Question: I'm an IV certified PCP. A question came up last week in regards to aortic aneurysms and different blood pressures bilaterally. If one BP is hypotensive, and the other is normo- or hyper- do we bolus? Ideas that have come up include: Adding fluid may increase the overall pressure, causing the dissection to enlarge; however, the patient is losing fluid and therefore is compensating and needs more.
Great question. You have hit on a number of concepts that are medically controversial and we will try to address them.
The first is the significance of unequal blood pressures. There are a number of causes for unequal blood pressures between extremities including but not limited to: pre-existing subclavian stenosis, aortic dissection, autonomnic instability (since blood pressures are rarely taken in both arms simultaneously), aortic dissection, and lastly measurement error / cuff malfunction. Treating this finding depends on making a clinical decision on what is causing the unequal BP for the patient in front of you.
Presuming the patient has an Aortic Dissection based on the history (sudden onset chest pain radiating through to the back with fluctuating neurologic symptoms being the classic history) then the current guidelines suggest health care providers attempt to maintain a low to normal BP (ie. 90-110 SBP). The patient meets the fluid therapy directive if they are hypotensive (SBP < 90 mmHG). If the patient has consistently unequal BPs (ie measured a couple times in each arm) and has no other signs of hypotension - than their "true" BP would be represented by the arm that is perfused by normal vascular anatomy (non obstructed arteries) and therefore the higher BP. If both arms have SBPs < 90 we would bolus. If one arm SBP is above 90 mmHG and the other is below, you believe the patient has an aortic dissection, and there are no other signs of hypotension, then starting an IV but withholding the bolus would be ideal practice. However, bolusing the same patient would definitely be acceptable practice.
Another concept that you describe in your questions is that of "hypotensive resuscitation". Hypotensive resuscitation means tolerating a mean arterial pressure of 60 (or even less) in trauma patients to limit blood loss until surgical repair. To date this is really only practiced in Trauma. The same principles may apply to patients with other non-traumatic diseases like aortic dissection. However, this is not standard of care currently so we would suggest following the directives and bolusing hypotensive patients.