Sandbox: sadaf

Acid Base Disorders

Blood Gas Analysis

Blood gas analysis	Vessel	Range	Interpretation
Oxygen Partial Pressure (pO₂)	Arterial	80 to 100 mmHg	Normal
	Arterial	<80  mmHg	Hypoxia
	Venous	35 to 40 mmHg	Normal
Oxygen Saturation (SO₂)	Arterial	>95%	Normal
	Arterial	<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	Expected paCO₂ = 1.5 x serum HCO₃⁻ + 8 ± 2 (Winters' formula) Expected paCO₂ = Serum HCO₃⁻ + 15
Metabolic alkalosis	↑	↑	↑	Respiratory	Expected paCO₂ = 0.5 − 1 increase/ every 1 unit increase in serum HCO₃⁻ from 24
Respiratory acidosis	↓	↑	↑	Renal	Acute: HCO₃⁻ increases by 1mEq/L for every 10 mmHg increase in paCO2 above 40 Chronic: HCO₃⁻ increases by 3.5mEq/L for every 10 mmHg increase in paCO2 above 40
Respiratory alkalosis	↑	↓	↓	Renal	Acute: HCO₃⁻ decreases by 2mEq/L for every 10 mmHg derease in paCO2 above 40 Chronic: HCO₃⁻ decreases by 5mEq/L for every 10 mmHg decrease in paCO2 above 40

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

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
						Symptoms				Signs				ABG			CBC		Chemistry								Renal		Enzyme	U/A			Imaging
			↑ 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]	Methanol Ethylene glycol Propylene glycol	+	−	−	−	+	−	−	+	↓ ↑	+	↓	↓	↓	↓	Nl	Nl	↑	↑	↑	Nl	+	↑	↑	↑	Nl or ↑	Nl or ↑	Nl	↓	↑	+		Hypodensity in the putamen and caudate nucleus	Clinical	Positive oxalate crystals in urine
	Alcohol^[5]^[6]	Isopropyl alcohol^[7]	+	−	−	−	+	−	−	+	↓	+	↓	↓	↓	↓	Nl	Nl	Nl	↑	↑	Nl	+	↑	Nl	↑	Nl	Nl or ↑	Nl	↓	↑	+			Clinical
	Paraldehyde		+																						↑
	Toluene		+		+																			↑	Nl or ↑
	Salicylates		+																						↑											Paradoxical alkalosis
	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		+	-	-	+	+	+	+	+	↓	+	+	↓	↓	Nl to ↓	↑	Nl to ↑	↑↑	Nl	↓	Nl	↑	↑	↑	↑	Nl to ↑	Nl		↓	+	+			Clinical + hyperglycemia + ketosis
	Starvation		+																						↑
	Alcoholic (Ethanol)^[8]		+	−	−	−	+	±	−	+	↓ ↑	+	Agitated	↓	↓	↓	Nl to ↑	Nl to ↑	↓ Nl ↑	Nl	↓	↓	↑↑	↑	↑	↑↑	↑	Nl	Nl	↓	+	+	NA	NA	Clinical + ketosis	Chronic alcohol abuse Zero or low alcohol level
Systemic	Sepsis^[9]		+	-	-	+	+	-	+	+	↓ ↑	+	+	↓	↓	Nl to ↓	↑	Nl	Nl	Nl	↑	↓	Nl	Nl to ↑	Nl	Nl	↑	↑	↑	Nl	Nl	Nl			Clinical and lab finding
	Ischemia^[10]		+	-	-	-	+	-	+	+	↓	+	-	↓	↓ ↑	Nl to ↓	Nl to ↑	Nl	Nl	Nl	↑	↓	Nl	Nl to ↑	Nl	Nl	Nl to ↑	Nl to ↑	↑	Nl	Nl	Nl			Clinical and lab finding
	Lactic acidosis^[11]		+	-	-	±	+	-	-	+	↓ ↑	↓ ↑	Agitated	↓	↓	↓	Nl to ↑	↓	Nl	Nl	Nl	Nl	Nl	↑	↑	Nl or ↑	Nl or ↑	Nl	Nl	↓	-	-			Clinical and lab finding
Renal	Uremia																								↑
	Ureteral diversion			+																					Nl
	Renal failure				+															↑					↑
	Renal tubular acidosis^[12]	Type I	-	-	+	±	±	-	-	-	↓ ↑	-	-	↓	↓	Nl	Nl	Nl	Nl	↑	↓	↓	Nl	Nl	Nl	Nl	↑	↑	↓	↑	+	-	NA	NA	Clinical and lab finding	Associated with autoimmune diseases Growth retardation in children
		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	Hypoaldosteronism
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^[13]		+	+	-	-	±	-	+	+	↓ ↑	+	-	↓	↓ ↑	↓	Nl	Nl	Nl	Nl	↓	↓	Nl	Nl	Nl	Nl	Nl to ↑	Nl to ↑	↑	Nl	Nl	Nl			Clinical and echocardiogram	Hypoalbuminemia Elevated serum natriuretic peptide
Heart	MI^[14]		+	-	-	-	+	-	+	+	↓ ↑	-	+	↓	↓ ↑	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
Endocrine	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
					Symptoms			Signs			Lab data							Imaging
					Symptoms			Signs			ABG		U/A	Electrolytes			Renin	Imaging
		↑ acid production	Loss of bicarbonate	↓ renal acid excretion	Fever	Dyspnea	Edema	Toxic/ill	BP	Dehydration	pH	Serum AG	Urine Cl⁻	Cl⁻	K⁺	Na⁺	Renin	US	CT scan
Exogenous HCO₃⁻ loads	Acute alkali administration
Exogenous HCO₃⁻ loads	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				↓
Endocrine	Hyperaldosteronism								↑				Nl				↓
Other	Licorice ingestion								−				Nl				↓

Mixed Acid−Base Disorders

Disorder	Key features	Examples
Metabolic acidosis & respiratory alkalosis	High− or normal−AG metabolic acidosis Prevailing PaCO₂ below predicted value	Lactic acidosis Sepsis in ICU
Metabolic acidosis & respiratory acidosis	High− or normal−AG metabolic acidosis Prevailing PaCO₂ above predicted value	Severe pneumonia Pulmonary edema
Metabolic alkalosis & respiratory alkalosis	PaCO₂ does not increase as predicted pH higher than expected	Liver disease Diuretics
Metabolic alkalosis & respiratory acidosis	PaCO₂ higher than predicted pH normal	COPD on diuretics
Metabolic acidosis & metabolic alkalosis	Only detectable with high−AG acidosis ∆AG >> ∆[HCO₃⁻]	Uremia with vomiting
Metabolic acidosis & metabolic acidosis	Mixed high−AG & normal−AG acidosis ∆[HCO₃⁻] accounted for by combined change in ∆AG and ∆Cl⁻	Diarrhea and lactic acidosis Toluene toxicity Treatment of diabetic ketoacidosis

Related Chapters

↑ 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.
↑ Ashurst JV, Nappe TM. Toxicity, Isopropanol. [Updated 2018 Mar 8]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2018 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK493181/
↑ Howard RD, Bokhari S. PMID 28613672. Vancouver style error: initials (help); Missing or empty |title= (help)
↑ Ganesh K, Sharma RN, Varghese J, Pillai MG (2016). "A profile of metabolic acidosis in patients with sepsis in an Intensive Care Unit setting". Int J Crit Illn Inj Sci. 6 (4): 178–181. doi:10.4103/2229-5151.195417. PMC 5225760. PMID 28149822.
↑ Kimmoun, Antoine; Novy, Emmanuel; Auchet, Thomas; Ducrocq, Nicolas; Levy, Bruno (2015). "Hemodynamic consequences of severe lactic acidosis in shock states: from bench to bedside". Critical Care. 19 (1). doi:10.1186/s13054-015-0896-7. ISSN 1364-8535.
↑ Kraut, Jeffrey A.; Ingelfinger, Julie R.; Madias, Nicolaos E. (2014). "Lactic Acidosis". New England Journal of Medicine. 371 (24): 2309–2319. doi:10.1056/NEJMra1309483. ISSN 0028-4793.
↑ 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.

[pmid20859488-1] 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.

[pmid17936961-2] Lim S (2007). "Metabolic acidosis". Acta Med Indones. 39 (3): 145–50. PMID 17936961.

[MorrisLow2008-3] 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.

[pmid18336491-4] 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.

[pmid15902789-5] 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.

[RobertsYates2015-6] 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.

[7] Ashurst JV, Nappe TM. Toxicity, Isopropanol. [Updated 2018 Mar 8]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2018 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK493181/

[pmid28613672-8] Howard RD, Bokhari S. PMID 28613672. Vancouver style error: initials (help); Missing or empty |title= (help)

[pmid28149822-9] Ganesh K, Sharma RN, Varghese J, Pillai MG (2016). "A profile of metabolic acidosis in patients with sepsis in an Intensive Care Unit setting". Int J Crit Illn Inj Sci. 6 (4): 178–181. doi:10.4103/2229-5151.195417. PMC 5225760. PMID 28149822.

[KimmounNovy2015-10] Kimmoun, Antoine; Novy, Emmanuel; Auchet, Thomas; Ducrocq, Nicolas; Levy, Bruno (2015). "Hemodynamic consequences of severe lactic acidosis in shock states: from bench to bedside". Critical Care. 19 (1). doi:10.1186/s13054-015-0896-7. ISSN 1364-8535.

[KrautIngelfinger2014-11] Kraut, Jeffrey A.; Ingelfinger, Julie R.; Madias, Nicolaos E. (2014). "Lactic Acidosis". New England Journal of Medicine. 371 (24): 2309–2319. doi:10.1056/NEJMra1309483. ISSN 0028-4793.

[Gil-PeñaMejía2014-12] 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.

[ParkChoi2015-13] 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.

[MannBajulaiye2014-14] 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.

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