Vasoconstrictors are often given to raise blood pressure which is seductively reassuring because vasoconstrictors increase the resistance to blood flow. This raises the blood pressure by reducing blood flow which is the opposite of what is desired. This reduction in blood flow is not apparent and is not detected . We generally can’t measure or test that the perfusion is decreasing. Blissfully we are unaware of it, mistakenly deceived by the increase in blood pressure. We might see in the short term an initial rise in blood pressure which is easily measured, mistakenly reassuring, but we should expect the worsening of perfusion. Vasoconstrictors have long been misused by clinicians arrogant in their misunderstanding. Commonly it is thought that blood pressure reflects flow or perfusion. It does not seem possible to many that flow and perfusion is going down as blood pressure is rising.
Blood Pressure Redistribution
Blood Pressure and flow may be redistributed to different vascular beds. If the flow is redistributed to the brain this may may quickly be noticed. In other vascular beds the worsening of perfusion will not be noticed immediately. Urine output is an index of organ perfusion but still delayed but only the kidneys. If a catheter is placed in the bladder this helps, but comes at a cost of increasing the chance for infection. It could be that flow in important vascular beds is improving when the overall flow of blood is decreasing. It is still not flow in real time as it is somewhat delayed. Even more than the kidney other organ systems can suffer the lack of perfusion and go unnoticed. As flow is so difficult to measure it is difficult to detect an overall deterioration. Swapping short term increases in blood pressure for long term deterioration in perfusion is seductive. The phrase Levophed to “Leave um Dead” reflects this misunderstanding. This reflects the attitude of the arrogant but ignorant.