BP basics

• • low BP can result in organ hypoperfusion, possibly interrupting organ function and risking tissue viability and sometimes (as in the case of the heart) causing irreparable tissue damage with long term functional consequences
  • Most people with low BP do not have a BP low enough to cause problems and indeed their low but totally functional BP is protective against cardiovascular disease
• • We normally see dangerously low blood pressures only in the acutely ill e.g. the patient in ITU with septicaemia, or following sudden acute haemorrhage e.g. rupture of an aortic aneurysm
  • Conversely hypertension is a major cause of death
• • To maintain health, BP must be kept in the “Goldilocks zone” - neither too low to inadequately perfuse organs or too high to cause tissue/organ damage – but just right to allow optimal organ functioning
  • As a rule of thumb BP should be as low as possible without inappropriate organ perfusion i.e. without producing symptoms
  • Symptoms of a too low BP include postural hypotension, visual disturbances, dizziness, fatigue and an increased tendency to fall
• Increased BP is caused by:

  • increased blood volume
  • increased viscosity
  • increased heart rate
  • increased stroke volume
  • increased vasoconstriction