Anesthesia and analgesia
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Predicting flow through an IV cannula is useful to clinicians if changes in flow are required and to guide selection of cannula. We sought the usefulness of manufacturers' quoted flows in predicting actual flow and to characterize that flow. ⋯ Flow through cannulae is not laminar at the upper range of clinically used flows, therefore Poiseuille's law is not useful in predicting flow and the effect of changing radius is less than commonly believed. The quoted maximum flows are also not useful. There are many conditions for laminar flow apart from Reynolds number. Further work would determine useful predictors of flow.
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Anesthesia and analgesia · Apr 2009
Current threshold for nerve stimulation depends on electrical impedance of the tissue: a study of ultrasound-guided electrical nerve stimulation of the median nerve.
Understanding the mechanisms causing variation in current thresholds for electrical nerve stimulation may improve the safety and success rate of peripheral nerve blocks. Electrical impedance of the tissue surrounding a nerve may affect the response to nerve stimulation. In this volunteer study, we investigated the relationship between impedance and current threshold needed to obtain a neuromuscular response. ⋯ Our results demonstrate an inverse relationship between impedance measurements and current thresholds and suggest that current settings used for nerve stimulation may require adjustment based on the tissue type. Further studies should be performed to investigate the clinical impact of our findings.
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Anesthesia and analgesia · Apr 2009
Randomized Controlled TrialMelatonin provides anxiolysis, enhances analgesia, decreases intraocular pressure, and promotes better operating conditions during cataract surgery under topical anesthesia.
Melatonin has anxiolytic and potential analgesic effects. In this study, we assessed the effects of melatonin premedication on pain, anxiety, intraocular pressure (IOP), and operative conditions during cataract surgery under topical analgesia. ⋯ We concluded that oral melatonin premedication for patients undergoing cataract surgery under topical anesthesia provided anxiolytic effects, enhanced analgesia, and decreased IOP resulting in good operating conditions.
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Anesthesia and analgesia · Apr 2009
Case ReportsCrisis resource management of the airway in a patient with Klippel-Feil syndrome, congenital deafness, and aortic dissection.
Klippel-Feil syndrome is a visually arresting deformity wherein severe restriction of cervical motion predicts a difficult airway. Even minor distraction of the neck risks cervical spine or neurologic injury, so regional techniques, awake fiberoptic intubation, or awake tracheostomy are recommended anesthetic approaches. We present a case of aortic dissection in a Klippel-Feil syndrome patient for whom congenital bilateral deafness, coupled with the urgency of the surgery, mitigated against the recommended first-choice techniques. Using anesthesia crisis resource management methods, a multi-member team rehearsed predefined roles and then managed the airway via inhaled induction of anesthesia, followed by flexible fiberoptic intubation.
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Anesthesia and analgesia · Apr 2009
Comparative StudyTime to a 90% change in gas concentration: a comparison of three semi-closed anesthesia breathing systems.
The speed with which gas concentration can be changed in the anesthesia breathing system affects the rate of denitrogenation, anesthesia induction, and emergence. Breathing system design also affects the speed at which gas concentration can be changed during maintenance. In this study, we sought to determine the speed of changes in gas concentration in modern semi-closed breathing systems. We hypothesized that equilibrium would be reached most quickly in breathing systems with smaller volume, and at high fresh gas flows. ⋯ We concluded that, other than fresh gas flow rate, breathing system volume has the biggest effect on time to equilibrium when the composition of the fresh gas inflow is changed. The position of components (e.g., valves, carbon dioxide absorber, fresh gas inlet, ventilator bellows or piston) within the breathing system has a less pronounced effect.