Oxygenation Impairment during Anesthesia: Influence of Age and Body Weight.

Hedenstierna, Göran; Tokics, Leif; Scaramuzzo, Gaetano; Rothen, Hans Ulrich; Edmark, Lennart; Öhrvik, John (2019). Oxygenation Impairment during Anesthesia: Influence of Age and Body Weight. Anesthesiology, 131(1), pp. 46-57. Wolters Kluwer Health 10.1097/ALN.0000000000002693

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WHAT WE ALREADY KNOW ABOUT THIS TOPIC During anesthesia oxygenation is impaired, especially in the elderly or obese, but the mechanisms are uncertain. WHAT THIS ARTICLE TELLS US THAT IS NEW Pooled data were examined from 80 patients studied with multiple inert gas elimination technique and computed tomography. Oxygenation was impaired by anesthesia, more so with greater age or body mass index. The key contributors were low ventilation/perfusion ratio (likely airway closure) in the elderly and shunt (atelectasis) in the obese. BACKGROUND Anesthesia is increasingly common in elderly and overweight patients and prompted the current study to explore mechanisms of age- and weight-dependent worsening of arterial oxygen tension (PaO2). METHODS This is a primary analysis of pooled data in patients with (1) American Society of Anesthesiologists (ASA) classification of 1; (2) normal forced vital capacity; (3) preoxygenation with an inspired oxygen fraction (FIO2) more than 0.8 and ventilated with FIO2 0.3 to 0.4; (4) measurements done during anesthesia before surgery. Eighty patients (21 women and 59 men, aged 19 to 69 yr, body mass index up to 30 kg/m) were studied with multiple inert gas elimination technique to assess shunt and perfusion of poorly ventilated regions (low ventilation/perfusion ratio [VA/Q]) and computed tomography to assess atelectasis. RESULTS PaO2/FIO2 was lower during anesthesia than awake (368; 291 to 470 [median; quartiles] vs. 441; 397 to 462 mm Hg; P = 0.003) and fell with increasing age and body mass index. Log shunt was best related to a quadratic function of age with largest shunt at 45 yr (r =0.17, P = 0.001). Log shunt was linearly related to body mass index (r = 0.15, P < 0.001). A multiple regression analysis including age, age, and body mass index strengthened the association further (r = 0.27). Shunt was highly associated to atelectasis (r = 0.58, P < 0.001). Log low VA/Q showed a linear relation to age (r = 0.14, P = 0.001). CONCLUSIONS PaO2/FIO2 ratio was impaired during anesthesia, and the impairment increased with age and body mass index. Shunt was related to atelectasis and was a more important cause of oxygenation impairment in middle-aged patients, whereas low VA/Q, likely caused by airway closure, was more important in elderly patients. Shunt but not low VA/Q increased with increasing body mass index. Thus, increasing age and body mass index impaired gas exchange by different mechanisms during anesthesia.

Item Type:

Journal Article (Original Article)

Division/Institute:

04 Faculty of Medicine > Department of Intensive Care, Emergency Medicine and Anaesthesiology (DINA) > Clinic of Intensive Care

UniBE Contributor:

Rothen, Hans Ulrich

Subjects:

600 Technology > 610 Medicine & health

ISSN:

1528-1175

Publisher:

Wolters Kluwer Health

Language:

English

Submitter:

Mirella Aeberhard

Date Deposited:

31 Jul 2019 09:34

Last Modified:

22 Oct 2019 16:37

Publisher DOI:

10.1097/ALN.0000000000002693

PubMed ID:

31045901

BORIS DOI:

10.7892/boris.130779

URI:

https://boris.unibe.ch/id/eprint/130779

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