Oral saline consumption and pressor responses to acute physical stress

Sodium induced volume loading may alter pressor responses to physical stress, an early symptom of cardiovascular disease.

Study 1: Determine the time point where total blood volume and serum sodium were elevated following saline consumption. Study 2: Examine the BP response to isometric handgrip (HG) and the cold pressor test (CPT) following saline consumption.

Study 1: Eight participants drank 423 mL of normal saline (sodium 154 mmol/L) and had blood draws every 30 min for 3 h. Study 2: Sixteen participants underwent two randomized data collection visits; a control and experimental visit 90 min following saline consumption. Participants underwent 2 min of isometric HG, post exercise ischemia (PEI), and CPT.

Study 1: Total blood volume (3.8 ± 3.0 Δ%) and serum sodium (3.5 ± 3.6 Δ%) were elevated (P < 0.05) by the 90 min time point. Study 2: There were no differences in mean arterial pressure (MAP) during HG (EXP: 17.4 ± 8.2 ΔmmHg; CON: 19.1 ± 6.0 ΔmmHg), PEI (EXP: 16.9 ± 11.7 ΔmmHg; CON: 16.9 ± 7.8 ΔmmHg), or the CPT (EXP: 20.3 ± 10.8 ΔmmHg; CON: 20.9 ± 11.7 ΔmmHg) between conditions (P > 0.05). MAP recovery from the CPT was slower following saline consumption (1 min recovery: EXP; 15.7 ± 7.9 ΔmmHg, CON; 12.3 ± 8.9 ΔmmHg, P < 0.05).

Data showed no difference in cardiovascular responses during HG or the CPT between conditions. BP recovery was delayed by saline consumption following the CPT.