Blood Pressure Monitoring Flashcards
What is autoregulation, and what is the normal value?
Most organs, perfusion is dependent upon blood pressure except brain, kidneys and heart.
The amount of blood flow in these organs remain constant, no matter the blood pressure - autoregulation
Normal renal autoregulation range?
80-180mmHg
Normal coronary autoregulation range?
50-120mmHg
What conditions can impair autoregulation?
- Ischemia
- Hypercarbia
- Acidosis
- High end tidal concentration of volatile agent
What are etiologies of hypotension?
- Hypovolemia (NPO, blood loss, etc)
- Vasodilation (from anesthetics, sepsis, anaphylaxis, acidosis, etc)
- Patient positioning (Reverse Trendelenburg, beach chair, etc)
- Vagal response
- Need for stress dose of steroids (for steroid dependent patients)
- Decreased cardiac contractility/ejection fraction (leading to drop in cardiac output)
- A blood pressure cuff that is too large?
- Lateral decubitus position?
Treatments for hypotension?
- Cause vasoconstriction
- Administer vasopressors, or consider decreasing the inhalational agent concentration - Increase intravascularvolume (if the patient is hypovolemic)
- Change the patient’s position (Trendelenburg)
- Administer inotropes (if the cause of the hypotension is heart failure/decreased contractility)
- Give a stress dose of steroids? (An option if the patient is on chronic steroid therapy)
What are different types of blood pressure measurements?
- Auscultation
- Doppler
- Only measures systolic - NIBP (Oscillometry)
- Noninvasive arterial line (tonometry)
- Arterial line
What is doppler blood pressure monitoring?
Only systolic reading
Noninvasive Blood Pressure Monitoring (Oscillometry)
- Noninvasive blood pressure cuffs determine the systolic, diastolic, and mean arterial pressures separately
- Oscillometry is fairly accurate with regular rhythms, but is more inaccurate with irregular rhythms
How much higher is blood pressure taken on the leg compared to the arm (supine)?
Normally, systolic pressure in the leg is 10-20mmHg greater than in the arm
Where to NOT place the blood pressure cuff?
- The operative arm
- An arm that is on the same side as a prior mastectomy or lymph node removal
- Can cause lymphedema - An arm withan AV fistula
What are disadvantages of a Non-Invasive A-line (Tonometry)?
- It is very sensitive to movement and “exact” placement
- Very sensitive to movement
- Needs frequent calibration
- No arterial access for labs
Explain the process of dialysis
- A large vein and an artery are accessed
- The machine draws blood from the artery and sends it to the machine
- The machine “purifies” the blood and returns it to the patient through the vein
What is an AV fistula?
An artificial connection between an artery and a vein) in order to give these renal failure patients a larger vein (usually in the arm) so they can tolerate dialysis
Usually completed under MAC anesthesia
What is an AV graft for dialysis?
An AV graft is an artificial tube that connects the artery to the vein, and is an alternative procedure to an AV fistula
Matures quicker, but more prone to clotting
When is a central line used for dialysis?
This is only meant to be a short term solution until a fistula or graft can be established
Basic anesthesia management for renal failure patients?
- These patients are USUALLY anemic
–From decreased erythropoietin (EPO)/RBC production - The anesthetist should restrict fluids as much as possible
–500mL bag saline on microdrip tubing - The anesthetist should be cautious of anything that could potentially increase the serum potassium concentration of the patient
–Lactated Ringer’s solution should be avoided
–Succinylcholine administration is relatively contraindicated
How do you estimate BP in the head when a patient is sitting and not supine?
- Measure the distance from the cuff to the head
- Calculate the difference in blood pressure at the level of the head
For each 1cm height difference, the MAP will be 0.77mmHg lower at the head
