Investigation of air bubble behaviour after gas embolism events induced in a microfluidic network mimicking microvasculature.

Gas embolism is a medical condition that occurs when gas bubbles are present in veins or arteries, decreasing blood flow and potentially reducing oxygen delivery to vital organs, such as the brain. Although usually reported as rare, gas embolism can lead to severe neurological damage or death. However, presently, only limited understanding exists regarding the microscale processes leading to the formation, persistence, movement, and resolution of gas emboli, as modulated by microvasculature geometrical features and blood properties. Because gas embolism is initially a physico-chemical-only process, with biological responses starting later, the opportunity exists to fully study the genesis and evolution of gas emboli using in vitro microfluidic networks mimicking small regions of microvasculature. The microfluidics networks used in this study, which aim to mimic microvasculature geometry, comprise linear channels with T-, or Y-junction air inlets, with 20, 40, and 60 µm widths (arterial or venous), and a 30 µm width honeycombed network (arterial) with three bifurcation angles (30°, 60°, and 90°). Synthetic blood, equivalent to 46% haematocrit concentrations, and water were used to study the modulation of gas embolism-like events by liquid viscosity. Our study shows that (i) longer bubbles with lower velocity occur in narrower channels, e.g., with 20 µm width; (ii) the resistance of air bubbles to the flow increases with the higher haematocrit concentration; and lastly (iii) the propensity of gas embolism-like events in honeycomb architectures increases for more acute, e.g., 30°, bifurcation angles. A dimensionless analysis using Euler, Weber, and capillary numbers demarcated the conditions conducive to gas embolism. This work suggests that in vitro experimentation using microfluidic devices with microvascular tissue-like structures could assist medical guidelines and management in preventing and mitigating the effects of gas embolism.

Guidelines to the Practice of Anesthesia Revised Edition 2012.

OVERVIEW: The Guidelines to the Practice of Anesthesia Revised Edition 2012 (the guidelines) were prepared by the Canadian Anesthesiologists' Society (CAS), which reserves the right to determine their publication and distribution. Because the guidelines are subject to revision, updated versions are published annually. Whereas previous versions of the guidelines appeared as special supplements to the Canadian Journal of Anesthesia (the Journal), this edition of the guidelines is published within the Journal. This allows for improved archiving and online access to complement the printed version--a new offering for CAS members and Journal subscribers. The Guidelines to the Practice of Anesthesia Revised Edition 2012 supersedes all previously published versions of this document. Although the CAS encourages Canadian anesthesiologists to adhere to its practice guidelines to ensure high-quality patient care, the society cannot guarantee any specific patient outcome. Each anesthesiologist should exercise his or her own professional judgement in determining the proper course of action for any patient's circumstances. The CAS assumes no responsibility or liability for any error or omission arising from the use of any information contained in its Guidelines to the Practice of Anesthesia.

Guidelines to the Practice of Anesthesia: Revised edition 2011.

The Guidelines to the Practice of Anesthesia Revised Edition 2011 (the guidelines) were prepared by the Canadian Anesthesiologists' Society (CAS), which reserves the right to determine their publication and distribution. Because the guidelines are subject to revision, updated versions are published annually. Whereas previous versions of the guidelines appeared as special supplements to the Canadian Journal of Anesthesia (the Journal), this edition of the guidelines is published within the Journal. This allows for improved archiving and online access to complement the printed version-a new offering for CAS members and Journal subscribers. The Guidelines to the Practice of Anesthesia Revised Edition 2011 supersedes all previously published versions of this document. Although the CAS encourages Canadian anesthesiologists to adhere to its practice guidelines to ensure high-quality patient care, the society cannot guarantee any specific patient outcome. Each anesthesiologist should exercise his or her own professional judgement in determining the proper course of action for any patient's circumstances. The CAS assumes no responsibility or liability for any error or omission arising from the use of any information contained in its Guidelines to the Practice of Anesthesia.

Guidelines to the Practice of Anesthesia Revised Edition 2010.

OVERVIEW: The Guidelines to the Practice of Anesthesia Revised Edition 2010 (the guidelines) were prepared by the Canadian Anesthesiologists' Society (CAS), which reserves the right to determine their publication and distribution. Because the guidelines are subject to revision, updated versions are published annually. Whereas previous versions of the guidelines appeared as special supplements to the Canadian Journal of Anesthesia (the Journal), this edition of the guidelines is published within the Journal. This allows for improved archiving and online access to complement the printed version-a new offering for CAS members and Journal subscribers. The Guidelines to the Practice of Anesthesia Revised Edition 2010 supersedes all previously published versions of this document. Although the CAS encourages Canadian anesthesiologists to adhere to its practice guidelines to ensure high-quality patient care, the society cannot guarantee any specific patient outcome. Each anesthesiologist should exercise his or her own professional judgement in determining the proper course of action for any patient's circumstances. The CAS assumes no responsibility or liability for any error or omission arising from the use of any information contained in its Guidelines to the Practice of Anesthesia.

Hyperbaric treatment of cerebral air embolism in an infant with cyanotic congenital heart disease.

PURPOSE: Infants with cyanotic congenital heart disease are at risk for cerebral arterial gas embolism (CAGE) from iv infusion lines. Concern about the hazards and difficulty of caring for such patients inside a hyperbaric chamber may deter referral. We report a complex case in which a small infant was managed successfully using a modified hyperbaric oxygen treatment (HBOT) schedule. CLINICAL FEATURES: A four-month-old 6.19 kg male infant with a recent Glenn shunt for double-outlet right ventricle had a seizure and became unstable immediately after an iv drug infusion. The patient was sedated, intubated and ventilated and dobutamine was commenced. A computerized tomography (CT) scan performed ten hours later demonstrated three intracranial air bubbles. About ten hours later the patient was referred for HBOT which commenced soon afterwards in a multiplace chamber. Since the right-to-left shunt would greatly increase the risk of decompression illness from breathing hyperbaric air HBOT was modified by the use of an abbreviated schedule at reduced pressure. Two 90-min HBOT sessions were administered within 24 hr at 38 feet of sea-water pressure, equivalent to 2.15 atmospheres absolute without any air break. During treatment the infant was ventilated using an Oxford Penlon ventilator. A subsequent CT scan demonstrated the absence of air. After extubation he appeared neurologically intact except for some weakness of the left arm. CONCLUSION: Hyperbaric oxygen may be utilized to treat CAGE in small infants with right-to-left shunt and should be commenced promptly.