Week 12 Handout Arterial Line

Question 1

What is arterial line monitoring indicated for?

Answer 1

Hemodynamic instability, severe comorbidities, respiratory compromise, neuro patients, and fluid shifts/metabolic derangements.

Question 2

What are some conditions that indicate arterial line monitoring due to hemodynamic instability?

Answer 2

Cardiac surgeries, aortic aneurysm repairs, trauma surgeries, craniotomies, and carotid endarterectomy.

Question 3

What severe comorbidities indicate the need for arterial line monitoring?

Answer 3

Coronary artery disease (CAD), valvular disease, heart failure, and history of cerebrovascular accident (CVA).

Question 4

What respiratory conditions indicate arterial line monitoring?

Answer 4

Acute respiratory distress syndrome (ARDS), pulmonary embolism (PE), pulmonary hypertension, and single-lung ventilation cases.

Question 5

What neuro conditions indicate arterial line monitoring?

Answer 5

Increased intracranial pressure (ICP) due to traumatic brain injury (TBI), subarachnoid hemorrhage (SAH), and thrombectomy.

Question 6

What are the pros and cons of using the radial artery for insertion?

Answer 6

Pros: Most common, easy access, collateral flow (Allen’s test). Cons: Risk if ulnar circulation is inadequate.

Question 7

What are the pros and cons of using the ulnar artery for insertion?

Answer 7

Pros: Alternative if radial unavailable. Cons: Deeper, more tortuous course.

Question 8

What are the pros and cons of using the brachial artery for insertion?

Answer 8

Pros: Accurate waveform (close to aorta). Cons: No collateral flow; kinks easily near elbow.

Question 9

What are the pros and cons of using the femoral artery for insertion?

Answer 9

Pros: Good in low-flow states; large vessel. Cons: Higher infection and pseudoaneurysm risk.

Question 10

What are the pros and cons of using the axillary artery for insertion?

Answer 10

Pros: Useful for burn patients. Cons: Near brachial plexus, risk of nerve injury.

Question 11

What are the pros and cons of using the dorsalis pedis artery for insertion?

Answer 11

Pros: Alternative if upper extremities unavailable. Cons: Most distorted waveform; higher SBP estimates.

Question 12

What is Allen’s test used for?

Answer 12

Confirms ulnar artery patency prior to radial cannulation.

Question 13

What are the steps of Allen’s test?

Answer 13

Compress both ulnar and radial arteries while patient tightens fist, release pressure on ulnar artery, confirm collateral flow by flushing of the thumb within 5 seconds.

Question 14

What are the limitations of Allen’s test?

Answer 14

Unreliable; consider using Doppler or pulse oximetry for more reliability.

Question 15

What are the steps for radial artery insertion?

Answer 15

1. Supinate & extend wrist. 2. Palpate or use ultrasound. 3. Sterile prep with chlorhexidine & local lidocaine. 4. Insert catheter at 45°, drop to 30° on flashback. 5. Advance catheter 2cm, secure, and apply sterile dressing.

Question 16

What is the purpose of zeroing the transducer?

Answer 16

To ensure the transducing system is zeroed to atmospheric pressure.

Question 17

Where should the transducer be zeroed?

Answer 17

At the phlebostatic axis (4th ICS, midaxillary line) or at the Circle of Willis for neurosurgery seated patients.

Question 18

What does the upstroke of the arterial waveform indicate?

Answer 18

Cardiac contractility after QRS during systole.

Question 19

What does the downstroke of the arterial waveform indicate?

Answer 19

Systemic vascular resistance (SVR) during diastole.

Question 20

What is the dicrotic notch in an arterial waveform?

Answer 20

It represents aortic valve closure after the T wave.

Question 21

What are the characteristics of an under-dampened waveform?

Answer 21

SBP overestimated, DBP underestimated, MAP accurate; > 2–3 oscillations after square-wave test.

Question 22

What are the characteristics of an over-dampened waveform?

Answer 22

SBP underestimated, DBP overestimated, MAP accurate; blunted waveform, decreased notch/loss of dicrotic notch.

Question 23

What is the square-wave test used for?

Answer 23

To determine the natural damping characteristics of the transducing system.

Question 24

What is pulse pressure variation (PPV)?

Answer 24

It occurs with patients on positive-pressure ventilation, indicating fluid responsiveness.

Question 25

What are the conditions for accurate pulse pressure variation measurement?

Answer 25

Intubated, no spontaneous breaths, normal sinus rhythm, closed chest, normal compliance.

Question 26

What are the contraindications for arterial line placement?

Answer 26

No absolute contraindications; however, precautions include inadequate collateral flow, coagulopathy, severe PAD, Raynaud’s/Buerger’s.

Question 27

What are some complications of arterial line placement?

Answer 27

Infection, thrombosis, embolus, skin necrosis, nerve injury, pseudoaneurysm, intra-arterial drug administration.

Question 28

Where should the arterial line transducer be zeroed to ensure accurate blood pressure readings? A. Umbilicus B. Phlebostatic axis (4th intercostal space, mid anteroposterior chest) C. At the level of the extremity the catheter was inserted D. Below the height of the patient bed

Answer 28

Answer: B Rationale: Arterial line transducers must be zeroed to atmospheric pressure before using them to measure blood pressure. For the majority of patients, except those in seated position (some neurosurgery cases), the transducer should be placed at the phlebostatic axis, which is the 4th intercostal space, midaxillary line, mid anteroposterior chest) when zeroing. This is the level of the right atrium, and allows for the most accurate blood pressure readings, so the anesthetist can accurately administer medications (Barash et al., 20

Question 29

Which of the following patients would most likely require continuous invasive blood pressure monitoring intraoperatively? A. 25-year-old female undergoing ACL repair B. 30-year-old male, ASA class I, undergoing laparoscopic cholecystectomy C. 73-year-old male requiring aortic dissection repair D. 40-year-old female undergoing cataract surgery

Answer 29

Answer: C Rationale: Continuous, invasive blood pressure monitoring is indicated in situations where there is current or anticipated hypotension, or where there may be wide deviations in blood pressure during the case (Butterworth et al., 2022). Aortic dissection repairs are critical surgeries, where large volumes of blood loss are possible, and there is significant risk for end-organ disease related to poor perfusion. Because of these factors, a patient requiring an aortic dissection repair would best be managed using arterial line blood pressure monitoring (Barash et al., 201

Question 30

Which of the following is the most common artery used for arterial line placement? A. Radial B. Brachial C. Dorsalis pedis D. Axillary

Answer 30

Answer: A Rationale: While there are multiple different locations available for the anesthetist to use for arterial line placement, the radial artery is the most common. This is due to its superficial location, and large amount of collateral flow to the region. Many patients have larger ulnar arteries than they do radial, allowing for optimal blood flow to the hand and digits when the radial artery is cannulated

Question 31

Which of the following is a common cause of an under-dampened arterial waveform? A. Air bubbles in the pressure tubing B. Low pressure in the flush bag C. Loose connections in the pressure tubing system D. Catheter whip

Answer 31

Answer: D Rationale: Air bubbles in the pressure tubing, low pressure in the flush bag, and loose connections in the pressure tubing system are all complications leading to over-dampened arterial waveforms (Butterworth et al., 2022). However, catheter whip, which is the exaggerated oscillation of arterial line tracing due to exaggerated and excessive catheter movement inside the artery.

Question 32

An anesthetist observes a patient’s arterial waveform tracing and notices a significant variation in pulse pressure. After doing some calculations, they determine that the patient’s PPV is 20%. Which of the following factors would make this number inaccurate? [Select 3] A. Normal sinus rhythm B. Supraventricular tachycardia C. Pressure support ventilation D. Low tidal volumes (4 mL/kg) E. Controlled mechanical ventilation

Answer 32

Answer: B, C, D Rationale: Variation in pulse pressure greater than 12-13% indicates the patient might respond positively to fluid administration (Butterworth et al., 2022). However, there are some factors that the patient must satisfy in order to trust the pulse pressure variation numbers, thereby using them to make clinical decisions. In order for the PPV to accurate, the patient must be mechanically ventilated on a controlled setting with no spontaneous effort, they must be in normal sinus rhythm, and there is some evidence to suggest the patient’s tidal volumes should be closer to 8mL/kg (Elisha et al., 2023). Therefore, in this situation, pressure support ventilation, an arrythmia, and small tidal volumes would make the 20% PPV inaccurate

Question 33

A 76-year-old male is undergoing a craniotomy and is placed in a sitting position. The anesthetist places a radial artery line and zeroes the transducer at the phlebostatic axis (level of the right Matthew McCormick atrium). If the MAP is reading 70mmHg, but the neurosurgeon is concerned about cerebral perfusion, what should the anesthetist do? A. Tell the surgeon the perfusion is adequate, and he may proceed B. Move the transducer up to the Circle of Willis and re-zero C. Lower the patient’s head to increase blood flow D. Remove the radial arterial line and place an axillary, as this is closer to the brain

Answer 33

Answer: B Rationale: Arterial blood pressure monitoring systems must be zeroed before use. In the majority of patients, zeroing of the transducer should occur at the level of the right atrium, or the phlebostatic axis. However, in some neurosurgery cases, the patient is placed in a seated, or upright position. In these patients, the transducer should be zeroed at the level of the Circle of Willis, in the brain. This ensures that the arterial pressure tracing adjusts for the height of the fluid column between the brain and the heart, representing arterial pressure at the base of the brain (Barash et al., 2017).