Neuromuscular Blockade with Rocuronium Bromide Increases the Tolerance of Acute Normovolemic Anemia in Anesthetized Pigs

Background: The patient's individual anemia tolerance is pivotal when blood transfusions become necessary, but are not feasible for some reason. To date, the effects of neuromuscular blockade (NMB) on anemia tolerance have not been investigated. Methods: 14 anesthetized and mechanically ventilated pigs were randomly assigned to the Roc group (3.78 mg/kg rocuronium bromide followed by continuous infusion of 1 mg/kg/min, n = 7) or to the Sal group (administration of the corresponding volume of normal saline, n = 7). Subsequently, acute normovolemic anemia was induced by simultaneous exchange of whole blood for a 6% hydroxyethyl starch solution (130/0.4) until a sudden decrease of total body O-2 consumption (VO2) indicated a critical limitation of O-2 transport capacity. The Hb concentration quantified at this time point (Hb(crit)) was the primary end-point of the protocol. Secondary endpoints were parameters of hemodynamics, O-2 transport and tissue oxygenation. Results: Hb(crit) was significantly lower in the Roc group (2.4 +/- 0.5 vs. 3.2 +/- 0.7 g/dl) reflecting increased anemia tolerance. NMB with rocuronium bromide reduced skeletal muscular VO2 and total body O-2 extraction rate. As the cardiac index increased simultaneously, total body VO2 only decreased marginally in the Roc group (change of VO2 relative to baseline -1.7 +/- 0.8 vs. 3.2 +/- 1.9% in the Sal group, p < 0.05). Conclusion: Deep NMB with rocuronium bromide increases the tolerance of acute normovolemic anemia. The underlying mechanism most likely involves a reduction of skeletal muscular VO2. During acellular treatment of an acute blood loss, NMB might play an adjuvant role in situations where profound stages of normovolemic anemia have to be tolerated (e.g. bridging an unexpected blood loss until blood products become available for transfusion). Copyright (C) 2011 S. Karger AG, Base

Importance of hemoglobin concentration to exercise: Acute manipulations

An acute reduction of blood hemoglobin concentration ([Hb]), even when the circulating blood volume is maintained, results in lower over (V̇O2max and endurance performance, due to the reduction of the oxygen carrying capacity of blood. Conversely, an increase of [Hb] is associated with enhanced over(V, ̇)O2max and endurance capacity, that is also proportional to the increase in the oxygen carrying capacity of blood. The effects on endurance capacity appear more pronounced and prolonged than on over(V̇O2max. During submaximal exercise, there is a tight coupling between O2 demand and O2 delivery, such that if [Hb] is acutely decreased muscle blood flow is increased proportionally and vice versa. During maximal exercise with either a small or a large muscle mass, neither peak cardiac output nor peak leg blood flow are affected by reduced [Hb]. An acute increase of [Hb] has no effect on maximal exercise capacity or over(V̇O2max during exercise in acute hypoxia. Likewise, reducing [Hb] in altitude-acclimatized humans to pre-acclimatization values has no effect on over(V̇O2max peak during exercise in hypoxia. © 2006 Elsevier B.V. All rights reserved

The association of total and abdominal obesity with health-related quality of life in a sample of Greek healthy adults

Background: in the Greek population, the association between obesity and Health-Related Quality of Life (HRQoL) has not been examined so far. Thus, the purpose of the present study is to explore obesity-related predictors of HRQoL in a sample of Greek healthy adults. Methods: a cross-sectional design was used. The sample consisted of three hundred twenty seven healthy men (N=105) and women (N=222), between the ages of 30 and 50 years (mean age=39.57 ± 6.68) who lived in Athens. Body mass index (BMI), waist to hip ratio (WHR), and body fat (BF) were assessed. HRQoL was evaluated using the short-form 36 (SF-36) health survey, which consists of eight subscales and two health factors (physical and psychological health). Socio-demographic variables and health-related behaviours were assessed by questionnaires. Separate hierarchical regression analyses were conducted to examine the associations between BMI, WHR, BF and SF-36 health survey subscales and factors. Results: socio-demographic and health-related variables were moderately associated with the HRQoL subscales and factors. Furthermore, after controlling the socio-demographic variables and health-related behaviours, (a) BMI negatively predicted the physical functioning, physical role, bodily pain, and social functioning subscales, as well as the physical health factor and (b) WHR and BF negatively predicted the physical functioning subscale. However, the obesity indexes did not predict other psychological health subscales. ConclusionS: the results indicated negative associations of BMI, WHR, BF with physical functioning and health in a sample of Greek healthy adults. Such data relating total and abdominal obesity to HRQoL, as assessed by BMI, WHR, and BF, have not been reported until now in the literature. One limitation of this study was that the sample size was relatively small and the results could not be generalized to the entire Greek population

Severe hypoxemia induced by prolonged expiration and reduced frequency breathing during submaximal swimming

The purpose of this study was to examine the metabolic responses during submaximal swimming with self-selected normal breathing (N) and prolonged expiration along with reduced frequency breathing (RB). Ten male swimmers (age: 23.1 ± 2.2 years; VO2max: 47.3 ± 7.2 ml · kg−1 · min−1) performed 75-, 100-, 175-, 200-, 275-, 300-, 375- and 400-m trials with N and RB at intensity corresponding to 90% of the critical speed. In RB condition, all trials longer than 75 m were interspersed with 25 m of self-selected N in regular intervals. In RB, oxygen saturation during recovery was decreased compared to starting values after 75, 100, 175, 275 and 375 m (78–91%, P &amp;lt; 0.05), while it remained unchanged after all trials in N condition (98 ± 2%, P &amp;gt; 0.05). Lactate concentration was higher in RB than in N after 400 m (4.3 ± 1.5 vs. 3.3 ± 1.7 mmol · l−1, P &amp;lt; 0.05). During recovery after the 375-m trial, partial pressure of carbon dioxide was increased and pH was decreased in RB compared to N condition. Prolonged expiration along with RB provokes severe hypoxemia during the recovery period after swimming, which is restored with self-selected N during submaximal swimming. © 2016 Informa UK Limited, trading as Taylor &amp; Francis Group

The Effect of Caffeine Intake on Body Fluids Replacement after Exercise-Induced Dehydration

We studied the effect of a plain espresso coffee (171 ± 8.9 mg caffeine) which is roughly the amount in a cup of regular coffee or caffeine soda drink on fluid replacement in mildly dehydrated healthy subjects following moderate exercise, which induced dehydration to approximately 1.2% of their body weight. Subjects then rehydrated by drinking either water alone as control or caffeinated beverage plus up to 150% of the body weight they had lost. All subjects underwent both conditions. There were differences between the control and caffeine in urine specific gravity (control: 1.018 ± 0.00 vs caffeine: 1.024 ± 0.00, P =.001), urine volume (control: 200 ±71 mL vs caffeine: 302 ± 151 mL, P =.05), and urine color (control: 2 ± 0.9 and caffeine: 4 ± 1.66, P =.00). We conclude that intake of an espresso coffee possibly impedes replacement of body fluids. © 2020 Wolters Kluwer Health, Inc. All rights reserved

No ergogenic effects of a 10-day combined heat and hypoxic acclimation on aerobic performance in normoxic thermoneutral or hot conditions

Purpose: Hypoxic acclimation enhances convective oxygen delivery to the muscles. Heat acclimation-elicited thermoregulatory benefits have been suggested not to be negated by adding daily exposure to hypoxia. Whether concomitant acclimation to both heat and hypoxia offers a synergistic enhancement of aerobic performance in thermoneutral or hot conditions remains unresolved. Methods: Eight young males (V˙ O 2 max: 51.6 ± 4.6 mL min−1 kg−1) underwent a 10-day normobaric hypoxic confinement (FiO2 = 0.14) interspersed with daily 90-min normoxic controlled hyperthermia (target rectal temperature: 38.5 °C) exercise sessions. Prior to, and following the confinement, the participants conducted a 30-min steady-state exercise followed by incremental exercise to exhaustion on a cycle ergometer in thermoneutral normoxic (NOR), thermoneutral hypoxic (FiO2 = 0.14; HYP) and hot (35 °C, 50% relative humidity; HE) conditions in a randomized and counterbalanced order. The steady-state exercise was performed at 40% NOR peak power output (Wpeak) to evaluate thermoregulatory function. Blood samples were obtained from an antecubital vein before, on days 1 and 10, and the first day post-acclimation. Results: V˙ O 2 max and ventilatory thresholds were not modified in any environment following acclimation. Wpeak increased by 6.3 ± 3.4% in NOR and 4.0 ± 4.9% in HE, respectively. The magnitude and gain of the forehead sweating response were augmented in HE post-acclimation. EPO increased from baseline (17.8 ± 7.0 mIU mL−1) by 10.7 ± 8.8 mIU mL−1 on day 1 but returned to baseline levels by day 10 (15.7 ± 5.9 mIU mL−1). Discussion: A 10-day combined heat and hypoxic acclimation conferred only minor benefits in aerobic performance and thermoregulation in thermoneutral or hot conditions. Thus, adoption of such a protocol does not seem warranted. © 2019, Springer-Verlag GmbH Germany, part of Springer Nature

Erythropoietin treatment elevates haemoglobin concentration by increasing red cell volume and depressing plasma volume

Erythropoietin (Epo) has been suggested to affect plasma volume, and would thereby possess a mechanism apart from erythropoiesis to increase arterial oxygen content. This, and potential underlying mechanisms, were tested in eight healthy subjects receiving 5000 IU recombinant human Epo (rHuEpo) for 15 weeks at a dose frequency aimed to increase and maintain haematocrit at approximately 50%. Red blood cell volume was increased from 2933 ± 402 ml before rHuEpo treatment to 3210 ± 356 (P &lt; 0.01), 3117 ± 554 (P &lt; 0.05), and 3172 ± 561 ml (P &lt; 0.01) after 5, 11 and 13 weeks, respectively. This was accompanied by a decrease in plasma volume from 3645 ± 538 ml before rHuEpo treatment to 3267 ± 333 (P &lt; 0.01), 3119 ± 499 (P &lt; 0.05), and 3323 ± 521 ml (P &lt; 0.01) after 5, 11 and 13 weeks, respectively. Concomitantly, plasma renin activity and aldosterone concentration were reduced. This maintained blood volume relatively unchanged, with a slight transient decrease at week 11, such that blood volume was 6578 ± 839 ml before rHuEpo treatment, and 6477 ± 573 (NS), 6236 ± 908 (P &lt; 0.05), and 6495 ± 935 ml (NS), after 5, 11 and 13 weeks of treatment. We conclude that Epo treatment in healthy humans induces an elevation in haemoglobin concentration by two mechanisms: (i) an increase in red cell volume; and (ii) a decrease in plasma volume, which is probably mediated by a downregulation of the rennin-angiotensin-aldosterone axis. Since the relative contribution of plasma volume changes to the increments in arterial oxygen content was between 37.9 and 53.9% during the study period, this mechanism seems as important for increasing arterial oxygen content as the well-known erythropoietic effect of Epo. © 2007 The Authors. Journal compilation © 2007 The Physiological Society