Hello,
first of all you should make sure that the measurements are right. I can explain that to you in detail, if you believe you need an explanation.
If the measurements were right, the next thing we should consider is the timing of the measurements. A blood pressure of 75/57 when the patient has just woke up is not considered too low because many individuals have a 10-20% lower blood pressure during their sleep.
Blood pressures above 90mmHg (systolic) are considered normal.
Lower than that could be normal also, particularly if no symptoms are associated with it.
Low blood pressure in an old individual may suggest
heart failure, drug effects, arrhythmia or Addison's disease but it could be normal as well. Sometimes it is associated with frailty due to the old age.
If he had no symptoms, no
dehydration, no bleeding, no
black stool, no arrhythmia then he doesn't need the ER. A laboratory investigation is appropriate though which should include a
complete blood count, urea,
creatinine, sodium, potassium, calcium, creatine phosphokinase and others (I just mentioned the absolutely essential tests).
I hope you find my answer helpful!
Kind Regards!