Anesthesia and analgesia
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Anesthesia and analgesia · Mar 2013
Medication and volume delivery by gravity-driven micro-drip intravenous infusion: potential variations during "wide-open" flow.
Gravity-driven micro-drip infusion sets allow control of medication dose delivery by adjusting drops per minute. When the roller clamp is fully open, flow in the drip chamber can be a continuous fluid column rather than discrete, countable, drops. We hypothesized that during this "wide-open" state, drug delivery becomes dependent on factors extrinsic to the micro-drip set and is therefore difficult to predict. We conducted laboratory experiments to characterize volume delivery under various clinically relevant conditions of wide-open flow in an in vitro laboratory model. ⋯ Laboratory simulation of clinical situations with gravity-driven micro-drip infusion sets under wide-open flow conditions revealed that infusion rate (drug and/or volume delivery) can vary widely depending on extrinsic factors including catheter size, fluid column height, and carrier flow. The variable resistance implies nonlaminar flow in the micro-drip model that cannot be easily predicted mathematically. These findings support the use of mechanical pumps instead of gravity-driven micro-drips to enhance the precision and safety of IV infusions, especially for vasoactive drugs.
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Anesthesia and analgesia · Mar 2013
Single-dose application of antithrombin as a potential alternative anticoagulant during continuous renal replacement therapy in critically ill patients with advanced liver cirrhosis: a retrospective data analysis.
Adequate anticoagulation is essential to achieve efficient and cost-effective continuous renal replacement therapy (CRRT). However, in critically ill patients with advanced liver cirrhosis, this goal is challenging because of the concomitant bleeding disorder. Therefore, the evaluation of alternative anticoagulants is necessary. ⋯ Our data suggest that anticoagulation with single doses of AT may be an alternative to continuously administered low-dose heparin in critically ill patients with advanced liver cirrhosis during CRRT. However, additional controlled trials are necessary to confirm our findings.
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Anesthesia and analgesia · Mar 2013
Kinetics of uptake and washout of lidocaine in rat sciatic nerve in vitro.
The potency and efficacy of local anesthetics injected clinically for peripheral nerve block depends strongly on the rate of neural drug uptake. However, because diffusion into surrounding tissues and removal by the vascular system are major factors in the overall distribution of lidocaine in vivo, true kinetics of drug/neural tissue interactions must be studied in the absence of those confounding factors. ⋯ Lidocaine enters a nerve by a process other than free diffusion, through an epineurial sheath that is a slight obstacle. Given the rapid entry in vitro compared with the much smaller and transient content measured in vivo, it seems highly unlikely that lidocaine equilibrates with the nerve during a peripheral blockade.
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Anesthesia and analgesia · Mar 2013
Volume-independent elastance: a useful parameter for open-lung positive end-expiratory pressure adjustment.
A decremental positive end-expiratory pressure (PEEP) trial after full lung recruitment allows for the adjustment of the lowest PEEP that prevents end-expiratory collapse (open-lung PEEP). For a tidal volume (Vt) approaching zero, the PEEP of minimum respiratory system elastance (PEEP(minErs)) is theoretically equal to the pressure at the mathematical inflection point (MIP) of the pressure-volume curve, and seems to correspond to the open-lung PEEP in a decremental PEEP trial. Nevertheless, the PEEP(minErs) is dependent on Vt and decreases as Vt increases. To circumvent this dependency, we proposed the use of a second-order model in which the volume-independent elastance (E1) is used to set open-lung PEEP. ⋯ PEEPminE1 better identifies the open-lung PEEP independently of the adjusted Vt, and may be a practical, more individualized approach for PEEP titration.