In a double-blind, randomized, controlled prospective study, 30 grade ASA I/II patients received a continuous i.v. infusion of normal saline or esmolol hydrochloride before induction of anaesthesia and tracheal intubation. Arterial pressure and heart rate were measured to assess the pressor response to laryngoscopy and intubation. The heart rate decreased in the esmolol group before induction of anaesthesia. The pressor response to laryngoscopy was significantly less marked in the esmolol group.

The spleen contains a reservoir of red blood cells that are mobilized into circulation when under physiological stress. Despite the spleen having an established role in compensation to acute hypoxia, no previous work has assessed the role of the spleen during ascent to high altitude. Twelve participants completed 2 min of handgrip exercise at 30% of maximal voluntary contraction at 1,045, 3,440, and 4,240 m. In a subset of eight participants, an infusion of phenylephrine hydrochloride was administered at a dosage of 30 µg/l of predicted blood volume at each altitude. The spleen was imaged by ultrasound via a 2- to 5.5-MHz curvilinear probe. Spleen volume was calculated by the prolate ellipsoid formula. Finger capillary blood samples were taken to measure hematocrit. Spleen images and hematocrit were taken both before and at the end of both handgrip and phenylephrine infusion. No changes in resting spleen volume were observed between altitudes. At low altitude, the spleen contracted in response to handgrip [272.8 ml (SD 102.3) vs. 249.6 ml (SD 105.7), P = 0.009], leading to an increase in hematocrit (42.6% (SD 3.3) vs. 44.3% (SD 3.3), P = 0.023] but did not contract or increase hematocrit at the high-altitude locations. Infusion of phenylephrine led to spleen contraction at all altitudes, but only lead to an increase in hematocrit at low altitude. These data reveal that the human spleen may not contribute to acclimatization to chronic hypoxia, contrary to its response to acute sympathoexcitation. These results are explained by alterations in spleen reactivity to increased sympathetic activation at altitude. NEW & NOTEWORTHY The present study demonstrated that, despite the known role of the human spleen in increasing oxygen delivery to tissues during acute hypoxia scenarios, the spleen does not mobilize red blood cells during ascent to high altitude. Furthermore, the spleen’s response to acute stressors at altitude depends on the nature of the stressor; the spleen’s sensitivity to neurotransmitter is maintained, while its reflex response to stress is dampened.

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Blood pressure regulation during pregnancy is poorly understood. Cardiovagal baroreflex gain (BRG) is an important contributor to blood pressure regulation via its influence on heart-rate. Heart-rate fluctuations occur in response to various physiological stimuli and can be measured using heart-rate variability (HRV). It is unclear how these mechanisms operate during pregnancy, particularly related to exercise. We examined BRG and HRV prior to, during, and following prenatal exercise. Forty-three pregnant (n=10 first trimester [TM1], n=17 second trimester [TM2]; n=16 third trimester [TM3]) and 20 non-pregnant (NP) women underwent an incremental peak exercise test. Beat-by-beat blood pressure (photoplethysmography) and heart-rate (lead II ECG) were measured throughout. BRG (slope of the relationship between fluctuations in systolic blood pressure and R-R interval) and HRV (root mean square of the successive differences; RMSSD) were assessed at rest, during steady-state exercise (EX), and during active recovery. BRG decreased with gestation and was lower in TM3 compared to NP (17.9±6.9 vs 24.8±7.4 ms/mmHg, p=0.017). BRG was reduced during EX in all groups. Resting HRV (RMSSD) also decreased with gestation and was lower in TM3 compared to NP (29±17 vs 48±20 ms, p<0.001). RMSSD was blunted during EX for all groups compared to REST. During active recovery, RMSSD was further blunted compared to EX in NP, but not during pregnancy (TM1, TM2, and TM3). Compared to non-pregnant controls, pregnant women had lower BRG and HRV at rest, but comparable cardioautonomic control during both exercise and active recovery following peak exercise.

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Acute increases in blood glucose are associated with heightened muscle sympathetic nerve activity (MSNA). Animal studies have implicated a role for peripheral chemoreceptors in this response, but this has not been examined in humans. Heart rate, cardiac output (CO), mean arterial pressure (MAP), total peripheral conductance (TPC), and blood glucose (BG) concentrations were collected in 11 participants. MSNA was recorded in a subset of 5 participants via microneurography. Participants came to the lab on two separate days (i.e. one control and one experimental day). On both days, participants ingested 75g of glucose following baseline measurements. On the experimental day, participants breathed 100% oxygen for 3 minutes at baseline and again at 20, 40, and 60 min post glucose ingestion to deactivate peripheral chemoreceptors. Supplemental oxygen was not given to participants on the control day. There was a main effect of time on blood glucose (P<0.001), heart rate (P<0.001), CO (P<0.001), sympathetic burst frequency (P<0.001), burst incidence (P=0.01), and total MSNA (P=0.001) for both days. Blood glucose concentrations and burst frequency were positively correlated on the control day (r=0.42; P=0.03) and experimental day (r=0.62; P=0.003). There was a time x condition interaction (i.e. normoxia vs. hyperoxia) on burst frequency, in which hyperoxia significantly blunted burst frequency at 20 and 60 min post glucose ingestion only. Given that hyperoxia blunted burst frequency only during hyperglycemia, our results suggest that the peripheral chemoreceptors are involved in activating MSNA post glucose ingestion.

Introduction eHealth exercise interventions have the unique ability to leverage the benefits of in-person programming (tailoring and supervision) with the benefits of home programming (flexibility). There may be a role for eHealth-delivered exercise for people with multiple myeloma (MM), as exercise tailoring and supervision are critical for successful outcomes due to the significant impacts/risks of myeloma-related side effects. The purpose of this study was to determine the safety, feasibility, and preliminary efficacy of a 12-week virtually supported eHealth exercise program. Methods Participants with MM completed a 12-week virtually supported home exercise program involving virtually supervised group workouts, independent workouts, and aerobic exercise. Tailoring was facilitated by the functionality of HEAL-Me, a novel eHealth app. Participants completed virtual fitness assessments and questionnaires at baseline and week 12. Results Twenty-nine participants consented, 26 completed all follow-up testing (90%). Exercise adherence was 90% (group), 83% (independent), and 90% (aerobic). No serious adverse events (grade ≥3) occurred. Significant improvements were found for quality of life and physical fitness. There was a high level of program/app satisfaction: 96% of participants agreed or strongly agreed that the exercise program was beneficial, 93% found it enjoyable, 89% were satisfied or very satisfied with delivery through the HEAL-Me app, and 48% felt that the eHealth program helped them manage cancer-related symptoms and side-effects. Conclusion An eHealth intervention that is individually tailored and includes virtual supervision and active support from the healthcare team is feasible and acceptable to people with MM. The findings from this study warrant investigation using a large-scale randomized controlled trial.