 = chronic |
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What is the equation for corrected sodium in hyperglycaemia?
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Corrected Na+ =
Measured Na+ PLUS [ Glucose - 5 ] / 4 |
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What is the equation for the Osmolar Gap ?
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Osmolar Gap =Calculated - Measured osmolality
Calculated = Laboratory Measured = ( 2 x Na+) + Urea + Glucose + Ethanol Normal Osmolality = 285 - 295 mOsm/kg Normal Osmolar Gap = - 4 to 10 |
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What are the causes of an increased Osmolar Gap?
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1. Toxicological
- Toxic alcohols (Methanol ; Ethylene glycol ) - Lithium - Mannitol / Sorbitol 2. Non-Toxicological - DKA / AKA - Severe Lactic acidosis - Shock / Trauma / Burns - Chronic Renal Failure 3. Other - Laboratory error - Decreased Serum water content ( Hyperlipidaemia / Hyperproteinaemia) |
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Which is incorrect regarding Compensation for Metabolic Alkalosis?
A. Expected PCO2 = 0.9 x HCO3 + 9 B. For every 1 mmol/L increase in HCO3, PCO2 increases by 0.5 mmHg C. Expected PCO2 = Last 2 digits of pH between 7.1 and 7.6 D. PCO2 increase by 0.6 mmHg for every 1 mmol/L increase in HCO3. |
B.
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Which is correct regarding compensation for Respiratory Alkalosis?
A. For every 10mmHg decrease in PCO2, HCO3 should decrease by 2 (acute) and 4 (chronic). B. CO2 : HCO3 ratio for acute = 10: 1 C. CO2 : HCO3 ratio = 10: 2 for chronic. D. HCO3 decreases by 2 (acute) or 4 (chronic) for every 5 mmHg drop in PCO2. |
A.
B = 10: 2 C = 10: 4 D = 10 mmHg drop in PCo2 |
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Which is incorrect regarding the compensation for a respiratory acidosis ?
A. CO2 : HCO3 ratio = 10:1 for acute B. As PCO2 increases, compensation is via increased HCO3. C. The chronic compensation ratio for CO2 : HCO3 = 10:4 D. For every 10 mmHg increase in PCO2, HCO3 should increase by 4 mmol/L for acute and 5 for chronic. |
D. 1 mmol/L for acute and 4mmol/L for chronic.
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List the causes of a Low / reduced anion Gap.
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Present in conditions of increased unmeasured cations:
1. Calcium 2. Magnesium 3. Lithium Plus: 4. Multiple Myeloma ( + charged proteins) 5. Bromide 6. Iodine toxicity |
