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  • Primary care respiratory journal: journal of the General Practice Airways Group 05/2013; 22(2). DOI:10.4104/pcrj.2013.00051
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    ABSTRACT: There has been an increase in both recreational and adventure travel to extreme environments. Humans can successfully acclimatize to and perform reasonably well in extreme environments, provided that sufficient time is given for acclimatization (where possible) and that they use appropriate behavior. This is aided by a knowledge of the problems likely to be encountered and their prevention, recognition, and treatment.
    Infectious disease clinics of North America 09/2012; 26(3):707-23. DOI:10.1016/j.idc.2012.07.001
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    ABSTRACT: Neuromuscular blocking agents are commonly used in critical care. However, concern after observational reports of a causal relationship with skeletal muscle dysfunction and intensive care-acquired weakness (ICU-AW) has resulted in a cautionary and conservative approach to their use. This integrative review, interpreted in the context of our current understanding of the pathophysiology of ICU-AW and integrated into our current conceptual framework of clinical practice, challenges the established clinical view of an adverse relationship between the use of neuromuscular blocking agents and skeletal muscle weakness. In addition to discussing data, this review identifies potential confounders and alternative etiological factors responsible for ICU-AW and provides evidence that neuromuscular blocking agents may not be a major cause of weakness in a 21st century critical care setting.
    American Journal of Respiratory and Critical Care Medicine 05/2012; 185(9):911-7. DOI:10.1164/rccm.201107-1320OE
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    ABSTRACT: To develop a tool for identifying and quantifying morbidity following cardiac surgery (cardiac postoperative morbidity score [C-POMS]). Morbidity was prospectively assessed in 450 cardiac surgery patients on postoperative days 1, 3, 5, 8, and 15 using POMS criteria (nine postoperative morbidity domains in general surgical patients) and cardiac-specific variables (from expert panel). Other morbidities were noted as free text and included if prevalence was more than 5%, missingness less than 5%, and mean expert-rated severity-importance index score more than 8. Construct validity was assessed by expert panel review, Cronbach's alpha (internal consistency), and linear regression (predictive ability of C-POMS for length of stay [LOS]). A 13-domain model was derived. Internal consistency (>0.7) on D3-D15 permits use as a summative score of total morbidity burden. Mean C-POMS scores were 3.4 (D3), 2.6 (D5), 3.4 (D8), and 3.8 (D15). Patient LOS was 4.6 days (P=0.012), 5.3 days (P=0.001), and 7.6 days (P=0.135) longer in patients with C-POMS-defined morbidity on D3, D5, D8, and D15, respectively, than in those without. For every unit increase in C-POMS summary score, subsequent LOS increased by 1.7 (D3), 2.2 (D5), 4.5 (D8), and 6.2 (D15) days (all P=0.000). C-POMS is the first validated tool for identifying total morbidity burden after cardiac surgery. However, further external validation is warranted.
    Journal of clinical epidemiology 04/2012; 65(4):423-33. DOI:10.1016/j.jclinepi.2011.11.004
  • Osteoporosis International 01/2012; 23(7):1947-56. DOI:10.1007/s00198-011-1853-1
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    ABSTRACT: The skeletal response to short-term exercise training remains poorly described. We thus studied the lower limb skeletal response of 723 Caucasian male army recruits to a 12-wk training regime. Femoral bone volume was assessed using magnetic resonance imaging, bone ultrastructure by quantitative ultrasound (QUS), and bone mineral density (BMD) using dual-energy X-ray absorptiometry (DXA) of the hip. Left hip BMD increased with training (mean ± SD: 0.85 ± 3.24, 2.93 ± 4.85, and 1.89 ± 2.85% for femoral neck, Ward's area, and total hip, respectively; all P < 0.001). Left calcaneal broadband ultrasound attenuation rose 3.57 ± 0.5% (P < 0.001), and left and right femoral cortical volume by 1.09 ± 4.05 and 0.71 ± 4.05%, respectively (P = 0.0001 and 0.003), largely through the rise in periosteal volume (0.78 ± 3.14 and 0.59 ± 2.58% for right and left, respectively, P < 0.001) with endosteal volumes unchanged. Before training, DXA and QUS measures were independent of limb dominance. However, the dominant femur had higher periosteal (25,991.49 vs. 2,5572 mm(3), P < 0.001), endosteal (6,063.33 vs. 5,983.12 mm(3), P = 0.001), and cortical volumes (19,928 vs. 19,589.56 mm(3), P = 0.001). Changes in DXA, QUS, and magnetic resonance imaging measures were independent of limb dominance. We show, for the first time, that short-term exercise training in young men is associated not only with a rise in human femoral BMD, but also in femoral bone volume, the latter largely through a periosteal response.
    Journal of Applied Physiology 11/2011; 112(4):615-26. DOI:10.1152/japplphysiol.00788.2011
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    ABSTRACT: Transcranial Doppler is a widely used noninvasive technique for assessing cerebral artery blood flow. All previous high altitude studies assessing cerebral blood flow (CBF) in the field that have used Doppler to measure arterial blood velocity have assumed vessel diameter to not alter. Here, we report two studies that demonstrate this is not the case. First, we report the highest recorded study of CBF (7,950 m on Everest) and demonstrate that above 5,300 m, middle cerebral artery (MCA) diameter increases (n=24 at 5,300 m, 14 at 6,400 m, and 5 at 7,950 m). Mean MCA diameter at sea level was 5.30 mm, at 5,300 m was 5.23 mm, at 6,400 m was 6.66 mm, and at 7,950 m was 9.34 mm (P<0.001 for change between 5,300 and 7,950 m). The dilatation at 7,950 m reversed with oxygen. Second, we confirm this dilatation by demonstrating the same effect (and correlating it with ultrasound) during hypoxia (FiO(2)=12% for 3 hours) in a 3-T magnetic resonance imaging study at sea level (n=7). From these results, we conclude that it cannot be assumed that cerebral artery diameter is constant, especially during alterations of inspired oxygen partial pressure, and that transcranial 2D ultrasound is a technique that can be used at the bedside or in the remote setting to assess MCA caliber.
    Journal of cerebral blood flow and metabolism: official journal of the International Society of Cerebral Blood Flow and Metabolism 06/2011; 31(10):2019-29. DOI:10.1038/jcbfm.2011.81
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    ABSTRACT: The association of red blood cell (RBC) storage on morbidity outcome after cardiac surgery is debated. We sought to clarify the association of the age of transfused blood on outcome in patients undergoing cardiac surgery. Data were drawn from a prospective, observational cohort study of morbidity outcome in patients undergoing cardiac surgery. Blood transfusion data were obtained retrospectively via the Trust blood bank electronic records. Old blood was defined as more than 14 days old. The primary outcome measure was postoperative length of stay (PLOS). Secondary outcome measures included renal failure and morbidity as defined within the postoperative morbidity survey. A total of 176 (39.6%) of 444 participants received a blood transfusion. Patients transfused with new blood had a reduced PLOS compared with patients receiving exclusively old or any old blood (old blood ± new blood; 7 days vs. 8 days, p = 0.04 and vs. 10 days, p = 0.002, respectively). In patients who only had 1 unit transfused, PLOS was longer in those receiving only old blood compared with those receiving only new blood (8 days vs. 6 days, p = 0.02) with a 3.8-fold risk of longer stay. Compared with patients receiving exclusively new blood, patients receiving any old blood had a higher incidence of new renal complications (65.7% vs. 43.9%, p = 0.008). Each 1-day increase in storage was associated with a 7% increase in risk of new renal complications. Our data support previous suggestions of an association between transfusion of older RBCs and poorer outcome in cardiac surgery patients. Randomized controlled trials are required to determine the true causal nature of any such association.
    Transfusion 05/2011; 51(11):2286-94. DOI:10.1111/j.1537-2995.2011.03170.x
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    ABSTRACT: Cardiopulmonary bypass during cardiac surgery can result in a shortfall in oxygen delivery relative to demand, marked by a decrease in muscle tissue oxygen saturation as blood flow is redistributed to vital organs. Such "tissue shock" might impair postoperative recovery. To determine the association of changes in tissue oxygen saturation with postoperative outcome in cardiac surgery patients. In 74 adults undergoing cardiac surgery, tissue oxygen saturation in the thenar eminence was recorded using near-infrared spectroscopy before and during induction of anesthesia, throughout surgery, and in the intensive care unit until extubation or for a maximum monitoring time of 24 hours. The measurements were related to postoperative outcome. Mean tissue oxygen saturation increased from 81.7% to 88.5% with induction of anesthesia and decreased to 78.9% and 69.9% during surgery and on arrival in the intensive care unit, respectively. Saturation increased to 77.8% by 6 hours after surgery and remained stable. Mean saturation during the first minutes of anesthesia and 20 minutes in the intensive care unit was lower in patients with a postoperative morbidity than in patients without such morbidity on day 15 (81.1% vs 87.6%; P = .04) and on day 3 (72.9% vs 85.5%; P = .009). No associations with other outcome measures were observed. In patients undergoing cardiac surgery, reduced tissue oxygen saturation in the thenar eminence may be associated with poor postoperative outcome. Further studies are needed to confirm these findings and to determine whether measures to improve the balance between oxygen delivery and consumption might improve both tissue oxygen saturation and outcome.
    American Journal of Critical Care 03/2011; 20(2):138-45. DOI:10.4037/ajcc2011739
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    ABSTRACT: In the mountain environment sudden cardiac death (SCD) has been shown to be responsible for the deaths of up to 52% of downhill skiers and 30% of hikers. The majority of SCD's are precipitated by a ventricular arrhythmia. Although most are likely to result from structural abnormalities associated with conditions such as ischaemic heart disease, a small but significant number may be due to abnormalities in ion channel activity, commonly known as, "channelopathies". Channelopathies have the potential to lengthen the time between ventricular depolarisation and repolarisation that can result in prolongation of the corrected QT interval (QTc) and episodes of polymorphic ventricular tachycardia (PVT) and eventually, ventricular fibrillation. This review examines the factors that prolong the QTc interval in the mountain environment and outlines a practical framework for preventing the life threatening arrhythmias that are associated with this condition.
    Journal of the Royal Army Medical Corps 03/2011; 157(1):63-7. DOI:10.1136/jramc-157-01-11
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