Effect of Intravenous 25OHD Supplementation on Bone Turnover and Inflammation in Prolonged Critically Ill Patients.

Critically ill patients have low circulating 25-hydroxyvitamin D (25OHD), vitamin D binding protein (DBP), and 1,25-dihydroxyvitamin D [1,25(OH)2D]. Low 25OHD is associated with poor outcomes, possibly explained by its effect on bone and immunity. In this prospective, randomized double-blind, placebo-controlled study, we investigated the feasibility of normalizing 25OHD in prolonged (>10 days) critically ill patients and the effects thereof on 1,25(OH)2D, bone metabolism, and innate immunity. Twenty-four patients were included and compared with 24 matched healthy subjects. Patients were randomized to either intravenous bolus of 200 µg 25OHD followed by daily infusion of 15 µg 25OHD for 10 days, or to placebo. Parameters of vitamin D, bone and mineral metabolism, and innate immune function were measured. As safety endpoints, ICU length of stay and mortality were registered. Infusion of 25OHD resulted in a sustained increase of serum 25OHD (from median baseline 9.2 -16.1 ng/ml at day 10), which, however, remained below normal levels. There was no increase in serum 1,25(OH)2D but a slight increase in serum 24,25(OH)2D. Mineral homeostasis, innate immunity and clinical safety endpoints were unaffected. Thus, intravenous 25OHD administration during critical illness increased serum 25OHD concentrations, though less than expected from data in healthy subjects, which suggests illness-induced alterations in 25OHD metabolism and/or increased 25OHD distribution volume. The increased serum 25OHD concentrations were not followed by a rise in 1,25(OH)2D nor were bone metabolism or innate immunity affected, which suggests that low 25OHD and 1,25OHD levels are part of the adaptive response to critical illness.

Accuracy of inhaled agent usage displays of automated target control anesthesia machines.

Automated low flow anesthesia machines report how much inhaled anesthetic agent has been used for each anesthetic. We compared these reported values with the amount of agent that had disappeared by weighing the vaporizer/injectors before and after each anesthetic. The vaporizers/injectors of the Aisys, Zeus and FLOW-i were weighed with a high precision weighing scale before and after anesthesia with either desflurane in O2/air or sevoflurane in O2/N2O. These values were compared with the values reported by the cumulative agent use display tools of the respective anesthesia machines using a linear curve fit. Twenty-five measurements were performed in each group, except for the sevoflurane data with the Aisys that were available from another study (87 pairs). We also determined the amount lost by inserting and removing the vaporizers/injectors or by performing a machine checkout, corrected the measured amounts for these artifacts and repeated the linear fits. The average amount of sevoflurane and desflurane wasted by inserting and removing the cassette for the Aisys, Zeus, and FLOW-i were 0.21, 0.12, and 0.04 mL and 0.12, 0.61, and 1.13 mL liquid agent, respectively. The average amount of sevoflurane and desflurane wasted by the machine checkout with the Aisys, Zeus, and FLOW-i were 1.78, 0.21, and 1.67 mL and 2.39, 0.67, and 4.19 mL, respectively. Performance error of the displayed amount of agent use remained within 10 % of the weighed amount, expect for amounts less than 3 mL sevofurane with the FLOW-i and less than 20 mL desflurane with the Aisys and FLOW-i. Cumulative agent usage displayed by the Aisys, Zeus, and FLOW-i is within 10 % of the measured consumption, except for low consumption cases (<3 mL sevoflurane, <20 mL desflurane). The differences may be due to either measurement error or cumulative agent display error. The current results can help the researchers decide whether the displayed amounts are accurate enough for their study purposes. The extent to which these discrepancies differ between different units of the same machine remains unstudied.

In vitro performance of prefilled CO2 absorbers with the Aisys®.

Low flow anesthesia increases the use of CO2 absorbents, but independent data that compare canister life of the newest CO2 absorbents are scarce. Seven different pre-packed CO2 canisters were tested in vitro: Amsorb Plus, Spherasorb, LoFloSorb, Medisorb, Medisorb EF, LithoLyme, and SpiraLith. CO2 (160 mL min(-1)) flowed into the tip of a 2 L breathing bag that was ventilated with a tidal volume of 500 mL, a respiratory rate of 10/min, and an I:E ratio of 1:1 using the controlled mechanical ventilation mode of the Aisys (®) (GE, Madison, WI, USA). In part I, canister life of each brand (all of the same lot) was tested with 12 different fresh gas flows (FGF) ranging from 0.25 to 4 L min(-1). In part II, canister life of six canisters each of two different lots of each brand were tested with a 350 mL min(-1) FGF. Canister life is presented as "FCU", fractional canister usage, the fraction of a canister used per hour, and is defined for the inspired CO2 concentration (FICO2) that denotes exhaustion. In part III, canister life per 100 g fresh granule content was calculated. FCU decreased linearly with increasing FGF. The relative position of the FCU-FGF curves of the different brands depends on the FICO2 threshold because the exhaustion rate (the rate of rise once FICO2 starts to increase) differs among the brands. Intra-lot variability was 18 % or less. The different prepacks can be ranked according their efficiency (least to most efficient) as follows: Amsorb Plus = Medisorb EF < LoFloSorb < Medisorb = Spherasorb = LithoLyme < SpiraLith (all for an FICO2 threshold = 0.5 %). Canister life per 100 g fresh granule content is almost twice as long when LiOH is used as the primary absorbent. The most important factors that determine canister life of prepacks in a circle breathing system are the chemical composition of the canister, the absolute amount of absorbent present in the canister, and the FICO2 replacement threshold. The use of the fractional canister usage allows cost comparisons among different prepacks. Results should not be extrapolated to prepacks that fit onto other anesthesia machines.