II. EQUIPMENT, INSTRUMENTATION AND TECHNOLOGY

INFUSION DEVICES

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INFUSION DEVICES

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Infusion Devices

Rate of flow

Q = ∆P / R

Q- flow

∆P- change in pressure

R- resistance

The change in pressure depends on:

    • Density
    • Gravity
    • Height difference between the fluid reservoir and the infusion location (AKA head height)

 

  • Resistance to constant laminar flow is determined by Poiseuille’s Law:
    • R = (8nL) / (∏r4)
      • n- liquid viscosity
      • L- tubing length
      • r- radius
        • Radius has the greatest effect on resistance.
        • Doubling the radius decreases the resistance by 16 times.

PUMP TYPE

ADVANTAGES

DISADVANTAGES

REGULATED GRAVITY-INDUCED FLOW

-Detects clotting, infiltrations, and occlusions

-Prevents IVs from “running dry”

-Driving force is low, lower severity of infiltrations

-Low cost

-Requires less clinical supervision than a gravity IV

-No free-flow clamping

-Need to know viscosity

-Chambers have specific sized drips

-Low pressure, slow infusions

-Max infusion rate depends on fluid viscosity, head height, and other factors

ELASTOMERIC RESERVOIR

-Low cost

-Portable and discreet

-Low accuracy

-Flow rate not easily adjustable

SPRING-POWERED PASSIVE

SYRINGE PUMPS

-Low cost

-Can be used with most syringes

-Low accuracy

-Requires special microbore tubing

PERISTALTIC PUMPS

-Similar accuracy to drip counters

-Used in invasive lines

-Infusion rates up to 1200 mL/h

-Fewer programming errors than drip counters

-Pulsatile flow

-Tubing deforms over time, leading to less precise doses

-Requires specific tubing set

-High cost

-Not as accurate for low-flow

CASSETTE (VOLUMETRIC)

-Similar accuracy to drip counters, peristaltic pumps

-Similar function to peristaltic pumps but easier to load

-More difficult to prime

-More expensive sets b/c of cartridge

-Pulsatile flow

-Not as accurate at low-flow

SYRINGE PUMP

-Highest accuracy

-Can use third-party syringes

-Can infuse highly concentrated drugs with accuracy at low-flow rates

-Limited volume (50-60 mL)

-Susceptible to start-up delays

-Takes longer to confirm an occlusion b/c of low-flow rates

GRAVITY-DRIVEN INFUSIONS

  • The height difference between the fluid reservoir and the infusion location is the head height.

 

  • Head height is the primary factor for gravity infusions.
    • The flow is adjusted manually with a roller clamp to increase or decrease resistance.

POSITIVE-PRESSURE PUMPS

  • Elastomeric Reservoir
    • One of the simplest methods
    • A balloon-like reservoir that exerts constant pressure on the medication within the balloon.

 

  • Spring-powered passive
    • Similar to electromechanical pumps but the pressure is applied with a constant-pressure spring.

 

  • Peristaltic Pumps
    • Can be linear or rotary
      • Linear- compresses the fluid-filled tubing sequentially with small fingerlike projections
      • Rotary- uses two or more rotary cams; infrequently used

 

  • Cassette (Volumetric)
    • These systems contain a cassette of a measured chamber volume placed inside a pump.
      • Example- plum pump with plum cassette

 

  • Syringe Pump
    • Motor-driven lead screw or a gear mechanism drives the plunger into the syringe barrel
      • The rate of infusion depends on the speed of the motor and the size of the syringe barrel.
    • Example- Baxter InfusO.R

PATIENT-CONTROLLED ANALGESIA

  • These devices have a medication-demand interface, or button, that the patient can use to self-administer medication and a locking mechanism to securely contain the drug being administered.
  • Positive-pressure electromechanical pump

 

  • 2 modes:
    • Demand only
    • Demand combined with a baseline infusion of medication
      • Safety concern for overdosing
      • Features to program
        • Number of boluses within a certain time frame
        • Minimum time between boluses (lockout)

MODERN INFUSION PUMP FEATURES

  • Smart pumps
    • Software that helps detect and alert potential pump errors.
    • Specific medications are only able to be infused at acceptable rates

 

  • Multitherapy pumps
    • System integrates different functions/modes
      • eg. large volume, microinfusion syringe, PCA, small volume infusion, etc

 

  • Barcode
      • Incorporates the “five rights” of medication safety (right patient; right drug; right dose; right route; and right time) to reduce medication errors
      • The patient’s ID bracelet must be scanned to select the patient and then the medication is scanned.
      • This system often integrates computerized order entry

REFERENCE: Ehrenwerth J, Eisenkraft J, Berry J, eds. Anesthesia Equipment: Principles and Applications. 3rd edition, pages 351-367. Elsevier; 2020.

Rapid Infusers

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