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TOTAL INTRAVENOUSANESTHESIA (TIVA) & PUMPS

Juan E Gonzalez, CRNA, MSClinical Assistant Professor

Florida International University

Anesthesiology Nursing Program

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TIVA

Total Intravenous Anesthesia

General Anesthesia Anesthesia via IV drugs (usually Propofol,

Narcotics, Versed) drips and/or boluses

No Volatile Agents

N2O sometimes used (not really a TIVA!)

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Receptors

Propofol, barbiturates, etomidate, benzos Enhance the inhibitory effects of GABA (gamma-

aminobutyric acid) GABA activation increases Chloride conductance

hyperpolarizes membrane inhibition of synapse

Ketamine

Blocks excitatory effects of glutamic acid Four types of receptors

Ketamine inhibits one of these receptors (N-methyl-D-aspartate) decrease in Sodium flux and decrease inintracellular Calcium levels

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Receptors (Cont)

Opioids: receptor activation of mu, kappa,

delta receptors Decrease excitability by increasing influx of K+1

and decreasing outflow of Na+1 via a G-proteinmechanism linking the receptors to the ionchannels

Muscle Relaxants: act as the n-typeacetylcholine receptors at the NMJ

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Selection of Cases

Any case can be done as TIVA (preference

vs. cost) Malignant Hyperthermia (triggered by VAA, Sux)

Spine surgery. If monitoring of:Somatosensory Evoked Potentials (SSEP),

Motor Evoked Potentials (MEP),Electromyography (EMG).

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Indications for SSEP monitoring

Any surgery with the potential for mechanical orvascular compromise of the sensory pathways along

the peripheral nerve, within the spinal canal, orwithin the brain stem or cerebral cortex. Neuro: resection of tumor or vascular lesion in spinal cord,

tethered cord release, resection of a sensory cortex lesion(aneurysm, thalamic tumor), repair of AAA or TAA, carotid

endarterectomy. Ortho: scoliosis (Harrington rods), spinal cord

decompression/stabilization after acute injury, spinal fusion

Brachial plexus exploration

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SSEPs

SSEP: electrophysiologic responses of the

nervous system to the application of adiscrete stimulus at a peripheral nerveanywhere in the body.

SSEPs reflect the ability of a specific neural

pathway to conduct an electrical signal fromthe periphery to the cerebral cortex

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How are SSEPs generated

A skin surface disc electrode or a SQ fine-needleelectrode is placed near a major peripheral sensory

nerve (median/ulnar nerve at the wrist, commonperoneal nerve at the popliteal fossa, posterior tibialnerve at the ankle, etc)

An electrical stimulus is applied with an intensity toproduce minimal muscle contraction

The resulting electrical potential is recorded atvarious points along the neural pathway from theperipheral nerve to the cerebral cortex

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Some SSEPs Recording Sites

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SSEP waveform

Amplitude: measured from baseline topeak. Any decrease in amplitude (50%OR greater) may indicate disruption ofthe sensory nerve pathways.

Latency: time from onset of stimulus to

occurrence of a peak. Any increase inlatency (10% or greater) may indicatedisruption of the sensory nervepathways.

* The spinal cord can tolerate ischemia

for 20 minutes before SSEPs are lost

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Anesthetic Implications on SSEPs

All VAA cause dose-dependent decreases inamplitude and increases in latency

The above can be worsened with theaddition of N2O

If possible, bolus injections of drugs should

be avoided, especially during critical stagesof surgery

Continuous infusions are preferable

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Neuro Monitoringhttp://analgesic.anest.ufl.edu/anest2/mahla/snacc/eps/index.htm

Always check with Neuro Technician what isgoing to be monitored (SSEP, MEP, EMG)and what is their preference in terms of theanesthetic (no VAA, half MAC on VAA, N2Oat 50%, keep 1 to 2 twitches in TOF or 4/4 atcertain point of Surgery, etc)

For long procedures, can start with VAA andswitch over to Propofol, narcotic drips ASAP(few minutes after induction)

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Other factors can affect SSEPs

Temperature

Hypothermia increases latency

Hyperthermia decreases amplitude Hypoxia

Decreases amplitude

Hypotension

Decreases amplitude

Hypocarbia Increased latency with ETCO2

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Corrective Measures

if SSEPs change significantly

Anesthesia Provider can: Increase MAP (especially if induced hypotension is used) Correct anemia, if present Correct hypovolemia, if present Improve O2 tension Goal: find the proper anesthetic combination that does not affect

SSEPs and keep it constant (avoid drastic changes since it willconfuse the cause of a negative change noticed in the neuromonitor: is it the anesthetic or the surgery?)

Surgeon can: Reduce excessive retractor pressure Reduce surgical dissection in affected area

Decrease Harrington rod traction if indicated

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Motor Evoked Potentials (MEPs)

SSEP monitoring is useful in preventing neurologic damage butit is no foolproof

Because motor tracts are not monitored, the patient may wakeup with preserved sensation but lost motor function

Motor pathways: blood supply from anterior spinal artery

Sensory pathways: blood supply from posterior spinal artery

The use of Motor Evoked Potentials (MEPs) along withSSEPs provides a more complete assessment of neural

pathway integrity Electrical stimulation done by Neuro Tech b/w key surgical

periods (when twitching does not affect operative field)

MEPs are more sensitive to VAA (may choose TIVA).

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TIVA and Awareness

TIVA recipe: Propofol/opioid +/- ketamine

Ketamine is controversial since Ketamine (as wellas Etomidate) enhance both SSEPs and MEPs

Wake up test (rarely done anymore!)

BIS monitoring

Small bolus (eg, 1-2mg) of Midazolamintraop (too much will affect monitoring!!)

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Drugs commonly used in TIVA

(titrate to effect)

Propofol (Diprivan) Induction: 2-2.5 mg/kg Maintenance: 50-200 mcg/kg/min

Remifentanil (Ultiva) Induction: 0.5-1 mcg/kg (over 30-60 sec) Maintenance:

0.1-2 mcg/kg/min with 50% N2O 0.05-2 mcg/kg/min with Propofol at 100-200 mcg/kg/min 0.05-2 mcg/kg/min with Isoflurane at 0.4-1.5 MAC

After turning off drip, make sure IV tubing is free of Remifentanil

Dexmedetomidine (Precedex) (alpha-2 agonist) Maintenance:

Loading infusion: 1mcg/kg over 10 minutes Maintenance infusion: 0.2-0.7 mcg/kg/hr

Can keep infusion going after extubation

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Drugs commonly used in TIVA

(titrate to effect)

Fentanyl Induction 5.75mcg/kg

Maintenance 0.01-0.05mcg/kg/min Sufentanyl

Induction 1-10mcg/kg

Maintenance 0.0025-0.15mcg/kg/min

Ketamine

Induction 0.5-2mg/kg Maintenance 20-90mcg/kg/min Can combine w/propofol 4:1 e.g.200mgpropfol+50mg

ketamine

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Mixing and Diluting

Remifentanil (Ultiva) Usually comes as powder in vial (5mg vial)

Dilute to 50 mcg/cc (by adding 5mg to 100 N.S.)

Dexmedetomidine (Precedex)

Usually come as 100mcg/ml in 2ml vial Dilute to 4 mcg/cc (by adding 2 vials of 200mcg

each to 96cc of N.S.) Total solution will be400mcg in 100 cc = 4 mcg/cc

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Drugs commonly used in TIVA

(titrate to effect)

Equations

Loading dose (mcg/kg) Vd (ml/kg) x Cp (mcg/ml)

Maintenance infusion (mcg/kg/min)

Cl ml/kg/min x Cp mcg/ml

Source NZ 3rd Ed. P. 154

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Drugs commonly used in TIVAContext sensitive half times

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Pumps

The safe and continuous administration of IVanesthetics depends upon a reliable deliverysystem and a vigilant anesthetist

A simple gravity intravenous infusion can bepiggy-backed to a carrier line

A pump offers the advantages of moreprecise dose selection, lower risk ofoverdose and minimal flow variation fromchanges in venous pressure or bag height

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Types of Pumps

Syringe Pumps:

Use a driver that pushes fluid out of a syringe by advancing

its plunger while the barrel is kept stationary.

Small units, light weight, cordless, accurate at very low flowrates. May have program library

Volumetric Pumps:

Use a disposable cassette within IV system that controlsrate by a variety of methods

Larger size, added cost of cassette tubing, more susceptibleto air bubbles

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Infusion Pumps

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Infusion Pumps

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General Recommendations

Vigilant anesthetist will continuously monitor: Connection of pump tubing to IV

Possible occlusion and retrograde flow up thecarrier line

Misassembly of pump

It is recommended that: Anesthetic infusions have a dedicated IV line

Infusion line is placed as close to the patient aspossible

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Manual Calculations

Cant blame the pump!!!

Use whatever method lets you double checkmannually the desired dosed given by thepump

Just a review from Nursing 101!!

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Manual Calculations

Dose/concentration

If you only have a basic pump that gives you cc/hr only,can you deliver the desired dose?

My SIMPLE method of manual calculations:

Dose = ml/hr Example: dose 80mcg/kg/min (propofol)

Concentration concentration 10mg/cc

weight: 75kg

(80mcg)(75kg)(60min) = 36cc/hr

10,000mcg/cc

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Manual Calculations (Examples)

Remi

Dose: 0.1mcg/kg/minConcentration: 50mcg/cc

Weight: 60kg

(0.1mcg)(60kg)(60min) = 7.2 cc/hr50mcg/cc

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More Calculations

Dopamine

Renal dose: 3mcg/kg/minConcentration: 400mg/250cc = 1.6mg/cc = 1600mcg/cc

Weight: 90kg

(3mcg)(90kg)(60min) = 10.1cc/hr1600mcg/cc

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More Examples

Precedex

Dose: 0.5mcg/kg/hrConcentration: 4mcg/cc

Weight: 65kg

(0.5mcg)(65kg)(1hr) = 8.1 cc/hr(4mcg/1cc)

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Shortcut

Only works with 250cc bag

Does not take into consideration pts weight Dose is eye-balled to an initial rate of 15cc/hr

Rule

Any X amount of mg added to a 250cc bag will give

that X amount in mcg/min if you set the pump at

15cc/hr

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Example of shortcut

(Any X amount of mg added to a 250cc bag will

give that X amount in mcg/min if you set the

pump at 15cc/hr)

Example:

Neosynephrine comes in a 10mg/cc vial

If you add 10mg of Neosynephrine to a 250cc bagand run it at 15cc/hr, you will be delivering10mcg/min

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PATIENT SAFETY ISSUES

Warm air devices (Bair Hugger)

DO NOT USE HOSE BY ITSELF

Can cause 3rd degree burns

C/I in AAA surgery

Fires

Pacers/ICDs and Magnets an attractiveoverview

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References

http://analgesic.anest.ufl.edu/anest2/mahla/snacc/eps/index.htm

Clinical Anesthesia Procedures of theMassachusetts General Hospital

Anesthesia Secrets

Physicians Drug Handbook

Morgan and Mikhail