Lecture 3 - Perioperative Hypertension

Question 1

What organ systems do HTN effect?

Answer 1

All of ‘em

Question 2

What are the 3 components that impact blood pressure?

Answer 2

Cardiac ejection

Intravascular volume

Vascular elasticity/tone

Question 3

Where does systolic blood pressure originate? How about diastolic blood pressure?

Answer 3

Systolic pressure represents how stiff our arteries are (resistance to LV ejection)

Diastolic pressure represents the elastic property of our arteries during recoil. (relaxation after arterial wall stretch)

Question 4

What is the general effect of age on our blood pressures? Why?

Answer 4

Aging leads to higher systolic pressure, but normal or lower diastolic pressure.

Higher systolic pressure: our vascular system stiffens as we age. Elastic tissue is replaced by stiffer fibers and artherosclerotic plaques, leading to higher resistance during systole.

Normal to lower diastolic pressure: lack of recoil due to decreased elasticity

(diastolic may stay the same because stiffer arteries would require less recoil since they distend less)

Question 5

In normal situations, our bodies’ blood pressures will increase in response to noxious stimuli.

Is this cause for concern in the peri-operative setting?

Answer 5

It depends.

In normal patients, autoregulatory functions maintain BP in a narrow range.

In elderly patients (and other susceptible groups), autoregulation is not as robust and so the range of BP will be much higher which can be detrimental to perfusion, etc, etc..

Question 6

What are the respective weaknesses of using mechanical measurement and automated measurement of blood pressures?

Answer 6

Mechanical (Korotkoff sounds): human error

Auto-NIBP: profound BP changes may impact accuracy due to automated range adjustment

Question 7

What does the dichrotic notch of an arterial pressure reading represent? How about the peak and the trough?

Answer 7

Dichrotic notch: point at which aortic valve closes (@ end of cardiac ejection) to prevent blood from leaking back into the heart ; upward stroke (increased pressure) comes from elastic recoil of the artery

Peak: systolic

Trough: diastolic

Question 8

Why is excessively high BP dangerous?

Answer 8

Chronically high BP in the perioperative setting (outside of patient’s normal hemodynamic range) may lead to:

• scarring/inflammation of end organs
• high pressure on end organs leading to pathologies (ESRD, CHF)

Question 9

Why is excessively low BP dangerous?

Answer 9

Chronically low BP perioperatively may lead to hypoperfusion of organs, hypo-oxygenation of organs –> organ failure / damage (esp the brain)

Question 10

What can happen if we drop a patient’s BP too quickly?

Answer 10

Acute hypoperfusion of end organs, especially the brain (may cause light-headedness or unconsciousness)

Question 11

Mean arterial pressure equation is..

Answer 11

MAP = [2(DBP) + SBP]/3

DBP = diastolic BP, SBP = systolic BP

Question 12

What does MAP represent?

Answer 12

Estimation of how much total blood volume is being ejected per LV stroke

Question 13

What may happen if we increase vascular bed resistance too much through vasoconstricting meds?

Answer 13

Heart failure from overwork (strain due to resistance)

Damage to vessel walls can cause artherosclerosis (scarring of vessel walls) or end organ damage

Question 14

What is the pulse pressure indicative of?

Answer 14

It is a measure of the difference/gradient between SBP and DBP.

It is proportional to the amount of blood ejected per cardiac cycle.

Can also be used as an indicator of the patient’s volume status.

Question 15

What is the pulse pressure equation?

Answer 15

PP = SBP - DBP

Question 16

What does an increase in systolic pressure without a significant change in diastolic pressure usually mean?

Answer 16

Blood volume of cardiac ejection increased with minimal change to the vascular tone

Question 17

How would vasodilitation effect your blood pressure reading if ejection fraction remained relatively constant?

Answer 17

Lower diastolic pressure.

Ejection fraction may go up due to increase in vascular pool due to dilitation.

(May need peer review on this one)

Question 18

BP signs of pre-hypertension.

Answer 18

Systolic: 120-139 mm Hg

Diastolic: 80-89 mm Hg

Mean pressure < 93 mm Hg

*Considered high-end normal/pt is at risk

Question 19

BP signs of hypertension stage 1.

Answer 19

Systolic > 140 mm Hg

Diastolic > 90 mm Hg

Mean pressure > 93 mm Hg

Question 20

BP signs of hypertensive crisis.

Answer 20

Systolic > 180 mm Hg

Diastolic > 110 mm Hg

Question 21

When does a hypertensive crisis escalate into a hypertensive emergency?

Answer 21

Organ dysfunction or damage.(must lower BP ASAP!)

Question 22

What are the categories of hypertension? Describe them.

Answer 22

> Essential hypertension: HTN caused by autoregulation of smooth muscle walls; effected by electrolyte fluxes

> Chemical hypertension: HTN due to vascular volume and electrolyte retention in body; will effect vascular tone of the body

> Renal-vascular hypertension: HTN caused by autoregulation of renal perfusion + fluids and electrolytes at the level of the kidney; can cause excessive BP elevations

Question 23

How do hypertensive patients differ from non-hypertensive patients in the autoregulation of their BP and HR? Why is this concerning to anesthetists?

Answer 23

HTN pts have an exaggerated BP rise in response to peri-op stimulation.

Their BP can fluctuate up to ~90 mm Hg (VS 20-30) and HR can also reflexively fluctuate up to 40 beats (VS 15-20).

We need to be concerned about this because wide hemodynamic swings can lead to excessive stress on heart and end organs

Question 24

How should we manage the BP of a HTN patient?

Answer 24

Ensure that their BP is well-controlled (usually with beta blockers) for a certain period of time prior to surgery.

We want to maintain a narrow BP range to minimize wide hemodynamic swings at/around their baseline hemodynamic range.

We don’t want to induce what we believe to be ‘normal’ BPs because their hearts are used to autoregulating its own rhythm and maintaining end organ perfusion at these hypertensive states.

End organs will also learn how to autoregulate its own perfusion to provide adequate feedback to the heart in this chronic baseline range so we don’t want to induce stress by taking the pt too far out of that range.

Question 25

What are possible (and often seen) effects of anesthesia on physiological components that effect BP?

Answer 25

Baroreceptor response blunting

Intravascular reduction due to dehydration and blood loss

Sympathetic inhibition

Vasodilation

Cardiac depression

Question 26

Hemodynamic expectations during induction

Answer 26

Elevated BP due to vasoconstriction in response to meds and stimulation

Tachycardia

(Symp NS activation, Parasymp NS blockade)

Question 27

Hemodynamic expectations during emergence

Answer 27

Elevated BP due to pain, bladder distention, fluid overload

Restoration of vascular tone can also elevate BP (decrease in vessel compliance –> vascular pool (think diastolic) decreases –> more resistance against LV contraction)

Hypoxia and hypercarbia can also lead to higher BP

Question 28

Normal tensive vs well-controlled hypertensives: how should we manage their hemodynamics?

Answer 28

You don’t really have to manage them differently peri-operatively.

They will both respond similarly to medication. However, do think about what medications HTN pts are on.

Question 29

What are the threshold BP that indicates a pt is in a poorly controlled state and should not proceed with elective surgery?

Answer 29

Systolic > 170

or

Diastolic > 110

or both (including 170/110)

We need to get these pts on some meds or therapy to better control their BP prior to surgery.