Apex unit 6 Flashcards

Question

The normal QT interval is: 0. 10 seconds. 0. 25 seconds. 0. 40 seconds. 0. 55 seconds.

Answer 1

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.

Answer 2

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

Answer 3

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.

Answer 4

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.

Answer 5

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.

Answer 6

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.

Answer 7

-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).

Answer 8

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.

Answer 9

VT SVT ST AFlutter

Answer 10

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.

Answer 11

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) ```

Answer 12

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.

Answer 13

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.

Answer 14

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.

Answer 15

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.

Answer 16

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.

Answer 17

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.

Answer 18

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!

Answer 19

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.

Answer 20

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.

Answer 21

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.

Answer 22

Hypokalemia + Flat T wave and presence of U wave Hyperkalemia + Wide QRS and peaked T wave Hypocalcemia + Prolonged QT interval Hypercalcemia + Short QT interval

Answer 23

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.

Answer 24

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.

Answer 25

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.

Answer 26

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.

Answer 27

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.

Answer 28

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

Answer 29

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%.

Answer 30

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.

Answer 31

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 >>> Sevo). Compound A production in increased with sevoflurane in desiccated soda lime.

Answer 32

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.

Answer 33

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.

Answer 34

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

Answer 35

Oxygen - 2, 5 Nitrous Oxide - 3, 5 Air - 1, 5

Answer 36

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

Answer 37

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.

Answer 38

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).

Answer 39

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

Answer 40

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

Answer 41

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.

Answer 42

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.

Answer 43

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

Answer 44

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.

Answer 45

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.

Answer 46

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.

Answer 47

P wave + a wave QRS complex + c wave ST segment + x descent T wave + v wave

Answer 48

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.

Answer 49

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 ```

Answer 50

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).

Answer 51

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 ```

Answer 52

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

Answer 53

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.

Answer 54

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.

Answer 55

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. ```

Answer 56

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.

Answer 57

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.

Answer 58

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

Answer 59

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.

Answer 60

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

Answer 61

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

Answer 62

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.

Answer 63

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.

Answer 64

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.

Answer 65

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.