hypoxia
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Introduction
Inadequate oxygenation of tissues, short of anoxia.
Etiology
- pulmomary ischemia
- loss of oxygen carrying capacity of blood
- inadequate supply of oxygen
- carboxyhemoglobin due to carbon monoxide
- methemoglobinemia
- respiratory hypoxia
- right to left pulmonary shunting
- anemia
- inadequate supply of oxygen
- increased oxygen requirements
- in patients with fixed cardiac output
- anaerobic exercise
- inhibition of oxygen utilization
- low atmospheric oxygen content
- high altitude
Pathology
- with reduced paO2, cerebrovascular resistance decreases & cerebral blood flow increases
- chemoreptors in the brainstem, carotid & aortic bodies increase ventilation
- when hypoxia is accompanied by hyperventilation & decreased pCO2, cerebrovascular resistance increases,cerebral blood flow is diminished & hypoxia is intensified
- compared with the brain, the spinal cord & peripheral nerves are relatively resistant to hypoxia (cortex is most sensitive)
- hypoxia causes pulmonary arterial constriction which shunts blood away from poorly ventilated lung regions but increases pulmonary vascular resistance & right ventricular afterload
- diminished paO2 results in vasodilation & increased cardiac output
- congestive heart failure
- causes hypoxia via pulmonary edema with collapse of alveolar space
- may be exacerbated by increased cardiac output
- ischemia may exacerbate coronary artery disease
- loss of aerobic metabolism -> formation of lactic acid
- depletion of high-energy phosphate stores (ATP & creatine phosphate)
- brainstem centers, liver & kidney affected with more severe hypoxia
- death usually results from respiratory failure
Clinical manifestations
- acute effects
- impaired judgement
- motor incoordination
- similar to alcohol intoxication
- chronic effects
- fatigue
- drowsiness
- apathy
- inattentiveness
- delayed reaction time
Diagnostic procedures
Management
- supplemental oxygen
- SaO2 <= 88 mm Hg at rest or with exercise
- high-flow oxygen delivered by nasal cannula for hypoxemic acute respiratory failure with lower mortality at 90 days, more ventilator- free days, & less respiratory discomfort than BiPAP[4][6]
- endotracheal intubation & mechanical ventilation rate similar for BiPAP vs high-flow oxygen[4]
- hypoxia due to pulmonary shunts will not correct with supplemental oxygen (heart failure, ARDS)[3]
More general terms
More specific terms
- anoxia
- anoxic/hypoxic encephalopathy
- asphyxia (suffocation)
- high-altitude cerebral edema (HACE)
- ischemia
Additional terms
References
- ↑ Cotran et al Robbins Pathologic Basis of Disease, 5th ed. W.B. Saunders Co, Philadelphia, PA 1994 pg 3
- ↑ Harrison's Principles of Internal Medicine, 14th ed. Fauci et al (eds), McGraw-Hill Inc. NY, 1998, pg 205-206
- ↑ 3.0 3.1 Medical Knowledge Self Assessment Program (MKSAP) 15, American College of Physicians, Philadelphia 2009
- ↑ 4.0 4.1 4.2 Frat J-P et al. High-flow oxygen through nasal cannula in acute hypoxemic respiratory failure. N Engl J Med 2015 Jun 4; 372:2185. PMID: https://www.ncbi.nlm.nih.gov/pubmed/25981908
Stephan F et al. High-flow nasal oxygen vs noninvasive positive airway pressure in hypoxemic patients after cardiothoracic surgery: A randomized clinical trial. JAMA 2015 Jun 16; 313:2331. PMID: https://www.ncbi.nlm.nih.gov/pubmed/25980660 - ↑ Rodriguez-Roisin R, Roca J. Mechanisms of hypoxemia. Intensive Care Med. 2005 Aug;31(8):1017-9. Epub 2005 Jun 14. PMID: https://www.ncbi.nlm.nih.gov/pubmed/16052273
- ↑ 6.0 6.1 Qaseem A et al. Appropriate use of high-flow nasal oxygen in hospitalized patients for initial or postextubation management of acute respiratory failure: A clinical guideline from the American College of Physicians. Ann Intern Med 2021 Apr 27; [e-pub]. PMID: https://www.ncbi.nlm.nih.gov/pubmed/33900796 https://www.acpjournals.org/doi/10.7326/M20-7533
Baldomero AK et al. Effectiveness and harms of high-flow nasal oxygen for acute respiratory failure: An evidence report for a clinical guideline by the American College of Physicians. Ann Intern Med 2021 Apr 27; [e-pub]. PMID: https://www.ncbi.nlm.nih.gov/pubmed/33900793 https://www.acpjournals.org/doi/10.7326/M20-4675
Baldomero AK, et al Effectiveness and harms of high-flow nasal oxygen (HFNO) for acute respiratory failure: a systematic review protocol. BMJ Open. 2020. PMID: https://www.ncbi.nlm.nih.gov/pubmed/32051320 Free PMC article. - ↑ National Institute of Neurological Disorders and Stroke (NINDS) NINDS Cerebral Hypoxia Information Page https://www.ninds.nih.gov/Disorders/All-Disorders/Cerebral-Hypoxia-Information-Page