What question did this study set out to answer?

To compare hemodynamic and blood analyte responses to reductions in central venous pressure and pulse pressure induced by graded lower body negative pressure versus graded blood loss in conscious humans.

May 30, 2014Journal of Applied Physiology

Reductions in central venous pressure by lower body negative pressure or blood loss elicit similar hemodynamic responses

Q: What is the clinical evidence from this study?

Study design: Other. Intervention: Lower body negative pressure (LBNP) vs. Blood loss (BL) (1,000 ml total). Primary outcome: CVP-MAP trajectory slope (p=0.037).

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Key result

Lower body negative pressure mimics hemodynamic stimulus-response trajectories of blood loss, with the CVP-MAP slope being the only CVP-response difference (0.93 vs 0.13; P=0.037).

Why the study?

Does lower body negative pressure elicit similar hemodynamic and blood analyte responses compared to graded blood loss in men?

Population

12 men

Comparison

Graded lower body negative pressure consisting… vs Graded blood loss consisting of 5 min at…

Design

Other

Authors

BJBlair D. JohnsonVascular Medicine NHNoud van HelmondCooper University Hospital TCTimothy B. CurryMayo Clinic

Discussion

Member takes

Implication

LBNP largely replicates blood loss hemodynamics in healthy men; leaves open validation for clinical translation or broader populations.

Key Points

To compare hemodynamic and blood analyte responses to reductions in central venous pressure and pulse pressure induced by graded lower body negative pressure versus graded blood loss in conscious humans.
Assessed 12 men across two protocols: graded lower body negative pressure (5-minute stages at 0, 15, 30, and 45 mmHg suction) and graded blood loss (5-minute baseline followed by three 333-ml hemorrhage stages totaling 1,000 ml).
Measured central venous pressure, pulse pressure, mean arterial pressure, heart rate, and blood analytes including catecholamines, hematocrit, hemoglobin, and arginine vasopressin, evaluating stimulus-response slopes via linear regression.
Stimulus-response trajectories were largely equivalent, though the central venous pressure-mean arterial pressure slope was significantly higher during lower body negative pressure compared with blood loss (0.93 ± 0.27 vs. 0.13 ± 0.26; P = 0.037).
The pulse pressure-heart rate slope was significantly steeper during lower body negative pressure than during blood loss (-1.85 ± 0.45 vs. -0.46 ± 0.27; P = 0.024).
Norepinephrine, hematocrit, and hemoglobin concentrations were significantly lower at termination in the blood loss protocol compared with lower body negative pressure (P < 0.05).

Structured PICO

Does lower body negative pressure elicit similar hemodynamic and blood analyte responses compared to graded blood loss in men?

Population

12 men undergoing graded lower body negative pressure and graded blood loss to compare hemodynamic responses.

Intervention

Graded lower body negative pressure (LBNP) consisting of 5-min stages at 0, 15, 30, and 45 mmHg of suction

Comparator

Graded blood loss (BL) consisting of 5 min at baseline and following three stages of 333 ml of hemorrhage (1,000 ml total)

Outcome

Stimulus-response relationships of central venous pressure (CVP) and pulse pressure (PP) to hemodynamic responses (heart rate, mean arterial pressure)surrogate

Main Result

Absolute Event Rate: 0.93% vs 0.13%

p-value: p=0.037

Lower body negative pressure is a valid experimental model that largely mimics the hemodynamic stimulus-response trajectories of actual blood loss in humans.

Cite This Study

Johnson et al. (2014) studied this question. Lower body negative pressure (LBNP) vs. Blood loss (BL) (1,000 ml total) was evaluated on CVP-MAP trajectory slope (p=0.037). Lower body negative pressure mimics hemodynamic stimulus-response trajectories of blood loss, with the CVP-MAP slope being the only CVP-response difference (0.93 vs 0.13; P=0.037).

synapsesocial.com/papers/6a96c78dff8a6b2115f6c48d https://doi.org/10.1152/japplphysiol.00070.2014

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