Anesthesia Monitoring: EKG Rhythms and BP Monitoring

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Questions and Answers

What is the optimal device positioning for arterial blood pressure monitoring in neurosurgery?

At the circle of Willis

What is the recommended cuff size width for non-invasive blood pressure monitoring?

40% of extremity circumference

What is the effect of underdamping on arterial waveform analysis?

Overestimates SBP and underestimates DBP

What is the principle behind pulse oximetry?

Beer-Lambert Law Signup and view all the answers

What is the effect of carboxyhemoglobin on pulse oximetry?

Falsely high SpO2 readings Signup and view all the answers

What is the treatment for carboxyhemoglobin poisoning?

100% FiO2 Signup and view all the answers

What is the normal percentage of methemoglobin?

<1% Signup and view all the answers

What is the purpose of the double-burst stimulation test?

To detect residual paralysis during recovery Signup and view all the answers

What is the frequency of the stimulus in the tetanus test?

30, 50, or 100 Hz Signup and view all the answers

What is the purpose of the post-tetanic count?

To detect severe neuromuscular blockade Signup and view all the answers

What is the effect of an air bubble in the tubing or low pressure on arterial waveform analysis?

Overdamping - overestimating DBP Signup and view all the answers

What is the purpose of the pulse oximeter sensor?

To measure the absorption of infrared and red light by hemoglobin Signup and view all the answers

What is the effect of sulfahemoglobin on pulse oximetry readings?

Falsely low readings Signup and view all the answers

What is the recommended position for non-invasive blood pressure cuffs in relation to IV sites?

On the opposite arm from the IV site Signup and view all the answers

What is the recommended frequency of non-invasive blood pressure monitoring?

Every 5 minutes Signup and view all the answers

What is the effect of methemoglobin on pulse oximetry readings?

Falsely low readings for SPO2<85% Signup and view all the answers

What is the primary reason for minimizing stopcocks in arterial blood pressure monitoring?

To optimize the accuracy of the waveform analysis Signup and view all the answers

What is the effect of a small amount of fluid in the arterial blood pressure monitoring system?

It optimizes the accuracy of the waveform analysis Signup and view all the answers

What is the effect of sulfahemoglobin on pulse oximetry readings?

It results in falsely high oxygen saturation readings Signup and view all the answers

What is the primary advantage of using ETCO2 monitoring in moderate sedation or higher?

It helps to detect respiratory depression earlier Signup and view all the answers

What is the effect of underdamping on arterial waveform analysis?

It results in falsely low diastolic blood pressure readings Signup and view all the answers

What is the recommended frequency of non-invasive blood pressure monitoring?

Every 5 minutes Signup and view all the answers

What is the minimum monitoring requirement for anesthesia care?

BP, HR, EKG, RR, Pulse Ox and add ETCO2 when using moderate sedation or higher Signup and view all the answers

Which of the following factors optimize the accuracy of arterial blood pressure monitoring?

All of the above Signup and view all the answers

Arterial transducers are typically positioned at what level?

The level of the right atrium Signup and view all the answers

What is unique about an underdamped arterial waveform?

It has a high amplitude with multiple artifacts present Signup and view all the answers

What is the primary cause of underdamping in an EKG rhythm?

Opposite of what increases accuracy Signup and view all the answers

What does overdamping look like on an arterial waveform?

A waveform with a flat, shallow peak - loss of dicrotic notch Signup and view all the answers

In both overdamping and underdamping, MAP is accurate

True Signup and view all the answers

Frequent BP measurements can cause nerve damage or IV extravasation

True Signup and view all the answers

What percentage of the extremity should the BP cuff encircle?

80% Signup and view all the answers

What is the impact of blood pressure cuff readings if the cuff is too small or too loose?

The readings will be falsely high. Signup and view all the answers

In critically ill patients, why can SPO2 readings be different?

Due to the dependency of SPO2 on pulsatility Signup and view all the answers

What principle is used by pulse oximeters to measure oxygen saturation?

Absorption spectrometry - by measuring the light absorption of a chemical substance as it passes through solution Signup and view all the answers

What law states that light absorbed by a solution is related to its concentration?

Beer-Lambert Law Signup and view all the answers

What is true about reduced hemoglobin?

It absorbs more light in the infrared band Signup and view all the answers

What does SPO2 measure?

Ratio of oxyhemoglobin to hemoglobin Signup and view all the answers

What components are typically found in a pulse ox sensor?

2 LEDs (light emitting diodes) and a photodetector to measure the ratio of infrared and red light Signup and view all the answers

What do fractional saturation and co-oximetry measure in anesthesia monitoring?

The ratio between oxyhemoglobin and other forms of hemoglobin (methemoglobin, carboxyhemoglobin, sulfahemoglobin) Signup and view all the answers

What results from the presence of iron in oxidized form?

Methemoglobin Signup and view all the answers

Methemoglobin absorbs light less than Hgb

False Signup and view all the answers

What is the treatment for methemoglobinemia?

Administration of methylene blue 1-2 mg/kg as a 1% solution over 3-5 mins Signup and view all the answers

What results from irreversible binding of sulfur to hemoglobin?

Sulfhemoglobin Signup and view all the answers

What is the characteristic of blood in sulfahemoglobin-induced cyanosis?

Greenish hued blood Signup and view all the answers

What are the causes of methemoglobinemia?

All of the above Signup and view all the answers

What are the causes of sulfahemoglobin?

All of the above Signup and view all the answers

What is the treatment for sulfahemoglobin?

Blood transfusion Signup and view all the answers

What are the limitations of pulse oximetry?

All of the above Signup and view all the answers

What is the main difference between capnometry and a capnogram?

Capnometry measures end-tidal CO2, while a capnogram is a graphical representation of CO2 levels Signup and view all the answers

What do the four phases of capnography in ETCO2 monitoring represent?

Phase I: Anatomic dead space, Phase II: Alveolar emptying, Phase III: Alveolar-expiratory plateau phase, Phase IV: Expiratory down stroke to inspiratory phase Signup and view all the answers

What is ETCO2 measured at?

End-expiration (beta wave on capnography) Signup and view all the answers

Which of the following are methods used for ETT placement confirmation?

All of the above Signup and view all the answers

What does observing positive ETCO2 on 3 consecutive breaths suggest about ETT placement?

The ETT is in the trachea Signup and view all the answers

Endotracheal tubes (ETT) with leaks are likely to do what to ETCO2?

Underestimate Signup and view all the answers

What is true about peripheral nerve stimulators?

They deliver monophasic current Signup and view all the answers

What is the effect of PNS placement on the Adductor pollicis muscle?

Adduction of the thumb to the center of the palm Signup and view all the answers

What is the effect of PNS stimulation on the facial nerve at orbicularis oculi and corrugator supercilii muscles?

Eyelid closes or brow furrows Signup and view all the answers

What type of movement does PNS stimulation at the posterior tibial nerve at the flexor hallucis brevis muscle cause in the big toe?

Flexion Signup and view all the answers

In peripheral nerve stimulator placement, which lead is proximal and closest to the heart?

Red lead Signup and view all the answers

Where is the onset of neuromuscular blockade best measured?

Facial muscles Signup and view all the answers

Which nerve best approximates the conditions of the laryngeal adductor muscles?

Facial nerve Signup and view all the answers

Where does blockage develop faster and recover more quickly in the airway?

Central muscles Signup and view all the answers

During neuromuscular blocker monitoring, which muscle should recover before the adductor pollicus?

Diaphragm Signup and view all the answers

Where is neuromuscular blockade recovery best measured at?

Adductor pollicis muscle (hand) Signup and view all the answers

What is the purpose of single twitch stimulation during induction?

To identify optimal conditions for intubation Signup and view all the answers

What is the purpose of the train of four, which involves 4 supramaximal stimuli at 0.5 sec intervals (2 Hz)?

To assess the neuromuscular blockade Signup and view all the answers

If zero twitches are present during TOF monitoring, what is the state of the neuromuscular blockade?

Deep/profound blockade Signup and view all the answers

If 1-2 twitches are present during TOF monitoring, what is the state of the block?

Partial blockade Signup and view all the answers

What percentage of receptor occupancy of a non-depolarizing NMB can occur even at a TOF count of 4 and TOF ratio >0.9?

70-75% Signup and view all the answers

What is a benefit of double burst stimulation when assessing neuromuscular blockade?

It may help to detect fade easier than TOF monitoring Signup and view all the answers

What is tetanus in peripheral nerve stimulation and why should it be used sparingly?

A high-frequency stimulation for 5 seconds that helps in identifying the optimal dose of muscle relaxant, but should be used sparingly due to muscle fatigue/pain. Signup and view all the answers

What is a TET fade over 5 seconds equivalent to?

TOF fade Signup and view all the answers

What are the indications for post-tetanic count (PTC) stimulation?

Used in presence of 100% paralysis to provide rough estimate of time to recovery Signup and view all the answers

When TOF and double burst are absent, what type of nerve stimulation is indicated?

Post-tetanic count Signup and view all the answers

What does a count of less than 8 during post-tetanic count stimulation indicate?

Deep block and prolonged recovery is likely Signup and view all the answers

What happens to Ach in post tetanic count stimulation when intense stimulation is applied transiently?

It is mobilized to potentiate a response Signup and view all the answers

What is the definition of fade in anesthesia monitoring?

A reduction in amplitude from first twitch to last twitch that is seen only in phase II blockade Signup and view all the answers

How many twitches must be present to administer a reversal agent?

1 Signup and view all the answers

What criteria must be met before a patient is considered ready for extubation, and reversal of neuromuscular blockade is considered complete?

Reversal criteria met with full TOF or sustained tetanus Signup and view all the answers

When should a PNS be placed during general anesthesia?

Before induction of anesthesia over the facial nerve Signup and view all the answers

What are the signs of inadequate blockade recovery?

Weakness, inability to sit or speak at regular volume, fatigue Signup and view all the answers

Why is PNS (Peripheral Nerve Stimulation) used during the maintenance phase of general anesthesia?

To avoid over/under dosage of anesthetic Signup and view all the answers

What are the indications for central venous pressure (CVP) monitoring?

All of the above Signup and view all the answers

What does CVP approximate?

Right atrial pressure and Left ventricular end-diastolic pressure in healthy individuals Signup and view all the answers

What is the primary risk associated with central line access in the right internal jugular (IJ) vein?

Higher risk of carotid artery puncture Signup and view all the answers

What are the complications of central venous pressure (CVP) insertion?

All of the above Signup and view all the answers

In atrial fibrillation, what is unique about the CVP waveform?

It lacks a wave and may have a prominent c wave Signup and view all the answers

What does the 'a' wave in a CVP (Central Venous Pressure) indicate?

Atrial contraction Signup and view all the answers

What does the 'c' wave in CVP indicate?

right ventricular contraction Signup and view all the answers

Why is bispectral index (BIS) monitoring used in total intravenous anesthesia (TIVA)?

To monitor depth of anesthesia due to increased risk of awareness Signup and view all the answers

What is the BIS target for sedation?

65-85 Signup and view all the answers

What is the BIS target for general anesthesia?

40-60 Signup and view all the answers

What are the characteristics of a perfect emergence during anesthesia?

Spontaneous respirations, follows commands, and no coughing during extubation Signup and view all the answers

In which of the following situations is bispectral index (BIS) monitoring contraindicated?

Facial trauma patients, surgical procedures on upper face, prone patients Signup and view all the answers

Which of the following pressures most closely approximates LVEDP?

PAOP Signup and view all the answers

In which of the following clinical situations may PAOP not accurately reflect LVEDP?

All of the above Signup and view all the answers

What are some complications related to PA catheter use?

All of the above Signup and view all the answers

Which of the following statements is true about methods of CO monitoring?

All methods of CO monitoring depend on assessing the rate of flow through the right ventricular outflow tract located between the pulmonary valve and the supraventricular crest in the RV. Signup and view all the answers

What is normothermia?

A normal body temperature, 37 degrees C Signup and view all the answers

What temperatures in Celsius are typically classified as hypothermia and hyperthermia?

Below 36°C and above 38°C Signup and view all the answers

What is the most common type of heat loss in the operating room?

Radiation Signup and view all the answers

Intraoperative hypotension in adults is a MAP <55-60 mmHg

True Signup and view all the answers

Where is the V lead placed in an EKG?

5th ICS in the anterior axillary line Signup and view all the answers

5 lead EKGs preferred in adults. 3 lead EKG preferred in pediatrics

True Signup and view all the answers

V3-V5 are useful for detecting ischemia in 5 lead EKG

True Signup and view all the answers

Lead II and V5 are the best leads for intraoperative monitoring of dysrhythmias and ischemia

True Signup and view all the answers

3 lead monitoring is inadequate for diagnosing complex arrhythmias

True Signup and view all the answers

Junctional rhythms are common under anesthesia

True Signup and view all the answers

LBBB occurs in healthy individuals while RBBB is an ominous sign

False Signup and view all the answers

What is the recommended setting for ST segment alarms in relation to the baseline in patients with Coronary Artery Disease (CAD)?

1mm above and below baseline Signup and view all the answers

What myocardial wall abnormalities are associated with myocardial infarction?

Dyskinesia (paradoxical movement) Signup and view all the answers

What is the effect of a loss of atrial kick during atrial fibrillation on ventricular filling?

Reduces ventricular filling by 20% Signup and view all the answers

What is hypokinesia?

Abnormal lack of movement Signup and view all the answers

What is the normal range of the QT interval?

350-450 milliseconds Signup and view all the answers

Study Notes

Monitoring Standards

For every anesthetic monitor, the following parameters should be monitored: BP, HR, EKG, RR, Pulse Ox, and ETCO2 when using moderate sedation or higher (deep or GA)
HR and RR should be monitored continuously, while BP should be monitored continually every 5 minutes

BP Monitoring

Arterial Blood Pressure Monitoring

Accuracy is optimized by using stiff catheters and tubing, a small amount of fluid in the system, shorter length of tubing, and minimizing stopcocks
Transducers must be zeroed and positioned at the level of the RA (typically), or at the circle of Willis (in neurosurgery for cerebral perfusion)
Complications can be mitigated by using small catheters, minimizing attempts, and monitoring sites
Arterial waveform analysis can be used to assess for damping, with:
- Fast flush to assess for damping
- Underdamping: multiple artifacts present in waveform, overestimates SBP, underestimates DBP, and MAP is accurate
- Overdamping: dicrotic notch is lost, underestimates SBP, overestimates DBP, and MAP is accurate

Noninvasive Blood Pressure Monitoring

Cuff size should be 40% of the extremity circumference and encircle 80% of the extremity
If the cuff is too small, readings obtained are falsely high
Position the cuff opposite to the IV if possible, and change position for longer cases
Frequent measurements can cause nerve damage or IV extravasation

Pulse Oximetry and Co-Oximetry

Pulse Oximetry

Arterial O2 sat is typically 95-100%
Numbers should correlate but not exactly match PaO2
Works through absorption spectrometry, measuring light absorption of a chemical substance as it passes through a solution
Based on Beer-Lambert Law, where light absorbed by a solution is related to its concentration
SPO2 is the ratio of oxyhemoglobin to hemoglobin
Pulse ox sensor contains 2 LEDs and a photodetector, measuring the ratio of infrared and red light, and averaging data over a time period to calculate SPO2

Co-Oximetry

Fractional saturation and co-oximetry measure the ratio of oxyhemoglobin to Hgb, carboxyhemoglobin, methemoglobin, and other forms of hemoglobin
Carboxyhemoglobin:
- Has a higher affinity for Hgb than O2 (250x)
- Hgb binding sites occupied by CO cannot carry O2
- SPO2 will read falsely high
- Treatment is 100% FiO2
- Signs and symptoms: cherry red lips
Methemoglobin:
- Results from the presence of iron in an oxidized form
- Normally 1%
- Falsely high for sats 40%, pulse ox will read 80-85%
- Treatment is methylene blue 1-2 mg/kg as 1% solution over 3-5 minutes
Sulfahemoglobin:
- Results from irreversible binding of sulfur to Hgb
- Normally 0.9%
- May be caused by certain medications, such as migraine medication and certain antibiotics

Monitoring Standards

For every anesthetic monitor, the following parameters should be monitored: BP, HR, EKG, RR, Pulse Ox, and ETCO2 when using moderate sedation or higher (deep or GA)
HR and RR should be monitored continuously, while BP should be monitored continually every 5 minutes

BP Monitoring

Arterial Blood Pressure Monitoring

Accuracy is optimized by using stiff catheters and tubing, a small amount of fluid in the system, shorter length of tubing, and minimizing stopcocks
Transducers must be zeroed and positioned at the level of the RA (typically), or at the circle of Willis (in neurosurgery for cerebral perfusion)
Complications can be mitigated by using small catheters, minimizing attempts, and monitoring sites
Arterial waveform analysis can be used to assess for damping, with:
- Fast flush to assess for damping
- Underdamping: multiple artifacts present in waveform, overestimates SBP, underestimates DBP, and MAP is accurate
- Overdamping: dicrotic notch is lost, underestimates SBP, overestimates DBP, and MAP is accurate

Noninvasive Blood Pressure Monitoring

Cuff size should be 40% of the extremity circumference and encircle 80% of the extremity
If the cuff is too small, readings obtained are falsely high
Position the cuff opposite to the IV if possible, and change position for longer cases
Frequent measurements can cause nerve damage or IV extravasation

Pulse Oximetry and Co-Oximetry

Pulse Oximetry

Arterial O2 sat is typically 95-100%
Numbers should correlate but not exactly match PaO2
Works through absorption spectrometry, measuring light absorption of a chemical substance as it passes through a solution
Based on Beer-Lambert Law, where light absorbed by a solution is related to its concentration
SPO2 is the ratio of oxyhemoglobin to hemoglobin
Pulse ox sensor contains 2 LEDs and a photodetector, measuring the ratio of infrared and red light, and averaging data over a time period to calculate SPO2

Co-Oximetry

Fractional saturation and co-oximetry measure the ratio of oxyhemoglobin to Hgb, carboxyhemoglobin, methemoglobin, and other forms of hemoglobin
Carboxyhemoglobin:
- Has a higher affinity for Hgb than O2 (250x)
- Hgb binding sites occupied by CO cannot carry O2
- SPO2 will read falsely high
- Treatment is 100% FiO2
- Signs and symptoms: cherry red lips
Methemoglobin:
- Results from the presence of iron in an oxidized form
- Normally 1%
- Falsely high for sats 40%, pulse ox will read 80-85%
- Treatment is methylene blue 1-2 mg/kg as 1% solution over 3-5 minutes
Sulfahemoglobin:
- Results from irreversible binding of sulfur to Hgb
- Normally 0.9%
- May be caused by certain medications, such as migraine medication and certain antibiotics

Monitoring Standards

For every anesthetic monitor, the following parameters should be monitored: BP, HR, EKG, RR, Pulse Ox, and ETCO2 when using moderate sedation or higher (deep or GA)
HR and RR should be monitored continuously, while BP should be monitored continually every 5 minutes

BP Monitoring

Arterial Blood Pressure Monitoring

Accuracy is optimized by using stiff catheters and tubing, a small amount of fluid in the system, shorter length of tubing, and minimizing stopcocks
Transducers must be zeroed and positioned at the level of the RA (typically), or at the circle of Willis (in neurosurgery for cerebral perfusion)
Complications can be mitigated by using small catheters, minimizing attempts, and monitoring sites
Arterial waveform analysis can be used to assess for damping, with:
- Fast flush to assess for damping
- Underdamping: multiple artifacts present in waveform, overestimates SBP, underestimates DBP, and MAP is accurate
- Overdamping: dicrotic notch is lost, underestimates SBP, overestimates DBP, and MAP is accurate

Noninvasive Blood Pressure Monitoring

Cuff size should be 40% of the extremity circumference and encircle 80% of the extremity
If the cuff is too small, readings obtained are falsely high
Position the cuff opposite to the IV if possible, and change position for longer cases
Frequent measurements can cause nerve damage or IV extravasation

Pulse Oximetry and Co-Oximetry

Pulse Oximetry

Arterial O2 sat is typically 95-100%
Numbers should correlate but not exactly match PaO2
Works through absorption spectrometry, measuring light absorption of a chemical substance as it passes through a solution
Based on Beer-Lambert Law, where light absorbed by a solution is related to its concentration
SPO2 is the ratio of oxyhemoglobin to hemoglobin
Pulse ox sensor contains 2 LEDs and a photodetector, measuring the ratio of infrared and red light, and averaging data over a time period to calculate SPO2

Co-Oximetry

Fractional saturation and co-oximetry measure the ratio of oxyhemoglobin to Hgb, carboxyhemoglobin, methemoglobin, and other forms of hemoglobin
Carboxyhemoglobin:
- Has a higher affinity for Hgb than O2 (250x)
- Hgb binding sites occupied by CO cannot carry O2
- SPO2 will read falsely high
- Treatment is 100% FiO2
- Signs and symptoms: cherry red lips
Methemoglobin:
- Results from the presence of iron in an oxidized form
- Normally 1%
- Falsely high for sats 40%, pulse ox will read 80-85%
- Treatment is methylene blue 1-2 mg/kg as 1% solution over 3-5 minutes
Sulfahemoglobin:
- Results from irreversible binding of sulfur to Hgb
- Normally 0.9%
- May be caused by certain medications, such as migraine medication and certain antibiotics

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