CA-1 Questions JANUARY 22, 2020 

1) Which of the following drugs causes the greatest decrease in amplitude of somatosensory evoked potentials (SSEPs)? A) Etomidate B) Ketamine C) Fentanyl D) Propofol 

 Propofol decreases the amplitude of SSEPs. Propofol increases SSEP latency. The effect is less pronounced than with volatile anesthetics or barbiturates. SSEPs are used to assess the integrity of peripheral nerves, posterior and lateral spinal cord, the thalamus, and the sensory cortex. It is a useful modality during spinal cord, brain surgery, and carotid endarterectomy to monitor for neurologic changes. Changes in amplitude and latency can be due to multiple factors, such as ischemia or traction on the spinal cord. Multiple anesthetic drugs affect SSEPs. Increasing doses of volatile anesthetics depress the amplitude and increase the latency of SSEPs. Nitrous oxide has no effect on latency but does produce a dose-dependent decrease in amplitude. Answer A: Etomidate increases the amplitude of SSEPs. Answer B: Fentanyl can decrease the amplitude of SSEPs but does so to a lesser extent than propofol. Answer C: Ketamine can increase SSEP amplitude in high doses. Bottom Line: Propofol causes a dose-dependent decrease in amplitude of SSEPs. Propofol increases SSEP latency 

 2) Which of the following is TRUE regarding the airway of a full-term infant? A) The epiglottis is flat and broad B) The larynx is located at the C3-4 interspace C) The narrowest point is at the level of the thyroid cartilage D) The vocal cords are perpendicular to the trachea 

 5 features distinguish the pediatric airway from the adult airway 1) Large tongue 2) More cephalad larynx (C3-4 vs C5-6 in adult) 3) Omega or U shaped epiglottis 4) Anterior insertion of vocal cords is caudad to posterior insertion 5) Funnel shaped larynx (narrowest portion of airway is below glottic opening) 

 3) Which of the following is the most difficult predictor of difficult laryngoscopy? A) Neck circumference B) Thyromental distance C) Presence of beard D) Obesity 

 Of the choices given, thyromental distance is the best predictor of difficult laryngoscopy. Other factors include: Oropharyngeal view (mallampati score) Jaw slide grade (upper lip bite test) Small mouth opening 

 4) A 74 year old female with PMHx of Rheumatoid Arthritis (RA) and HTN presents in "PAT" clinic for pre-operative evaluation for hip replacement. She does not take any medications, and prefers to treat her RA and HTN with "natural medications." Neck movement is otherwise normal, but she does report mild "neck pain." BP is 140/86, with otherwise normal vitals. On exam, her hands show joint deformities. She is able to climb a flight of stairs without chest pain or SOB. What is appropriate advice for her? A) NSAIDs for symptomatic relief. B) Request PCP to order C-Spine imaging prior to surgery. C) Request Cardiology clearance with Cardiac Stress Test. D) No further testing / proceed to surgery. 

 B - Imaging should be obtained to rule out Atlanto-Axial (C1-C2) subluxation in patients with RA (may be asymptomatic), as neck movement during intubation can lead to spinal cord injury (quadriplegia) and/or vertebral artery compression. 

5) Pregnant females have the largest increase in their Cardiac Output at which stage? A. End of first trimester B. End of second trimester C. Onset of labor D. Immediately after delivery 

 D - Cardiac output immediately after delivery is increased by as much as 80% above pre-labor values, which presents the highest risk for patients with cardiac disease such as fixed valvular stenosis.  This is due to the contraction of the uterus and the shunting of blood from the gravid uterus back to the systemic circulation. 

 6) What is a correct statement about Cefazolin and Cefotetan? A. Cefazolin has gram positive, gram negative, and anaerobic coverage. B. Cefotetan has gram positive, gram negative, and anaerobic coverage. C. Cefazolin has activity against MRSA. D. Cefotetan has activity against Pseudomonas. 

 B - The primary difference between Cefazolin (1st generation Cephalosporin) and Cefotetan (2nd generation) is that Cefotetan has additional anaerobic coverage (e.g. Bacteroides) making it suitable for intra- abdominal and pelvic surgeries. C and D are untrue. 

 7) Which of the following correctly pairs a chemical property of a local anesthetic molecule with its affected pharmacological property? A) pKa- onset; hydrophobicity- duration; protein binding- potency B) pKa- potency; hydrophobicity- onset; protein binding- duration C) pKa- onset; hydrophobicity- potency; protein binding- duration D) pKa- duration; hydrophobicity- potency; protein binding- onset E) pKa- duration; hydrophobicity- onset; protein binding- potency 

 C - pKa is the primary factor affecting the onset of a local anesthetic. The pKa determines the ratio of the unionized form able to cross the neuronal membrane.  Hydrophobicity or lipid solubility is correlated with potency.  Protein binding serves to retain anesthetic within the nerve and thus is correlated with duration of action. 

 8) Which of the following is the strongest patient specific risk factor for PONV? A) Female gender B) History of PONV/motion sickness C) Non-smoking status D) Age E) Use of volatile anesthetics 

 Answer: A  Female gender is the strongest risk factor for PONV, followed by history of PONV/motion sickness, non-smoking status, and younger age. 

9) Which of the following arterial blood gas results is MOST likely from an otherwise healthy 30 year-old patient with carbon monoxide poisoning? A B C D pH 7.25 7.25 7.25 7.25 pCO2 30 30 30 30 PaO2 60 100 100 60 HCO3- 14 14 14 14 BE -11 -11 -11 -11 Calc SaO2 75% 100% 100% 85% SpO2 75% 100% 85% 100% 

 B  Carbon monoxide binds to hemoglobin with an affinity 200-300 times greater than oxygen which creates carboxyhemoglobin (creating a leftward oxyhemoglobin dissociation curve shift)  PaO2 levels will be unaffected as this represents oxygen dissolved in the blood  Pulse oximetry cannot differentiate carboxyhemoglobin from oxyhemoglobin (so pulse ox will likely be 100%)  SaO2 is a calculated number (not directly measured) and assumes that all hemoglobin is normal hemoglobin  Therefore, this is often abnormally high due to the high affinity of CO for hemoglobin  Co-oximetry is needed (can differentiate oxy and carboxyhemoglobin)  Choice C is what would be expected for methemoglobinemia 

 10) Which of the following is MOST likely found in modern endotracheal tubes? A) Low volume, high pressure cuff B) Silicone construction C) Ultra-thin polyurethane cuff D) Universal 20 mm external diameter ventilating circuit adapter 

 ETT cuffs that are made of polyurethane have been shown to best prevent liquid from leaking around them even at pressures as low as 15 cmH2O.  These cuffs are high-volume / low-pressure  The goal of an endotracheal tube cuff is to  1) have an airtight seal  2) prevent micro-aspiration around the cuff  3) prevent tissue necrosis from pressure exerted on the tissues by the cuff  Generally pressures of less than 25 cm H20 are used to balance these conflicting goals