Oftentimes persons say that they have low blood pressure (hypotension) and there is a fair understanding about its potential dangers. There are misunderstandings, however, about what constitutes low blood pressure, even among persons who provide health care. Is it as prevalent as we think? How serious is it?
Blood pressure has two components, systolic and diastolic. A typical blood pressure would be 120/80, where the 120 would be the systolic reading and 80 the diastolic reading. The systolic pressure is produced when the heart contracts pumping blood through the arteries around the body. The pressure surges upwards then reduces until the heart pumps again and the pressure just before the next beat is the diastolic pressure. The blood pressure is usually measured manually with a sphygmomanometer and a stethoscope, or with automated blood pressure machine.
The normal range for the systolic blood pressure is 90-139 and for the diastolic it's 60-85. A blood pressure reading lower than 90/60 is considered as low (e.g. 85/60 or 90/55). There are persons, however, with this type of low reading who are functioning normally without any symptoms. There are also persons with a higher reading than that and they have symptoms. This may happen if the person is used to having a significantly higher reading than that. There are some persons who wrongfully believe that a blood pressure lower than 120/80 is low.
Hypotension can cause light-headedness, fainting, blurred vision, lack of concentration, nausea, cold, pale and sweaty skin, fatigue and thirst. Blood pressure usually drops during pregnancy, but not usually low enough to cause symptoms. Very low or high heart rate or low pumping force can cause hypotension. Some hormonal problems like hypo/hyperthyroidism can also cause it. Dehydration from vomiting, diarrhoea and excessive sweating can reduce the blood volume leading to hypotension. Excessive bleeding can cause it too.
Severe allergic reactions and serious infections can cause the blood vessels to relax and also allow excessive fluid to leave the circulation and enter the body tissues and cause a life-threatening drop in blood pressure. Some medications can cause it by reducing the heart rate or pumping force, blood volume or by relaxing the blood vessels too much. Large clots in the lung arteries (pulmonary embolism) can block the flow of blood to the heart causing dangerous blood pressure drop.
If hypotension is causing symptoms the cause will need to be discovered and treated.
Dr Douglas Street is a general practitioner and has private practices at Trinity Medical Centre, Trinity Mall at 3 Barnett Street in Montego Bay, and Omega Medical Centre at Plaza de Negril, Negril. Send feedback to firstname.lastname@example.org.