Monitoring for Anesthesia Flashcards
Define Monitoring?
To watch & check a situation carefully for a period of time
Why is Monitoring done in anesthesia?
Maintain normal patient physiology and homeostasis throughout the period of anaesthesia
What are the Standards for basic anaesthetic monitoring based on ?
The American Society of anaesthesiologists’ committee
What are the standards for basic anesthetic monitoring?
Standard 1 states that an anesthesia provider will be present with the patient throughout the anesthetic
Standard 2 states that the patient’s oxygenation, ventilation, circulation and temperature will be continually monitored.
According to international standards, what is the most important monitor?
The presence of the anaesthesia clinician throughout anesthesia.
What are the standard monitors used to monitor patients?(4)
1.pulse oximeter, 2.Electrocardiography
3.Noninvasive blood pressure device
6.Temperature monitor
How often should an ECG and BPs be measured?
Every 5mins
What two parameters are assessed when monitoring Oxygenation? And how are they monitored?
Inspired gas -Oxygen analyzer
Blood oxygenation-Pulse oximeter
Describe how a pulse oximeter works?
The oximeter probe consists of two parts, the light emitting diodes (LED’s) and a light detector (called a photo-detector),which emits red and infrared light. Beams of light are shone through the tissues from one side of the probe to the other. The blood and tissues absorb some of the light emitted by the probe. Oxygenated hemoglobin (HbO2) absorbs more infrared light, while deoxygenated hemoglobin (Hb) absorbs more red light. The light absorbed by the blood varies with the oxygen saturation of haemoglobin. A photodetector on the other side of the sensor measures the amount of light that passes through the tissue. The device calculates the ratio of absorbed red light to infrared light. This ratio is used to determine the percentage of hemoglobin that is saturated with oxygen (SpO2).
List factors can affect a pulse oximeter reading(6)
1.Shivering – movement may make it difficult for the probe to pick up a signal.
2.Pulse volume – the oximeter only detects pulsatile flow. When the blood pressure is low due to hypovolaemic shock or the cardiac output is low or the patient has an arrhythmia, the pulse may be very weak and the oximeter may not be able to detect a signal.
3.Vasoconstriction reduces blood flow to the peripheries. The oximeter may fail to detect a signal if the patient is very cold and peripherally vasoconstricted.
4.Carbon monoxide poisoning gives a falsely high saturation reading. Carbon monoxide binds very well to haemoglobin and displaces oxygen to form a bright red compound called carboxyhaemoglobin. This is misinterpreted by the oximeter as oxyhaemoglobin and the oximeter may read 100%, even though the true oxygen saturation is very low and the patient may be very hypoxic. This is only an issue in patients following smoke inhalation from a fire
5.Nail polish or artificial nails
6.External light-Bright light can interfere with oximeter’s sensors
What two parameters are monitored when assessing Ventilation? And what is used?
1.Qualitative clinical signs-physical exam( If breathing spontaneously check for signs of airway obstruction, listening to breath sounds, observing chest movements and symmetry and auscultating, looking at a reservoir bag)
2.Quantitative monitoring-Capnometry
What is the normal end tidal CO2 level?
35-45mmHg
What does a normal capnogram inidcate?
Intubation?
What does a sudden drop in expired CO2?
It is the first sign in pulmonary artery embolism and in air embolism.
What does a sudden increase in CO2 indicate?
It is the first warning in malignant hyperthemia
What other ways can be used to assess adequacy of ventilation besides a capnograph?
Inspection and auscultation of the chest movements.
NB: Inspection of chest and diaphragmatic movements is more reliable that auscultation.
Besides measuring expired CO2 what are other functions of a capnography?
- 2.Diagnose obstruction of natural or artificial airways .
3.Can give a warning about malignant hyperthermia
4.Can give signs about Pulmonary embolism or air embolism
What are the factors cause an increase in ETCO2?
Changes in CO2 Elimination :
1.Hypoventilation
2.Rebreathing
3.Partial airway obstruction
4.Laparoscopy-CO2 absorption
Changes in CO2 Production
1.Fever
2.Thyroid Storm
3.Malignant Hyperthermia
What are the factors cause a decrease in ETCO2?
Changes in CO2 Elimination :
1.Hyperventilation
2.Hypoperfusion
3.Pulmonary Embolism
Changes in CO2 Production
1.Hyporthermia
What two parameters are monitored when assessing Circulation? And what is used?
Qualitative clinical signs -Physical exam (Assessment of skin color and temperature, the quality of a palpable pulse, and heart tones via an esophageal or precordial stethoscope, Urine Output)
Quantitative methods -BP (Invasive and Noninvasive) and an ECG
What are the two ways to assess BP?
Non-invasive: BP cuff
Invasive : Invasive arterial blood pressure
Describe how to choose the correct cuff size?
The width of the cuff should be 1.5 times limb diameter and should occupy at least 2/3 of the arm.
What are the 2 colors for cuff sizes and what do they represent?
-adult: blue: for most adult individuals (60-90 Kg)
-red: for morbid obese.
Why is selection of a coreect cuff size important?
Because a tight cuff leads to false high readings, while a loose cuff gives false low readings.
What are the causes of a reading error besides cuff size? (5)
1.Pressure line is disconnected.
2.Leakage from damaged cuff.
3.Line is compressed (under someone’s foot or under a weal).
4.Line contains water from washing!
5.Monitor error: cuff cannot inflate due to infant or neonate limits.
What is one thing that superior to the monitor ?
The anesthesia’s clinical judgement
What pulses are check to assess for circulation? And what values are considered to be in normal range?
1.Palpation of Radial A → systolic BP ˃ 90 mmHg.
2.Palpation of Dorsalis Pedis A → systolic BP ˃ 80 mmHg.
3.Palpation of Superficial Temporal A → systolic BP ˃ 80 mmHg.
How do your that the peripheral pulses are lost?
If Radial A pulsations are lost = systolic BP is < 90 mmHg
If dorsalis pedis & superficial temporal pulsations are lost = systolic BP is < 80 mmHg
Check pt colour for pallor: lips, tongue, nails, conjunctiva.
What is used to assess IBP?
An arterial cannula by beat to beat monitoring of ABP
What is the indication for IBP?(3)
1.major surgeries
2.during deliberate hypotensive anesthesia
3.during the use of inotropes, cardiac surgery in surgeries involving extreme hemodynamic changes/instability eg. pheochromocytoma, repeated ABG sampling.
What parameters from an ECG are essential to an anesthesiologist?
(1) heart rate,
(2) cardiac rhythm
(3) information about possible myocardial ischemia (via ST segment analysis)
How is Temperature monitored?
1.Clinical monitoring: your hands.
2.Monitors: temperature probe: nasopharyngeal, esophageal
Why is it important to monitor temperature?
To avoid hypothermia
Why is it necessary to avoid hypothermia?
To avoid complications of hypothermia.
1.Cardiac arrhythmias: VT & cardiac arrest.
2.Myocardial depression.
3.Delayed recovery (delays drug metabolism).
4.Delayed enzymatic drug metabolism.
5.Metabolic acidosis (tissue hypoperfusion → anerobic glycolysis → lactic acidosis) & hyperkalemia.
6.Coagulopathy
Which age group is crucial to avoid hypothermia in?
Especially in pediatrics & geriatrics (extremes of age).
What other parameters can be monitored in anesthesia?
Movement, facial expressions
Nerve stimulators
Gas monitoring
Blood loss
Urine output
Cns awareness
What is the triad of death?
1.Hypothermia
2.Acidosis
3. Coagulopathy
What are the rules to never forget?
1.Never start induction with a missing monitor: ECG, BP, SpO2.
Never remove any monitors before extubation & recovery.
2.NEVER ignore an alarm by the ventilator.
3.ALWAYS remember than your clinical sense & judgement is better than & superior to any monitor. U are a doctor u are not a robot. The monitor is present to help u not to be ignored and not to cancel your brain.
4.ALWAYS remember that there is NO such thing as “all monitors disconnected” → check that your pt is ALIVE!! Immediately check peripheral & carotid pulsations to make sure that your pt is not ARRESTED!! Once u have ensured pt safety reattach your monitors once
What are the 4 basic monitors displayed on a monitoring screen?
1.ECG.
2.BP.
3.SpO2.
4.± Capnogram (EtCO2).
