share
play prev play next
play fullscreen
1 / 61
Sıra DOSYA ADI Format Bağlantı
01. Changes Bicarbonate Anion Disorder ppt Sunumu İndir

Transkript

[1]
Introduction to acid-baseJoel Topf, M.D.Assistant Clinical Professor of MedicineOakland University William Beaumont School of Medicinehttp://www.pbfluids.com
[2]
[3]
[4]
Getting acid-base• Acid base physiology is the regulation of hydrogen ion concentration• A normal hydrogen concentration is 40 nmol/L• This is .00004 mmol/L So• It is measured on a negative log scale called pH, normal is 7.440 nanomol/L = 0.00004 milimol/L Every change of 0.3 pH units represents a change in H+ by a factor of 2
[5]
Grand mal seizureIs this patient sick?pH = 6.8Methanol toxicity
[6]
It’s the disease, stupid.• Hydrogen ion concentration can dramatically impact protein structure and enzyme function.• The absolute pH is less important than the etiology of the acid-base disturbance.
[7]
Since the disease is important• It is imperative to rapidly assess the cause of an acid-base disturbance.• Using an arterial blood gas and an electrolyte panel, one can quickly classify a patient’s primary and compensatory acid-base physiology.• Patients may have multiple, simultaneous acid-base disorders. This should be determined.
[8]
Determine the primary Acid-Base disorderMetabolic acidosisMetabolic alkalosisRespiratory acidosisRespiratory alkalosisDetermine the anion gapNon-Anion gap Anion gapDetermine the osmolar gapDetermine the bicarbonate beforeOsmolar gap Non-osmolar gapPre-existing met. alkalosis Pre-existing NAGMA No pre-existing acid-base disordersDetermine the urinary anion gapPositive gap (RTA)Negative gap (GI, IVF)Winter’s formula⅓ the Δ HCO3 1:10 acute3:10 chronic2:10 acute4:10 chronicDetermine if the compensation is appropriateIs there an anion gap? If there is then there is a metabolic acidosis, regardless of pH or HCO3
[9]
Step 1: determine the primary disorder
[10]
The Henderson-Hasselbalch formula is the mantra of acid-base physiology
[11]
There are 4 primary ways that pH can changeIncrease in HCO3, increases pH. Metabolic alkalosis
[12]
There are 4 primary ways that pH can changeIncrease in HCO3, increases pH. Metabolic alkalosisDecrease in HCO3, decreases pH. Metabolic acidosis
[13]
There are 4 primary ways that pH can changeIncrease in HCO3, increases pH. Metabolic alkalosisDecrease in HCO3, decreases pH. Metabolic acidosisIncrease in pCO2, decreases pH. Respiratory acidosis
[14]
There are 4 primary ways that pH can changeIncrease in HCO3, increases pH. Metabolic alkalosisDecrease in HCO3, decreases pH. Metabolic acidosisIncrease in pCO2, decreases pH. Respiratory acidosisDecrease in pCO2, increases pH. Respiratory alkalosis
[15]
• In respiratory disorders, the kidney modifies the serum bicarbonate to return pH toward normal.Patients with primary acid-base disorders compensate to restore normal pH.• In metabolic disorders, breathing is altered to change the pCO2 in order to return pH toward normal.
[16]
Compensation minimizes changes in pHIncreased HCO3, increases pH.Increased CO2 compensates to reduce the change in pH.
[17]
Compensation minimizes changes in pHDecreased HCO3, decreases pH.Decreased CO2 compensates to reduce the change in pH.
[18]
Compensation minimizes changes in pHIncreased CO2, decreases pH.Increased HCO3 compensates to reduce the change in pH.
[19]
Compensation is always in the same direction as the primary disorder.pCO2HCO3Metabolic acidosispCO2HCO3Metabolic alkalosisHCO3pCO2Respiratory acidosisHCO3pCO2Respiratory alkalosisPrimary Compensation
[20]
If all three variables move in the same direction the disorder is metabolic; Primary CompensationpCO2HCO3Metabolic acidosispCO2HCO3Metabolic alkalosisHCO3pCO2Respiratory acidosisHCO3pCO2Respiratory alkalosispHif they move in discordant directions it is respiratory
[21]
Determine the primary disorder1. Acidosis or alkalosis– If the pH is less than 7.4 it is acidosis– If the pH is greater than 7.4 it is alkalosis2. Determine if it is respiratory or metabolic– If the pH, bicarbonate and pCO2 all move in the same direction (up or down) it is metabolic– If the pH, bicarbonate and pCO2 move in discordant directions (up and down) it is respiratorypH / pO2 / pCO2 / HCO3
[22]
Determine the primary disorder1. Acidosis or alkalosis– If the pH is less than 7.4 it is acidosis– If the pH is greater than 7.4 it is alkalosis2. Determine if it is respiratory or metabolic– If the pH, bicarbonate and pCO2 all move in the same direction (up or down) it is metabolic– If the pH, bicarbonate and pCO2 move in discordant directions (up and down) it is respiratory7.2 / 78 / 25 / 16pH / pO2 / pCO2 / HCO3 the pH is less than 7.4 it is ac dosis he pH, bicarbonate and pCO2 all move in the same direction (up or down) it is metabolic do n) it is respiratoryMetabolic Acidosis
[23]
1. Respiratory acidosis2. Metabolic acidosis3. Respiratory alkalosis4. Respiratory alkalosis7.5 / 55 / 24 / 22pH / pO2 / pCO2 / HCO3alosisM tabolic alkalosisiratory acido isiratory alkalo isRespiratory alkalosisDetermine the primary disorder
[24]
Now let’s do some questions
[25]
Determine the primary Acid-Base disorderMetabolic acidosisMetabolic alkalosisRespiratory acidosisRespiratory alkalosisWinter’s formula⅓ the Δ HCO3 1:10 acute3:10 chronic2:10 acute4:10 chronicDetermine if the compensation is appropriateStep 2: is there the correct degree of compensation?
[26]
• The direction of the compensation is always in the same direction as the primary disorder.• The magnitude of the compensation is determined solely by the magnitude of the primary disorder.– If, in a case of metabolic acidosis, the bicarbonate falls to 10 then the pCO2 should fall to 23±2 to compensate.– If the pCO2 is not in that range a second primary disorder is present• If the pCO2 is less than 21, then the patient also has a respiratory alkalosis• If the pCO2 is over 25, the patient has an additional respiratory acidosis
[27]
• Each primary acid base disorder has its own formula for prediction:– Metabolic acidosis: Winter’s Formula• 1.5 × HCO3 + 8 ± 2– Metabolic alkalosis: • pCO2 rises 0.7 per mmol rise in HCO3– Respiratory acidosis: • 1 or 3 mmol rise in HCO3 for 10 rise in pCO2– Respiratory alkalosis: • 2 or 4 mmol fall in HCO3 for 10 fall in pCO2
[28]
Predicting pCO2 in metabolic acidosis• In metabolic acidosis the expected pCO2 can be estimated from the HCO3Expected pCO2 = (1.5 x HCO3) + 8 ± 2• If the pCO2 is higher than predicted then there is an addition respiratory acidosis• If the pCO2 is lower than predicted there is an additional respiratory alkalosis
[29]
• Example:– Expected pCO2 = (1.5 x HCO3) + 8 ±2– Expected pCO2 = 18-22– Actual pCO2 is 19, which is within the predicted range, indicating a simple metabolic acidosisPredicting pCO2 in metabolic acidosis7.23 / 78 / 19 / 8 pH / pO2 / pCO2 / HCO3
[30]
• Example:– Expected pCO2 = (1.5 x HCO3) + 8 ±2– Expected pCO2 = 24-28– Actual pCO2 is 34, which is above the predicted range, indicating an additional respiratory acidosisPredicting pCO2 in metabolic acidosis7.15 / 112 / 34 / 12 pH / pO2 / pCO2 / HCO3
[31]
Predicting pCO2 in metabolic alkalosis• In metabolic acidosis the expected pCO2 can be estimated from the HCO3pCO2 should rise 0.7 for every increase in HCO3 of one, ±27.46 / 78 / 49 / 34 pH / pO2 / pCO2 / HCO3Example:– HCO3 is 34-24 = 10 above normal, so pCO2 should be 7 over normal, 47±2– Actual pCO2 is 49, which is within the predicted range, indicating a simple metabolic alkalosis
[32]
Respiratory disorders• Metabolic compensation for respiratory acid-base disorders is slow.• So the predicted bicarbonate needs to be calculated for pre-compensation, called acute, and after compensation, called chronic.– Chronic compensation is complete so the pH will be closer to normal at the expense of increased alteration of serum bicarbonate.
[33]
Why is metabolic compensation slow?• The lungs ventilate 12 moles of acid per day as carbon dioxide• The kidneys excrete less than 0.1 mole of acid per day as ammonia, phosphate and free hydrogen ions• The high excretion capacity of the lungs relative to the kidneys means that metabolic disorders are rapidly compensated by the lungs while respiratory disorders take hours to days for compensation by the kidneys.
[34]
• Example:• pCO2 is 38 above normal, so – if the condition is acute the HCO3 should be 28±2– If the condition is chronic the HCO3 should be 35 ±2– Actual HCO3 is 30, which is within the predicted range, for acute respiratory acidosis and outside of the range for chronic.Respiratory acidosisFor every increase in pCO2 of 10 mmHg the bicarbonate should increase:• 1 mEq/L in acute • 3 mEq/L in chronic 7.19 / 78 / 78 / 30 pH / pO2 / pCO2 / HCO3
[35]
• Example:• pCO2 is 15 below normal, so – If the condition is acute the HCO3 should be decreased by 3 or 21±2– If the condition is chronic the HCO3 should be decreased by 6 or 18 ±2Respiratory alkalosisFor every decrease in pCO2 of 10 mmHg the bicarbonate should decrease:• 2 mEq/L in acute • 4 mEq/L in chronic 7.44 / 78 / 25 / 17 pH / pO2 / pCO2 / HCO3
[36]
Summary of metabolic compensation for respiratory acid-base disordersRespiratory acidosisRespiratory alkalosis10:1 10:210:3 10:4For every rise of 10 in the pCO2 the HCO3 will rise by 1 or 3For every fall of 10 in pCO2 the HCO3 will fall by 2 or 4.PCO2 : HCO3AcuteChronic
[37]
Now let’s do some questions
[38]
Determine the primary Acid-Base disorderMetabolic acidosisMetabolic alkalosisRespiratory acidosisRespiratory alkalosisDetermine the anion gapNon-Anion gap Anion gapWinter’s formula⅓ the Δ HCO3 1:10 acute3:10 chronic2:10 acute4:10 chronicDetermine if the compensation is appropriateStep 3: if you have metabolic acidosis, is there an anion gap?
[39]
What is the anion?• Metabolic acidosis is further evaluated by determining the anion associated with the increased H+ cationIt is either chloride Or it is not chloride• These can be differentiated by measuring the anion gap.Non-Anion Gap Met Acid Anion Gap Met Acid
[40]
Anion gap=
[41]
Anion gap=
[42]
Calculating the anion gap• Anion gap = Na – (HCO3 + Cl)• Normal is 12– Varies by hospital– Average anion gap in healthy controls is 6 ±3• Improving chloride assays have resulted in increased chloride levels and a decreased normal anion gap.
[43]
Other causes of a low anion gap• Increased chloride– Hypertriglyceridemia– Bromide– Iodide• Decreased “Unmeasured anions”– Albumin– Phosphorous• Increased “Unmeasured cations”– Hyperkalemia– Hypercalcemia– Hypermagnesemia– Lithium– Increased cationic paraproteins• IgGAlbuminPhosIgAChlorideBicarbSodiumPotassiumCalciumMagnesiumIgGNormalaniongap
[44]
7.38 / 212 / 27 / 16• Metabolic or RespiratoryEvaluate the ABG• Acidosis or Alkalosisi osis or Alkalosistabolic or Respiratory• Anion gap or Non-Anion Gapion gap or Non-Anion • Predicted pCO2 (16 x 1.5) + 8 ±2 = 30-34• Anion gap 144 – (110 + 16) = 18• Isolated metabolic acidosis? No. There is concomitant respiratory alkalosis. pH / pO2 / pCO2 / HCO3144 110 3.4 16
[45]
The anion gap acidosis• Uremia (mild)• Ingestions– Methanol– Ethylene glycol• Ketoacidosis– DKA– Starvation– Alcoholic• Sepsis• L-Lactic acidosis– Salicylate intoxication– Ischemia– Cyanide intoxication• Nitroprusside– Malignancy– Metformin– Liver failure– Thiamine deficiency• D-Lactic acidosis• Pyroglutamic acidosis
[46]
GOLDMARK• The classic mnemonic, MUD PILES, sucks. The new mnemonic is GOLD MARK. Know it.• G Glycols• O Oxoproline: Pyroglutamic• L L-lactic acidosis• D D-Lactic acidosis• M Methanol• A Aspirin• R Renal failure• K KetoacidosisAN Mehta, JB Emmett , M Emmett, Lancet, 372, 9642, p 892, 2008
[47]
Now let’s do some questions
[48]
Determine the primary Acid-Base disorderMetabolic acidosisMetabolic alkalosisRespiratory acidosisRespiratory alkalosisDetermine the anion gapNon-Anion gap Anion gapDetermine the osmolar gapOsmolar gap Non-osmolar gapWinter’s formula⅓ the Δ HCO3 1:10 acute3:10 chronic2:10 acute4:10 chronicDetermine if the compensation is appropriateStep 4: if you have an AGMA, is there an osmolar gap?
[49]
Osmolar gap• In the presence of a large anion gap (>20-25) of undetermined etiology you must rule out a toxic alcohol.– Methanol– Ethylene Glycol• The low molecular weight of the alcohols means that modest ingestions have a relatively large impact on the serum osmolality• Few grams equals many milimoles• Molecular weights• Methanol: 32• Ethylene Glycol: 62• Acetaminophen: 151• Phenytoin 252
[50]
Osmolar gap• Their presence can be detected by comparing the measured osmolality (which includes the alcohol) to a calculated osmolality (which does not account for the alcohol).• If the measured osmolality is significantly more (>10) than the calculated osmolality you have an osmolar gap.€ Calculated osmolality = (2 × Na) +BUN2.8+Glucose18+Ethanol3.7
[51]
7.16 / 212 / 22 / 8• Metabolic or RespiratoryQuestion 4: evaluate the ABG• Acidosis or Alkalosisi osis or Alkalosistabolic or Respiratory• Anion gap or Non-Anion Gapion gap or • Predicted pCO2 (8 x 1.5) + 8 ±2 = 18-22Anion gap142 – (110 + 8) = 24• Isolated metabolic acidosis? Yes. There is no concomitant respiratory disorder. pH / pO2 / pCO2 / HCO3142 110 46 5.4 8 2.2Serum Osmolality: 312 Osmolar gapCalc Osmolality (2 x 142) + 46/2.8 + 88/18 = 284 + 16 + 5 = 305 Osmolality Gap 312 – 305 = 7• Osmolar gap or Non-Osmolar Gap-Osmolar Gap88
[52]
No metabolic acidosisNo anion gapTrue positiveOsmolar gap is not specific• Elevated osmolar gap will be found with:– Ethylene glycol– Methanol– Isopropyl alcohol– Ketoacidosis– Lactic acidosis– Mannitol infusion– Hypertriglyceridemia
[53]
Now let’s do some questions
[54]
Determine the primary Acid-Base disorderMetabolic acidosisMetabolic alkalosisRespiratory acidosisRespiratory alkalosisDetermine the anion gapNon-Anion gap Anion gapDetermine the osmolar gapDetermine the bicarbonate beforeOsmolar gap Non-osmolar gapPre-existing met. alkalosis Pre-existing NAGMA No pre-existing acid-base disordersWinter’s formula⅓ the Δ HCO3 1:10 acute3:10 chronic2:10 acute4:10 chronicDetermine if the compensation is appropriateStep 5: if you have an AGMA, determine what the bicarbonate was before the anion gap
[55]
• If you have an anion gap metabolic acidosis the anion gap should increase as the bicarbonate falls.The acid-base time machine=• Assume that the loss of bicarbonate due to addition of an anion is roughly 1:1• So for every increase in the anion gap of one the bicarbonate should drop by one
[56]
• Assume that the loss of bicarbonate due to addition of an anion is roughly 1:1• So for every increase in the anion gap of one the bicarbonate should drop by oneHCO3 before = HCO3 now + (AGcurrent – AGnormal)The acid-base time machine∆ HCO3 = ∆ Anion GapHCO3 before – HCO3 now = AGcurrent – AGnormal
[57]
7.14 / 212 / 18 / 6• Metabolic or RespiratoryEvaluate:• Acidosis or Alkalosisi osis or Alkalosistabolic or Respiratory• Anion gap or Non-Anion Gapion gap or Non-Anion • Predicted pCO2 (8 x 1.5) + 8 ±2 = 18-22• Anion gap 134 – (104 + 8) = 22• Isolated metabolic acidosis? Yes. pH / pO2 / pCO2 / HCO3134 104 3.4 8• Additional metabolic disorder?• Bicarbonate prior to anion gap HCO3 + (AG – 12) = HCO3 before 8 + (22 – 12) = 18 Yes. Non-anion gap metabolic acidosis
[58]
Now let’s do some questions
[59]
Most common error in acid-basePersonal observation
[60]
AE• 66 yo white male• PMHx DM, paraplegia 2° MVA• Klebsiella urosepsis induced ARF• Blood Cxrs + for Klebsiella
[61]
• 8/16/04139 107 315.4 20 1.2• 8/26/04138 104 384.4 21 1.9• 8/28/04137 108 533.8 16 2.9– Start oral bicarbonate• 8/29/04139 111 563.9 14 2.8– Start bicarbonate gtt• 8/30/04137 104 623.5 22 3.0• 7.52 / 31 / 46 / 25alkalosisRespiratoryPredicted HCO3: Acute: 23 Chronic: 21