Sandbox: sadaf
Acid Base Disorders
Blood Gas Analysis
Blood gas analysis | Vessel | Range | Interpretation |
---|---|---|---|
Oxygen Partial Pressure (pO2) | Arterial | 80 to 100 mmHg | Normal |
<80 mmHg | Hypoxia | ||
Venous | 35 to 40 mmHg | Normal | |
Oxygen Saturation (SO2) | Arterial | >95% | Normal |
<95% | Hypoxia | ||
Venous | 70 to 75% | Normal | |
pH | Arterial | <7.35 | Acidemia |
7.35 to 7.45 | Normal | ||
>7.45 | Alkalemia | ||
Venous | 7.26 to 7.46 | Normal | |
Carbon Dioxide Partial Pressure (pCO2) | Arterial | <35 mmHg | Low |
35 to 45 mmHg | Normal | ||
>45 mmHg | High | ||
Venous | 40 to 45 mmHg | Normal | |
Bicarbonate (HCO3−) | Arterial | <22 mmol/L | Low |
22 to 26 mmol/L | Normal | ||
>26 mmol/L | High | ||
Venous | 19 to 28 mmol/L | Normal | |
Base Excess (BE) | Arterial | <−3.4 | Acidemia |
−3.4 to +2.3 mmol/L | Normal | ||
>2.3 | Alkalemia | ||
Venous | −2 to −5 mmol/L | Normal | |
Osmolar gap = Osmolality – Osmolarity | >10 | Abnormal | |
Anion gap = [Na+] – {[Cl−]+[HCO3−]}
Corrected AG = (measured serum AG) + (2.5 x [4.5 − Alb]) |
<8 | Low | |
8 to 16 | Normal | ||
>16 | High |
Compensation
- There are compensation mechanisms in the body in order to normalizing the pH inside the blood.[1]
- The amount of compensation depends on proper functioning of renal and respiratory systems. However, it is uncommon to compensate completely. Compensatory mechanisms might correct only 50–75% of pH to normal.
- Acute respiratory compensation usually occurs within first day. However, chronic respiratory compensation takes 1 to 4 days to occur.
- Renal compensation might occur slower than respiratory compensation.
Primary disorder | pH | PaCO2 | [HCO3−] | Compensation | Compensation formula |
---|---|---|---|---|---|
Metabolic acidosis | ↓ | ↓ | ↓ | Respiratory |
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Metabolic alkalosis | ↑ | ↑ | ↑ | Respiratory |
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Respiratory acidosis | ↓ | ↑ | ↑ | Renal |
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Respiratory alkalosis | ↑ | ↓ | ↓ | Renal |
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Approach to acid–base disorders
Check pH on ABG | |||||||||||||||||||||||||||||||||||||||||
pH < 7.35= Acidosis | pH > 7.45= Alkalosis | ||||||||||||||||||||||||||||||||||||||||
Check PaCO2 | |||||||||||||||||||||||||||||||||||||||||
PaCO2 > 45mm Hg = Respiratory acidosis | PaCO2 Normal or < 35mm Hg = Metabolic acidosis | Check PaCO2 | |||||||||||||||||||||||||||||||||||||||
PaCO2 > 45mm Hg = Metabolic alkalosis | PaCO2 < 35mm Hg = Respiratory alkalosis | ||||||||||||||||||||||||||||||||||||||||
[HCO3-] > 29 | Check [HCO3-] | ||||||||||||||||||||||||||||||||||||||||
Normal or slight decrease = Acute respiratory alkalosis | Decreased < 24 = Chronic respiratory alkalosis | ||||||||||||||||||||||||||||||||||||||||
Management of Acidosis
pH < 7.35 | |||||||||||||||||||||||||||||||||||||||||||||||||||
Acidosis | |||||||||||||||||||||||||||||||||||||||||||||||||||
Determine the primary disorder Metabolic or respiratory? | |||||||||||||||||||||||||||||||||||||||||||||||||||
Check [HCO3-] and PaCO2 | |||||||||||||||||||||||||||||||||||||||||||||||||||
Low [HCO3-] and Low to normal PaCO2 | High PaCO2 and High to normal [HCO3-] | ||||||||||||||||||||||||||||||||||||||||||||||||||
Metabolic acidosis | Respiratory acidosis | ||||||||||||||||||||||||||||||||||||||||||||||||||
Check for respiratory compensation Calculate expected PCO2 | Check for renal compensation Calculate expected [HCO3-] | ||||||||||||||||||||||||||||||||||||||||||||||||||
Decrease in PaCO2=1.25 x (24- measured HCO3-)? | Acute acidosis? Increase [HCO3-]=0.1 x (measure PaCO2-40)? | Chronic acidosis? Increase [HCO3-]=0.1 x (measure PaCO2-40)? | |||||||||||||||||||||||||||||||||||||||||||||||||
PaCO2 too low? Mixed metabolic acidosis with respiratory alkalosis | PaCO2 too high? Mixed metabolic acidosis with respiratory acidosis | [HCO3-] too low? Mixed respiratory acidosis with metabolic acidosis | [HCO3-] too high? Mixed respiratory acidosis with metabolic alkalosis | [HCO3-] too low? Mixed respiratory acidosis with metabolic acidosis | E04=[HCO3-] too high? Mixed respiratory acidosis with metabolic alkalosis | ||||||||||||||||||||||||||||||||||||||||||||||
Measured PaCO2 is equal to expected value? Compensated metabolic acidosis | Measured [HCO3-] is equal to expected value? Compensated respiratory acidosis | Measured [HCO3-] is equal to expected value? Compensated respiratory acidosis | |||||||||||||||||||||||||||||||||||||||||||||||||
Click here for the management of metabolic acidosis | Click here for the management of respiratory acidosis | ||||||||||||||||||||||||||||||||||||||||||||||||||
Metabolic Acidosis
Differential diagnosis of metabolic acidosis is as follow:[2][3][4]
Category | Disease | Mechanism | Clinical | Paraclinical | Gold standard diagnosis | Other findings | ||||||||||||||||||||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Symptoms | Signs | Lab data | Imaging | |||||||||||||||||||||||||||||||||
ABG | CBC | Chemistry | Renal | Enzyme | U/A | |||||||||||||||||||||||||||||||
↑ acid production |
Loss of bicarbonate |
↓ renal acid excretion |
Fever | N/V | Diarrhea | Dyspnea | Toxic/ill | BP | Dehydration | LOC | HCO3− | paCO2 | O2 | WBC | Hb | BS | Cl− | K+ | Na+ | Ketones | Lactic acid | Serum AG | Osmolar gap | Bun | Cr | Renin | Urine pH | Urine AG | Urine ketone | US | CT scan | |||||
Toxin/Medication | Alcohol[5][6] |
|
+ | − | − | − | + | − | − | + | ↓ ↑ | + | ↓ | ↓ | ↓ | ↓ | Nl | Nl | ↑ | ↑ | ↑ | Nl | + | ↑ | ↑ | ↑ | Nl or ↑ | Nl or ↑ | Nl | ↓ | ↑ | + | Hypodensity in the putamen and caudate nucleus | Clinical | Positive oxalate crystals in urine | |
|
+ | − | − | − | + | − | − | + | ↓ | + | ↓ | ↓ | ↓ | ↓ | Nl | Nl | Nl | ↑ | ↑ | Nl | + | ↑ | ↑ | ↑ | Nl or ↑ | ↑ | Nl | ↓ | ↑ | + | Clinical | |||||
Paraldehyde | + | ↑ | ||||||||||||||||||||||||||||||||||
Toluene | + | + | ↑ | Nl or ↑ | ||||||||||||||||||||||||||||||||
Salicylates | + | ↑ |
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Metformin | ↑ | ↑ | ||||||||||||||||||||||||||||||||||
Isoniazid | ↑ | |||||||||||||||||||||||||||||||||||
Acetazolamide | + | Nl | ||||||||||||||||||||||||||||||||||
Amphotericin B | Nl | |||||||||||||||||||||||||||||||||||
CO | ↑ | ↑ | ||||||||||||||||||||||||||||||||||
Cyanide | ↑ | ↑ | ||||||||||||||||||||||||||||||||||
Category | Disease | ↑ acid production |
Loss of bicarbonate |
↓ renal acid excretion |
Fever | N/V | Diarrhea | Dyspnea | Toxic/ill | BP | Dehydration | LOC | HCO3− | paCO2 | O2 | WBC | Hb | BS | Cl− | K+ | Na+ | Ketones | Lactic acid | Serum AG | Osmolar gap | Bun | Cr | Renin | Urine pH | Urine AG | Urine ketone | US | CT scan | Gold standard diagnosis | Other findings | |
Ketoacidosis | Diabetic | + | ↑ | |||||||||||||||||||||||||||||||||
Starvation | + | ↑ | ||||||||||||||||||||||||||||||||||
Alcoholic (Ethanol)[7] | + | − | − | − | + | ± | − | + | ↓ ↑ | + | Agitated | ↓ | ↓ | ↓ | Nl to ↑ | Nl to ↑ | ↓ Nl ↑ | Nl | ↓ | ↓ | ↑↑ | ↑ | ↑ | ↑↑ | ↑ | Nl | Nl | ↓ | ↑ | + | NA | NA | Clinical + ketosis |
| ||
Systemic | Sepsis | ↑ | ↑ | |||||||||||||||||||||||||||||||||
Ischemia | ↑ | ↑ | ||||||||||||||||||||||||||||||||||
Lactic acidosis | + | ↑ | ↑ | |||||||||||||||||||||||||||||||||
Seizure | ↑ | ↑ | ||||||||||||||||||||||||||||||||||
Renal | Uremia | ↑ | ||||||||||||||||||||||||||||||||||
Ureteral diversion | + | Nl | ||||||||||||||||||||||||||||||||||
Renal failure | + | ↑ | ↑ | |||||||||||||||||||||||||||||||||
Renal tubular acidosis[8] | Type I | - | - | + | ± | ± | - | - | - | ↓ ↑ | - | - | ↓ | ↓ | Nl | Nl | Nl | Nl | ↑ | ↓ | ↓ | Nl | Nl | Nl | Nl | ↑ | ↑ | ↓ | ↑ | + | - | NA | NA | Clinical and lab finding |
| |
Type II | - | + | - | ± | ± | - | - | - | ↓ ↑ | - | - | ↓ | ↓ | Nl | Nl | Nl | Nl | ↑ | ↓ | Nl | Nl | Nl | Nl | Nl | Nl | Nl | ↓ | Nl | - | - | NA | NA | Clinical and lab finding | |||
Type IV | - | - | + | ± | ± | ± | - | - | ↓ | - | - | ↓ | ↓ | Nl | Nl | Nl | Nl | ↑ | ↑ | Nl | Nl | Nl | Nl | Nl | Nl | Nl | ↓ | Nl | + | - | NA | NA | Clinical and lab finding |
| ||
Category | Disease | ↑ acid production |
Loss of bicarbonate |
↓ renal acid excretion |
Fever | N/V | Diarrhea | Dyspnea | Toxic/ill | BP | Dehydration | LOC | HCO3− | paCO2 | O2 | WBC | Hb | BS | Cl− | K+ | Na+ | Ketones | Lactic acid | Serum AG | Osmolar gap | Bun | Cr | Renin | Urine pH | Urine AG | Urine ketone | US | CT scan | Gold standard diagnosis | Other findings | |
Heart | Heart failure[9] | + | + | - | - | ± | - | + | + | ↓ ↑ | + | - | ↓ | ↓ ↑ | ↓ | Nl | Nl | Nl | Nl | ↓ | ↓ | Nl | Nl | Nl | Nl | Nl to ↑ | Nl to ↑ | ↑ | Nl | Nl | Nl | Clinical and echocardiogram |
| |||
MI[10] | + | - | - | - | + | - | + | + | ↓ ↑ | - | + | ↓ | ↓ ↑ | Nl to ↓ | Nl to ↑ | Nl | Nl | Nl | ↑ | ↓ | Nl | ↑ | Nl | Nl | Nl to ↑ | Nl to ↑ | ↑ | Nl | Nl | Nl | Clinical and ECG | |||||
GI | Diarrhea | + | ↑ | Nl | ||||||||||||||||||||||||||||||||
Hyperalimentation | Nl | |||||||||||||||||||||||||||||||||||
Liver failure | Nl | |||||||||||||||||||||||||||||||||||
Endocrine | Hyperparathyroidism | + | Nl | |||||||||||||||||||||||||||||||||
Addison's disease | Nl | |||||||||||||||||||||||||||||||||||
Category | Disease | ↑ acid production |
Loss of bicarbonate |
↓ renal acid excretion |
Fever | N/V | Diarrhea | Dyspnea | Toxic/ill | BP | Dehydration | LOC | HCO3− | paCO2 | O2 | WBC | Hb | BS | Cl− | K+ | Na+ | Ketones | Lactic acid | Serum AG | Osmolar gap | Bun | Cr | Renin | Urine pH | Urine AG | Urine ketone | US | CT scan | Gold standard diagnosis | Other findings |
Metabolic Alkalosis
Category | Disease | Mechanism | Clinical | Paraclinical | Gold standard diagnosis | Other findings | |||||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Symptoms | Signs | Lab data | Imaging | ||||||||||||||||||
ABG | U/A | Electrolytes | Renin | ||||||||||||||||||
↑ acid production |
Loss of bicarbonate |
↓ renal acid excretion |
Fever | Dyspnea | Edema | Toxic/ill | BP | Dehydration | pH | Serum AG | Urine Cl− | Cl− | K+ | Na+ | US | CT scan | |||||
Exogenous HCO3− loads | Acute alkali administration | ||||||||||||||||||||
Milk−alkali syndrome | |||||||||||||||||||||
Gastrointestinal origin | Vomiting | + | ↓ | ||||||||||||||||||
Nasogastric tube suction | + | ↓ | |||||||||||||||||||
Gastric aspiration | |||||||||||||||||||||
Congenital chloridorrhea | |||||||||||||||||||||
Villous adenoma | |||||||||||||||||||||
Renal origin | Diuretics | + | ↓ | ||||||||||||||||||
Posthypercapnic state | |||||||||||||||||||||
Hypercalcemia/hypoparathyroidism | |||||||||||||||||||||
Recovery from lactic acidosis or ketoacidosis | |||||||||||||||||||||
Nonreabsorbable anions including penicillin, carbenicillin | |||||||||||||||||||||
Hypomagnesemia | − | Nl | |||||||||||||||||||
Hypokalemia | − | Nl | |||||||||||||||||||
Bartter's syndrome | − | Nl | |||||||||||||||||||
Gitelman’s syndrome | |||||||||||||||||||||
Renal artery stenosis | ↑ | Nl | ↑ | ||||||||||||||||||
Endocrine | Cushing's syndrome | ↑ | Nl | ↓ | |||||||||||||||||
Hyperaldosteronism | ↑ | Nl | ↓ | ||||||||||||||||||
Other | Licorice ingestion | − | Nl | ↓ |
Mixed Acid−Base Disorders
Disorder | Key features | Examples |
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Metabolic acidosis & respiratory alkalosis |
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Metabolic acidosis & respiratory acidosis |
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Metabolic alkalosis & respiratory alkalosis |
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Metabolic alkalosis & respiratory acidosis |
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Metabolic acidosis & metabolic alkalosis |
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Metabolic acidosis & metabolic acidosis |
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Related Chapters
- Acid–base homeostasis
- Acid–base imbalance
- Arterial blood gas
- Metabolic acidosis
- Metabolic alkalosis
- Respiratory acidosis
- Respiratory alkalosis
- Anion gap
- ↑ Sood P, Paul G, Puri S (April 2010). "Interpretation of arterial blood gas". Indian J Crit Care Med. 14 (2): 57–64. doi:10.4103/0972-5229.68215. PMC 2936733. PMID 20859488.
- ↑ Lim S (2007). "Metabolic acidosis". Acta Med Indones. 39 (3): 145–50. PMID 17936961.
- ↑ Morris, C. G.; Low, J. (2008). "Metabolic acidosis in the critically ill: Part 1. Classification and pathophysiology". Anaesthesia. 63 (3): 294–301. doi:10.1111/j.1365-2044.2007.05370.x. ISSN 0003-2409.
- ↑ Morris CG, Low J (April 2008). "Metabolic acidosis in the critically ill: part 2. Causes and treatment". Anaesthesia. 63 (4): 396–411. doi:10.1111/j.1365-2044.2007.05371.x. PMID 18336491.
- ↑ Zehtabchi S, Sinert R, Baron BJ, Paladino L, Yadav K (2005). "Does ethanol explain the acidosis commonly seen in ethanol-intoxicated patients?". Clin Toxicol (Phila). 43 (3): 161–6. PMID 15902789.
- ↑ Roberts, Darren M.; Yates, Christopher; Megarbane, Bruno; Winchester, James F.; Maclaren, Robert; Gosselin, Sophie; Nolin, Thomas D.; Lavergne, Valéry; Hoffman, Robert S.; Ghannoum, Marc (2015). "Recommendations for the Role of Extracorporeal Treatments in the Management of Acute Methanol Poisoning". Critical Care Medicine. 43 (2): 461–472. doi:10.1097/CCM.0000000000000708. ISSN 0090-3493.
- ↑ Howard RD, Bokhari S. PMID 28613672. Vancouver style error: initials (help); Missing or empty
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(help) - ↑ Gil-Peña, Helena; Mejía, Natalia; Santos, Fernando (2014). "Renal Tubular Acidosis". The Journal of Pediatrics. 164 (4): 691–698.e1. doi:10.1016/j.jpeds.2013.10.085. ISSN 0022-3476.
- ↑ Park, Jin Joo; Choi, Dong-Ju; Yoon, Chang-Hwan; Oh, Il-Young; Lee, Ju Hyun; Ahn, Soyeon; Yoo, Byung-Su; Kang, Seok-Min; Kim, Jae-Joong; Baek, Sang-Hong; Cho, Myeong-Chan; Jeon, Eun-Seok; Chae, Shung Chull; Ryu, Kyu-Hyung; Oh, Byung-Hee (2015). "The prognostic value of arterial blood gas analysis in high-risk acute heart failure patients: an analysis of the Korean Heart Failure (KorHF) registry". European Journal of Heart Failure. 17 (6): 601–611. doi:10.1002/ejhf.276. ISSN 1388-9842.
- ↑ Mann, Sarah; Bajulaiye, Akinyemi; Sturgeon, Kathleen; Sabri, Abdelkarim; Muthukumaran, Geetha; Libonati, Joseph R. (2014). "Effects of acute angiotensin II on ischemia reperfusion injury following myocardial infarction". Journal of the Renin-Angiotensin-Aldosterone System. 16 (1): 13–22. doi:10.1177/1470320314554963. ISSN 1470-3203.