Metabolic and hemodynamic changes during recovery and tracheal extubation in neurosurgical patients: immediate versus delayed recovery.

Delayed recovery has been advocated to limit the postoperative stress linked to awakening from anesthesia, but data on this subject are lacking. In this study, we measured oxygen consumption (V(O2)) and plasma catecholamine concentrations as markers of postoperative stress. We tested the hypothesis that delayed recovery and extubation would attenuate metabolic changes after intracranial surgery. Thirty patients were included in a prospective, open study and were randomized into two groups. In Group I, the patients were tracheally extubated as soon as possible after surgery. In Group II, the patients were sedated with propofol for 2 h after surgery. V(O2), catecholamine concentration, mean arterial pressure (MAP), and heart rate (HR) were measured during anesthesia, at extubation, and 30 min after extubation. V(O2) and noradrenaline on extubation and mean V(O2) during recovery were significantly higher in Group II than in Group I (V(O2) for Group I: preextubation 215 +/- 46 mL/min, recovery 198 +/- 38 mL/min; for Group II: preextubation 320 +/- 75 mL/min, recovery 268 +/- 49 mL/min; noradrenaline on extubation for Group I: 207 +/- 76 pg/mL, for Group II: 374 +/- 236 pg/ mL). Extubation induced a significant increase in MAP. MAP, HR, and adrenaline values were not statistically different between groups. In conclusion, delayed recovery after neurosurgery cannot be recommended as a mechanism of limiting the metabolic and hemodynamic consequences from emergence from general anesthesia. IMPLICATIONS: In this study, we tested the hypothesis that delayed recovery after neurosurgery would attenuate the consequences of recovery from general anesthesia. As markers of stress, oxygen consumption and noradrenaline blood levels were higher after delayed versus early recovery. Thus, delayed recovery cannot be recommended as a mechanism of limiting the metabolic and hemodynamic consequences from emergence after neurosurgery.

The effect of mountain bike suspensions on vibrations and off-road uphill performance.

AIM: This study evaluates the effect of front suspension (FS) and dual suspension (DS) mountain-bike on performance and vibrations during off-road uphill riding. METHODS: Thirteen male cyclists (27+/-5 years, 70+/-6 kg, VO(2max)59+/-6 mL.kg(-1).min(-1), mean+/-SD) performed, in a random sequence, at their lactate threshold, an off-road uphill course (1.69 km, 212 m elevation gain) with both type of bicycles. Variable measured: a) VO(2) consumption (K4b2 analyzer, Cosmed), b) power output (SRM) c) gain in altitude and d) 3-D accelerations under the saddle and at the wheel (Physilog, EPFL, Switzerland). Power spectral analy- sis (Fourier) was performed from the vertical acceleration data. RESULTS: Respectively for the FS and DS mountain bike: speed amounted to 7.5+/-0.7 km.h(-1) and 7.4+/-0.8 km.h(-1), (NS), energy expenditure 1.39+/-0.16 kW and 1.38+/-0.18, (NS), gross efficiency 0.161+/-0.013 and 0.159+/-0.013, (NS), peak frequency of vibration under the saddle 4.78+/-2.85 Hz and 2.27+/-0.2 Hz (P<0.01) and median-frequency of vertical displacements of the saddle 9.41+/-1.47 Hz and 5.78+/-2.27 Hz (P<0.01). CONCLUSION: Vibrations at the saddle level of the DS bike are of low frequencies whereas those of the FS bike are mostly of high frequencies. In the DS bike, the torque produced by the cyclist at the pedal level may generate low frequency vibrations. We conclude that the DS bike absorbs more high frequency vibrations, is more comfortable and performs as well as the FS bicycle.

Dairy calcium supplementation in overweight or obese persons: its effect on markers of fat metabolism

BACKGROUND: Dairy calcium supplementation has been proposed to increase fat oxidation and to inhibit lipogenesis. OBJECTIVE: We aimed to investigate the effects of calcium supplementation on markers of fat metabolism. DESIGN: In a placebo-controlled, crossover experiment, 10 overweight or obese subjects who were low calcium consumers received 800 mg dairy Ca/d for 5 wk. After 4 wk, adipose tissue was taken for biopsy for analysis of gene expression. Respiratory exchange, glycerol turnover, and subcutaneous adipose tissue microdialysis were performed for 7 h after consumption of 400 mg Ca or placebo, and the ingestion of either randomized slow-release caffeine (SRC; 300 mg) or lactose (500 mg). One week later, the test was repeated with the SRC or lactose crossover. RESULTS: Calcium supplementation increased urinary calcium excretion by 16% (P = 0.017) but did not alter plasma parathyroid hormone or osteocalcin concentrations. Resting energy expenditure (59.9 +/- 3.0 or 59.6 +/- 3.3 kcal/h), fat oxidation (58.4 +/- 2.5 or 53.8 +/- 2.2 mg/min), plasma free fatty acid concentrations (0.63 +/- 0.02 or 0.62 +/- 0.03 mmol/L), and glycerol turnover (3.63 +/- 0.41 or 3.70 +/- 0.38 micromol . kg(-1) . min(-1)) were similar with or without calcium, respectively. SRC significantly increased free fatty acid concentrations, resting fat oxidation, and resting energy expenditure. During microdialysis, epinephrine increased dialysate glycerol concentrations by 250% without and 254% with calcium. Expression of 7 key metabolic genes in subcutaneous adipose tissue was not affected by calcium supplementation. CONCLUSION: Dairy calcium supplementation in overweight subjects with habitually low calcium intakes failed to alter fat metabolism and energy expenditure under resting conditions and during acute stimulation by caffeine or epinephrine

Two days of hypoxic exposure increased ventilation without affecting performance.

The aim of this study was to test the short-term effects of using hypoxic rooms before a simulated running event. Thirteen subjects (29 +/- 4 years) lived in a hypoxic dormitory (1,800 m) for either 2 nights (n = 6) or 2 days + nights (n = 7) before performing a 1,500-m treadmill test. Performance, expired gases, and muscle electrical activity were recorded and compared with a control session performed 1 week before or after the altitude session (random order). Arterial blood samples were collected before and after altitude exposure. Arterial pH and hemoglobin concentration increased (p < 0.05) and PCO2 decreased (p < 0.05) upon exiting the room. However, these parameters returned (p < 0.05) to basal levels within a few hours. During exercise, mean ventilation (VE) was higher (p < 0.05) after 2 nights or days + nights of moderate altitude exposure (113.0 +/- 27.2 L.min) than in the control run (108.6 +/- 27.8 L.min), without any modification in performance (360 +/- 45 vs. 360 +/- 42 seconds, respectively) or muscle electrical activity. This elevated VE during the run after the hypoxic exposure was probably because of the subsistence effects of the hypoxic ventilatory response. However, from a practical point of view, although the use of a normobaric simulating altitude chamber exposure induced some hematological adaptations, these disappeared within a few hours and failed to provide any benefit during the subsequent 1,500-m run.

Impact of lung function changes after induction radiochemotherapy on resected T4 non-small cell lung cancer outcome.

BACKGROUND: Induction radiochemotherapy, followed by resection, for T4 non-small cell lung cancer, has shown promising long-term survival but may be associated with increased postoperative morbidity and death, depending on patient selection. Here, we determined the effect of induction radiochemotherapy on pulmonary function and whether postinduction pulmonary function changes predict hospital morbidity and death and long-term survival. METHODS: A consecutive prospective cohort of 72 patients with T4 N0-2 M0 non-small cell lung cancer managed by radiochemotherapy, followed by resection, is reported. All patients underwent thoracoabdominal computed tomography or fusion positron emission tomography-computed tomography, brain imaging, mediastinoscopy, echocardiography, ventilation-perfusion scintigraphy, and pulmonary function testing before and after induction therapy. Resection was performed if the postoperative forced expiratory volume in 1 second and diffusion capacity of the lung for carbon monoxide exceeded 30% predicted and if the postoperative maximum oxygen consumption exceeded 10 mL/kg/min. RESULTS: The postoperative 90-day mortality rate was 8% (lobectomy, 2%; pneumonectomy, 21%; p=0.01). All deaths after pneumonectomy occurred after right-sided procedures. The 3-year and 5-year survival was 50% (95% confidence interval, 36% to 62%) and 45% (95% confidence interval, 31% to 57%) and was significantly associated with completeness of resection (p=0.004) and resection type (pneumonectomy vs lobectomy, p=0.01). There was no correlation between postinduction pulmonary function changes and postoperative morbidity or death or long-term survival in patients managed by lobectomy or pneumonectomy. CONCLUSIONS: In properly selected patients with T4 N0-2 M0 non-small cell lung cancer, resection after induction radiochemotherapy can be performed with a reasonable postoperative mortality rate and long-term survival, provided the resection is complete and a right-sided pneumonectomy is avoided. Postinduction pulmonary function changes did not correlate with postoperative morbidity or death or with long-term outcome.

Maximal lipid oxidation during exercise: a target for individualizing endurance training in obesity and diabetes?

This review summarizes the rationale for personalized exercise training in obesity and diabetes, targeted at the level of maximal lipid oxidation as can be determined by exercise calorimetry. This measurement is reproducible and reflects muscles' ability to oxidize lipids. Targeted training at this level is well tolerated, increases the ability to oxidize lipids during exercise and improves body composition, lipid and inflammatory status, and glycated hemoglobin, thus representing a possible future strategy for exercise prescription in patients suffering from obesity and diabetes.

Combined effects of endurance training and dietary unsaturated fatty acids on physical performance, fat oxidation and insulin sensitivity.

Endurance training improves exercise performance and insulin sensitivity, and these effects may be in part mediated by an enhanced fat oxidation. Since n-3 and n-9 unsaturated fatty acids may also increase fat oxidation, we hypothesised that a diet enriched in these fatty acids may enhance the effects of endurance training on exercise performance, insulin sensitivity and fat oxidation. To assess this hypothesis, sixteen normal-weight sedentary male subjects were randomly assigned to an isoenergetic diet enriched with fish and olive oils (unsaturated fatty acid group (UFA): 52 % carbohydrates, 34 % fat (12 % SFA, 12 % MUFA, 5 % PUFA), 14 % protein), or a control diet (control group (CON): 62 % carbohydrates, 24 % fat (12 % SFA, 6 % MUFA, 2 % PUFA), 14 % protein) and underwent a 10 d gradual endurance training protocol. Exercise performance was evaluated by measuring VO2max and the time to exhaustion during a cycling exercise at 80 % VO2max; glucose homeostasis was assessed after ingestion of a test meal. Fat oxidation was assessed by indirect calorimetry at rest and during an exercise at 50 % VO2max. Training significantly increased time to exhaustion, but not VO2max, and lowered incremental insulin area under the curve after the test meal, indicating improved insulin sensitivity. Those effects were, however, of similar magnitude in UFA and CON. Fat oxidation tended to increase in UFA, but not in CON. This difference was, however, not significant. It is concluded that a diet enriched with fish- and olive oil does not substantially enhance the effects of a short-term endurance training protocol in healthy young subjects.

Effects of mental stress on insulin-mediated glucose metabolism and energy expenditure in lean and obese women.

The effects of the sympathetic activation elicited by a mental stress on insulin sensitivity and energy expenditure (VO(2)) were studied in 11 lean and 8 obese women during a hyperinsulinemic-euglycemic clamp. Six lean women were restudied under nonselective beta-adrenergic blockade with propranolol to determine the role of beta-adrenoceptors in the metabolic response to mental stress. In lean women, mental stress increased VO(2) by 20%, whole body glucose utilization ([6,6-(2)H(2)]glucose) by 34%, and cardiac index (thoracic bioimpedance) by 25%, whereas systemic vascular resistance decreased by 24%. In obese women, mental stress increased energy expenditure as in lean subjects, but it neither stimulated glucose uptake nor decreased systemic vascular resistance. In the six lean women who were restudied under propranolol, the rise in VO(2), glucose uptake, and cardiac output and the decrease in systemic vascular resistance during mental stress were all abolished. It is concluded that 1) in lean subjects, mental stress stimulates glucose uptake and energy expenditure and produces vasodilation; activation of beta-adrenoceptors is involved in these responses; and 2) in obese patients, the effects of mental stress on glucose uptake and systemic vascular resistance, but not on energy expenditure, are blunted.

Enteral nutrition and cardiovascular failure: from myths to clinical practice.

Cardiovascular failure and low flow states may arise in very different conditions from both cardiac and noncardiac causes. Systemic hemodynamic failure inevitably alters splanchnic blood flow but in an unpredictable way. Prolonged low splanchnic blood flow causes intestinal ischemia, increased mucosal permeability, endotoxemia, and distant organ failure. Mortality associated with intestinal ischemia is high. Why would enteral nutrition (EN) be desirable in these complex patients when parenteral nutrition could easily cover energy and substrate requirements? Metabolic, immune, and practical reasons justify the use of EN. In addition, continuous enteral feeding minimizes systemic and myocardial oxygen consumption in patients with congestive heart failure. Further, early feeding in critically ill mechanically ventilated patients has been shown to reduce mortality, particularly in the sickest patients. In a series of cardiac surgery patients with compromised hemodynamics, absorption has been maintained, and 1000-1200 kcal/d could be delivered by enteral feeding. Therefore, early EN in stabilized patients should be attempted, and can be carried out safely under close clinical monitoring, looking for signs of incipient intestinal ischemia. Energy delivery and balance should be monitored, and combined feeding considered when enteral feeds cannot be advanced to target within 4-6 days.

Effects of 2 different prior endurance exercises on whole-body fat oxidation kinetics: light vs. heavy exercise.

This study aimed to compare the effects of 2 different prior endurance exercises on subsequent whole-body fat oxidation kinetics. Fifteen men performed 2 identical submaximal incremental tests (Incr2) on a cycle ergometer after (i) a ∼40-min submaximal incremental test (Incr1) followed by a 90-min continuous exercise performed at 50% of maximal aerobic power-output and a 1-h rest period (Heavy); and (ii) Incr1 followed by a 2.5-h rest period (Light). Fat oxidation was measured using indirect calorimetry and plotted as a function of exercise intensity during Incr1 and Incr2. A sinusoidal equation, including 3 independent variables (dilatation, symmetry and translation), was used to characterize the fat oxidation kinetics and to determine the intensity (Fat(max)) that elicited the maximal fat oxidation (MFO) during Incr. After the Heavy and Light trials, Fat(max), MFO, and fat oxidation rates were significantly greater during Incr2 than Incr1 (p < 0.001). However, Δ (i.e., Incr2-Incr1) Fat(max), MFO, and fat oxidation rates were greater in the Heavy compared with the Light trial (p < 0.05). The fat oxidation kinetics during Incr2(Heavy) showed a greater dilatation and rightward asymmetry than Incr1(Heavy), whereas only a greater dilatation was observed in Incr2(Light) (p < 0.05). This study showed that although to a lesser extent in the Light trial, both prior exercise sessions led to an increase in Fat(max), MFO, and absolute fat oxidation rates during Incr2, inducing significant changes in the shape of the fat oxidation kinetics.

Brain multimodality monitoring: an update.

PURPOSE OF REVIEW: An important goal of neurocritical care is the management of secondary brain injury (SBI), that is pathological events occurring after primary insult that add further burden to outcome. Brain oedema, cerebral ischemia, energy dysfunction, seizures and systemic insults are the main components of SBI. We here review recent data showing the clinical utility of brain multimodality monitoring (BMM) for the management of SBI. RECENT FINDINGS: Despite being recommended by international guidelines, standard intracranial pressure (ICP) monitoring may be insufficient to detect all episodes of SBI. ICP monitoring, combined with brain oxygen (PbtO(2)), cerebral microdialysis and regional cerebral blood flow, might help to target therapy (e.g. management of cerebral perfusion pressure, blood transfusion, glucose control) to patient-specific pathophysiology. Physiological parameters derived from BMM, including PbtO(2) and microdialysis lactate/pyruvate ratio, correlate with outcome and have recently been incorporated into neurocritical care guidelines. Advanced intracranial devices can be complemented by quantitative electroencephalography to monitor changes of brain function and nonconvulsive seizures. SUMMARY: BMM offers an on-line comprehensive scrutiny of the injured brain and is increasingly used for the management of SBI. Integration of monitored data using new informatics tools may help optimize therapy of brain-injured patients and quality of care.

A whole body transportable indirect calorimeter for human use in the tropics.

A transportable, whole body indirect calorimeter, designed for use in the tropics, is described. The calorimeter was built to study energy expenditure of people having chronically or acutely low levels of food intake, and it will help to determine energy adaptations made by individuals with restricted food intake. The calorimeter comprises two units: a 27 m3 ventilated chamber connected to an office housing control and monitoring equipment. The system also allows the experimenter to assess the rate of energy expenditure by means of a ventilated hood or a baby respiration chamber. The incoming air flow rate is variable and is typically set at approximately 30 l/min. Carbon dioxide production (VCO2) and oxygen consumption (VO2) are continuously monitored by means of differential gas analysers via a computerized data acquisition unit. Gas production/consumption rates are measured with a delay of 80 s, the complete response to step changes in VCO2 or VO2 consumption being calculated over 15 min using the rate of change terms in the gas exchange equations. The total electrical power required for the whole system is 12 kW. The calorimeter has been functioning for nearly 4 years in a rural village of The Gambia during which ambient temperatures have ranged from 16 to 44 degrees C and dewpoints from -8 to 24 degrees C. The performance and accuracy of the calorimeter were tested using 20 per cent CO2 in N2 infusion and butane burning. Agreement between the theoretical and the measured values was found to be 99 per cent for VO2 and 100 per cent for VCO2 with a precision for both gases of +/- 10 ml/min over a 1-h period.