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Adequate Compensation Metabolic Acidosis

Acid-base (anesthesia Text)

Acid-base (anesthesia Text)

There are four native buffer systems – bicarbonate, hemoglobin, protein, and phosphate systems. Bicarbonate has a pKa of 6.1, which is not ideal. Hemoglobin has histidine residues with a pKa of 6.8. Chemoreceptors in the carotid bodies, aortic arch, and ventral medulla respond to changes in pH/pCO2 in a matter of minutes. The renal response takes much longer. Arterial vs. Venous Gases Venous blood from the dorsum of the hand is moderately arterialized by general anesthesia, and can be used as a substitute for an ABG. pCO2 will only be off by ~ 5 mm Hg, and pH by 0.03 or 0.04 units [Williamson et. al. Anesth Analg 61: 950, 1982]. Confounding variables include air bubbles, heparin (which is acidic), and leukocytes (aka “leukocyte larceny”). VGB/ABG samples should be cooled to minimize leukocyte activity, however when blood is cooled, CO2 solubility increases (less volatile), and thus pCO2 drops. As an example – a sample taken at 37°C and at 7.4 will actually read as a pH of 7.6 if measured at 25°C. Most VBG/ABGs are actually measured at 37°C. A-aDO2 increases with age, as well as with increased FiO2 and vasodilators (which impair hypoxic pulmonary vasoconstriction). In the setting of a shunt, pulse oximetry can be misleading, thus the A-aDO2 should be calculated. If PaO2 is > 150 mm Hg (i.e., Hg saturation is essentially 100%), every 20 mm Hg of A-aDO2 represents 1% shunting of cardiac output. A/a is even better than A-aDO2 because it is independent of FiO2. PaO2/FiO2 is a reasonable alternative, with hypoxia defined as PaO2/FiO2 < 300 (a PaO2/FiO2 < 200 suggests a shunt fraction of 20% or more). Mixed venous blood should have a pO2 of ~ 40 mm Hg. Values < 30 mm Hg suggest hypoxemia, although one must always keep in mind that peripheral shunting and cyanide tox Continue reading >>

Respiratory Compensation

Respiratory Compensation

Metabolic Acidosis Respiratory compensation for metabolic disorders is quite fast (within minutes) and reaches maximal values within 24 hours. A decrease in Pco2 of 1 to 1.5 mm Hg should be observed for each mEq/L decrease of in metabolic acidosis.27 A simple rule for deciding whether the fall in Pco2 is appropriate for the degree of metabolic acidosis is that the Pco2 should be equal to the last two digits of the pH. For example, compensation is adequate if the Pco2 decreases to 28 when the pH is 7.28. Alternatively, the Pco2 can be predicted by adding 15 to the observed (down to a value of 12). Although reduction in Pco2 plays an important role in correcting any metabolic acidosis, evidence suggests that it may in some respects be counterproductive because it inhibits renal acid excretion. Fetoplacental Elimination of Metabolic Acid Load Fetal respiratory and renal compensation in response to changes in fetal pH is limited by the level of maturity and the surrounding maternal environment. However, although the placentomaternal unit performs most compensatory functions,3 the fetal kidneys have some, although limited, ability to contribute to the maintenance of fetal acid–base balance. The most frequent cause of fetal metabolic acidosis is fetal hypoxemia owing to abnormalities of uteroplacental function or blood flow (or both). Primary maternal hypoxemia or maternal metabolic acidosis secondary to maternal diabetes mellitus, sepsis, or renal tubular abnormalities is an unusual cause of fetal metabolic acidosis. Pregnant women, at least in late gestation, maintain a somewhat more alkaline plasma environment compared with that of nonpregnant control participants. This pattern of acid–base regulation in pregnant women is present during both resting and after maximal e Continue reading >>

Uncompensated, Partially Compensated, Or Combined Abg Problems

Uncompensated, Partially Compensated, Or Combined Abg Problems

Arterial Blood Gas (ABG) analysis requires in-depth expertise. If the results are not understood right, or are wrongly interpreted, it can result in wrong diagnosis and end up in an inappropriate management of the patient. ABG analysis is carried out when the patient is dealing with the following conditions: • Breathing problems • Lung diseases (asthma, cystic fibrosis, COPD) • Heart failure • Kidney failure ABG reports help in answering the following questions: 1. Is there acidosis or alkalosis? 2. If acidosis is present, whether it is in an uncompensated state, partially compensated state, or in fully compensated state? 3. Whether acidosis is respiratory or metabolic? ABG reports provide the following descriptions: PaCO2 (partial pressure of dissolved CO2 in the blood) and PaO2 (partial pressure of dissolved O2 in the blood) describe the efficiency of exchange of gas in the alveolar level into the blood. Any change in these levels causes changes in the pH. HCO3 (bicarbonate in the blood) maintains the pH of the blood within normal range by compensatory mechanisms, which is either by retaining or increasing HCO3 excretion by the kidney. When PaCO2 increases, HCO3 decreases to compensate the pH. The following table summarizes the changes: ABG can be interpreted using the following analysis points: Finding acidosis or alkalosis: • If pH is more it is acidosis, if pH is less it is alkalosis. Finding compensated, partially compensated, or uncompensated ABG problems: • When PaCO2 is high, but pH is normal instead of being acidic, and if HCO3 levels are also increased, then it means that the compensatory mechanism has retained more HCO3 to maintain the pH. • When PaCO2 and HCO3 values are high but pH is acidic, then it indicates partial compensation. It means t Continue reading >>

Metabolic Acidosis Treatment & Management: Approach Considerations, Type 1 Renal Tubular Acidosis, Type 2 Renal Tubular Acidosis

Metabolic Acidosis Treatment & Management: Approach Considerations, Type 1 Renal Tubular Acidosis, Type 2 Renal Tubular Acidosis

Metabolic AcidosisTreatment & Management Author: Christie P Thomas, MBBS, FRCP, FASN, FAHA; Chief Editor: Vecihi Batuman, MD, FASN more... Treatment of acute metabolic acidosis by alkali therapy is usually indicated to raise and maintain the plasma pH to greater than 7.20. In the following two circumstances this is particularly important. When the serum pH is below 7.20, a continued fall in the serum HCO3- level may result in a significant drop in pH. This is especially true when the PCO2 is close to the lower limit of compensation, which in an otherwise healthy young individual is approximately 15 mm Hg. With increasing age and other complicating illnesses, the limit of compensation is likely to be less. A further small drop in HCO3- at this point thus is not matched by a corresponding fall in PaCO2, and rapid decompensation can occur. For example, in a patient with metabolic acidosis with a serum HCO3- level of 9 mEq/L and a maximally compensated PCO2 of 20 mm Hg, a drop in the serum HCO3- level to 7 mEq/L results in a change in pH from 7.28 to 7.16. A second situation in which HCO3- correction should be considered is in well-compensated metabolic acidosis with impending respiratory failure. As metabolic acidosis continues in some patients, the increased ventilatory drive to lower the PaCO2 may not be sustainable because of respiratory muscle fatigue. In this situation, a PaCO2 that starts to rise may change the plasma pH dramatically even without a significant further fall in HCO3-. For example, in a patient with metabolic acidosis with a serum HCO3- level of 15 and a compensated PaCO2 of 27 mm Hg, a rise in PaCO2 to 37 mm Hg results in a change in pH from 7.33 to 7.20. A further rise of the PaCO2 to 43 mm Hg drops the pH to 7.14. All of this would have occurred whi Continue reading >>

Intro To Arterial Blood Gases, Part 2

Intro To Arterial Blood Gases, Part 2

Arterial Blood Gas Analysis, Part 2 Introduction Acute vs. Chronic Respiratory Disturbances Primary Metabolic Disturbances Anion Gap Mixed Disorders Compensatory Mechanisms Steps in ABG Analysis, Part II Summary Compensatory Mechanisms Compensation refers to the body's natural mechanisms of counteracting a primary acid-base disorder in an attempt to maintain homeostasis. As you learned in Acute vs. Chronic Respiratory Disturbances, the kidneys can compensate for chronic respiratory disorders by either holding on to or dumping bicarbonate. With Chronic respiratory acidosis: Chronic respiratory alkalosis: the kidneys hold on to bicarbonate the kidneys dump bicarbonate With primary metabolic disturbances, the respiratory system compensates for the acid-base disorder. The lungs can either blow off excess acid (via CO2) to compensate for metabolic acidosis, or to a lesser extent, hold on to acid (via CO2) to compensate for metabolic alkalosis. With Metabolic acidosis: Metabolic alkalosis: ventilation increases to blow off CO2 ventilation decreases to hold on to CO2 The body's response to metabolic acidosis is predictable. With metabolic acidosis, respiration will increase to blow off CO2, thereby decreasing the amount of acid in the blood. Recall that with metabolic acidosis, central chemoreceptors are triggered by the low pH and increase the drive to breathe. For now, it is only important to learn (qualitatively) that there is a predictable compensatory response to metabolic acidosis. Later, during your 3rd or 4th year rotations, you might learn how to (quantitatively) determine if the compensatory response to metabolic acidosis is appropriate by using the Winter's Formula. The body's response to metabolic alkalosis is not as complete. This is because we would need to hypov Continue reading >>

Metabolic Acidosis

Metabolic Acidosis

Patient professional reference Professional Reference articles are written by UK doctors and are based on research evidence, UK and European Guidelines. They are designed for health professionals to use. You may find one of our health articles more useful. See also separate Lactic Acidosis and Arterial Blood Gases - Indications and Interpretations articles. Description Metabolic acidosis is defined as an arterial blood pH <7.35 with plasma bicarbonate <22 mmol/L. Respiratory compensation occurs normally immediately, unless there is respiratory pathology. Pure metabolic acidosis is a term used to describe when there is not another primary acid-base derangement - ie there is not a mixed acid-base disorder. Compensation may be partial (very early in time course, limited by other acid-base derangements, or the acidosis exceeds the maximum compensation possible) or full. The Winter formula can be helpful here - the formula allows calculation of the expected compensating pCO2: If the measured pCO2 is >expected pCO2 then additional respiratory acidosis may also be present. It is important to remember that metabolic acidosis is not a diagnosis; rather, it is a metabolic derangement that indicates underlying disease(s) as a cause. Determination of the underlying cause is the key to correcting the acidosis and administering appropriate therapy[1]. Epidemiology It is relatively common, particularly among acutely unwell/critical care patients. There are no reliable figures for its overall incidence or prevalence in the population at large. Causes of metabolic acidosis There are many causes. They can be classified according to their pathophysiological origin, as below. The table is not exhaustive but lists those that are most common or clinically important to detect. Increased acid Continue reading >>

Arterial Blood Gas Analysis: Example Set 3

Arterial Blood Gas Analysis: Example Set 3

Step 2: The PCO2 is low (respiratory alkalosis) and the bicarbonate is low (metabolic acidosis). Therefore, the respiratory alkalosis is the primary process. Step 4: The metabolic acidosis is the compensatory process for the respiratory alkalosis. If you had measured the ABG immediately upon arrival, the bicarbonate would have been close to normal and the pH would have been much higher. This is because it takes several days for metabolic compensation to occur. A 65 year-old man with very severe COPD (FEV1 = 25% predicted) has an arterial blood gas done as part of routine pulmonary function testing to help determine if he requires home oxygen therapy. The sample shows PCO2 60 PO2 60 HCO3- 36. The anion gap is 8. Step 2: The PCO2 is high(respiratory acidosis) and the bicarbonate is high (metabolic alkalosis). Therefore, the respiratory acidosis is the primary process. Step 3: The serum anion gap is normal at 8. Step 4: The metabolic alkalosis is the compensatory process for the respiratory acidosis. This patient likely has chronic carbon dioxide retention due to his very severe COPD. Because this is a long-standing process, he has had adequate time for metabolic compensation to occur. A 40 year-old woman develops a severe case of diarrhea with multiple loose bowel movements over the course of a one-day period. When she presents to the ER, an arterial blood gas is obtained and shows Step 2: The PCO2 is low (respiratory alkalosis) and the bicarbonate is low (metabolic acidosis). Therefore, the metabolic acidosis is the primary process. Step 3: The serum anion gap is normal at 10. The metabolic acidosis from Step 2, therefore, is a non-gap acidosis. Step 4: The respiratory alkalosis is the compensatory process for the metabolic acidosis. The patients metabolic acidosis is l Continue reading >>

The Quick And Dirty Guide To Acid Base Balance | Medictests.com

The Quick And Dirty Guide To Acid Base Balance | Medictests.com

Your patient has a ph of 6.9 Is he acidic or alkalotic? Your patient has a ph of 7.4 Is he acidic or alkalotic? Your patient has a ph of 7.7 Is he acidic or alkalotic? Your patient has a ph of 7.25 Is he acidic or alkalotic? Your patient has a ph of 7.43 Is he acidic or alkalotic? Your patient has a ph of 8.0 Is he acidic or alkalotic? 1. acidic 2. normal 3. Alkaline 4. Acidic 5. Normal 6. Alkaline You take in oxygen by inhaling, your body turns oxygen into carbon dioxide, you exhale and remove the carbon dioxide from your body. Carbon dioxide is "respiratory acid."When you're not breathing adequately, you are not getting rid of this "respiratory acid" and it builds up in the tissues. The extra CO2 molecules combine with water in your body to form carbonic acid and makes your pH go up. This is bad. We can measure the amount of respiratory acid in the arterial blood using blood gases. They measure the amount of each gas in your blood. We measure the pH, the amount of carbon dioxide (PaCO2) and the amount of oxygen in the blood (PaO2). PaCO2 is the partial pressure of carbon dioxide. We can measure it to see how much respiratory acid (CO2) there is in the blood. We use arterial blood gas tests to check it. How much respiratory acid (CO2) should there be? The normal value is 35-45 mmHg (mmHg just means millimeters of mercury, its a measurement of pressure.) The (a) in PaCO2 just stands for arterial. If you measured venous blood gasses, the levels are different and PvCO2 is used. If CO2 is HIGH, it means there is a buildup of respiratory acids because he's not breathing enough CO2 away. If your pH is acidic, and your CO2 is HIGH, its considered respiratory acidosis. If CO2 is LOW, it means there are not enough respiratory acids because he's probably hyperventilating too mu Continue reading >>

How To Compute Expected Pco2 In Chronic Metabolic Acidosis ?

How To Compute Expected Pco2 In Chronic Metabolic Acidosis ?

How to compute PaCO2 during chronic metabolic acidosis? We dont have to compute for chronic metabolic acidosis (CMA) since the PaCO2 value in mmHg is equal to the two digits of the pH value For instance IF pH = 7.25, PaCO2 should be about 25 mmHg, With this formula, we can immediately focus on the respiratory compensation: If PaCO2 is significantly greater than 25 mmHg, the respiratory compensation is inadequate, thus a respiratory insufficiency is associated; If PaCO2 is largely lower than 25 mmHg, the respiratory is higher than CMA required, therefore a respiratory alkalosis is associated to CMA. Furthermore, according to the alveolar gas equation (Fi02 of 21%): Pa02 + PaCO2= 140 mmHg; in this case, in absence of pulmonary disease, PaO2 should be elevated, near 115 mmHg FG Brivet, FM Jacobs: Anomalies de lEquilibre Acido-basique dOrigine Mtabolique in Ranimation Mdicale ; Collge National des Enseignants de Ranimation Mdicale, Masson Paris 2009 PP 1356-1365. In the same way for ACUTE Metabolic Acidosis, instead of using Narinss formula: It is easier to use Schlichtigs formula: Delta PaCO2 (mmHg) = Standard base excess (2) Thus in case of acute metabolic acidosis, with the same value of pH (7.25) and an SBE of 18, for instance (SBE value being systematically reported by lab but rarely used.), PaC02 should be near 22 mmHg (40- 18). If PaCO2 value is greater than the expected value, respiratory compensation is inadequate, the patient is at risk of respiratory failure, whereas if PaCO2 is lower than 18 we can claim that a respiratory alkalosis is associated. With this approach I can say goodbye Mr. Davenport, you are too sophisticated for me at 5 in the morning 1/ Narins RG, Emmet M. Simple and mixed acid-base disorders: a practical approach. Medicine, 1980, 59: 161-167. Continue reading >>

Winters Formula For Metabolic Acidosis Compensation Calculator

Winters Formula For Metabolic Acidosis Compensation Calculator

Winters Formula for Metabolic Acidosis Compensation Calculator This Winters formula for metabolic acidosis compensation calculator checks metabolic and mixed acidosis cases and establishes the level of PCO2 compensation. Discover more about the formula used and the situations that require it below the form. How does this Winters formula for metabolic acidosis compensation calculator work? This is a tool designed to help clinicians and any medical personnel evaluate PCO2 compensation in connection with the level of bicarbonate [HCO3-]. The form is very simple to use and only requires inputting bicarbonate in mEq/L and press calculate. The result will be displayed as an interval with the lower and upper values of partial CO2 pressure in mmHg. The formula used by this metabolic acidosis compensation calculator is explained below: Which means the interval between: 1.5 x HCO3- + 6 and 1.5 x HCO3- + 10 As a rule of thumb, there is a 1.2 mmHg PCO2 reduction for every 1 mEq/L reduction of plasma bicarbonate but only to a minimum of 10 - 15 mmHg. Taking an example, it shows that in order to compensate for a plasma concentration of HCO3- of 9 mEq/L it would be required a partial pressure of CO2 between 19.5 and 23.5 mmHg. The patients data is then compared to the computed value: If the value retrieved in patients data corresponds, this means that the respiratory compensation is adequate. If the value is higher this is indicative of primary respiratory acidosis and if the value is lower than the calculated value, it is indicative of primary respiratory alkalosis. However, the Winters formula is used mostly for metabolic acidosis and in the second case a different set of equations should be used as provided below: PCO2 = 0.7 x HCO3- + 20 +/- 5 mmHg meaning the interval between 0.7 Continue reading >>

Physiology, Acidosis, Metabolic

Physiology, Acidosis, Metabolic

Acid-base disorders, including metabolic acidosis, are disturbances in the homeostasis of plasma acidity. Any process that increases the serum hydrogen ion concentration is a distinct acidosis. The term acidemia is used to define the total acid-base status of the serum pH. For example, a patient can have multiple acidoses contributing to a net acidemia.Its origin classifies acidosis as either a respiratory acidosis which involves changes in carbon dioxide, or metabolic acidosis which is influenced by bicarbonate (HCO3). Metabolic acidosis is characterized by an increase in the hydrogen ion concentration in the systemic circulation resulting in a serum HCO3 less than 24 mEq/L. Metabolic acidosis is not a benign condition and signifies an underlying disorder that needs to be corrected to minimize morbidity and mortality. The many etiologies of metabolic acidosis are classified into 4 main mechanisms: increased production of acid, decreased excretion of acid, acid ingestion, and renal or gastrointestinal (GI) bicarbonate losses. Determining the type of metabolic acidosis can help clinicians narrow down the cause of the disturbance. Acidemia refers to a pH less than the normal range of 7.35 to 7.45. In addition, metabolic acidosis requires a bicarbonate value less than 24 mEq/L. Further classification of metabolic acidosis is based on the presence or absence of an anion gap, or concentration of unmeasured serum anions. Plasma neutrality dictates that anions must balance cations to maintain a neutral charge. Therefore, sodium(Na), the primary plasma cation, is balanced by the sum of the anions bicarbonate and chloride in addition to the unmeasured anions, which represent the anion gap. Unmeasured anions include lactate and acetoacetate, and these are often some of the main Continue reading >>

Bun, Glucose, Creatinine

Bun, Glucose, Creatinine

Normal Values pH = 7.38 - 7.42 [H+] = 40 nM/L for a pH of 7.4 PaCO2 = 40 mm Hg [HCO3] = 24 meq/L Acid base definitions Acid base disorder is considered present when there is abnormality in HCO3 or PaCO2 or pH. Acidosis and alkalosis refer to in-vivo derangement's and not to any change in pH. Acidemia (pH < 7.38) and Alkalemia (pH >7.42) refer to derangement's of blood pH. Kidney and Respiratory system play a key roles in maintaining the acid base status. Primary Acid base disorders Metabolic acidosis loss of [HCO3] 0r addition of [H+] Metabolic alkalosis loss of [H+] or addition of [HCO3] Respiratory acidosis increase in pCO2 Respiratory alkalosis decrease in pCO2 Recquired lab values/information Arterial blood gases: pH, PaCO2,PaO2,Sat,CO BUN, Glucose, Creatinine FIO2 and Clinical history Anion and Cations ANIONS CATIONS Chloride Sodium Bicarbonate(Total CO2) Potassium Proteins Calcium Organic acids Magnesium Phosphates Sulfates Electrochemical balance means that the total anions are the same as total Cations. For practical purposes anion gap is calculated using only Sodium, Chlorides and Total CO2.((140-(104+24)) = 12. Compensatory measures Buffering---occurs immediately Respiratory regulation of pCO2 is intermediate (12-24 hours) Renal regulation of [H] and [HCO3] occurs more slowly (several days) Extracellular almost entirely through bicarbonate whose concentration highest of all buffers small contribution from phosphate Intracellular Hemoglobin can directly buffer protons H+ entry into RBC matched by exit of Na and K+ Hemoglobin can directly buffer dissolved intracellular conversion of Buffer systems Hemoglobin can directly buffer protons H+ entry into RBC matched by exit of Na and K+ Hemoglobin can directly buffer dissolved intracellular conversion of Bicarbonate Continue reading >>

Assessment Of Compensation: Boston And Copenhagen Methods - Deranged Physiology

Assessment Of Compensation: Boston And Copenhagen Methods - Deranged Physiology

Assessment of Compensation: Boston and Copenhagen Methods This page acts as a footnote to the "Boston vs. Copenhagen" chapter from Acid-Base Physiology by Kerry Brandis. The aforementioned chapter in my opinion remains the definitive resource on the topic. Brandis' chapter explores the epistemology of acid-base interpretation systems by means of which we might be able to determine whether a patient has a single or mixed acid base disorder; i.e. whether there is a purely metabolic or a purely respiratory disturbance, or some mixture of the two. As it happens, there are two well-accepted systems for doing this, each with its own merits and demerits. These are the Boston and Copenhagen methods of acid-base interpretation. There is also another not-so-well accepted system, the physicochemical method proposed by Peter Stewart - which possess a satisfying explanatory power as an instrument of academic physiology. Unfortunately, it is rather complicated, and difficult to apply at the bedside. Furthermore, there does not seem to be much of a difference in hard outcomes, regardless of which system one uses. Thus, this chapter will focus on the Boston and Copenhagen systems, which have equivalent validity as far as acid-base interpretation is concerned. "Which is the system I need to rote-learn to pass my primaries?" Such a question is expected from the fairweather intensivist, who will flee from the ICU as soon as a position opens in a more cushy training program. For the rest, one might remark that these analytical tools are all in common use, and any sufficiently advanced ICU trainee is expected to be intimately familiar with all of these systems. However, the time-poor exam candidate may need to focus their attention on the area which would yield the greatest number of marks Continue reading >>

Acid Base Disorders

Acid Base Disorders

Arterial blood gas analysis is used to determine the adequacy of oxygenation and ventilation, assess respiratory function and determine the acid–base balance. These data provide information regarding potential primary and compensatory processes that affect the body’s acid–base buffering system. Interpret the ABGs in a stepwise manner: Determine the adequacy of oxygenation (PaO2) Normal range: 80–100 mmHg (10.6–13.3 kPa) Determine pH status Normal pH range: 7.35–7.45 (H+ 35–45 nmol/L) pH <7.35: Acidosis is an abnormal process that increases the serum hydrogen ion concentration, lowers the pH and results in acidaemia. pH >7.45: Alkalosis is an abnormal process that decreases the hydrogen ion concentration and results in alkalaemia. Determine the respiratory component (PaCO2) Primary respiratory acidosis (hypoventilation) if pH <7.35 and HCO3– normal. Normal range: PaCO2 35–45 mmHg (4.7–6.0 kPa) PaCO2 >45 mmHg (> 6.0 kPa): Respiratory compensation for metabolic alkalosis if pH >7.45 and HCO3– (increased). PaCO2 <35 mmHg (4.7 kPa): Primary respiratory alkalosis (hyperventilation) if pH >7.45 and HCO3– normal. Respiratory compensation for metabolic acidosis if pH <7.35 and HCO3– (decreased). Determine the metabolic component (HCO3–) Normal HCO3– range 22–26 mmol/L HCO3 <22 mmol/L: Primary metabolic acidosis if pH <7.35. Renal compensation for respiratory alkalosis if pH >7.45. HCO3 >26 mmol/L: Primary metabolic alkalosis if pH >7.45. Renal compensation for respiratory acidosis if pH <7.35. Additional definitions Osmolar Gap Use: Screening test for detecting abnormal low MW solutes (e.g. ethanol, methanol & ethylene glycol [Reference]) An elevated osmolar gap (>10) provides indirect evidence for the presence of an abnormal solute which is prese Continue reading >>

More Abg Examples - Resus

More Abg Examples - Resus

This is an elderly man with vomiting for 3 days, who presents with tachycardia. It would be expected that there be a metabolic alkalosis with loss of gastric contents. His pH shows an alkalosis and he has raised bicarb. He is hypokalaemic and hypocloraemic, with a raised BSL. The Na is low, when corrected for increased BSL it is 134. With this metabolic alkalosis the expected pCO2 is (0.9 x HCO3) + 16 = 43. The actual pCO2 is 28.5. Therefore this is a mixed picture ofMetabolic and Respiratory Alkalosis i.e.,he has his metabolic alkalosis but is also breathing up more than he should. Expected Aa gradient is age/4 +4 = 22.5 so a very high Aa gradient indicating a V/Q mismatch, or diffusion defect. So when we think of causes, take both things into account- the vomiting and the Aa. Pneumonia(although afebrile- elderly may be) A 21 year old man is brought in by his father with a one week history of vomiting. He has not been able to keep any food down. He has been diagnosed with Hashimotos thyroiditis by his local doctor 4 months previously. Today his blood pressure is 90/48 and pulse rate 104. These are his venous blood gas results: Is it acidosis or alkalosis? ACIDOSIS What is the primary cause? Given the low HCO3 and the not so high pCO2 it isMETABOLIC ACIDOSIS. Expected pCO2 is [(1.5xHCO3) +8]+2 i.e.., [(~30) + 8]+2 = 38-39 sothere is adequate compensation Na -(Cl + HCO3) = 108-(72 + 19) = 17 so raised anion gap metabolic acidosis. (reference is 8-16) Is there any other process going on? Look at the delta gap. change in AG/change in HCO3 = 17-12(use 12 as the expected AG)/24-19(24 is the expected HCO3) = 5/5 = 1 so this is a pure anion gap metabolic acidosis. ( Given what I say below, I might have also expected a normal anion gap metabolic acidosis) The Na is very low an Continue reading >>

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