Marinos- Vascular Access

Question 1

Difference in catheters made from polyurethane vs. silicone

Answer 1

Most of our catheters (PVLs, CVLs, PA catheters) are polyurethane

Silicone- more pliable than poly-urethane => reduced risk of vascular injury => used for longer term vascular access
PICCs made of silicone

Question 2

Law that describes flow through a catheter (rigid tube)

Answer 2

Question 3

Differentiate gauge vs. french

Answer 3

Gauge is arbitrary and just assigned a number inversely related to the diameter

While French (named after the country) x 0.33 = outer diameter (mm)
ex: 7F CVL has a 2.3mm outer diameter

Question 4

Commonly used

(a) French size for central venous catheters
(b) French size for single lumen PICC
(c) Length of PICCs
(d) Size and lumen size of HD catheter

Answer 4

Commonly used

(a) 7F, 13 or 20cm
(b) 5F
(c) PICC: 50 or 70cm long
(d) HD catheters- typically 12F, containing 12 or 16G lumens depending on length, can flow about 20 L/hr of saline

Question 5

Flow rate of different catheter sizes in L/hr of isotonic saline hanging to gravity

(a) 18G standard peripheral IV
(b) 20G standard PIV
(c) 18G port of standard 7 Fr, 20cm long CVL

Answer 5

Catheter flow rates in L/hr

(a) 18G IV standard 30mm (1.2in) length: 6.0L/hr
(b) 20G 30mm length = 3.6 L/hr
(c) 18G through 20cm = 1.5 L/hr

Question 6

PICC

(a) inserted into what vein
(b) advanced to where

Answer 6

PICC line- typically 50-70cm, 16G if single lumen, 18 + 20 if double lumen

(a) Basilic or cephalic vein, just above the antecubital fossa
(b) Advance to SVC

Question 7

Why not place HD lines in subclavian vein?

Answer 7

Propensity for subclavian vein stenosis => arm can’t be used to make AV shunt

Question 8

2 main reasons for limited life expectancy of PVLs

Answer 8

Smaller veins

1. inflammation from mechanical injury and chemical injury from drug infusion
2. thrombosis risk, less laminar flow given smaller radius

Question 9

Major benefits of CVL over PVL

Answer 9

CVLs
-larger diameter => higher flow rate => lower thrombosis rate
-more lumens = more drugs infused per stick = higher efficiency of vascular access
-higher flow rates = reduced damaging effect of infused fluids (ex: vasoconstricting agents)

Question 10

Why does TPN require central access?

Answer 10

Larger lumen = higher flow rates = less local inflammation for caustic infusions such as vasoconstricting agents and hypertonic solutions (parenteral nutrition)

Question 11

% increase in diameter of the IJ in Trendelenburg position

Answer 11

Optimal body tilt down to 15 degrees increases the diameter of the IJ in a healthy subject by 20-25%
-beyond 15 degrees little or no increase in diameter

Question 12

When to avoid Trendelenberg for CVL placement

Answer 12

-increased ICP
-aspiration risk
-pulmonary edema

Question 13

Anatomy of neck veins for CVL insertion –> SVC

Answer 13

At the thoracic inlet, IJ joints subclavian to form brachiocephalic (innominate), then R and L brachiocephalic (innominate) veins join to form SVC

Subclavian is a continuation of the axillary vein as it passes under the first rib

Question 14

Describe IJ CVL placement by landmarks

Answer 14

Anterior approach- locate carotid pulse in the triage created by two heads of the SCM and the clavicle- insert needle (bevel up) at apex of triangle towards ipsilateral nipple

Question 15

Mechanism of air embolism

Answer 15

Negative intrathoracic pressure during spontaneous breathing draws in air

Air obstructs RV outflow => acute RV failure => obstructive shock and circulatory collapse

Question 16

Air embolism

(a) tips for prevention
(b) tips for mgmt if you suspect one

Answer 16

Air embolism

(a) Trendelenberg, exhalation, easier on positive pressure ventilation (less negative intrathoracic pressure)
(b) Aspirate blood back from line, L lateral decubitus to try to relieve RV outflow obstruction (but not clear how well that works)

Question 17

Why a lot of post-line PTX are missed on ICU patients

Answer 17

Supine position air accumulates anteriorly (not apically)- easy to miss on CXR => use ultrasound!

Question 18

Ideal location for CVL tip of catheter

(a) Helpful landmark on CXR
(b) Why do you not want catheter tip in the RA?

Answer 18

CVL tip ideally in distal third of SVC just above SVC/RA junction

(a) Carina is typically at the level of the SVC/RA junction, so look for catheter tip just above the level of the carina
(b) Rare but possible risk of RA perforation => hemotamponade

Question 19

What type of line is most likely to cause SVC perforation

Answer 19

L IJ or subclavian- abut the wall of the SVC if they dont make the acute turn downward into the RA

Question 20

Buzzword Mill-wheel murmur

Answer 20

‘Splashing’ sound of gas in the cardiac chamber due to air embolism

Question 21

Pathogenesis of CLABSI (where does the bacteria come from?)

Answer 21

Most commonly microbes on the skin migrate along the subcutaneous tract of the indwelling catheter, then colonize the intravascular portion of the catheter

-less commonly through contaminated infusates, contaminated internal catheter lumen, seeding from elsewhere to catheter