Effect of needle-EMG on blood-pressure and heart-rate

Though immediate pain is reported by nearly all patients undergoing needle-EMG,little is known about its cardiovascular risk from changes in blood-pressure orheart-rate. This study was thus conducted to investigate if, and to whichdegree, blood-pressure and heart-rate are influenced by needle-EMG. In 50patients, 24 women, 26 men, aged 26–78 years, conventional needle-EMGs from 54muscles were recorded. Pain was assessed on a verbal analogue pain-scale (1–10)and blood-pressure and heart-rate were measured before, during and after EMG.Mean pain-ratings before, during and after EMG were 0.8, 4.1 and 1.0,respectively. Mean systolic/diastolic blood-pressure was 144/87mmHg before,145/86mmHg during and 144/87mmHg after EMG. Mean heart-rate before, during andafter EMG was 77, 77 and 78 beats/min, respectively. Systolic/diastolicblood-pressure increased above 145/85mmHg in only 2/6 patients during EMG. Theweak affection of blood-pressure and heart-rate by pain from needle-EMG wasfound in patients with and without hypertension. Mean blood-pressure, heart-rateand pain-ratings before, during and after EMG were independent of age, sex andmuscle. The correlation between pain-ratings and blood-pressure and heart-ratewas not significant. This study shows that needle-EMG moderately hurts but doesnot increase blood-pressure or heart-rate, irrespective of known arterialhypertension. Based upon these findings, the cardiovascular risk of needle-EMGfrom changes in blood-pressure or heart-rate is regarded negligibly low.