In:
Anesthesia & Analgesia, Ovid Technologies (Wolters Kluwer Health), Vol. 129, No. 2 ( 2019-08), p. 371-379
Abstract:
Volatile anesthetics are increasingly used for sedation in intensive care units. The most common administration system is AnaConDa-100 mL (ACD-100; Sedana Medical, Uppsala, Sweden), which reflects volatile anesthetics in open ventilation circuits. AnaConDa-50 mL (ACD-50) is a new device with half the volumetric dead space. Carbon dioxide (CO 2 ) can be retained with both devices. We therefore compared the CO 2 elimination and isoflurane reflection efficiency of both devices. METHODS: A test lung constantly insufflated with CO 2 was ventilated with a tidal volume of 500 mL at 10 breaths/min. End-tidal CO 2 (Et co 2 ) partial pressure was measured using 3 different devices: a heat-and-moisture exchanger (HME, 35 mL), ACD-100, and ACD-50 under 4 different experimental conditions: ambient temperature pressure (ATP), body temperature pressure saturated (BTPS) conditions, BTPS with 0.4 Vol% isoflurane (ISO-0.4), and BTPS with 1.2 Vol% isoflurane. Fifty breaths were recorded at 3 time points (n = 150) for each device and each condition. To determine device dead space, we adjusted the tidal volume to maintain normocapnia (n = 3), for each device. Thereafter, we determined reflection efficiency by measuring isoflurane concentrations at infusion rates varying from 0.5 to 20 mL/h (n = 3), for each device. RESULTS: Et co 2 was consistently greater with ACD-100 than with ACD-50 and HME (ISO-0.4, mean ± standard deviations: ACD-100, 52.4 ± 0.8; ACD-50, 44.4 ± 0.8; HME, 40.1 ± 0.4 mm Hg; differences of means of Et co 2 [respective 95% confidence intervals]: ACD-100 − ACD-50, 8.0 [7.9–8.1] mm Hg, P 〈 .001; ACD-100 − HME, 12.3 [12.2–12.4] mm Hg, P 〈 .001; ACD-50 − HME, 4.3 [4.2–4.3] mm Hg, P 〈 .001). It was greatest under ATP, less under BTPS, and least with ISO-0.4 and BTPS with 1.2 Vol% isoflurane. In addition to the 100 or 50 mL “volumetric dead space” of each AnaConDa, “reflective dead space” was 40 mL with ACD-100 and 25 mL with ACD-50 when using isoflurane. Isoflurane reflection was highest under ATP. Under BTPS with CO 2 insufflation and isoflurane concentrations around 0.4 Vol%, reflection efficiency was 93% with ACD-100 and 80% with ACD-50. CONCLUSIONS: Isoflurane reflection remained sufficient with the ACD-50 at clinical anesthetic concentrations, while CO 2 elimination was improved. The ACD-50 should be practical for tidal volumes as low as 200 mL, allowing lung-protective ventilation even in small patients.
Type of Medium:
Online Resource
ISSN:
0003-2999
DOI:
10.1213/ANE.0000000000003452
Language:
English
Publisher:
Ovid Technologies (Wolters Kluwer Health)
Publication Date:
2019
detail.hit.zdb_id:
2018275-2
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