Clarification of the circulatory patho-physiology of anaesthesia - Implications for high-risk surgical patients

AbstractThe paper examines the effects of anaesthesia on circulatory physiology and their implications regarding improvement in perioperative anaesthetic management. Changes to current anaesthetic practice, recommended recently, such as the use of flow monitoring in high risk patients, are already beginning to have an impact in reducing complications but not mortality [1]. Better understanding of the patho-physiology should help improve management even further. Analysis of selected individual clinical trials has been used to illustrate particular areas of patho-physiology and how changes in practice have improved outcome. There is physiological support for the importance of achieving an appropriate rate of oxygen delivery (DO2), particularly following induction of anaesthesia. It is suggested that ensuring adequate DO2 during anaesthesia will avoid development of oxygen debt and hence obviate the need to induce a high, compensatory, DO2 in the post-operative period. In contrast to the usual assumptions underlying strategies requiring a global increase in blood flow [1] by a stroke volume near maximization strategy, blood flow control actually resides entirely at the tissues not at the heart. This is important as the starting point for understanding failed circulatory control as indicated by ‘volume dependency’. Local adjustments in blood flow at each individual organ – auto-regulation – normally ensure the appropriate local rate of oxygen supply, i.e. local DO2. Inadequate blood volume leads to impairment of the regulation of blood flow, particularly in the individual tissues with least capable auto-regulatory capability. As demonstrated by many studies, inadequate blood flow first occurs in the gut, brain and kidney. The inadequate blood volume which occurs with induction of anaesthesia is not due to blood volume loss, but probably results from redistribution due to veno-dilation. The increase in venous capacity renders the existing blood volume inadequate to maintain venous return and pre-load. Blood volume shifted to the veins will, necessarily, also reduce the arterial volume. As a result stroke volume and cardiac output fall below normal with little or no change in peripheral resistance. The resulting pre-load dependency is often successfully treated with colloid infusion and, in some studies, ‘inotropic’ agents, particularly in the immediate post-operative phase. Treatment during the earliest stage of anaesthesia can avoid the build up of oxygen debt and may be supplemented by drugs which maintain or restore venous tone, such as phenylephrine; an alternative to volume expansion. Interpretation of circulatory patho-physiology during anaesthesia confirms the need to sustain appropriate oxygen delivery. It also supports reduction or even elimination of supplementary crystalloid maintenance infusion, supposedly to replace the “mythical” third space loss. As a rational evidence base for future research it should allow for further improvements in anaesthetic management

Reirradiation to the abdomen for gastrointestinal malignancies

<p>Abstract</p> <p>Background</p> <p>Reirradiation to the abdomen could potentially play a role in palliation of symptoms or local control in patients with gastrointestinal malignancies. Our goal was to retrospectively determine rates of toxicity, freedom from local progression and overall survival in gastrointestinal cancer patients treated with reirradiation to the abdomen.</p> <p>Methods</p> <p>Between November 2002 and September 2008, 13 patients with a prior history of abdominal radiotherapy (median dose 45 Gy) were treated with reirradiation for recurrent or metastatic gastrointestinal malignancies. The median interval between the two courses of radiotherapy was 26 months. Patients were treated with a hyperfractionated accelerated regimen, using 1.5 Gy fractions twice daily, with a median dose of 30 Gy (range 24-48 Gy). Concurrent chemotherapy was administered to 8 (62%) patients.</p> <p>Results</p> <p>The 1-year rate of freedom from local progression was 50%, and the median duration of freedom from local progression was 14 months. The 1-year rate of overall survival was 62%, and the median duration of overall survival was 14 months. One patient developed grade 3 acute toxicity (abdominal pain and gastrointestinal bleeding), requiring hospitalization during radiotherapy; subsequently, that patient experienced a grade 4 late toxicity (gastrointestinal bleeding). No other patients developed grade 3-4 acute or late toxicity or required hospitalization during radiotherapy.</p> <p>Conclusion</p> <p>Hyperfractionated accelerated reirradiation to the abdomen was well-tolerated with low rates of acute and late toxicity. Reirradiation could play a role in providing a limited duration of local control in gastrointestinal cancer patients with a history of prior abdominal radiotherapy.</p

Influence of Xpand Nitric Oxide Reactor, L-Arginine Alpha-Ketoglutarate, and Caffeine Supplementation on Calf Muscle Re-Oxygenation During and after Acute Resistance Exercise

Xpand Nitric Oxide Reactor is a "cocktail" supplement proposed to improve skeletal muscle blood flow via arginine's effect on nitric oxide synthesis and vasodilation. Two other major ingredients, caffeine and creatine, cause vasoconstriction, which could potentially counteract the proposed hemodynamic effects of arginine. The purpose of this study was to examine the influence of Xpand Nitric Oxide Reactor on muscle re-oxygenation after resistance exercise compared to supplementation with constituent ingredients L-arginine alpha-ketoglutarate and caffeine. Nine recreationally active men (21±1y) performed 3 sets of 20 repetitions of seated single-leg calf raise at 60% 1-RM with 3 min rests. The same calf raise exercise was performed following 4 separate supplementation conditions: L-arginine alpha-ketoglutarate (AAKG), caffeine (CAFF), Xpand Nitric Oxide Reactor (XPAND), and placebo (PLAC). Soleus muscle re-oxygenation time was measured before, during, and immediately after exercise using near infrared spectroscopy. Supplementation with XPAND (0.43±0.03), AAKG (0.34±0.02), and CAFF (0.45±0.05) did not significantly affect muscle re-oxygenation halftime (minutes) compared to placebo (0.35±0.04). An arginine containing "cocktail" supplement did not affect skeletal muscle re-oxygenation after resistance exercise, possibly due to a wash-out effect caused by the multiple ingredients

Influence of Differences in Exercise-intensity and Kilograms/Set on Energy Expenditure During and After Maximally Explosive Resistance Exercise

With resistance exercise, greater intensity typically elicits increased energy expenditure, but heavier loads require that the lifter perform more sets of fewer repetitions, which alters the kilograms lifted per set. Thus, the effect of exercise-intensity on energy expenditure has yielded varying results, especially with explosive resistance exercise. This study was designed to examine the effect of exercise-intensity and kilograms/set on energy expenditure during explosive resistance exercise. Ten resistance-trained men (22±3.6 years; 84±6.4 kg, 180±5.1 cm, and 13±3.8 %fat) performed squat and bench press protocols once/week using different exercise-intensities including 48% (LIGHT-48), 60% (MODERATE-60), and 72% of 1-repetition-maximum (1-RM) (HEAVY-72), plus a no-exercise protocol (CONTROL). To examine the effects of kilograms/set, an additional protocol using 72% of 1-RM was performed (HEAVY-72MATCHED) with kilograms/set matched with LIGHT-48 and MODERATE-60. LIGHT-48 was 4 sets of 10 repetitions (4x10); MODERATE-60 4x8; HEAVY-72 5x5; and HEAVY-72MATCHED 4x6.5. Eccentric and concentric repetition speeds, ranges-of-motion, rest-intervals, and total kilograms were identical between protocols. Expired air was collected continuously throughout each protocol using a metabolic cart, [Blood lactate] using a portable analyzer, and bench press peak power were measured. Rates of energy expenditure were significantly greater (p≤0.05) with LIGHT-48 and HEAVY-72MATCHED than HEAVY-72 during squat (7.3±0.7; 6.9±0.6 \u3e 6.1±0.7 kcal/min), bench press (4.8±0.3; 4.7±0.3 \u3e 4.0±0.4 kcal/min), and +5min after (3.7±0.1; 3.7±0.2 \u3e 3.3±0.3 kcal/min), but there were no significant differences in total kcal among protocols. Therefore, exercise-intensity may not effect energy expenditure with explosive contractions, but light loads (~50% of 1-RM) may be preferred because of higher rates of energy expenditure, and since heavier loading requires more sets with lower kilograms/set

Energy Cost of Active and Sedentary Music Video Games: Handheld Gaming vs. Walking and Sitting

International Journal of Exercise Science 10(7): 1038-1050, 2017. To compare energy expenditure during and after active and handheld video game drumming compared to walking and sitting. Ten experienced, college-aged men performed four protocols (one per week): no-exercise seated control (CTRL), virtual drumming on a handheld gaming device (HANDHELD), active drumming on drum pads (DRUM), and walking on a treadmill at ~30% of VO2max (WALK). Protocols were performed after an overnight fast, and expired air was collected continuously during (30min) and after (30min) exercise. DRUM and HANDHELD song lists, day of the week, and time of day were identical for each participant. Significant differences (p \u3c 0.05) among the average rates of energy expenditure (kcal.min-1) during activity included WALK \u3e DRUM \u3e HANDHELD. No significant differences in the rates of energy expenditure among groups during recovery were observed. Total energy expenditure was significantly greater (p \u3c 0.05) during WALK (149.5 ± 30.6 kcal) compared to DRUM (118.7 ± 18.8 kcal) and HANDHELD (44.9±11.6 kcal), and greater during DRUM compared to HANDHELD. Total energy expenditure was not significantly different between HANDHELD (44.9 ± 11.6 kcal) and CTRL (38.2 ± 6.0 kcal). Active video game drumming at expert-level significantly increased energy expenditure compared to handheld, but it hardly met moderate-intensity activity standards, and energy expenditure was greatest during walking. Energy expenditure with handheld video game drumming was not different from no-exercise control. Thus, traditional aerobic exercise remains at the forefront for achieving the minimum amount and intensity of physical activity for health, individuals desiring to use video games for achieving weekly physical activity recommendations should choose games that require significant involvement of lower-body musculature, and time spent playing sedentary games should be a limited part of an active lifestyle

Psychology as a natural science in the eighteenth century

Psychology considered as a natural science began as Aristotelian "physics" or "natural philosophy" of the soul. C. Wolff placed psychology under metaphysics, coordinate with cosmology. Scottish thinkers placed it within moral philosophy, but distinguished its "physical" laws from properly moral laws (for guiding conduct). Several Germans sought to establish an autonomous empirical psychology as a branch of natural science. British and French visual theorists developed mathematically precise theories of size and distance perception; they created instruments to test these theories and to measure visual phenomena such as the duration of visual impressions. These investigators typically were dualists who included mental phenomena within nature

Comparison of In-Situ, Model and Ground Based In-Flight Icing Severity

As an aircraft flies through supercooled liquid water, the liquid freezes instantaneously to the airframe thus altering its lift, drag, and weight characteristics. In-flight icing is a contributing factor to many aviation accidents, and the reliable detection of this hazard is a fundamental concern to aviation safety. The scientific community has recently developed products to provide in-flight icing warnings. NASA's Icing Remote Sensing System (NIRSS) deploys a vertically--pointing Ka--band radar, a laser ceilometer, and a profiling multi-channel microwave radiometer for the diagnosis of terminal area in-flight icing hazards with high spatial and temporal resolution. NCAR s Current Icing Product (CIP) combines several meteorological inputs to produce a gridded, three-dimensional depiction of icing severity on an hourly basis. Pilot reports are the best and only source of information on in-situ icing conditions encountered by an aircraft. The goal of this analysis was to ascertain how the testbed NIRSS icing severity product and the operational CIP severity product compare to pilot reports of icing severity, and how NIRSS and CIP compare to each other. This study revealed that the icing severity product from the ground-based NASA testbed system compared very favorably with the operational model-based product and pilot reported in-situ icing