Effect of applied muscle tension on cerebral oxygenation in female blood donors

Counter pressure maneuvers for syncope prevention: A semi-systematic review and meta-analysis

Physical counter pressure maneuvers (CPM) are movements that are recommended to delay or prevent syncope (fainting) by recruiting the skeletal muscle pump to augment cardiovascular control. However, these recommendations are largely based on theoretical benefit, with limited data evaluating the efficacy of CPM to prevent syncope in the real-world setting. We conducted a semi-systematic literature review and meta-analysis to assess CPM efficacy, identify literature gaps, and highlight future research needs. Articles were identified through a literature search (PubMed, April 2022) of peer-reviewed publications evaluating the use of counter pressure or other lower body maneuvers to prevent syncope. Two team members independently screened records for inclusion and extracted data. From 476 unique records identified by the search, 45 met inclusion criteria. Articles considered various syncopal conditions (vasovagal = 12, orthostatic hypotension = 8, postural orthostatic tachycardia syndrome = 1, familial dysautonomia = 2, spinal cord injury = 1, blood donation = 10, healthy controls = 11). Maneuvers assessed included hand gripping, leg fidgeting, stepping, tiptoeing, marching, calf raises, postural sway, tensing (upper, lower, whole body), leg crossing, squatting, “crash” position, and bending foreword. CPM were assessed in laboratory-based studies (N = 28), the community setting (N = 4), both laboratory and community settings (N = 3), and during blood donation (N = 10). CPM improved standing systolic blood pressure (+ 14.8 ± 0.6 mmHg, p < 0.001) and heart rate (+ 1.4 ± 0.5 bpm, p = 0.006), however, responses of total peripheral resistance, stroke volume, or cerebral blood flow were not widely documented. Most patients experienced symptom improvement following CPM use (laboratory: 60 ± 4%, community: 72 ± 9%). The most prominent barrier to employing CPM in daily living was the inability to recognize an impending faint. Patterns of postural sway may also recruit the skeletal muscle pump to enhance cardiovascular control, and its potential as a discrete, proactive CPM needs further evaluation. Physical CPM were successful in improving syncopal symptoms and producing cardiovascular responses that may bolster against syncope; however, practical limitations may restrict applicability for use in daily living.

Prevention of Blood Donation-related Vasovagal Response by Applied Muscle Tension: a Meta-analysis

Objective

Vasovagal reaction (VVR) is an adverse reaction to blood donation. Applied muscle tension (AMT) has been reported to reduce the probability of VVR during blood donation; however, the results have been controversial. We therefore conducted a meta-analysis to systematically evaluate the effect of AMT in reducing VVR.

Methods

We searched six major databases using “applied muscle tension” and “blood donation-related vasovagal response” as keywords. Relevant articles published in English or Chinese between 1 January 2000 and 30 June 2021 were included in the analysis. The quality of the included articles was evaluated and publication bias was assessed by forest and funnel plots and by Egger's test.

Results

Fifty-one articles were identified, of which six were included according to the pre-defined inclusion and exclusion criteria. A fixed-effects model was adopted for effect size combination and revealed a relative risk of 0.52 (95% confidence interval 0.40 to 0.67). The AMT group was superior to the control in terms of VVR prevention. A funnel plot and Egger's test suggested that the findings were accurate and reliable with low publication bias.

Conclusion

AMT could effectively reduce VVR during blood donation. Further multicenter studies with large sample sizes are needed to confirm these results.

Predicting COVID-19 and seasonal influenza vaccine uptake: The impact of fear and vasovagal symptoms

Vaccines are vital to protecting health. However, fear and experiencing vasovagal symptoms (e.g., dizziness) are deterrents to medical procedures. Thus, study aims were to test (1) if vaccine relevant fears predict vasovagal symptoms during or following seasonal influenza vaccination and (2) if vaccine relevant fears and vasovagal symptoms predict seasonal influenza and COVID-19 vaccine uptake. Using a prospective design, 1077 participants recruited online completed surveys during Oct 2019 assessing vaccine relevant fears, and May-June 2020 assessing 2019-2020 seasonal influenza vaccine uptake, ratings of vasovagal symptoms, and seasonal influenza and COVID-19 vaccination intention. A behavioral follow up assessing 2020-2021 seasonal influenza and COVID-19 vaccine uptake took place June-July 2021. Heightened vaccine relevant fears predicted reduced 2019-2020 seasonal influenza vaccine uptake and greater vasovagal symptoms among those who did receive a seasonal influenza vaccine. Serial mediation analyses identified significant indirect effects with greater vaccine relevant fears reducing 2020-2021 seasonal influenza vaccine uptake through intention and reducing COVID-19 vaccine uptake through vasovagal symptoms and intention. Intervention research to reduce fear and prevent vasovagal symptoms to support vaccine uptake is warranted.

Effects of Performing Applied Muscle Tension during Recovery after Phlebotomy in Young, First-Time Donors: A Pilot Study

Vasovagal reaction (VVR) compromises donor safety and reduces the subsequent return rates. Performing applied muscle tension (AMT) during phlebotomy may reduce the incidence of VVR. However, the effectiveness of performing AMT after phlebotomy to reduce delayed VVR remains unclear. With ethics approval, 12 young, first-time donors (YFTD) were recruited to study the effects on stroke volume (SV), cardiac output (CO) and systemic vascular resistance (SVR) while performing AMT from needle insertion to end of recovery. Measurements from 12 matched control YFTD were used for comparison. Pre-donation anxiety and VVR severity were assessed. Compared to controls, donors who performed AMT had higher SV (Control: 57 mL vs. AMT: 69 mL, p = 0.045), higher CO (Control: 3.7 L·min⁻¹ vs. AMT: 5.2 L·min⁻¹, p = 0.006) and lower SVR (Control: 1962 dyn·s·cm⁻⁵ vs. AMT: 1569 dyn·s·cm⁻⁵, p = 0.032) during mid-phlebotomy. During recovery, the AMT group retained higher SV, higher CO and lower SVR than the control, but not reaching statistical significance. Practicing AMT during recovery resulted in sustained haemodynamic improvements beyond the donation period, despite the reduction in delayed VVR was insignificant compared to the control group. A larger sample size is needed to validate the effectiveness of performing AMT after donation to mitigate delayed VVR.

Near Infrared Spectroscopy in Anemia Detection and Management: A Systematic Review

Red cell transfusions are intended to improve oxygen delivery to tissues. Although studies comparing hemoglobin concentration triggers for transfusion have been done, the hemoglobin threshold for clinical benefit remains uncertain. Direct measurement of tissue oxygenation with non-invasive near infrared spectroscopy has been proposed as a more physiological transfusion trigger, but its clinical role remains unclear. This systematic review examined the role of near infrared spectroscopy for detection of anemia and guiding transfusion decisions. Abstracts were identified up until May 2019 through searches of PubMed, EMBASE and The Web of Science. There were 69 studies meeting the inclusion criteria, most (n = 65) of which were observational studies. Tissue oxygen saturation had been measured in a wide range of clinical settings, with neonatal intensive care (n = 26) and trauma (n = 7) being most common. Correlations with hemoglobin concentration and tissue oxygenation were noted and there were correlations between changes in red cell mass and changes in tissue oxygenation through blood loss or transfusion. The value of tissue oxygenation for predicting transfusion was determined in only four studies, all using muscle oxygen saturation in the adult trauma setting. The overall sensitivity was low at 34% (27%-42%) and while it had better specificity at 78% (74%-82%), differing and retrospective approaches create a high level of uncertainty with respect to these conclusions. There were four prospective randomized studies involving 540 patients, in cardiac and neurological surgery and in neonates that compared near infrared spectroscopy to guide transfusion decisions with standard practice. These showed a reduction in the number of red cells transfused per patient (OR: 0.44 [0.09-0.79]), but not the number of patients who received transfusion (OR: 0.71 [0.46-1.10]), and no change in clinical outcomes. Measuring tissue oxygen saturation has potential to help guide transfusion; however, there is a lack of data upon which to recommend widespread implementation into clinical practice. Standardization of measurements is required and greater research into levels at which tissue oxygenation may lead to adverse clinical outcomes would help in the design of future clinical trials.

Effects of respiratory and applied muscle tensing interventions on responses to a simulated blood draw among individuals with high needle fear

Fear of blood and needles increases risk for presyncopal symptoms. Applied muscle tension can prevent or attenuate presyncopal symptoms; however, it is not universally effective. This study examined the effects of applied muscle tension, a respiratory intervention, and a no treatment control condition, on presyncopal symptoms and cerebral oxygenation, during a simulated blood draw with individuals highly fearful of needles. Participants (n = 95) completed questionnaires, physiological monitoring, and two trials of a simulated blood draw with recovery. Presyncopal symptoms decreased across trials; however, no group differences emerged. Applied muscle tension was associated with greater cerebral oxygenation during trial two, and greater end-tidal carbon dioxide during both trials. The respiratory intervention did not differ from the no treatment control. Applied muscle tension is an intervention that can increase cerebral oxygenation and end-tidal carbon dioxide. While the respiratory intervention is promising within therapeutic settings, it was not efficacious after a brief audio training.

Enhancing cerebral oxygenation during blood donation using biofeedback

Biofeedback of cerebral oxygenation was used to guide application of applied muscle tension during whole blood donation, and resulted in attenuated reductions compared to donors who did not receive feedback.

Donor anxiety, needle pain, and syncopal reactions combine to determine retention: a path analysis of two-year donor return data

BACKGROUND

Efforts to expand the donor pool by recruiting younger donors have resulted in higher numbers of initial donations, but retention of young donors continues to be challenging.

STUDY DESIGN AND METHODS

Path analysis was used to examine the simultaneous relationships among syncopal reactions, donation anxiety, needle pain, donor satisfaction, and donation intention in predicting repeat donation. Participants included 421 first- and second-time donors recruited for a study comparing the effects of predonation water loading with and without the use of applied muscle tension during donation (52% female, 60.8% first-time donor, mean age 20.3 years). For this longitudinal follow-up study, donor database records were accessed 2 years after the index donation to assess repeat donation.

RESULTS

Results of a series of path analyses demonstrated the influential role of donor anxiety in shaping donor retention (final model χ(2) = 35.75, root mean square error of approximation 0.03, comparative fit index 0.98, weighted root mean square residual 0.74). First, anxiety exerted a direct negative influence on donation intention, the proximal and sole direct predictor of repeat donation. Second, anxiety increased the likelihood of donor-reported needle pain, adversely affecting donation satisfaction and, subsequently, donation intention. Finally, anxiety was associated with donor ratings of syncopal reactions through its impact on needle pain, which also contributed to decreased donation intention.

CONCLUSION

These results provide novel evidence that donation anxiety plays a central role in shaping future donation behavior. Individual differences in anxiety must be considered when developing and testing strategies to enhance blood donor retention.