Minerva anestesiologica
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Minerva anestesiologica · Jun 2006
ReviewUsing the nerve stimulator for peripheral or plexus nerve blocks.
Conventional methodology for nerve location utilizes anatomical landmarks followed by invasive exploration with a needle to a suitable endpoint. An appropriate endpoint can be either anatomical in nature (e.g. transaterial technique) or functional (paresthesia or motor response to electrical stimulation). Ability to electrically stimulate a peripheral nerve or plexus depends upon many variables, including; 1) conductive area at the electrode, 2) electrical impedance, 3) electrode-to-nerve distance, 4) current flow (amperage), and 5) pulse duration. ⋯ The above parameters can be varied optimally to enhance successful nerve location and subsequent blockade. Unlike imaging modalities such as ultrasonography, electrical nerve stimulation depends upon nerve conduction. Similarly, percutaneous electrode guidance (PEG) makes use of the above variables to allow prelocation of the nerve by transcutaneous stimulation.
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Neuraxial blockade is commonly used to abolish sensations elicited by noxious stimuli during surgical procedures. Proven advantages of combined anesthesia include early recovery from general anesthesia and postoperative analgesia, together with likely decreases in blood loss, cardiac dysrhythmias, or ischemic events and postoperative deep vein thrombosis. The side effects of the technique are related to the dose or site of local anesthetic administration and to light general anesthesia, which can result in awareness during surgery. ⋯ Neuraxial blockade reduces sedative and anesthetic requirements by decreasing ascending sensory input into the brain. This has important clinical implications, as anesthetists should expect to reduce anesthetic and sedative drug doses during neuraxial blockade, unless the blockade involves lower dermatomes alone. Clinical practice of anesthesia is a polypharmacy, wherein the anesthetic state is the net result of the action of different drugs and their interaction in the presence of a surgical stimulus.
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Minerva anestesiologica · Jun 2006
ReviewMeaning of arterio-venous PCO2 difference in circulatory shock.
The arterovenous difference in carbon dioxide tension (DeltaPCO2) can be calculated after simultaneous sampling of arterial blood (PaCO2) and of mixed venous blood from the distal of a pulmonary artery catheter (PvCO2). Under physiological conditions, DeltaPCO2 ranges from 2 to 5 mmHg. The DeltaPCO2 depends on carbon dioxide and cardiac output by a complex fashion. ⋯ We bring evidence that DeltaPCO2 cannot serve as a marker of tissue hypoxia contrary to what was initially thought. However, DeltaPCO2 can be considered as a marker of the adequacy of venous blood flow (i.e. cardiac output) to remove the total CO2 produced by the peripheral tissues. In this regard, the knowledge of DeltaPCO2 should help the clinicians for the decision of giving therapy aimed at increasing cardiac output.
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Hypercapnia has traditionally been avoided in the quest to keep parameters normal. Recent understanding of the role of excessive tidal stretch has prompted clinicians to avoid high tidal volumes or plateau pressures, and the resulting permissive hypercapnia has been increasingly tolerated by clinicians. Newer data point to the potential for elevated CO2 to be protective, and in some experimental situations, to cause harm. The protective effects of so called therapeutic hypercapnia' remain experimental at present, but promising laboratory studies suggest potential roles for the eventual selective application at the bedside.
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Massive haemorrhage after trauma is a big challenge for care-givers, being a leading cause of early in-hospital mortality. Surgical bleeding may be easily controlled with several techniques. Otherwise, consumptive coagulopathy is often extremely difficult to stop. An adjunctive strategy to treat traumatic coagulopathic bleeding is recombinant activated factor VII (rFVIIa) (NovoSeven, Novo Nordisk A/S, Bagsvaerd, Denmark). ⋯ Off-label administration of rFVIIa was able to reverse life-threatening bleeding not manageable with standard strategies in our series of major trauma patients without systemic adverse effects.