1 Anesthesiology Continuing Education (ACE)Joel O. Johnson, MD, PhD Co-editor in Chief

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3 Disclosure Co-editor in Chief for Anesthesiology Continuing Education

4 Objectives Understand the goals of the ACE product in furthering education Appreciate the types of questions included in ACE Gauge the benefit that the ACE product will have on your individual learning goals

5 Question writing Each item is researched and written by an expert anesthesiologist The item is reviewed and edited by the co-editors-in-chief Each question and it’s content is discussed by the ACE Editorial Board at quarterly meetings 100 questions are chosen for publication semi-annually, after a final review for content and educational value

6 Content “Walking Around Knowledge” Concise explanationsIllustrations, Figures and Tables References including one textbook and at least one published paper

7 Publication Electronic, web-based Booklet

8 Audience Response and ParticipationPlease take out your mobile device/laptop. Go to The polling questions will appear in your browser.

9 Cardiac A patient scheduled for surgery has a preoperative electrocardiogram (ECG) 

10 Second-degree atrioventricular block Supraventricular tachycardia Which of the following rhythms is MOST likely to develop in this patient? Second-degree atrioventricular block Supraventricular tachycardia Pulseless electrical activity Ventricular fibrillation Delta waves in an ECG are associated with the presence of a myocardial accessory conducting pathway. Wolff–Parkinson–White (WPW) pattern on an ECG consists of a delta wave and a short P-R interval due to an accessory pathway in the conducting system of the heart. Some patients with a WPW pattern on ECG may develop WPW syndrome, which includes the presence of dysrhythmias, most commonly tachydysrhythmias such as supraventricular tachycardia (SVT). Neither second-degree atrioventricular block nor pulseless electrical activity is commonly associated with WPW syndrome. Although ventricular fibrillation has been reported in patients with WPW syndrome, it is not the most common dysrhythmia in this patient population.

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12 Delta waves in an ECG are associated with the presence of a myocardial accessory conducting pathway. Wolff–Parkinson–White (WPW) pattern on an ECG consists of a delta wave and a short P-R interval due to an accessory pathway in the conducting system of the heart. Some patients with a WPW pattern on ECG may develop WPW syndrome, which includes the presence of dysrhythmias, most commonly tachydysrhythmias such as supraventricular tachycardia (SVT). Neither second-degree atrioventricular block nor pulseless electrical activity is commonly associated with WPW syndrome. Although ventricular fibrillation has been reported in patients with WPW syndrome, it is not the most common dysrhythmia in this patient population.

13 Anesthesia Machine Which of the following properties of desflurane MOST likely necessitates the unique construction of the agent-specific desflurane vaporizer? Low blood–gas solubility High boiling point Low molecular weight High vapor pressure. The unique physicochemical properties of desflurane require a specially designed vaporizer for delivery of the agent to the patient. Compared with other volatile anesthetic agents, desflurane has a high vapor pressure, low boiling point, a high minimum alveolar concentration (MAC), and low blood:gas partition coefficient (Table 1). Among these, high vapor pressure and low boiling point preclude the use of a conventional vaporizer for the delivery of desflurane.

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15 Blood:Gas Partition CoefficientAgent Vapor Pressure (°C) Boiling Point (°C) MAC Blood:Gas Partition Coefficient Desflurane 664 22.8 6.0 0.43 Isoflurane 238 48.5 1.28 1.4 Halothane 243 50.2 0.75 2.3 Enflurane 175 56.5 1.58 1.9 Sevoflurane 157 58.5 2.05 0.68 The unique physicochemical properties of desflurane require a specially designed vaporizer for delivery of the agent to the patient. Compared with other volatile anesthetic agents, desflurane has a high vapor pressure, low boiling point, a high minimum alveolar concentration (MAC), and low blood:gas partition coefficient (Table 1). Among these, high vapor pressure and low boiling point preclude the use of a conventional vaporizer for the delivery of desflurane.

16 Variable Bypass vaporizerThe vapor pressure of a gas is directly proportional to temperature; an increase in temperature increases vapor pressure. The boiling point of desflurane, the temperature at which the vapor pressure exceeds atmospheric pressure, is 22.8°C, meaning it boils at room temperature. This phenomenon makes it difficult to control vapor output at a constant rate. When compared to other inhalational agents, desflurane is less potent (high MAC); thus, a larger amount of liquid is needed for vaporization. The latent heat of vaporization makes the container cooler, and decreased temperature decreases the vapor pressure. An external heat source is needed to adjust the vapor pressure. The low blood–gas solubility of desflurane, which facilitates rapid induction, does not necessitate special design of the vaporizer. The molecular weight of desflurane (168) is close to other inhalational agents and not a reason for the special vaporizer.

17 Desflurane vaporizer Again, in the figure above30, by contrast to variable-bypass vaporizers, the Tec 6 design specifically for desflurane (Suprane) diverts no fresh gas flow to the vaporizing chamber.  Note the blue dots depicting gas flowing from the machine flowmeters directly to and through a fixed resistor.  This fixed resistor referred to as Rmain above provides a resistance of about 10 cm H2O/L/min. The backpressure set by the fixed resistor in the main flow gas path sensed by the pressure transducer and in combination with control electronics adjusts the variable pressure control valve to equalize pressures.  The point is that the vapor pressure of desflurane (Suprane) is said equal to the main flow pressure and then the actual concentration desflurane (Suprane) is modified at the variable resistor stage

18 Effects of Aging (Geriatrics)Which of the following is MOST likely to be decreased as a consequence of aging? Total lung capacity Residual volume Vital capacity Closing capacity

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20 Aging is associated with a loss of elastic recoil in the lungAging is associated with a loss of elastic recoil in the lung. This leads to a 5% to 10% increase in residual volume each decade. As would be predicted based on the fact that total lung capacity is unchanged and residual volume is increased, vital capacity is decreased with advanced age.

21 Closing capacity increases with ageClosing capacity is the lung volume at which airways begin to close. If closing capacity exceeds functional residual capacity, closure of some lung units occurs during normal tidal breathing (Figure 2). With closure of lung units, blood that perfuses these units constitutes shunt (perfusion in the absence of ventilation), which causes an increase in the alveolar–arterial oxygen partial pressure gradient. The increase in closing capacity with age is one of the primary factors responsible for the decrease in arterial oxygenation with advanced age.

22 Pharmacology Which of the following statements about egg allergies is MOST likely true? Propofol contains the allergen egg white ovalbumin. Parenteral nutrition with fat emulsion containing egg lecithin is contraindicated in egg allergic patients. Egg allergy is more common in the adult population than in the pediatric population. Previous anaphylaxis to eggs is considered a contraindication to propofol. Propofol contains purified egg lecithin, derived from the yolk not the white of the egg. Egg white albumin is a major allergen in eggs. Parenteral nutrition with fat emulsion containing egg phosphatides (including egg lecithin) does not carry a contraindication of egg allergy. Egg allergy is a common food allergy in children, with an estimated prevalence of up to 9%. Egg allergy is less common in the adult population.

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24 Explanation It is likely that rare reports of allergic reactions to propofol are due to interactions with the propofol molecule itself, involving the phenol ring or isopropyl side chains. In particular, prior exposure to cosmetic and dermatological products containing isopropyl side chains may have cross-sensitized the patient, particularly in atopic individuals.

25 Morbid obesity Which of the following drugs is BEST dosed on total body weight in a morbidly obese patient? Succinylcholine Rocuronium Vecuronium Cisatracurium Obese patients have an increased level of plasma pseudocholinesterase as well as an increased volume of extracellular fluid. These are the main factors that affect duration of action of succinylcholine. A dose of 1 mg/kg of actual body weight is required for appropriate intubating conditions (Table 1). Dosing of all nondepolarizing neuromuscular blocking drugs, including rocuronium, vecuronium, and cisatracurium, should be based on lean body weight.

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28 Mask ventilation Which of the following is MOST predictive of difficult mask ventilation? Lack of teeth Body mass index greater than 26 kg/m2 Presence of a beard History of snoring Airway evaluation is among the most important preanesthesia assessments performed by the anesthesiologist. Elements of the patient’s history and physical exam are incorporated to make a judgment regarding the feasibility of mask ventilation, laryngoscopy, and intubation, or placement of a supraglottic airway. Given the obvious importance of mask ventilation in airway management, the clinician must be familiar with risk factors for difficult mask ventilation (Table 1).

29 Table 1. Identification of risk factors for difficult mask ventilation with multivariate analysis (n = 1,502). Used with permission, from Langeron O, Masso E, Huraux C, et al. Prediction of difficult mask ventilation. Anesthesiology. 2000;92(5): Table 1. Identification of risk factors for difficult mask ventilation with multivariate analysis (n = 1,502). Used with permission, from Langeron O, Masso E, Huraux C, et al. Prediction of difficult mask ventilation. Anesthesiology. 2000;92(5):

30 Intubation In the properly executed ramped or head-elevated laryngoscopy position (HELP), which of the following is MOST likely true? The cervical spine is in an extended position with respect to the thoracic spine. The head is in a flexed position with respect to the cervical spine. The external auditory meatus is in the same plane as the sternal notch. The oral axis is perpendicular to the pharyngeal axis.

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32 Sniffing position The sniffing position describes head extension and neck flexion, and improves alignment of the oral, pharyngeal, and laryngeal axes (Figure 1).

33 HELP (head elevated) Laryngoscopy may be facilitated by the addition of reverse-Trendelenburg positioning to the previously described HELP position. Potentially, laryngoscopy is made easier by displacing some of the weight of the patient away from the airway structures (Figure 2).

34 Intraoperative ComplicationsThe reported risk of perioperative venous gas embolism (VGE) is HIGHEST during which of the following procedures? Cesarean delivery Central line placement Stereotactic brain biopsy Laparoscopy

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36 Craniofacial procedures 66%‒83% Sitting craniotomy 10%‒80% Reported Risk Hysteroscopy 85%‒98% Cesarean delivery 30%‒97% Craniofacial procedures 66%‒83% Sitting craniotomy 10%‒80% Uterine myomectomy 40%‒70% Hepatic resection/surgery 44%‒68% Total hip arthroplasty 57% Operative hysteroscopy 10%‒50% Stereotactic brain biopsy 8%‒14% Deep brain stimulator implant 4.5% Laparoscopy <0.6% Central line placement 0.2%‒1% VGE during cesarean delivery has a reported risk as high as 97% (Table 1). Risk factors include exteriorization of the uterus, manual removal of the placenta, placenta previa, severe preeclampsia, placental abruption, and hypovolemia. Because the volume of gas entrained is small, the majority of these patients remain asymptomatic or, at most, experience a cough or a slight difficulty in breathing, which is likely to be overlooked.

37 Rare (case reports) of VGEProcedure Mechanism Intestinal endoscopy Air/CO2 under pressure Vitrectomy Entrainment through the central retinal vein Spine surgery Venous entrainment when the operative site is ≥ 5 cm above the level of the right ventricle Shoulder arthroscopy Entrainment of residual air in saline irrigation bags Infusions Gravity driven or pressurized venous entry of air Transurethral resection of the prostate Contrast injector in imaging studies Intravenous infusion bags Endoscopic retrograde cholangiopancreatography Forced air via the endoscope after a Kasai procedure

38 Risk The HIGHEST risk of seroconversion from a needlestick injury is from a patient infected with which of the following? Rabies Human immunodeficiency virus (HIV) Hepatitis C Hepatitis B

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40 The yearly risk of contaminated percutaneous (including needlestick) injuries is 3.9 per 100 full-time equivalents (FTEs), with a much higher rate of 19.1 per 100 FTEs in anesthesia residents. Seroconversion rates after a contaminated percutaneous exposure are well known for hepatitis B, hepatitis C (the major cause of non-A, non-B hepatitis), and human immunodeficiency virus (HIV)

41 Of note, a recent Cochrane Database report indicated that there is no clear evidence that devices used to prevent needlestick injuries in health care workers actually decrease the incidence of these injuries.

42 Pediatrics Postextubation croup in pediatric patients is MOST likely to be associated with: an audible leak at a peak inspiratory pressure of 20 cm H2O. supine position. patient age of 5 or 6 years. a recent history of croup The smaller diameter of the pediatric airway predisposes it to the adverse effects of swelling due to edema. Edema in an infant’s trachea has a profound effect on the cross-sectional area and resistance to flow (Figure 1). After placement of a tracheal tube, a leak should be audible at a peak inspiratory pressure less than 25 cm H2O. This pressure represents an estimation of capillary pressure of the mucosal tissues; exceeding 25 cm H2O may lead to tissue damage, resultant edema, and postextubation croup.

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45 Summary The benefits associated with the Anesthesiology Continuing Education product are: Refreshes the participants knowledge Introduces new concepts that are built on existing knowledge Provides continuing education that translates into useful clinical information

46 Electrical cardioversion AnticoagulationA 40-year-old patient in the postanesthesia care unit after laparoscopic cholecystectomy develops new-onset atrial fibrillation (AF). Vital signs include a heart rate of 135 beats/min and noninvasive blood pressure of 140/66. The patient is awake and oriented. What is the recommended initial next step? Heart rate control Echocardiogram Electrical cardioversion Anticoagulation heart rate control

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48 History of smoking cigarettes Male sex Longer duration of anesthesiaWhich of the following is MOST likely to be associated with an increased risk of postoperative nausea and vomiting (PONV)? Age greater than 75 years History of smoking cigarettes Male sex Longer duration of anesthesia Longer duration of anesthesia

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52 Exposure to which of the following is MOST likely to deactivate the color indicator in soda lime absorbent? Fluorescent lights Compound A Water Heat Fluorescent lights

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54 Each of the following medications is capable of causing burst suppression on the electroencephalogram (EEG) EXCEPT midazolam. pentobarbital. sevoflurane. sufentanil. sufentanil

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56 If an E-cylinder is providing 4 L/min flow of oxygen and the cylinder pressure gauge reads 600 psig, the cylinder will MOST likely become empty in 90 minutes. 60 minutes. 45 minutes. 15 minutes. 45 minutes

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58 Which of the following estimates of the total blood volume for a 1Which of the following estimates of the total blood volume for a 1.8-kg premature neonate is MOST accurate? 125 mL 150 mL 175 mL 240 mL 175

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60 Questions?