Hemodynamic Effects Induced by Transcutaneous Electrical Nerve Stimulation in Apparently Healthy Individuals: A Systematic Review With Meta-Analysis.

OBJECTIVE: To determine the immediate effects of transcutaneous electrical nerve stimulation (TENS) on heart rate, systolic blood pressure (SBP), and diastolic blood pressure (DBP) in apparently healthy adults (age ≥18y). DATA SOURCES: The Cochrane Library (online version 2014), PubMed (1962-2014), EMBASE (1980-2014), and LILACS (1980-2014) electronic databases were searched. STUDY SELECTION: Randomized controlled trials were included when TENS was administered noninvasively with surface electrodes during rest, and the effect of TENS was compared with that of control or placebo TENS. A sensitive search strategy for identifying randomized controlled trials was used by 2 independent reviewers. The initial search led to the identification of 432 studies, of which 5 articles met the eligibility criteria. DATA EXTRACTION: Two independent reviewers extracted data from the selected studies. Quality was evaluated using the PEDro scale. Mean differences or standardized mean differences in outcomes were calculated. DATA SYNTHESIS: Five eligible articles involved a total of 142 apparently healthy individuals. Four studies used high-frequency TENS and 3 used low-frequency TENS and evaluated the effect on SBP. Three studies using high-frequency TENS and 2 using low-frequency TENS evaluated the effect on DBP. Three studies using high-frequency TENS and 1 study using low-frequency TENS evaluated the effect on heart rate. A statistically significant reduction in SBP (-3.00mmHg; 95% confidence interval [CI], -5.02 to -0.98; P=.004) was found using low-frequency TENS. A statistically significant reduction in DBP (-1.04mmHg; 95% CI, -2.77 to -0.03; I(2)=61%; P=.04) and in heart rate (-2.55beats/min; 95% CI, -4.31 to -0.78; I(2)=86%; P=.005]) was found using both frequencies. The median value on the PEDro scale was 7 (range, 4-8).
CONCLUSIONS: TENS seems to promote a discrete reduction in SBP, DBP, and heart rate in apparently healthy individuals.