White blood cell concentrations during lower body negative pressure and blood loss in humans

Helmond, Noud van; Johnson, Blair D.; Curry, Timothy B.; Andrew, P.; Convertino, Víctor A.; Joyner, Michael J.

doi:10.1113/ep085952

Cited by 19 publications

(20 citation statements)

References 35 publications

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“…A reduction in coagulation time is even present during lower levels of LBNP-induced decreases of central venous pressure (CVP) insufficient to induce presyncope. This response is comparable to coagulation changes after CVP reductions caused by blood removal (up to 1000 ml total) [13].…”

supporting

confidence: 62%

The target of vasovagal syncope is hemostasis and not heart protection

Diehl

2017

Clin Auton Res

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supporting

confidence: 62%

The target of vasovagal syncope is hemostasis and not heart protection

Diehl

2017

Clin Auton Res

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“…Lower body negative pressure (LBNP) suction causes a pressure gradient that pulls fluid from the intravascular to the extravascular space in the lower body [ 1 ]. Generally, it leads to blood pooling in the legs, reduces venous return, and has been shown to be a non-invasive surrogate to study physiological responses to blood loss/hemorrhage, a leading cause of death in patients with trauma [ 2 , 3 ]. LBNP-induced hemoconcentration elevates plasma protein concentration and blood viscosity.…”

Section: Introductionmentioning

confidence: 99%

Menstrual Phase Affects Coagulation and Hematological Parameters during Central Hypovolemia

Goswami

Brix

Roessler

et al. 2020

JCM

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Background: It has been reported that women have a higher number of heart attacks in the “follicular phase” of the menstrual cycle. We, therefore, tested the hypothesis that women in the follicular phase exhibit higher coagulability. As lower body negative pressure (LBNP) has been used previously to assess coagulation changes in whole blood (WB) samples in men and women, effects of menstrual phase on coagulation was assessed during LBNP. Methods: Seven women, all healthy young participants, with no histories of thrombotic disorders and not on medications, were tested in two phases of the menstrual cycle (early follicular (EF) and mid-luteal (ML)). LBNP was commenced at −10 mmHg and increased by −10 mmHg every 5 min until a maximum of −40 mmHg. Recovery up to 10 min was also monitored. Blood samples were collected at baseline, at end of LBNP, and at end of recovery. Hemostatic profiling included comparing the effects of LBNP on coagulation values in both phases of the menstrual cycle using standard coagulation tests, calibrated automated thrombogram, thrombelastometry, impedance aggregometry, and markers of thrombin formation. Results: LBNP led to coagulation activation determined in both plasma and WB samples. During both phases, coagulation was affected during LBNP, as reflected in their decreased partial thromboplastin time (PTT) and elevated coagulation factor VIII FVIII, F1 + 2, and thrombin-antithrombin (TAT) levels. Additionally, during the ML phase, greater PT [%] and shorter time to peak (ttPeak) values (implying faster maximum thrombin formation) suggest that women in the ML phase are relatively hypercoagulable compared to the early follicular phase. Conclusions: These results suggest that thrombosis occurs more during the midluteal phase, a finding with substantial medical implications.

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“…Lower-body negative pressure (LBNP) has been shown to be an appropriate model for studying the physiological responses to the early 'pre-shock' stages of haemorrhage in healthy, conscious human subjects (Hinojosa-Laborde et al, 2014;Johnson et al, 2014;van Helmond et al, 2015van Helmond et al, , 2016. Both blood loss and LBNP elicit similar responses in key haemodynamic parameters, including heart rate, stroke volume, cardiac output, arterial pressure and cerebral blood velocity (Hinojosa-Laborde et al, 2014;Johnson et al, 2014;.…”

mentioning

confidence: 99%

Responses of cerebral blood velocity and tissue oxygenation to low‐frequency oscillations during simulated haemorrhagic stress in humans

Anderson

Sprick

Park

et al. 2019

Experimental Physiology

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New Findings What is the central question of this study?Do low‐frequency oscillations in arterial pressure and cerebral blood velocity protect cerebral blood velocity and oxygenation during central hypovolaemia? What is the main finding and its importance?Low‐frequency oscillations in arterial pressure and cerebral blood velocity attenuate reductions in cerebral oxygen saturation but do not protect absolute cerebral blood velocity during central hypovolaemia. This finding indicates the potential importance of haemodynamic oscillations in maintaining cerebral oxygenation and therefore viability of tissues during challenges to cerebral blood flow and oxygen delivery. Abstract Tolerance to both real and simulated haemorrhage varies between individuals. Exaggerated low‐frequency (∼0.1 Hz) oscillations in mean arterial pressure and brain blood flow [indexed via middle cerebral artery velocity (MCAv)] have been associated with improved tolerance to reduced central blood volume. The mechanism for this association has not been explored. We hypothesized that inducing low‐frequency oscillations in arterial pressure and cerebral blood velocity would attenuate reductions in cerebral blood velocity and oxygenation during simulated haemorrhage. Fourteen subjects (11 men and three women) were exposed to oscillatory (0.1 and 0.05 Hz) and non‐oscillatory (0 Hz) lower‐body negative pressure profiles with an average chamber pressure of −60 mmHg (randomized and counterbalanced order). Measurements included arterial pressure and stroke volume via finger photoplethysmography, MCAv via transcranial Doppler ultrasound, and cerebral oxygenation of the frontal lobe via near‐infrared spectroscopy. Tolerance was higher during the two oscillatory profiles compared with the 0 Hz profile (0.05 Hz, P = 0.04; 0.1 Hz, P = 0.09), accompanied by attenuated reductions in stroke volume (P < 0.001) and cerebral oxygenation of the frontal lobe (P ≤ 0.02). No differences were observed between profiles for reductions in mean arterial pressure (P = 0.17) and MCAv (P = 0.30). In partial support of our hypothesis, cerebral oxygenation, but not cerebral blood velocity, was protected during the oscillatory profiles. Interestingly, more subjects tolerated the oscillatory profiles compared with the static 0 Hz profile, despite similar arterial pressure responses. These findings emphasize the potential importance of haemodynamic oscillations in maintaining perfusion and oxygenation of cerebral tissues during haemorrhagic stress.

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White blood cell concentrations during lower body negative pressure and blood loss in humans

Cited by 19 publications

References 35 publications

The target of vasovagal syncope is hemostasis and not heart protection

The target of vasovagal syncope is hemostasis and not heart protection

Menstrual Phase Affects Coagulation and Hematological Parameters during Central Hypovolemia

Responses of cerebral blood velocity and tissue oxygenation to low‐frequency oscillations during simulated haemorrhagic stress in humans

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