Anesthesiology
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Comparative Study
Measurement of cardiac output with indocyanine green transcutaneous fluorescence dilution technique.
Cardiac output is an essential parameter for the hemodynamic assessment of patients with cardiovascular disease. The authors tested in an animal model the feasibility of measuring cardiac output by transcutaneous fluorescence monitoring of an intravenous bolus injection of indocyanine green. ⋯ The proposed technique yielded accurate estimates of the cardiac output in experimental animals. This study should provide an initial framework for clinical testing of this new minimally invasive method for measuring cardiac output.
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Factors contributing to subarachnoid catheter passage after epidural placement are not well understood. This study explored mechanisms that might explain its occurrence. ⋯ Catheter passage is unlikely in the presence of intact dura or after an uncomplicated combined spinal-epidural. Unintentional subarachnoid passage suggests dural damage with the epidural needle.
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Comparative Study
Endotracheal tubes coated with antiseptics decrease bacterial colonization of the ventilator circuits, lungs, and endotracheal tube.
Formation of a bacterial biofilm within the endotracheal tube (ETT) after tracheal intubation is rapid and represents a ready source of lung bacterial colonization. The authors investigated bacterial colonization of the ventilator circuit, the ETT, and the lungs when the ETT was coated with silver-sulfadiazine and chlorhexidine in polyurethane, using no bacterial/viral filter attached to the ETT. ⋯ Coated ETTs induced a nonsignificant reduction of the tracheal colonization, eliminated (seven of eight) or reduced (one of eight) bacterial colonization of the ETT and ventilator circuits, and prevented lung bacterial colonization.
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The authors have developed a new clinical bymixer that bypasses a constant fraction of gas flow through a mixing arm. A separate bymixer was interposed in the expiratory and inspiratory limbs of the ventilation circuit to measure mixed gas fractions. By utilizing nitrogen conservation, the clinical bymixer allows the determination of airway carbon dioxide elimination (VCO2) and oxygen uptake (VO2), whenever basic expired flow and gas monitoring measurements are used for the patient. Neither an expiratory exhaust gas collection bag nor expensive, complex equipment are needed. This study tested the accuracy of airway bymixer-flow measurements of VCO2 and VO2 in a new bench apparatus. ⋯ The new clinical bymixer, plus basic expired flow and gas fraction measurements, generated clinically accurate determinations of VCO2 and VO2. These measurements are helpful in the assessment of metabolic gas exchange in the critical care unit. In contrast to using the gas collection bag or complex metabolic monitor, the bymixer should measure mixed gas concentrations in the inspired or expired limb of the common anesthesia circle ventilation circuit.
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Comparative Study
Production of paradoxical sensory hypersensitivity by alpha 2-adrenoreceptor agonists.
Administration of opioid receptor agonists is followed by paradoxical sensory hypersensitivity. This hypersensitivity has been suggested to contribute to the antinociceptive tolerance observed with opioids. The authors hypothesized that alpha 2-adrenoreceptor agonists, which also produce antinociceptive tolerance, would produce sensory hypersensitivity. ⋯ alpha 2-Adrenoreceptor agonists produce sensory hypersensitivity that may be analogous to that produced by opioids. Sensory hypersensitivity was prevented by idazoxan, demonstrating that it is mediated by alpha 2 receptors. Clonidine infusion increased spinal dynorphin content. Sensory hypersensitivity was prevented or reversed by MK-801 and dynorphin antiserum, implicating N-methyl-D-aspartate receptors and spinal dynorphin in its production. Clinicians should be mindful of the possibility of drug-induced hyperalgesia in patients treated with alpha 2-adrenoreceptor agonists.