Biomedical subjects
G R Kleger
Publications and source records attributed to G R Kleger.
Acute metabolic acidosis decreases muscle protein synthesis but not albumin synthesis in humans.
Chronic metabolic acidosis induces negative nitrogen balance by either increased protein breakdown or decreased protein synthesis. Few data exist regarding effects of acute metabolic acidosis on protein synthesis. We investigated fractional synthesis rates (FSRs) of muscle protein and albumin, plasma concentrations of insulin-like growth factor-I (IGF-I), thyroid-stimulating hormone (TSH), and thyroid hormones (free thyroxin [fT(4)] and triiodothyronine [fT(3)]) in seven healthy human volunteers after a stable controlled metabolic period of 5 days and again 48 hours later after inducing metabolic acidosis by oral ammonium chloride intake (4.2 mmol/kg/d divided in six daily doses). Muscle and albumin FSRs were obtained by the [(2)H(5)ring]phenylalanine flooding technique. Ammonium chloride induced a significant decrease in pH (7.43 +/- 0.02 versus 7.32 +/- 0.04; P < 0.0001) and bicarbonate concentration (24.6 +/- 1.6 versus 16.0 +/- 2.7 mmol/L; P < 0.0001) within 48 hours. Nitrogen balance decreased significantly on the second day of acidosis. The FSR of muscle protein decreased (1.94 +/- 0.25 versus 1.30 +/- 0.39; P < 0.02), whereas the FSR of albumin remained constant. TSH levels increased significantly (1.1 +/- 0.5 versus 1.9 +/- 1.1 mU/L; P = 0.03), whereas IGF-I, fT(4), and fT(3) levels showed no significant change. We conclude that acute metabolic acidosis for 48 hours in humans induces a decrease in muscle protein synthesis, which contributes substantially to a negative nitrogen balance. In contrast to prolonged metabolic acidosis of 7 days, a short period of acidosis in the present study did not downregulate albumin synthesis.
Prevalence of tracheostomy in ICU patients. A nation-wide survey in Switzerland.
OBJECTIVE: To assess the frequency, timing and technique of tracheostomy and its variation between different intensive care units (ICUs) in Switzerland. DESIGN: Retrospective, descriptive prevalence study. SETTING: A questionnaire was sent to all intensive care units formally recognized by the Swiss Society of Intensive Care Medicine. Excluded were paediatric ICUs. A total of 48 ICUs (70 %) responded. PATIENTS: In 1995 and 1996 the participating units had admitted 90,412 patients for a total of 243,921 ICU days. RESULTS: Seventy percent of the contacted ICUs answered the questionnaire. The prevalence of tracheostomy was 10% in the long-term ventilated patients (defined as > 24 h), or 1.3 % of all patients. Most tracheostomies were performed during the 2nd week of ventilation. The frequency of tracheostomy varied widely (0-60 %) and was only slightly associated with the different language regions of our country and with the policy of hospitals to accept or refuse intubated patients on their normal wards. Most units offered either conventional surgical tracheostomy (69 %) and/or percutaneous procedures (57 %). The decision to perform a tracheostomy was made mostly by the intensivist and the procedure was more often performed in the ICU (65 %) than in the operating theatre (35 %). Units where the intensivist had exclusive control used only percutaneous techniques. An overall complication rate of 13 % was reported, bleeding and infections being at the top of the scale. Only 27 % of the units performed late follow-up protocols. CONCLUSIONS: Despite its frequency, tracheostomy in Swiss ICUs is far from being standardized with regard to indication, timing and choice of technique.
Inhaled nitric oxide for high-altitude pulmonary edema.
BACKGROUND: Pulmonary hypertension is a hallmark of high-altitude pulmonary edema and may contribute to its pathogenesis. When administered by inhalation, nitric oxide, an endothelium-derived relaxing factor, attenuates the pulmonary vasoconstriction produced by short-term hypoxia. METHODS: We studied the effects of inhaled nitric oxide on pulmonary-artery pressure and arterial oxygenation in 18 mountaineers prone to high-altitude pulmonary edema and 18 mountaineers resistant to this condition in a high altitude laboratory (altitude, 4559 m). We also obtained lung-perfusion scans before and during nitric oxide inhalation to gain further insight into the mechanism of action of nitric oxide. RESULTS: In the high-altitude laboratory, subjects prone to high-altitude pulmonary edema had more pronounced pulmonary hypertension and hypoxemia than subjects resistant to high-altitude pulmonary edema. Arterial oxygen saturation was inversely related to the severity of pulmonary hypertension (r=-0.50, P=0.002). In subjects prone to high-altitude pulmonary edema, the inhalation of nitric oxide (40 ppm for 15 minutes) produced a decrease in mean (+/-SD) systolic pulmonary-artery pressure that was three times larger than the decrease in subjects resistant to such edema (25.9+/-8.9 vs. 8.7+/-4.8 mm Hg, P<0.001). Inhaled nitric oxide improved arterial oxygenation in the 10 subjects who had radiographic evidence of pulmonary edema (arterial oxygen saturation increased from 67+/-10 to 73+/-12 percent, P=0.047), whereas it worsened oxygenation in subjects resistant to high-altitude pulmonary edema. The nitric oxide-induced improvement in arterial oxygenation in subjects with high-altitude pulmonary edema was accompanied by a shift in blood flow in the lung away from edematous segments and toward nonedematous segments. CONCLUSIONS: The inhalation of nitric oxide improves arterial oxygenation in high-altitude pulmonary edema, and this beneficial effect may be related to its favorable action on the distribution of blood flow in the lungs. A defect in nitric nitric oxide synthesis may contribute to high-altitude pulmonary edema.
Evidence against an increase in capillary permeability in subjects exposed to high altitude.
A potential pathogenetic cofactor for the development of acute mountain sickness and high-altitude pulmonary edema is an increase in capillary permeability, which could occur as a result of an inflammatory reaction and/or free radical-mediated injury to the lung. We measured the systemic albumin escape by intravenously injecting 5 muCi of 125I-labeled albumin and the plasma concentrations of cytokines, F2-isoprostanes (products of lipid peroxidation), and acute-phase proteins in 24 subjects exposed to 4,559 m. Ten subjects developed acute mountain sickness, and four subjects developed high-altitude pulmonary edema. The transcapillary escape rate of albumin was 6.9 +/- 2.0%/h (SD) at low (550 m) and 6.3 +/- 1.9%/h at high (4,559 m) altitude (P = 0.23; n = 24). The subjects with high-altitude pulmonary edema had a modest but insignificant increase in the transcapillary escape rate of albumin (4.6 +/- 1.9%/h at low vs. 5.7 +/- 1.9%/h at high altitude; P = 0.42; n = 4). Plasma concentrations of fibrinogen, alpha 1-acid glycoprotein, C-reactive protein, and interleukin-6 were unchanged in the early phases and significantly increased by the end of the observation period in the subjects with high-altitude pulmonary edema, whereas tumor necrosis factor-alpha and F2-isoprostanes did not change at all. This suggests that the inflammatory reaction was rather a consequence than a causative factor of high-altitude pulmonary edema. In summary, these data argue against a dominant role for increased systemic capillary permeability in the development of acute mountain sickness and high-altitude pulmonary edema.
Sumatriptan for high-altitude headache.
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