Apex unit 6 Flashcards
Identify the components that are absent in a Mapleson D. (Select 2.)
Reservoir bag
APL valve
Unidirectional valves
CO2 absorbent
Unidirectional valves
CO2 absorbent
Mapleson devised a classification system for nonrebreathing circuits, which are also known as semi-open circuits. All of the Mapleson circuits lack unidirectional valves and a CO2 absorber. Resistance is low, because there are no unidirectional valves or absorbent granules. This makes these circuits attractive for pediatrics. Since there is no CO2 absorbent, fresh gas flow and the circuit design determine the amount of rebreathing that occurs.
The Mapleson D has an APL valve and a reservoir bag. The Mapleson E (Ayre’s t-piece) is the only Mapleson design that does not contain an APL valve or reservoir bag.
A patient is receiving controlled ventilation with a fresh gas flow of 5 L/min. Click on the circuit that is MOST likely to cause hypercarbia.
A
Not only do you have to be able to identify each circuit, but you have to know which are best for controlled ventilation.
The Mapleson A is the worst configuration for controlled ventilation (best to worst): DFE > BC > A
Notice the fresh gas flow enters far from the patient and that the APL valve is close to the patient. This combination is what makes the Mapleson A the worst design for controlled ventilation. A fresh gas flow as high as 20 L/min is required to prevent rebreathing!
This specific configuration is also what makes the Mapleson A the best design for spontaneous ventilation (best to worst): A > DFE > CB
Which circuit does not contain dead space?
Open
Semiopen
Closed
Semiclosed
Open
An open circuit is open to the atmosphere and does not contain dead space.
All of the other circuits are not open to the atmosphere and contain some degree of dead space.
Which Mapleson circuits are MOST likely to be encountered in modern anesthetic practice? (Select 3.)
A B C D E F
DEF
The most common Mapleson circuits include: D, E, and F. You’d be hard pressed to find an A, B, or C. Yes, these circuits are archaic, but they are important in understanding the correlation between fresh gas, dead space, and alveolar gas with circuit design.
Mapleson D, E, and F are also labelled the “T piece” group. The fresh gas enters at the proximal end of the circuit and the APL valve is located distally near the reservoir bag. The Mapleson D is actually the reverse set up of a Mapleson A making it an excellent choice for controlled breathing.
Although “Basics of Anesthesia” is not listed on the NBCRNA bibliography, it does not mean the content within isn’t relevant. It does an excellent job of explaining each Mapleson circuit with a clear voice.
The Mapleson D is an example of a/an: semiopen circuit. open circuit. semiclosed circuit. closed circuit.
Semiopen circuit
Semiopen Circuit (Mapleson A-F, Bain system, circle system w/ FGF > Ve):
Bag reservoir = Yes
Rebreathing = No
Which circuit contains a reservoir bag but does not allow rebreathing of exhaled gases?
Semiopen
Open
Semiclosed
Closed
Semiopen
A semiopen circuit contains a breathing bag but does not allow rebreathing of exhaled gases.
Semiopen Circuit (Mapleson A-F, Bain system, circle system w/ FGF > Ve):
Bag reservoir = Yes
Rebreathing = No
A circle system with a fresh gas flow of 3 L/min is an example of a/an:
closed circuit.
semiclosed circuit.
semiopen circuit.
open circuit.
Semiclosed circuit
A circle system with a FGF of 3 L/min is a semiclosed circuit.
Semiopen Circuit (Mapleson A-F, Bain system, circle system w/ FGF > Ve):
Bag reservoir = Yes
Rebreathing = No
All of the following allow fresh gas to escape into the atmosphere EXCEPT a:
simple face mask.
Bain system.
T-piece.
nasal cannula.
Bain System
The Bain system is an example of a semiopen circuit.
All of the other answer choices are open circuits (nasal cannula, simple face mask and T-piece). Since there is no reservoir bag, an open circuit requires a spontaneously breathing patient. Entrapment of the exhaled gas is also not possible, therefore there is no way to scavenge exhaled gases. This can cause environmental pollution. Since oxygen is pumped into the atmosphere (it’s not contained within a circuit), there is a risk of fire if an ignition source and fuel are present.
Click on the circuit that is the predecessor to the Bain system.
The Mapleson D (2nd example) is the precursor to the Bain system.
What’s different about the Bain system is that the fresh gas travels towards the patient through a smaller tube INSIDE the corrugated tubing.
Exhaled gas travels inside the corrugated tubing (but outside of the small tube discussed above). This design passively warms the incoming fresh gas.
How do you perform the Pethick test during the pre-anesthetic checkout with a Bain circuit?
It is possible that the inner tubing of the Bain circuit can become kinked or disconnected. This situation converts the entire length of the corrugated tubing to dead space and greatly increases the risk of hypercarbia if FGF is not increased.
The Pethick test should be done as part of the pre-anesthetic checkout.
If the inner tubing is patent, the Venturi effect will cause the reservoir bag to collapse.
If the inner tubing is occluded, the reservoir bag will remain inflated. This circuit is not safe to use.
1st step + Occlude the elbow at the patient end of the circuit.
2nd step + Close the APL valve.
3rd step + Use the oxygen flush valve to fill the circuit.
4th step + Remove the occlusion at the elbow while flushing the circuit.
Click on the phase of the capnograph that BEST correlates with the ventilation-perfusion status of the lung. (Pic is ETCO2 waveform)
between C-D
Phase I = Exhalation of dead space
Phase II = Exhalation of dead space + alveolar gas
Phase III = Exhalation of alveolar gas (best correlates to V/Q status)
Phase IV = Inspiration
Point D = Point of EtCO2 measurement
Click on the beta angle.
There are two angles on the capnograph: alpha and beta
Alpha angle: Between phase II and III Normal = 100-110 degrees Increased by obstruction to expiration, such as COPD, kinked endotracheal tube, etc.
Beta angle:
Between phase III and IV
Normal = 90 degrees
Increased by an inspiratory valve stuck in the open position
Match each event with its MOST likely presentation on the capnograph.
Channeling + Elevated baseline
Incompetent inspiratory valve + Widened beta angle
Sample line leak + Peak at end of phase 3
Tournequet release + Increased EtCO2 with normal return to baseline
All of the following contribute to an increased PaCO2-EtCO2 gradient EXCEPT:
right-to-left shunt.
pulmonary embolism.
sample line leak.
laparoscopy.
Laparoscopy
Carbon dioxide follows a concentration gradient as it exits the body: blood > lungs > airway > sample line or atmosphere
The normal PaCO2-EtCO2 gradient is 2-5 mmHg. This gradient is increased by any condition that blocks CO2 removal or by a leak in the breathing system. Examples include:
Reduced CO2 transport through the lungs
Incomplete alveolar emptying
Increased dead space
Right-to-left shunt
Upper airway obstruction
Leak in the sample line, endotracheal tube, or LMA
Inadequate seal around endotracheal tube, or LMA
Insufflation of carbon dioxide during laparoscopy increases blood CO2, however as long as there is nothing preventing its escape, the PaCO2-EtCO2 gradient remains normal.
Infrared analysis is able to measure: (Select 3.)
carbon dioxide. helium. nitrous oxide. volatile anesthetics. xenon. oxygen.
Carbon dioxide
Nitrous oxide
Volatile anesthetics
Infrared analysis is the most common method of measuring carbon dioxide, nitrous oxide, and halogenated anesthetics.
Molecules that contain two or more dissimilar atoms absorb infrared light, and each of these molecules produces a unique infrared absorption footprint.
IR analysis cannot measure oxygen, helium, nitrogen, or xenon because these species contain only one type of atom.
When compared to a mainstream carbon dioxide sensor, which of the following is an advantage of a sidestream carbon dioxide sensor?
Less apparatus dead space
Absence of a pumping mechanism
Elimination of the water trap
Faster response time
Less apparatus dead space
There are two sampling methods used for capnography: mainstream and sidestream
The mainstream (in-line) measuring device is attached to the endotracheal tube. It provides a faster response time, and doesn’t require a water trap or pumping mechanism. Because it’s attached to the endotracheal tube, it does increase apparatus dead space as well as adds extra weight.
The sidestream (diverting) measuring device is located outside of the airway. A pumping mechanism continuously aspirates the gas sample from the breathing circuit, and for this reason, the response time is slower. Additionally, this arrangement requires a water trap to prevent contamination of the device.
Choose the statement that reflects the MOST complete understanding of pulse oximetry.
It emits two wavelengths of ultraviolet light.
At the trough of the waveform, the sample contains more arterial blood.
It is based on the Coanda effect.
660 nm light is preferentially absorbed by reduced hemoglobin.
660 nm light is preferentially absorbed by reduced hemoglobin
The pulse oximeter is based on the Beer-Lambert law, which relates the intensity of light transmitted through a solution and the concentration of the solute within the solution. In this instance, the solution is blood and solute is hemoglobin. As an aside, the Coanda effect describes the tendency of a jet fluid to be attracted to a nearby surface (think of a wall hugging jet created by mitral regurgitation on TEE).
The pulse oximeter emits two wavelengths of light:
Red light (660 nm) is preferentially absorbed by reduced Hgb.
Near-infrared light (990 nm) is preferentially absorbed by HgbO2.
You’ll see these numbers vary a bit from book to book.
The peak of the waveform contains relatively more arterial blood, while the trough of the waveform contains relatively more venous blood.
Which pulse oximeter location is associated with the SLOWEST response time?
Ear
Tongue
Nose
Finger
Finger
As a general rule, the closer the monitoring site is to the central circulation, the faster it will respond to arterial desaturation. Additionally, central monitoring sites are less resistant to the vasoconstrictive effects of SNS stimulation and hypothermia.
These sites are ordered from most to least responsive:
Fast = Ear, nose, tongue, esophagus, forehead
Middle = Finger
Slow = Toe
When SpO2 is monitored on the head or esophagus, the Trendelenburg position can cause venous engorgement resulting in a falsely decreased SpO2 measurement.
Which of the following is a contraindication to pulse oximetry?
Raynaud’s disease
Takayasu arteritis
Cardiopulmonary resuscitation
There are no contraindications to pulse oximetry.
There are no contraindications to pulse oximetry
Simply put, there are no contraindications to pulse oximetry. There are times, however, when direct PaO2 measurement better assesses arterial oxygenation than a pulse oximeter alone.
In which patients is the pulse oximeter MOST likely to provide an inaccurate measurement? (Select 2.)
7 year-old rescued from a basement fire
10 year-old with jaundice
15 year-old who received fluorescein
3 year-old toxic from EMLA cream overdose
Three year-old toxic from EMLA cream overdose
Seven year-old rescued from a basement fire
Hemoglobinopathies can contribute to erroneous pulse oximeter measurements:
Carbon monoxide poisoning:
Overestimates SpO2
Common in smoke inhalation patients
Treatment = oxygen therapy
Methemoglobinemia:
Underestimates SpO2 when oxygen saturation > 85%
Overestimates SpO2 when oxygen saturation < 85%
Methemoglobin is produced by: prilocaine, EMLA cream (contains prilocaine), benzocaine, cetacaine, nitroprusside, nitroglycerin, sulfonamides, and phenytoin
Treatment = methylene blue 1-2 mg/kg over 5 min or exchange transfusion if patient has glucose-6-phosphate dehydrogenase deficiency
Neither jaundice nor fluorescein interfere with the accuracy of the pulse oximeter.
Which of the following is the LEAST reliable monitor of endobronchial intubation?
Fiberoptic bronchoscope
Pulse oximeter
Pressure-volume loop
Lung auscultation
Pulse oximeter
Endobronchial intubation occurs when the distal end of the endotracheal tube advances into one of the mainstem bronchi. This situation creates a large shunt, as both of the lungs are perfused but only one is ventilated. Depending on the tube position, the Murphy eye may allow ventilation of the contralateral lung even through the endotracheal tube has advanced into the other mainstem bronchi.
Of the answer choices provided, the pulse oximeter is the least reliable monitor of endobronchial intubation. If the patient is receiving a high FiO2, then the SpO2 may not decline. Said another way, the absence of arterial desaturation does not rule out endobronchial intubation.
To that point, the pulse oximeter is not a reliable monitor for disconnections, leaks, esophageal intubation, or hypercarbia.
The mixed venous oxygen saturation monitor reads 70%. Estimate the PvO2.
(Enter your answer as a whole number in mmHg)
40 mmHg
It doesn’t matter if it’s an arterial, venous, or mixed venous sample, the same rule applies.
Remember 40, 50, 60 and 70, 80, 90.
PO2 40 ~ SpO2 70
PO2 50 ~ SpO2 80
PO2 60 ~ SpO2 90
Determinants of dynamic compliance include all of the following EXCEPT:
tidal volume.
peak inspiratory pressure.
plateau pressure.
positive end-expiratory pressure
Plateau pressure
Compliance is a change in volume for a given change in pressure (C = ∆V / ∆P).
We can measure compliance when gas is moving into the lung (dynamic compliance), or we can measure compliance when there is no gas flow at the inspiratory pause (static compliance).
Dynamic compliance is a function of airway resistance + lung/chest compliance.
Static compliance is a function of lung/chest compliance only.
Match each condition with its MOST likely effect on pulmonary pressure monitoring.
Endobronchial intubation
Mucus plug
Pulmonary embolism
Mucus plug + Decreased dynamic compliance
Endobronchial intubation + Decreased static compliance
Pulmonary embolism + No change in dynamic or static compliance
Compliance is a change in volume for a given change in pressure (C = ∆V / ∆P).
Dynamic Compliance is:
Measured while gas flows into the lungs.
A function of airway resistance + lung/chest wall compliance.
Assessed by peak pressure.
Decreased by anything that obstructs airflow, such as a kinked endotracheal tube, mucus plug, and bronchospasm.
Static compliance is
Measured when there is no gas flow (during the inspiratory pause).
A function of lung/chest wall compliance only (resistance only occurs during gas flow).
Assessed by plateau pressure.
Decreased by anything that reduces lung compliance, such as endobronchial intubation, tension pneumothorax, pneumonia, and pulmonary edema.
Pulmonary embolism does not affect pulmonary resistance or compliance.
The normal QT interval is:
- 10 seconds.
- 25 seconds.
- 40 seconds.
- 55 seconds.
0.40 seconds
Key facts about the QT interval:
It extends from the beginning of the Q wave (or R wave if there is no Q wave) through the end of the T wave.
It corresponds with the beginning of ventricular depolarization to the end of repolarization.
Hypercalcemia makes it shorter.
Hypocalcemia makes it longer.
It is inversely related to heart rate (faster heart rate = shorter QT interval).
Normal value = 0.35 - 0.45 seconds.
When it exceeds 0.5 seconds, there is an increased risk of torsades de pointes.
This EKG indicates:
normal axis.
left axis deviation.
right axis deviation.
extreme right axis deviation.
Left axis deviation
The electrical axis indicates the direction of depolarization as it travels through the myocardium.
We can illustrate the general direction of the movement of depolarization by using a vector.
The mean electrical vector is the summation of all of the vectors of ventricular depolarization.
The mean electrical vector tends to point towards ventricular hypertrophy and point away from myocardial infarction.
To determine the axis or the direction of the mean electrical vector, you have to look at the QRS complex in lead I and AVF.
Normal axis: lead I and AVF are positive
Extreme right axis: lead I and AVF are negative
Right axis: lead I is negative and AVF is positive
Left axis: lead I is positive and AVF is negative
All of the following are true of sinus arrhythmia EXCEPT:
inhalation increases heart rate.
it is caused by an ectopic pacemaker.
increased venous return increases heart rate.
it is a consequence of the Bainbridge reflex.
It is caused by an ectopic pacemaker
Sinus arrhythmia occurs when the SA node’s pacing rate varies with respiration.
Inhalation → ↑ heart rate
Exhalation → ↓ heart rate
Remember the Bainbridge reflex? This is the one where an increased venous return stretches the right atrium and SA node causing the heart rate to increase. It should also make sense that the Bainbridge reflex causes sinus arrhythmia.
Inhalation → ↓intrathoracic pressure → ↑venous return → ↑heart rate
Exhalation → ↑intrathoracic pressure → ↓ venous return → ↓ heart rate
Sinus arrhythmia is usually benign.
This EKG tracing represents a:
antidromic pathway.
sinus arrhythmia.
Mobitz type II block.
non-compensatory pause.
Non-compensatory pause
This EKG shows an example of a premature atrial contraction. A PAC originates from an ectopic focus in the atria. The P wave comes early and has a different morphology. The PAC is followed by a non-compensatory pause.
In this tracing, the QRS complexes are orthodromic (they are conducted through the AV node). The QRS morphology is normal.
An antidromic pathway is an accessory pathway that bypasses the AV node (think of the Bundle of Kent and Wolff-Parkinson-White syndrome). The QRS morphology is abnormally wide.
All of the following are appropriate treatments for symptomatic sinus bradycardia in a 70 kg adult EXCEPT:
dobutamine 5 mcg/kg/min.
atropine 0.2 mg.
glucagon 3 mg.
transcutaneous pacing.
Atropine 0.2 mg
Increased vagal tone is often the source of bradycardia. While atropine is a first-line treatment, not giving enough (< 0.5 mg IV) can cause paradoxical bradycardia. This is probably mediated by presynaptic muscarinic receptors.
Severely symptomatic patients (syncope or chest pain) should receive immediate transcutaneous pacing.
Glucagon is useful in the setting of beta blocker or calcium channel blocker overdose. By stimulating glucagon receptors on the myocardium, glucagon effectively increases cAMP leading to increased heart rate, contractility, and AV conduction. The initial dose is 50 - 70 mcg/kg q 3-5 min. This can be followed with an infusion at 2 - 10 mg/hr.
Click on the bipolar limb lead that is ALWAYS positive.
bottom left
There are three bipolar limb leads, and each one has a positive and a negative pole. The mean electrical vector travels away from the negative pole and towards the positive pole.
Lead I: Right arm (-) to Left arm (+)
Lead II: Right arm (-) to Left leg (+)
Lead III: Left arm (-) to Left leg (+)
Notice that the left leg is always positive and the right arm is always negative.
Click on the area of the hexagonal reference system that correlates with left axis deviation.
-90 to - 30 degrees
The electrical axis depicts the path of the mean electrical vector. This vector tends to move towards areas of hypertrophy and away from areas of infarction.
The normal axis is -30 to +90 degrees.
Here are an easy set of ranges to remember:
Left axis deviation = < -30 degrees
Right axis deviation = > 90 degrees
You will find some books that describe superior right axis deviation (+180 to - 90).
Which dysrhythmia is the MOST common cause of acute myocardial infarction?
Atrial fibrillation with rapid ventricular rate
Paroxysmal atrial tachycardia
Atrial flutter
Sinus tachycardia
Sinus tachycardia.
Sinus tachycardia simultaneously increases myocardial oxygen demand while decreasing oxygen supply. In patients with CAD, this can precipitate myocardial ischemia and/or infarction.
While any condition that increases heart rate can stress the heart, the most common rhythm associated with myocardial infarction is sinus tachycardia.
Match each dysrhythmia with its EKG tracing.
VT
SVT
ST
AFlutter
When compared to atrial fibrillation, which of the following statements about atrial flutter are true? (Select 2.)
Amiodarone is more likely to restore normal sinus rhythm.
It is an organized supraventricular dysrhythmia.
Each atrial depolarization is associated with an atrial contraction.
More current is required for synchronized cardioversion.
It (atrial flutter) is an organized supraventricular rhythm
Each atrial depolarization is associated with an atrial contraction
Unlike atrial fibrillation, atrial flutter is an organized supraventricular rhythm. You should recognize it by its characteristic “saw tooth” pattern.
The atrial rate is usually very fast (250-350 bpm).
Each atrial depolarization is associated with an atrial contraction, but not all atrial depolarizations are conducted past the AV node.
There is usually a defined ratio of atrial to ventricular contractions. For example, there may be 2 atrial contractions for every 1 ventricular contraction (2:1 ratio) or 3 atrial contractions for every 1 ventricular contraction (3:1 ratio).
The effective refractory period prevents all atrial impulses from being transmitted to the ventricles.
A rapid ventricular rate significantly reduces diastolic filling time, and this can lead to hemodynamic instability.
Hemodynamically unstable atrial flutter should be treated with cardioversion. As little as 50 joules (monophasic) will convert atrial flutter to normal sinus rhythm. By contrast, cardioversion for atrial fibrillation begins with 100 joules.
There is an increased risk of atrial thrombus formation if afib/aflutter lasts longer than 48 hours. These patients should be anticoagulated and undergo echocardiographic examination to rule out atrial thrombus prior to cardioversion.
Pharmacology therapy aimed at controlling ventricular rate includes amiodarone, diltiazem and verapamil. While these drugs can reduce the ventricular rate, they are unlikely to convert atrial flutter to normal sinus rhythm. By contrast, they are more effective at converting atrial fibrillation to NSR.
Which conditions are MOST closely associated with the following abnormality? (Select 2.) Parasympathetic stimulation Hypokalemia Digitalis toxicity Hypermagnesemia
Hypokalemia
Digitalis toxicity
Premature ventricular contractions originate from foci below the AV node. As such, the QRS complex is wide.
PVCs that arise from a single location are unifocal (the morphology is the same on the EKG).
PVCs that arise from multiple locations are multifocal (there are different QRS morphologies on the EKG).
There are many conditions that are associated with the development of PVCs. Examples include:
SNS stimulation (hypoxia, hypercarbia, acidosis, light anesthesia) Myocardial ischemia and/or infarction Valvular heart disease Cardiomyopathy Prolonged QT interval Hypokalemia Hypomagnesemia Digitalis toxicity Caffeine Cocaine Alcohol Mechanical irritation (central line insertion)
Click on the area where a PVC can cause ventricular tachycardia.
Relative refractory period (last 2/3’s of the T wave)
The T wave represents ventricular repolarization. During repolarization, there is the absolute refractory period and relative refractory period.
Absolute refractory period = a new action potential cannot be generated no matter how large the stimulus. This occurs between the Q wave and the first 1/3 of the T wave.
Relative refractory period = a new action potential can be generated, however a larger stimulus is required. This occurs during the last 2/3’s of the T wave.
If a PVC occurs during the relative refractory period, it is possible that sustained ventricular tachycardia or ventricular fibrillation can result. This is called the “R on T” phenomena. QT prolongation increases the risk of R on T.
As an aside, sync mode during cardioversion prevents shock delivery from occurring during ventricular repolarization.
Select the BEST drug for the treatment of symptomatic premature ventricular contractions.
Adenosine
Amiodarone
Lidocaine
Diltiazem
Lidocaine
Premature ventricular contractions can precipitate the R on T phenomenon. They should be treated when they are:
Frequent (> 6 per min)
In runs of 3 or more
Polymorphic (they arise from multiple foci)
The first step in treatment targets the underlying cause. This includes reversal of hypoxia/hypercarbia, correction of electrolyte imbalances, discontinuation of QT prolonging drugs, and repositioning a central line that’s tickling the atrium.
Symptomatic PVCs are treated with lidocaine 1.0 - 1.5 mg/kg. If PVCs continue, follow with an infusion of 1 - 4 mg/min.
Which of the following drugs is SAFEST to administer to a patient with prolonged QT syndrome?
Procainamide
Quinidine
Amiodarone
Metoprolol
Metoprolol
Beta blockers are shown to reduce the incidence of torsades de pointes.
The other antiarrhythmics mentioned may cause torsades de pointes in patients with a prolonged QT interval.
Which syndromes are MOST likely to cause prolonged QT syndrome? (Select 2.)
Brugada
Timothy
King Denborough
Romano-Ward
Romano-Ward
Timothy
Romano-Ward and Timothy syndrome are associated with a prolonged QT interval.
King Denborough syndrome is a genetic disorder linked to malignant hyperthermia.
Brugada syndrome is characterized by a pseudo right bundle branch block and ST elevation in V1-V3.
Wolff-Parkinson-White syndrome is associated with a: sigma wave. gamma wave. delta wave. beta wave.
Delta wave
In the patient with Wolff-Parkinson-White syndrome, atrial depolarization is conducted to the ventricles via the bundle of Kent. This accessory pathway bypasses the AV node.
Since the ventricles are prematurely excited, there is a short PR interval and an upsloping of the R wave. This is called a delta wave.
Potential causes of a first degree heart block include: (Select 2.) advanced age. sympathetic stimulation. amiodarone. anterior wall myocardial infarction.
Advanced age
Amiodarone
A first degree heart block occurs when there is a conduction delay at the AV node. It is defined as a PR interval > 0.20 seconds.
Each P wave is conducted
There is 1 QRS for every 1 P wave
Causes of first degree heart block include:
Degenerative changes that accompany aging
Posterior wall MI (a branch of the right coronary artery usually supplies the AV node)
Parasympathetic stimulation
Amiodarone
Digoxin
First degree heart block is usually benign and does not require treatment or additional work-up.
Anesthetic considerations include preventing situations that increase vagal tone or slow AV conduction.
Choose the BEST treatments for this patient. (Select 2.) (3HB) Epinephrine Atropine Transcutaneous pacing Isoproterenol
Transcutaneous pacing
Isoproterenol
This EKG is an example of third degree (complete) heart block. No conduction occurs through the AV node. Because of this, the atria and the ventricles depolarize at their own rates - that is to say that the atria and ventricles each have their own pacemaker.
Third degree heart block is an indication for transcutaneous or transvenous pacing. If heart block does not resolve, the patient should receive an implantable pacemaker. Isoproterenol can be used as a “chemical pacemaker” until other forms of pacing are available.
Antidysrhythmic medications should be avoided. They might suppress the rescue ventricular pacemaker that is responsible for maintaining the ventricular rate. A slow rate is better than no rate at all!
Click on the arrow representing the BEST lead for monitoring the P wave.
Lead 2 direction
Become familiar with the hexagonal reference system. This graphic illustrates the electrical axis of each limb lead.
Lead II is a bipolar limb lead that has a negative electrode on the right chest or arm and a positive electrode on the left leg.
Lead II is considered the best lead to monitor dysrhythmias because the P wave is best visualized with this lead.
Which of the following is the reference point for measuring changes in the ST segment? TR segment ST segment PR segment J point
PR segment
The PR segment is an isoelectric line. Because of this, it is used as the reference point for measuring ST elevation and depression.
The J point is where the QRS complex ends and the ST segment begins. By measuring this point relative to the PR segment, we can quantify the amount of ST elevation and depression.
Adenosine is BEST used in the treatment of torsades des pointes. atrial fibrillation. supraventricular tachycardia. ventricular tachycardia.
Supraventricular tachycardia
Adenosine is an endogenous nucleoside that slows conduction through the AV node. By stimulating the cardiac adenosine-1 receptor, adenosine causes potassium to exit the cell. This hyperpolarizes the cell membrane and reduces action potential duration.
It is efficacious for supraventricular tachycardia as well as WPW with a narrow QRS.
It is not efficacious for atrial fibrillation, atrial flutter, torsades des pointes, or ventricular tachycardia.
Match each electrolyte abnormality with EKG change that is MOST likely to occur. Hypercalcemia Hyperkalemia Hypokalemia Hypocalcemia
Hypokalemia + Flat T wave and presence of U wave
Hyperkalemia + Wide QRS and peaked T wave
Hypocalcemia + Prolonged QT interval
Hypercalcemia + Short QT interval
Which methods reduce the risk of inadvertent AICD discharge? (Select 2.)
Place a magnet over the pacer leads.
Keep the electrocautery at least 5 cm away from the pulse generator.
Use a harmonic scalpel instead of a monopolar cautery.
Place the return electrode as far as possible from the pulse generator.
Place the return electrode as far as possible from the pulse generator
Use a harmonic scalpel instead of a monopolar cautery
Before we get to the answer, we first need to clear up a huge source of confusion. Nobody in the OR should be grounded - not even the patient! But what about the grounding pad you say? Read on grasshopper…
When you are at home, all of your electrical devices plugged into the wall are grounded. If you touch a live wire, you’ll complete the circuit and you’ll receive a macroshock. In the OR, isolation transformers are used to isolate the equipment from the ground. This provides a margin of safety.
If there is one fault and you come into contact with it, you’ll become grounded, but since the circuit isn’t complete you won’t get shocked.
If there is a second fault and you come into contact with both faults, then the current will flow from the equipment → first fault → you → back through the second fault to complete the circuit.
The line isolation monitor alarms when it detects the first fault (usually > 2 - 5 mA). If it alarms, unplug the last piece of equipment that was plugged in.
When a monopolar device is used, electricity flows through the tip of the electrocautery, through the patient, and exits the patient’s body through the return electrode. Indeed, that cold sticky pad is a return electrode and NOT a grounding pad. We’re not suggesting that you boast your newfound knowledge to the old school nurses in the OR, but it’s ok to smirk behind your mask when you hear it called something that might actually harm the patient! And now back to the topic…
Here are some ways to reduce the risk of inadvertent AICD discharge:
Deactivate the AICD’s defibrillation function by placing a magnet over the pulse generator. Always consult with the manufacturer before doing this.
Use a harmonic scalpel or bipolar cautery instead of a monopolar cautery.
Keep the electrocautery at least 15 cm away (not 5 cm) from the pulse generator.
Place the return electrode as far from the pulse generator as possible, while making sure the current doesn’t cross the chest.
Which of the following impart the GREATEST risk of electromagnetic interference in the patient with an AICD?
The cut setting on an ultrasonic harmonic scalpel
The cut setting on a monopolar cautery
The coagulation setting on a monopolar cautery
The coagulation setting on a bipolar cautery
The coagulation setting of a monopolar cautery
The coagulation setting of a monopolar cautery causes the greatest risk of electromagnetic interference. This is followed by the cut setting of the monopolar cautery.
The bipolar cautery and Harmonic scalpel create the least amount of EMI.
What is the MAXIMUM flow rate delivered by the oxygen flush valve?
(Enter your answer as L/min)
75 L/min
The oxygen flush valve delivers a flow rate between 35 - 75 L/min. It provides a direct link between the oxygen pipeline (50 psi) and the breathing circuit. The O2 flush valve bypasses the flowmeters and the manifold.
Using the O2 flush valve can create two problems:
1. Because the ventilator spill valve is closed during inspiration, pressing the O2 flush valve during the inspiratory phase exposes the breathing circuit to pipeline pressure. This increases the risk of barotrauma.
2. Adding a large quantity of oxygen to the breathing circuit dilutes anesthetic vapors. This can increase the risk of awareness.
Soda lime that has changed color from purple to white:
is most common at the end of the day.
has regenerated.
indicates the pH has increased.
is normally observed during periods of nonuse.
Is normally observed during periods of nonuse
There are two problems that occur with CO2 absorbents: 1) it exhausts its ability to neutralize CO2 and, 2) it dries out - it becomes desiccated.
Soda lime is a strong base. As CO2 consumes the basic substrate, the pH of the soda lime decreases (it becomes more acidic). As the pH falls below 10.3 an indicator dye (ethylene violet) changes from colorless to purple. This indicates that the soda lime should be changed.
Color reversion means that soda lime that used to be purple has turned back to white. This commonly occurs during periods of nonuse, but it does NOT mean that the soda lime has regenerated. In fact, once it is exposed to CO2, the canister will quickly turn purple. Additionally, the indicator dye does not tell you if the absorbent has become desiccated.
According to OSHA’s recommended standards, what is the MAXIMUM accepted level of exposure to halogenated agents when nitrous oxide is not in use?
(Enter your answer as parts per million)
2 ppm
When halogenated agents are used alone, the maximum acceptable level of exposure is 2 ppm.
When halogenated agents are used in conjunction with nitrous oxide, the maximum acceptable level is 0.5 ppm and 25 ppm respectively.
Identify the final step in the soda lime reaction.
Na2CO3 + Ca(OH)2 —> CaCO3 + 2NaOH
You should be able to write out the soda lime reaction.
CO2 + H2O —> H2CO3
H2CO3 + 2NaOH —> Na2CO3 + 2H2O + energy
Na2CO3 + Ca(OH)2 —> CaCO3 + 2NaOH
What is the water content of soda lime?
15%
Neutralization of CO2 requires an aqueous environment on the surface of the soda lime granule. This is why soda lime is hydrated to 10-20%.
Which of the following components creates the GREATEST resistance to airflow? CO2 absorber 90 degree elbow Endotracheal tube Unidirectional valve
Endotracheal tube
Of the answer choices provided, a properly sized endotracheal tube imposes greater resistance than the anesthesia breathing circuit system. Resistance is any factor within a conduit that restricts flow. And yes, this is but another example of Poiseuille’s law in action. Resistance =
8 x viscosity x length of tube
3.14 x radius^4 x pressure difference
Since diameter is the most important factor in this equation, you should think about the answer choice with the smallest diameter. In this case, it’s the endotracheal tube.
The combination of sevoflurane and Baralyme increases the risk of: hepatotoxicity. compound A production. breathing circuit fire. carbon monoxide production.
Breathing circuit fire
The combination of desiccated Baralyme and sevoflurane has resulted in breathing system fires. Desiccated Baralyme produces flammable by-products such as formaldehyde, methanol, and formic acid. In an oxygen rich environment, the risk of fire is greatly increased. This is why Baralyme is no longer available on the market.
Carbon monoxide production is increased with desiccated soda lime (Des > Iso»_space;> Sevo).
Compound A production in increased with sevoflurane in desiccated soda lime.
All of the following accurately describe the flow tubes on the anesthesia machine EXCEPT:
flow tubes are tapered at the base.
a high fresh gas flow favors turbulent flow.
the density of the gas determines the flow rate.
the annular space is the cross sectional area of the flow tube.
The annular space is the cross sectional area of the flow tube.
The annular space is the area between the indicator float and side wall of the flow tube (not the cross sectional area of the tube). Since the flow tubes are tapered at the base and widen towards the top, the annular space is narrowest at the base and widest at the top. This “variable orifice” architecture provides a constant gas pressure throughout a wide range of flow rates.
A higher fresh gas flow creates a turbulent flow pattern.
The density of a gas determines whether flow is laminar or turbulent at a given flow rate. A gas of higher density will become turbulent at a given flow rate sooner than a gas of lower density. This is why a helium-oxygen mixture is used to promote laminar flow during an asthmatic attack.
What is the MAXIMUM service pressure in an oxygen e-cylinder?
(Enter your answer in psi)
1900, 2000, or 2200
What is the maximum service pressure in an oxygen e-cylinder?
Depending on the text you read, you’ll see 1900, 2000, and 2200 psi. On the NCE, we hope they’d take multiple answers to a question like this.
If you are hard pressed to pick one, then we’d go with 1900. This is the value listed in Nagelhout and Dorsch.
Match each E cylinder to its maximum capacity.
Oxygen - 660 L
Nitrous oxide - 1590 L
Air - 625 L
Each gas is followed by its max capacity (L) and max pressure (psi):
Oxygen: 660 L - 1900 psi
Nitrous oxide: 1590 L - 745 psi
Air: 625 L - 1900 psi
Match each E cylinder with its designated pin position.
Oxygen - 2, 5
Nitrous Oxide - 3, 5
Air - 1, 5
According to the World Health Organization, what color should an oxygen tank be painted? White Gray Black and white Green
White
Yes, you read that correctly. Oxygen tanks are green in the United States, but in many other countries they are white. We’re one of the few countries that still doesn’t use the metric system, so the fact that our E cylinders are different colors shouldn’t come as a surprise.
World Health Organization designed tank colors:
Oxygen is white
Nitrous oxide is blue
Air is black and white
What is the standard mesh size for soda lime?
4 - 8 mesh
The balance of granule surface area and airflow resistance was derived by heuristic methods over many years. A granule size that is too small provides a very high surface area with a high absorptive capacity. The downside to this is that small granules greatly increase airflow resistance as well as the work of breathing.
A granule that is too large has a small surface area and is not an efficient absorber of carbon dioxide. A benefit is that this reduces airflow resistance and the work of breathing.
To best balance these conflicting issues, 4 – 8 mesh granules are used. Said another way, each granule is between 1/8 to 1/4 inch in diameter and will pass through a mesh screens with 4 – 8 holes per square inch. This size provides the best combination of absorptive capacity and airflow resistance.
Which of the following actions reduce compound A production? (Select 2.)
Removal of NaOH
Removal of CaCl2
Addition of KOH
Addition of Ca(OH)2
Removal of NaOH
Addition of Ca(OH)2
Carbon dioxide absorbents contain NaOH and/or KOH. These strong bases function as activators that facilitate the reaction process. When exposed to volatile anesthetics, these compounds can produce carbon monoxide and compound A. Desiccated CO2 absorbent accelerates the production of these compounds.
Calcium hydroxide lime (Amsorb Plus) was formulated to decrease the production of these compounds. This was accomplished by replacing NaOH with Ca(OH)2 (calcium hydroxide).
Which of the following are located in the intermediate pressure system? (Select 2.)
Oxygen flush valve
Flowmeter control valve
Thorpe tube
Cylinder pressure regulator
Flowmeter control valve
Oxygen flush valve
The anesthesia machine can be divided into 3 systems based on the respective pressures in each.
High pressure system - Back up cylinders, cylinder yoke, cylinder gauge, and cylinder regulator
Intermediate pressure system - pipeline inlets, check valves, pressure gauges, ventilator power inlet, oxygen pressure system, flowmeter control valve, oxygen 2nd stage regulator, and oxygen flush valve
Low pressure system - Flowmeter tubes, vaporizers, common gas outlet, and check valves if present
Which of the following components are located in the high pressure system of the anesthesia machine? (Select 2.)
Hanger yoke
Cylinder pressure regulator
Flowmeter control valve
Oxygen flush valve
Hanger yoke
Cylinder pressure regulator
High pressure system - Back up cylinders, cylinder yoke, cylinder gauge and cylinder regulator
Intermediate pressure system - pipeline inlets, check valves, pressure gauges, ventilator power inlet, oxygen pressure system, flowmeter control valve, oxygen 2nd stage regulator, oxygen flush valve
Low pressure system - Flowmeter tubes, vaporizers, common gas outlet, check valves if present
The DISS system is used to:
diagram the pathway of gas through the anesthesia machine.
prevent misconnections of gas cylinders.
filter and exchange air in the operating room.
prevent misconnections of gas hoses.
Prevent misconnections of gas hoses
The DISS (diameter index safety system) system is used to decrease inadvertent misconnections of gas piping. Each gas pipe and connector are sized and threaded differently on the back of the anesthesia machine to avoid catastrophic mistakes. The PISS (pin index safety system) is used to decrease inadvertent misconnections of gas cylinders.
The SPDD model is used to understand the pathway of gas through the anesthesia machine.
When replacing an oxygen tank on the anesthesia machine, using more than one washer between the cylinder and the yoke can lead to a/an:
cylinder leak.
hypoxic mixture.
explosion.
inadvertent attachment of a nitrous oxide cylinder.
Inadvertent attachment of a nitrous oxide cylinder
The PISS (pin index safety system) is used to prevent the wrong cylinder from being attached to the wrong yoke. Since each pin configuration is specific to a specific gas, it is unlikely (although not impossible) that the wrong tank will be outfitted to the anesthesia machine.
Using more than one washer or using a cylinder with missing pins can defeat this safety mechanism.
A cylinder leak may have looked like an attractive option, however we can tell you from personal experience that using more than one washer won’t create a leak.
Which vaporizers are approved for the use of desflurane? (Select 2.)
Drager Vapor 2000
Drager D Vapor
GE-Datex-Ohmeda Tec 6
GE-Datex-Ohmeda Tec 4
GE-Datex-Ohmeda Tec 6
Drager D Vapor
The GE-Datex-Ohmeda Tec 6 and a newer version from Drager, the D Vapor, are the only vaporizers approved for the use of desflurane
The low pressure circuit leak test checks the integrity of the machine from the:
pipeline supply to the flowmeters.
flow control valves to the common gas outlet.
vaporizers to the oxygen analyzer.
pipeline supply to the common gas outlet.
Flow control valves to the common gas outlet
The low pressure circuit test is conducted by attaching a bulb to the common gas outlet and creating a negative pressure in the low pressure system. Specifically it tests for a leak between the flow control valves to the common gas outlet. The low pressure circuit leak test does not include the anesthesia circuit, which is beyond the common gas outlet.
The low pressure circuit leak test is the best method to detect a vaporizer leak.
The pipeline is part of the intermediate pressure system.
When the ambient temperature is increased, the bi-metallic strip in a variable bypass vaporizer directs: (Select 2.)
More fresh gas to the vaporizing chamber.
Less fresh gas to the vaporizing chamber.
Less fresh gas to the bypass chamber.
More fresh gas to the bypass chamber.
Less fresh gas to the vaporizing chamber
More fresh gas to the bypass chamber
Anesthetic vapor pressure is dependent on ambient temperature; the higher the temperature the higher the vapor pressure.
Since we need vaporizer output to be consistent over a wide range of ambient temperatures, a temperature compensating bi-metallic strip directs a fraction of the fresh gas to the vaporizing chamber and the remainder of the fresh gas to the bypass chamber. These two fractions combine as fresh gas exits the vaporizing outlet.
Since a higher temperature is associated with a higher vapor pressure, it should make sense that we want less fresh gas to enter the vaporizing chamber and more fresh gas to enter the bypass chamber. In this circumstance, the temperature compensating strip expands to accomplish this goal.
What changes would you expect if you move the non-invasive blood pressure cuff from the upper arm to the calf? (Select 3.) Systolic BP increases Systolic BP decreases Diastolic BP increases Diastolic BP decreases Pulse pressure increases Pulse pressure decreases
Systolic BP increases
Diastolic BP decreases
Pulse pressure increase
As the pulse moves from the aortic root towards the periphery, the SBP increases, DBP decreases, and the pulse pressure widens. MAP remains constant.
At the aortic root: SBP is lowest, DBP is highest, and PP is narrowest
At the dorsalis pedis: SBP is highest, DBP is lowest, and PP is widest
Be sure to understand how moving the cuff to a different location affects your measurement.
The automated noninvasive blood pressure cuff works equally well when used to measure blood pressure in the upper arm, forearm, wrist, or ankle. The exception here is its unreliability when placed on the calf for patients undergoing c-section.
Match each component of the EKG to the corresponding event on the CVP waveform.
P wave + a wave
QRS complex + c wave
ST segment + x descent
T wave + v wave
Central venous pressure is MOST accurately measured at the: beginning of inspiration. beginning of expiration. end of inspiration. end of expiration.
End of expiration
CVP is measured relative to atmospheric pressure. For example, a CVP reading of 7 mmHg means that it is 7 mmHg above ambient pressure. This also explains why CVP can never truly be negative; a CVP of -1 is 1 mmHg below ambient pressure and NOT a negative pressure.
Since we measure CVP relative to atmospheric pressure, we don’t want changes in intrathoracic pressure to impact the accuracy of our measurement.
During spontaneous breathing, inhalation creates negative pressure in the thorax and reduces intrathoracic pressure.
During positive pressure ventilation, inhalation increases intrathoracic pressure.
For both spontaneous and positive pressure ventilation, intrathoracic pressure is zero at end expiration. Therefore, CVP should be measured at end expiration during spontaneous or positive pressure breathing.
Match each component of the CVP waveform to its corresponding mechanical event.
a wave + Right atrial contraction
c wave + Right ventricular contraction
x descent + Right atrial relaxation
v wave + Passive filling of right atrium
On the CVP waveform, there are three positive deflections (a, c, v) and 2 negative deflections (x, y).
Here are the mechanical events of the right heart as they correspond to the CVP waveform.
a wave - Right atrial contraction c wave - Right ventricular contraction x descent - Right atrial relaxation v wave - Passive filling of right atrium y descent - Right atrium empties through open tricuspid valve
Which conditions increase the amplitude of the v wave on the CVP waveform? (Select 2.) Tricuspid regurgitation Complete heart block Papillary muscle ischemia Right ventricular hypertrophy
Tricuspid regurgitation
Papillary muscle ischemia
The CVP waveform is a measure of the right atrial pressure. It has three peaks (a, c, v) and two troughs (x, y). You should understand how pathology influences the CVP waveform.
Large v wave (enhanced RA filling):
During tricuspid regurgitation, a portion of the RV volume flows retrograde across the incompetent tricuspid valve. Papillary muscle ischemia can cause tricuspid regurgitation. On the CVP waveform, there will be a large v wave.
Lost a wave (loss of RA contraction):
Atrial kick is lost during atrial fibrillation. On the CVP waveform, the a wave is lost.
Cannon a wave (increased resistance to atrial ejection):
The a wave correlates with atrial contraction. A canon a wave is present when there is an increased resistance to atrial ejection. Examples include complete heart block, nodal rhythm, tricuspid stenosis, and decreased right ventricular compliance (RVH and RV ischemia).
When inserting a central line into the left internal jugular vein, how far should the catheter be advanced to achieve correct placement? 10 cm 15 cm 20 cm 25 cm
20 cm
The tip of the catheter should reside at the junction of the vena cava and right atrium. It should not rest inside the right atrium, as this can induce dysrhythmias or perforate the myocardium.
Here are the distances that you should know (access site to junction of vena cava and RA):
Left or right subclavian: 10 cm Right internal jugular: 15 cm Left internal jugular: 20 cm Femoral: 40 cm Right median basilic: 40 cm Left median basilic: 50 cm
What is the distance from the junction of the vena cava and the right atrium to the tip of this PA catheter? 10 cm 20 cm 40 cm 60 cm
20 cm (It’s usually 15-30 cm, but 20 cm was the only answer choice in this range)
We made this question easier than we could have, but in case you’re not so lucky on the NCE, here’s a simple way to calculate the distance from any insertion site to the tip of the PA catheter anywhere in the heart.
To do this, you’ll need to know two pieces of information: the distance from the insertion site to the junction of the VC and then the distance from the junction of the VC and RA to the tip of the catheter. Then add these numbers together.
Distance from the insertion site to the junction of the VC and RA:Left or right subclavian: 10 cm Right internal jugular: 15 cm Left internal jugular: 20 cm Femoral: 40 cm Right median basilic: 40 cm Left medial basilic: 50 cm Distance from the junction of the VC and RA to the tip of the catheter:
Right atrium: 0-10 cm
Right ventricle: 10-15 cm
Pulmonary artery: 15-30 cm
PAOP position: 25-35 cm
Which of the following is observed as the tip of the pulmonary artery catheter enters this cardiac chamber? (Select 2.) The diastolic pressure increases. The pulse pressure increases. There is a dicrotic notch. The systolic pressure increases.
The systolic pressure increases
The pulse pressure increases
The PA catheter has advanced from the right atrium into the right ventricle. Here, the systolic pressure increases, and this increases the pulse pressure.
As you advance the PA catheter further, it will transverse the pulmonic valve and enter the pulmonary artery. You’ll know you’ve arrived when you notice a dicrotic notch and a rise in diastolic pressure.
When reviewing questions, don’t just learn the question and move on. Quiz yourself about other key ideas related to the topic being addressed. For example, here you might want to consider intracardiac distances, the pressures in each chamber, or complications of PA catheter placement.
All of the following are complications of pulmonary artery catheter placement EXCEPT: left bundle branch block. air embolism. pneumothorax. neuropathy.
Left bundle branch block
The PA catheter does not increase the risk of a left BBB, but it does increase the risk of creating a right BBB. If you place a PA catheter in a patient with a pre-existing left BBB, there is a risk of inducing a right BBB thereby creating complete heart block.
Complications of PA catheter can be grouped according to when they occur during placement:
Obtaining venous access: arterial puncture, air embolism, neuropathy, and pneumothorax.
Floating the PA catheter: Right BBB, complete heart block (if pre-existing left BBB), PA rupture, and dysrhythmias such as PVCs, VT, and VF.
Catheter residence: bacterial colonization, sepsis, thrombus formation, thrombophlebitis, pulmonary infarction, and myocardial or valvular injury.
Factors that decrease mixed venous oxygen saturation include: (Select 2.) seizure. left-to-right shunt cyanide toxicity. fever.
Fever
Seizure
SvO2 is reduced by anything that increases oxygen consumption or decreases oxygen delivery.
Increased VO2: Fever Stress Seizures Shivering Thyrotoxicosis Pain Decreased DO2:
Hemorrhage Anemia Low CO Hypoxia SvO2 is increased by cyanide toxicity, sepsis, increased cardiac output, a wedged PA catheter, hypothermia, and a left-to-right shunt.
Cerebral oximetry: monitors global cerebral oxygenation. measures venous oxygen saturation in cerebral blood. is an invasive monitoring technique requires pulsatile flow.
Measures venous oxygen saturation in cerebral blood
Cerebral oximetry is a noninvasive technique that utilizes near infrared spectroscopy (NIRS) to measure regional (not global) cerebral oxygenation.
It is based on the principle that ↓ cerebral oxygen delivery → ↑ cerebral oxygen extraction → ↓ venous hemoglobin saturation.
Because it measures venous oxygen saturation, it does not require pulsatile flow.
A > 25 percent change from baseline suggests a reduction in cerebral oxygenation.
During anesthetic maintenance, the appearance of delta waves should raise suspicion of: impending patient movement. cerebral ischemia. seizure activity. awareness
Cerebral ischemia
EEG provides a sensitive measure of brain tissue at risk of infarction.
The brain requires an adequate perfusion pressure to provide a steady supply of oxygen and glucose.
In the absence of these substrates, the brain is unable maintain its electrical function.
The development of new delta waves during anesthetic maintenance may signify that brain is at risk for ischemia.
The following circumstances mimic cerebral ischemia: deep anesthesia, hypothermia, and hypocarbia.
When using the bispectral index monitor, what is the recommended range for anesthetic maintenance? 20 - 40 20 - 60 40 - 60 40 - 80
40 - 60
The bispectral index monitor (BIS) uses a computer algorithm to translate raw EEG data into a number between 0 – 100. This algorithm is proprietary, so it only applies to the BIS.
It’s recommended that the depth of anesthesia is titrated to 40 - 60 during maintenance.
0 = Absence of cerebral activity (isoelectric)
20 = Burst suppression
40 = Deep hypnotic state
60 = Upper limit of low probability of explicit recall
80 = Moderate sedation
100 = Fully awake
When using the patient safety index monitor, what is the recommended range for anesthetic maintenance? 15 - 45 25 - 50 35 - 60 45 - 75
25 - 50
Like the BIS, the patient safety index monitor (PSA) uses a computer algorithm to translate raw EEG data into a number between 0 – 100. It uses a different proprietary algorithm, so the interpretation o the reading is also different.
It is recommended that the depth of anesthesia is titrated to 25 - 50 during maintenance.
Match each electrical variable with its corresponding hemodynamic variable.
Current
Impedance
Voltage
Voltage + Blood pressure
Current + Cardiac output
Impedance + Systemic vascular resistance
Ohm’s law can be applied to electricity as well as hemodynamics.
Applied to electricity: Voltage = Current x Impedance
Applied to hemodynamics: BP = CO x SVR
What is the minimum macroshock current required to produce ventricular fibrillation?
(Enter your answer in mA)
100 mA
Macroshock is the amount of current that is applied to the external surface of the body. The impedance of the skin offers a high resistance, so it takes a larger current to induce ventricular fibrillation.
1 mA = Threshold for touch perception of shock
5 mA = Max current for harmless shock
10 - 20 mA = “Let go” current occurs before sustained contraction
50 mA = Loss of consciousness
100 mA = Ventricular fibrillation
What is the minimum microshock current required to produce ventricular fibrillation? 1 µA 10 µA 100 µA 1000 µA
100 µA
Microshock is the amount of current that is applied directly to the myocardium. The high resistance of the skin is bypassed, so it take a significantly smaller amount of current to induce ventricular fibrillation (ex: pacing wires or central line).
10 µA = Max allowable current leak in the OR
100 µA = Ventricular fibrillation
Notice that it’s 100 for both macro- and microshock. Only the units are different.
In the operating room: (Select 2.) power is grounded. power is not grounded. equipment is grounded. equipment is not grounded.
Power is not grounded
Equipment is grounded
The electrical systems in the OR are designed to reduce the risk of electric shock. For an electric shock to occur, there must be two faults in the system:
After the first fault, the system becomes grounded. There is no completed circuit and there is no shock.
After the second fault, the circuit is complete and electric shock occurs.
When you’re at home, an electric shock can occur with the first fault.
The line isolation monitor: prevents microshock. prevents macroshock. grounds the operating room. alarms when the operating room is grounded.
Alarms when the operating room is grounded
The line isolation monitor assesses the integrity of the ungrounded power system in the OR. It tells you when the OR becomes grounded and how much current could potentially flow through you or a patient if a second fault occurs.
The primary purpose of the LIM is to alert the OR staff of the first fault (this means the OR has become grounded).
The LIM does NOT (by itself) protect you or the patient from macro- or microshock.
If the alarm sounds, the last piece of equipment that was plugged in should be unplugged.
The LIM will alarm when 2 - 5 mA of leak current is detected.
All electrical devices leak a small amount of current. If the sum of all the currents exceeds 2 - 5 mA, the alarm will sound, however there is no risk of electric shock in this situation and no corrective action is required.
When using a bipolar electrocautery unit, the electricity exits the patient's body through the: forceps. grounding pad. floor. return pad.
Forceps
The surgical electrocautery device delivers a high frequency current (500,000 - 1 million Hz) that is used to cut, coagulate, dissect, or destroy tissue.
When using a monopolar device, electricity travels from the probe, through the patient, and then exits via the return pad to complete the circuit. It’s not a grounding pad! Remember, patients and OR staff aren’t grounded.
When using a bipolar device, the electricity travels from the active electrode, through the local tissue, and then exits the patient through the return electrode. Because the electricity leaves from and returns to the handheld component of the device, there is no need for a return pad.
