tiva pumps
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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