Clinical monitoring in sedation

Question 1

Why do we need to monitor in sedation?

Answer 1

1) to check depth of sedation
2) to check for adverse reactions to the drug or treatment
3) to detect respiratory or cardiac problems
4) for medicolegal reasons

Question 2

what can we monitor?

Answer 2

CLINICAL SIGNS:
-appearance
-conscious level
-airway
-breathing

ELECTROMECHANICAL:
-circulation
-oxygen saturation
-blood pressure

Question 3

What things do we look for in terms of appearance when monitoring in sedation?

Answer 3

ALERTNESS - Less muscle tone/slow movements but still alert at lighter levels.
Pt may close their eyes at deeper levels- difficult to tell using appearance if they are over-sedated.
SKIN- check for rashes/swelling (could indicate potential allergy? anaphylaxis due to allergy to midazolam?
SOFT TISSUE COLOUR - cyanosis (blue- sign of hypoxia. if tongue is blue= central cyanosis (NOT WELL!)

Question 4

How do you determine the conscious level of the pt?

Answer 4

When administering sedative drug, while waiting you must engage with the pt verbally so that you can judge how responsive they are.
-> Prompt response to verbal cues at lighter levels
-> Slower to respond as depth of sedation increases
-> Unconsciousness indicates over-sedation

Question 5

How do you determine the airway of the pt?

Answer 5

LISTEN to the clarity of airway (is there noise or lack of noise?-noisy or normal breathing?)
LOOK for potential obstructions (must remove them!)

Question 6

Why is it important to remove potential obstructions (eg tooth fragments/saliva) during tx under sedation?

Answer 6

Because the gag reflex of the pt under sedation is suppressed so need to pay extra attention to removing potential obstructions.

Question 7

How do you determine the breathing of the pt?

Answer 7

Checking the:

1) Respiratory movement
-movement of chest and/or abdomen (are they using their abdomen to breathe with a lot of effort?
-deep or shallow breaths?

2) Respiratory rate (normal: 12-15 bpm…DME SAYS 12-20 bpm)

Question 8

How do you determine the circulation of the pt?

Answer 8

Checking the pulse (Heart rate) using the pulse oximeter.
Check the:
-rate (fast/slow)
-character (strong/weak)
-regularity (regular/irregular)

Question 9

How do you determine the oxygen saturation of the pt?

Answer 9

using a pulse oximeter

Question 10

Define oxygen saturation

Answer 10

It is the percentage of haemoglobin saturated with oxygen

Question 11

What can hinder the pulse oximeter from picking up a reading?

Answer 11

-Nail polish (blue, black or green) or false nails
-cold or anxiety causing peripheral shut down
-movement of finger (eg tapping)
-under fluorescent/bright lights

Question 12

True or False: Blood CO2 levels drive respiration

Answer 12

True
Your drive to breathe is not by the lack of O2 but it is by the build up of CO2, making the blood more acidic. As CO2 levels increase, respiration increases to get rid of it.

Question 13

True or False: Blood O2 levels are never a drive for respiration

Answer 13

False
Only at very low levels of blood O2 is it a drive for respiration.

Question 14

What does the oxygen dissociation curve show?

Answer 14

As each O2 molecule is release by haemoglobin into the tissues, it is progressively easier for the next one to be released.

When the O2 saturation is at 100%, the Hb doesn’t want to give up the O2. So initially it will be a slow and gradual fall. Then the more oxygen is lost from the Hb, the easier and quicker it is for O2 to be lost. When it falls below 90%, we will notice the O2 saturation will drop really fast. We do not want O2 saturation to fall below 95%!

Question 15

What are the changes when the oxygen dissociation curve shifts to the right? What does this mean in terms of oxygen take up in the lungs as a result?
What is an example of a condition where there is a shift of the curve to the right?

Answer 15

-Low pH
-High CO2 (slightly acidic blood)
-High temp

As a result, there is less oxygen take up in the lungs, more oxygen available in the tissues (Hb is not as saturated with O2, so wants to take up O2 in the tissues).

Eg. asthma

Question 16

What are the changes when the oxygen dissociation curve shifts to the left? What does this mean in terms of oxygen take up in the lungs as a result?
What is an example of a condition where there is a shift of the curve to the left?

Answer 16

-High pH
-Low CO2 (slightly more alkaline blood)
-Low temp

As a result, more oxygen take up occurs in the lungs, less oxygen available in the tissues. (because the oxygen does not want to come away from the Hb so Hb can’t take up more oxygen in the tissues).

Eg. hyperventilation- get rid of too much CO2

Question 17

What can pulse oximetry show?

Answer 17

1) pulse rate and rhythm
2) oxygen saturation of Hb

Question 18

The pulse oximeter is not infallible (error-free). What conditions/scenarios prove this?

Answer 18

-Anaemic hypoxia (enough O2 but not enough Hb. O2 hanging about not carried by Hb so cannot be picked up by pulse oximeter)
-Cytotoxic hypoxia (cells cannot use O2 eg cyanide/carbon monoxide poisoning. Pulse oximeters cannot distinguish between oxygen and carbon monoxide carried by Hb. For instance, if your hemoglobin carries 85% oxygen and 10% carbon monoxide, the reading would show as 95%.)
-Factory calibrated thus there is room for error.

Question 19

What is the normal O2 sat level?

Answer 19

96% and above. (DME says 94% and above is normal!)

We would give supplementary oxygen through nasal cannula if the O2 sats drop below 95% and cannot be brought up with voluntary additional breaths.

Over-sedating a pt will drop their O2 sats significantly.

Question 20

True or false: O2 saturation is lower in people who smoke and people with lung disease.

Answer 20

True.
This is because of poorer lung function.

Question 21

Briefly describe how the pulse oximeter works.

Answer 21

Infra-red and red light directed onto nail (but can use earlobe or forehead). Pulse oximetry is based on the principle that O2Hb (oxyhaemoglobin-O2 + Hb) and HHb (Hb alone w/o O2) absorb red and infrared light differently. O2Hb absorbs greater amounts of infrared light and lower amounts of red light than does HHb

Question 22

How do you determine the blood pressure of the pt?

Answer 22

We use a sphygmomanometer.

We measure BP at start of tx and every 5 minutes (LTHT policy).

Question 23

What do we do if the BP reading is unusual?

Answer 23

Either:
-a medical emergency happening
-result of stress

If BP reading is very high during tx, confirm that it is not a medical emergency and monitor it afterwards. ECG available.

Question 24

True or False: The pulse oximeter reads O2 sats live and accurate on the dot.

Answer 24

False
The pulse oximeter is always behind events and takes time to catch up if the O2 saturation is falling rapidly. It takes the pulse oximeter a while to figure out the change whether O2 saturation is increasing or decreasing. But it is the most accurate measure available and far better than clinical observation alone. It is an essential piece of equipment.