Monitoring

Question 1

What is MAP and how is it calculated?

Answer 1

Mean arterial pressure is the time-weighted average of the arterial pressures during a pulse cycle.

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

Question 2

What factor effects the result of arterial pressure monitoring?

Answer 2

The location where the pressure is measured.

As a pulse moves peripherally, wave reflection distorts the pressure waveform, resulting in exaggeration of systolic and pulse pressures.

Figure 5-1.

Question 3

Name a situation where radial artery systolic pressure may underestimate central pressure.

Answer 3

In patient following hypothermic CABG. Vasodilating drugs further accentuates the discrepancy.

Question 4

What are the indications for non-invasive blood pressure monitoring?

Answer 4

All applications of anesthesia.

Question 5

What are contraindications for non-invasive BP monitoring?

Answer 5

Cuff monitoring should be avoided in extremities with vascular abnormalities (e.g. dialysis shunts) or IV-lines.

Question 6

When are Korotkoff sounds difficult to auscultate?

Answer 6

During episodes of hypotension.

During Marked peripheral vasoconstriction.

Question 7

How do oscillometric devices work?

Answer 7

Arterial pulsations cause oscillations in cuff pressure. The device detects the oscillations when the pass systolic pressure. They peak during MAP. The devise uses MAP to estimate systolic and diastolic pressures.

Question 8

How is organ blood flow estimated?

Answer 8

With Blood pressure. IT is only an indicator because flow is also affected by vascular resistance.

Flow = Pressure / resistance

Question 9

What are the indications of invasive arterial pressure monitoring?

Answer 9

Induced or anticipated hypotension.
Wide deviations in BP.
Need for multiple measurements of arterial BP.

Question 10

What are contraindications of arterial BP monitoring?

Answer 10

If possible, catheterization should be avoided in smaller end arteries with inadequate collateral blood flow or in extremities where there is a suspicion of preexisting vascular insuffciency.

Question 11

Which arteries can be cannulated for arterial BP monitoring?

Answer 11

a. radialis
a. ulnaris
a. brachialis
a. femoralis
a. dorsalis pedis & a. tibialis posterior
a. axillaris

Question 12

What are the pros and cons of a. brachialis cannulations for BP monitoring?

Answer 12

It is closer to the aorta and therefore the waveforms are less distorted. The positioning in the elbow makes it prone to kinking.

Question 13

What are the the risks of femoral artery cannulation?

Answer 13

Prone to atheroma and pseudoaneurysms.
Greater risk for infection.
Greater risk for arterial thrombosis.

Question 14

What are the potential complications of radial artery cannulations?

Answer 14

hematoma, bleeding (particularly with catheter tubing disconnections), vasospasm, arterial throm- bosis, embolization of air bubbles or thrombi, pseu- doaneurysm formation, necrosis of skin overlying the catheter, nerve damage, infection, necrosis of extremities or digits, and unintentional intraarterial drug injection.

Question 15

What factors are associated with increased rate of complications of radial artery cannulations?

Answer 15

prolonged cannullation, hyperlipidemia, repeated insertion attempts, female gender, extracorporeal circulation, the use of larger catheters in smaller vessels, and the use of vasopressors.

Question 16

How are the catheter-tubing-transducer system dynamics improved?

Answer 16

improved by minimizing tubing length, eliminating unnecessary stopcocks, removing air bubbles, and using low-compliance tubing.

Question 17

What are the indications of central venous catheterizations?

Answer 17

Monitoring of central venous pressure.
Administration of fluids to treat hypovolemia and shock.
Aspiration of air emboli.
IV-access when peripheral access not possible
Infusion of caustic drugs and total parenteral nutrition

Question 18

What are the contraindications of central venous catheterization?

Answer 18

Relative contraindications include:
Tumors
Clots
Tricuspid valve regurgitations that may be dislodged

Subclavian vein cannulation is relatively contraindicated in patients on anticoagulants, due to inability to provide direct compression to deep arteries in case of accidental puncture.

Question 19

What is the optimal location for the central venous catheters tip?

Answer 19

Just superior to or at the junction between SVC and right atrium.

Question 20

When (resp phase) should central venous pressure be measured?

Answer 20

During end expiration.

Question 21

What greater risk is subclavian vein cannulation associated with compared to other sites?

Answer 21

Pneumothorax.

Although it is more suitable for long-term catheterization.

Question 22

What greater risk is femoral vein access associated with?

Answer 22

Line-related sepsis.

Question 23

Name 3 cannulation techniques for central venous catheterization.

Answer 23

Catheter over needle, similar to peripheral cannulation.
Catheter through needle.
Catheter over a guide wire (Seldinger technique)

Question 24

Why is a pat placed in Trendelenburgs position during internal jugular vein cannulation?

Answer 24

To decrease risk of air embolism and to distend the veins.

Question 25

What are the risks of central venous catheterization?

Answer 25

line infection, blood stream infection
air or thrombus embolism
arrhythmias (indicating that the catheter tip is in the right atrium or ventricle)
hematoma
pneumothorax
hemothorax, hydrothorax, chylothorax
cardiac perforation
cardiac tamponade
trauma to nearby nerves and arteries
thrombosis.

Question 26

Describe the shape of the central venous waveform.

Answer 26

The shape of the central venous waveform corresponds to the events of cardiac contraction (Figure 5–19): a waves from atrial contraction are absent in atrial brillation and are exaggerated in junctional rhythms (“cannon” a waves); c waves are due to tricuspid valve elevation during early ven- tricular contraction; v waves re ect venous return against a closed tricuspid valve; and the x and y descents are probably caused by the downward dis- placement of the tricuspid valve during systole and tricuspid valve opening during diastole.

Question 27

What are the indications for peripheral nerve stimulation?

Answer 27

Monitoring the effect of neuromuscular blockade.
Assessing paralysis during RSI
Locating peripheral nerves in regional anesthesia.

Question 28

What sites are most often used for peripheral nerve stimulation?

Answer 28

Ulnar nerve stimulation of the adductor pollicis muscle and facial nerve stimulation of the orbicularis oculi are most commonly monitored.

Question 29

How does NMT-monitoring via TOF work?

Answer 29

Train-of-four stimulation denotes four suc- cessive 200-μs stimuli in 2 sec (2 Hz). The NMT-sensors monitors the muscle twitching and displays it as 4 staples. As the blockade gets more efficient the staple start to fade from last one and backwards.
When less than 4 staples are visible the monitor will display how many are visible (TOFcnt)
If all 4 stables are visible the monitor will display TOFratio which is the ratio between the last staple and the first one.

Question 30

What TOF values are desirable?

Answer 30

0 for complete muscular relaxation.
1-2 for invasive surgery.
2-4 for superficial surgery.
Extubation can be done when TOF shows > 90%