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  • A comparison of the laryngeal mask airway with facemask and oropharyngeal airway for manual ventilation by critical care nurses in children.

    3 July 2018

    The laryngeal mask airway is included as a first line airway device during adult resuscitation by first responders. However, there is little evidence for its role in paediatric resuscitation. Using anaesthetised children as a model for paediatric cardiopulmonary arrest, we compared the ability of critical care nurses to manually ventilate the anaesthetised child via the laryngeal mask airway compared with the facemask and oropharyngeal airway. The airway devices were inserted in random order and chest expansion was measured using an ultrasound distance transducer. The critical care nurses were able to place the laryngeal mask airway and achieve successful ventilation in 82% of children compared to 70% using the facemask and oropharyngeal airway, although the difference was not statistically significant (p = 0.136). The median time to first successful breath using the laryngeal mask airway was 39 s compared to 25 s using the facemask (p < 0.001). In this group of nurses, we did not show a difference in ventilation via a laryngeal mask airway or facemask, although facemask ventilation was achieved more quickly.

  • Increased cationic amino acid flux through a newly expressed transporter in cells overproducing nitric oxide from patients with septic shock.

    3 July 2018

    Increased production of nitric oxide (NO) is thought to be a factor in the pathogenesis of many human diseases - among them the hypotension that often accompanies sepsis. The supply of the cationic amino acid arginine is known to be rate-limiting for NO production. We hypothesized that cationic amino acid transport might be increased in cells producing excess NO from patients with septic shock. Peripheral blood mononuclear cells were isolated from patients with sepsis and from healthy control subjects. The rates of both NO production and cationic amino acid uptake were increased in cells from patients with septic shock. The increased transport was due almost entirely to an increase in the activity of one transporter, subtype y+. The activity of the other major cationic amino acid transporter (y+L) was unchanged. The expression of CAT2 mRNA, which encodes a y+ transporter protein, was also increased in these cells. We suggest that CAT2 might be a therapeutic target to prevent excess NO production in sepsis and possibly other human disease states, while leaving basal production unchanged.

  • Abnormal cerebral blood volume in regions of contused and normal appearing brain following traumatic brain injury using perfusion magnetic resonance imaging.

    2 July 2018

    Following traumatic brain injury, there may be secondary alterations in cerebrovascular parameters leading to ischemia and further cellular damage. To assess possible subacute hemodynamic disturbances following traumatic brain injury, we used conventional and perfusion magnetic resonance imaging (MRI) in 18 patients, on average 10 days following injury. Six of the 18 patients had focal contusions or edema visible on conventional MRI. These six patients had a significantly reduced normalized regional cerebral blood volume (rCBV) in the regions of focal pathology compared to equivalent areas in control subjects (patients 0.47 +/- 0.20 [means +/- SD], controls 1.02 +/- 0.11, p < 0.001). In addition, four of these six patients had an increased rCBV (outside control range) in the region of normal appearing brain immediately surrounding the contusion. These six patients were more significantly injured and had a worse clinical outcome compared to the remaining patients (p = 0.004,p = 0.03, respectively). There were five patients who had a region of reduced rCBV (outside control range) in a quadrant of normal appearing white matter, away from any visible abnormality, who were not more significantly injured than the remaining patients but went on to have a significantly poorer clinical outcome (p = 0.27, p = 0.01, respectively). Traumatic brain injury is a heterogeneous insult causing a variety of pathology, not all of which is visible using conventional imaging methods. The current study has shown that regions of both normal appearing and contused brain may have an abnormal rCBV and that alterations in rCBV may play a role in determining the clinical outcome of patients.

  • Power spectral analysis of the effects of epinephrine, norepinephrine, dobutamine and dopexamine on microcirculation following free tissue transfer

    3 July 2018

    Background: The use of pressor drugs after microsurgical free tissue transfer remains controversial because of potential vasoconstrictor effects on the free flap. Noninvasive monitoring of free flaps with laser Doppler flowmetry may provide further information regarding the local regulation of blood flow in the flap tissues during pressor infusions. This study evaluated the effects of four commonly used pressor agents. Methods: Twenty four patients (25 data sets) undergoing head and neck cancer resection and free flap reconstruction were recruited. Epinephrine, norepinephrine, dopexamine, and dobutamine were infused in a random order at four infusion rates, after surgery, with free flap and control area (deltoid region) laser Doppler skin blood flow monitoring. Frequency analysis of the Doppler waveform was performed utilizing the time period immediately before the first drug infusion for each patient as baseline. Results: At baseline there was less power at the 0.002-0.6 Hz frequency in the flap compared with control tissue consistent with surgical denervation. At maximum epinephrine infusion rates, the control of blood flow moved toward (i.e., proportion of power increased in) the lower frequencies, as smooth muscle mediated (myogenic) control began to dominate blood flow, an effect most marked with norepinephrine. Dobutamine and dopexamine had little effect on control of blood flow. Conclusions: Denervation of free flap tissue is demonstrable using spectral analysis of laser Doppler blood flow signals. With norepinephrine the control of blood flow shifts toward low frequency vasomotion where blood flow depends mostly on average blood pressure, making it potentially the most suitable agent following free tissue transfer. Copyright © 2013 Wiley Periodicals, Inc.

  • Power spectral analysis of the effects of epinephrine, norepinephrine, dobutamine and dopexamine on microcirculation following free tissue transfer.

    2 July 2018

    BACKGROUND: The use of pressor drugs after microsurgical free tissue transfer remains controversial because of potential vasoconstrictor effects on the free flap. Noninvasive monitoring of free flaps with laser Doppler flowmetry may provide further information regarding the local regulation of blood flow in the flap tissues during pressor infusions. This study evaluated the effects of four commonly used pressor agents. METHODS: Twenty four patients (25 data sets) undergoing head and neck cancer resection and free flap reconstruction were recruited. Epinephrine, norepinephrine, dopexamine, and dobutamine were infused in a random order at four infusion rates, after surgery, with free flap and control area (deltoid region) laser Doppler skin blood flow monitoring. Frequency analysis of the Doppler waveform was performed utilizing the time period immediately before the first drug infusion for each patient as baseline. RESULTS: At baseline there was less power at the 0.002-0.6 Hz frequency in the flap compared with control tissue consistent with surgical denervation. At maximum epinephrine infusion rates, the control of blood flow moved toward (i.e., proportion of power increased in) the lower frequencies, as smooth muscle mediated (myogenic) control began to dominate blood flow, an effect most marked with norepinephrine. Dobutamine and dopexamine had little effect on control of blood flow. CONCLUSIONS: Denervation of free flap tissue is demonstrable using spectral analysis of laser Doppler blood flow signals. With norepinephrine the control of blood flow shifts toward low frequency vasomotion where blood flow depends mostly on average blood pressure, making it potentially the most suitable agent following free tissue transfer.

  • Comparison of mortality prediction models after open abdominal aortic aneurysm repair.

    3 July 2018

    OBJECTIVES: Comparison of the accuracy of prediction of contemporary mortality prediction models after open Abdominal Aortic Aneurysm (AAA) surgery. METHODS: Post-operative data were collected from AAA patients from 2 UK Intensive Care Units (ICU). POSSUM and VBHOM based models were compared to the APACHE-AAA model which was able to adjust for the hospital-related effect on outcome. Model performance was assessed using measures of calibration, discrimination and subgroup analysis. RESULTS: 541 patients were studied. The in-hospital mortality rate for elective AAA repair (325 patients) was: 6.2% (95% confidence interval (c.i.) 3.5 to 8.8) and for emergency repair (216 patients) was: 28.7% (95% c.i. 22.5-34.9). The APACHE-based model had the best overall fit to the whole population of AAA patients, and also separately in elective and emergency patients. The V-POSSUM physiology-only (p<0.001) and VBHOM (p=0.011) models had a poor fit in elective patients. The RAAA-POSSUM physiology-only (p<0.001) and VBHOM models (p=0.010) had a poor fit in emergency patients. CONCLUSIONS: The APACHE-AAA model with its ability to adjust for both the hospital-related "effect" as well as the patient case-mix, was a more accurate risk stratification model than other contemporary models, in the post-operative AAA patient managed in ICU.

  • Nitric oxide production by human peripheral blood mononuclear cells.

    2 July 2018

    INTRODUCTION: There are conflicting data on the ability of human mononuclear cells to produce nitric oxide (NO). We investigated nitric oxide production from peripheral blood mononuclear cells (PBMs) by using a new sensitive fluorescent indicator. MATERIALS AND METHODS: PBMs from healthy volunteers were collected, plated in 96-well microplates, and loaded with the fluorescent nitric oxide probe, 4,5-diaminofluorescein diacetate (DAF-2DA). Experiments were performed in normal control and endotoxin-stimulated PBMs, with and without exogenous L-arginine. The exogenous nitric oxide donor S-nitroso-N-acetyl-penicillamine (SNAP) was used as a positive control. Fluorescence intensity was measured with a fluorescence microplate reader. RESULTS: Nitric oxide production by human PBMs can be demonstrated by the use of the fluorescent indicator, DAF-2DA, in both control and endotoxin-stimulated conditions. Nitric oxide production was independent of the concentration of exogenous L-arginine. The addition of endotoxin did not change nitric oxide production. PBMs treated with SNAP showed a concentration dependent increase in fluorescence. Nitric oxide production over 5 hours was constant and identical in both control and stimulated groups. CONCLUSION: This fluorescent indicator technique is useful for the study of NO production by human PBMs. Nitric oxide production by PBMs was independent of exogenous L-arginine concentration and was not affected by endotoxin.