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17 - IV Sedation Flashcards

1
Q

Spinal anesthesia

A
  • You are introducing anesthesia into the subarachnoid space
  • There is a 1-5% failure rate – unpredictable and unreliable
  • You will see a lot of this in your career because it is commonly used in foot surgery
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2
Q

Goals for spinal anesthesia

A
  • Prevention of pain
  • Adequate dermatomal level of anesthesia
  • Adequate duration of anesthesia
  • Skeletal muscle relaxation
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3
Q

Indications of spinal anesthesia

A
  • Lower extremity procedures
  • Hip and knee surgery
  • Perineal surgery
  • Lower abdominal surgery (C-section)
  • Posterior lower trunk surgery (hemorrhoids)
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4
Q

Contraindications of spinal anesthesia

A
  • Sepsis (hemodynamic instability)
  • Bacteremia (with caveats – on antibiotics and have been for a long time because you can get bleedings problems)
  • Skin infection at injection site (tattoos?) – issue in pregnant women (infectious area)
  • Severe hypovolemia
  • Coagulopathies and anticoagulants (can get hematoma)
  • Increased ICP (intracranial pressure)
  • Patient refusal, lack of cooperation
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5
Q

Technique for spinal anesthesia

A
  • Lateral, sitting, or prone position – having them sit up is the easiest way - Hard to determine midline, sagging back skin – iliac crest is L4 (landmark)
  • Cord ends at L1 – place needle between L2-3 and L5-S1
  • A larger gauge introducer can be placed through the skin into the interspace and the spinal needle is introduced through it
  • Approach can be midline or lateral (paramedian – alternate approach when midline doesn’t work due to calcification or other pathology)
    o This takes experience, need to practice to know what angle that will be
    o Trying to bypass area of surgery (from previous back surgery)
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6
Q

Epidural for labor

A

**Subarachnoid needle placement **

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7
Q

Spinal needles – different lengths, different shape of tips

A
  • Gertie marx – can shoot drug up or down depending on position
  • Sprotte
  • Whitacre
  • Quincke – can lead to spinal headache
  • **The smaller gauge needle you use, the less change of spinal headache **
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8
Q

Ultrasound guided spinal anesthesia

A
  • Can identify landmarks that are not easily identified by the skin alone
  • Used in obese individuals or anyone else
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9
Q

Height of spinal block

A

Dose of drug given - primary factor in what HEIGHT of spinal block you use
o Dose of drug give = volume x concentration
o “Weight of the agent” – heavier or lighter than CSF

  • Weight (baricity) of injected local anesthetic solution
  • Patient position – Sitting or lying (if they are lying are they head up or head down)
  • CSF volume (the “X” factor)
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10
Q

Height of block – Lesser determinants

A
  • Added vasoconstrictors
  • Coughing or bearing down (Valsalva)
  • Barbotage
  • Rate of injection ( hypobaric solution may be the exception )
  • Needle bevel direction ( except directional bevels )
  • Gender
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11
Q

Risks of spinal anesthesia

A
  • Nerve Damage
  • Bleeding
  • Infection
  • Headache
  • Failed block – can mean no block, low block, high block, unilateral block or total spinal block (total spinal anesthesia – some go unconscious when it reaches brain step, need to intubate because they cannot breathe)
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12
Q

Spinal local anesthetics

A

Bupivacaine is used mostly now for spinals

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13
Q

Isobaric bupivacaine spinal

A
  • Has a concentration of 0.5% and a baricity ( or specific gravity) approaching that of CSF
    o Used A LOT FOR CHARCOT – you will see this A LOT in your career
    o There will be a longer period of block so you can take longer to do this tricky procedure
  • Is given in a larger volume in the sitting or lateral position
  • Does not spread cephelad and settles in the lordotic area of the spinal cord
  • Has a longer duration of action - and very safe
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14
Q

Spinal additive drugs

A
  • You can add narcotics to blocks

- Fentanyl, morphine

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15
Q

Physiological effects of spinal anesthesia

A
  • Effects depend on the height and density of the block
  • The more thoracic segments blocked, the greater the effects (T5 and above)
  • Visceral blockade affects cardiovascular, pulmonary, GI, hepatic, renal, and endocrine systems
  • Unopposed parasympathetic nervous system activity leads to nausea and vomiting
  • Cardiovascular effects are a decrease SVR with pooling of blood in the vascular system below the level of the block (decreased venous return)
  • Decreased adrenal output (decreased catecholamine release)
  • Decreased activity of cardioaccelerator nerves(T3-5)
  • Decreased cardiac contractility
  • NOTE ALL of this leads to bradycardia and hypotension which has led to DEATH
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16
Q

Treatment for this physiological effect of spinal anesthesia

A
  • IV fluids
  • Vasopressors – ephedrine or phenylephrine
  • Trendelenberg position or raising of legs
  • Anticholinergic agent – atropine or glypyrrolate
  • Epinephrine if all else fails
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17
Q

Goals of conscious sedation

A
  • Understand need for a conscious sedation policy
  • Understand the concept of conscious sedation (sedation-analgesia)
  • Understand pharmacology of drugs used for conscious sedation
  • Understand pharmacology of reversal drugs
  • Understand monitoring requirements necessary for the safe conduct of conscious sedation
  • Understand what the JCAHO requires of the hospital (or facility) where conscious sedation is administered
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18
Q

Contraindications of conscious sedation

A
  • History of adverse reaction to sedative medication
  • Unstable cardiorespiratory status
  • Nonfasting state – relative contraindication since a lot of sedation is done in ER’s on patients with full stomachs – need to be careful
  • First trimester of pregnancy (elective cases you would never do)
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19
Q

Definitions

A
  • Minimal sedation
  • Moderate sedation/analgesia = Conscious Sedation - What we are talking about today
  • Deep sedation/analgesia
  • General anesthesia
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20
Q

Minimal sedation

A
  • Responds normally to verbal commands
  • Ventilatory & Cardiovascular function unaffected
  • Cognitive function & coordination may be impaired
  • Used commonly to treat anxiety
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21
Q

Moderate sedation/analgesia (conscious sedation)

A
  • Drug induced depression of consciousness
  • Pt’s respond purposely to verbal commands
  • Airway remains patent
  • Spontaneous ventilation and cardiovascular function usually maintained
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22
Q

Deep sedation/analgesia

A
  • Drug-induced L.O.C. from which pt’s are not easily aroused
  • May respond to repeated or painful stimuli
  • Ventilation may be impaired
  • Cardiovascular function usually maintained
23
Q

General anesthesia (skipped)

A
  • Drug induced L.O.C.
  • Pt’s do not respond to painful stimuli
  • Ventilation function often impaired
    o Airway assistance & positive pressure ventilation may be required
  • Cardiovascular function may be impaired
24
Q

MAC vs general anesthesia – Closed claim study

A
  • 35% of claims were for death
  • 13% were for brain damage
  • “In particular, inadequate oxygenation and/or ventilation – were the primary damaging event in a high percentage of MAC claims”
25
Q

REMEMBER

A

EVERYONE RESPONDS DIFFERENTLY TO ANESTHESIA – hard to predict

  • Can’t know in every case
  • What are some predictors of drug requirements – Risk Factors
26
Q

Predictors of how you will respond to anesthesia

A
  • Age
  • Single or multiple organ system disease
  • History of drug or alcohol use
  • Anatomic problems
    o Airway anomalies
    o Sleep apnea
  • Delayed mental development
  • Uncooperative
  • Emergencies
  • Morbid obesity
27
Q

Positioning for conscious sedation

A
  • You need to place you position so that they can breathe on their own during sedation while you give your drug
  • Small amounts of midazolam or morphine can lead to compromised airway (lack of swallowing to get rid of oral secretions)

Best position

  • Don’t lay flat, have them elevated at a 15 degree angle (or so)
  • Risk of dying when lying flat – want to maintain the “ear to sternal notch”
28
Q

Lung volume chart

A
  • You want their heads up because it is a mechanical issue
  • Residual volume cannot be eliminated (dead space in lungs)
  • When you are pregnant or obese, there is pressure on the diaphragm, leading to a decreased residual volume, compromising the oxygen reserve in the body
  • If you sit them up, there is greater diaphragmatic excursion and there is more space in the lungs
  • If there is a problem with the airway, you will “buy more time” if there is compromise of airway
29
Q

Pre-procedural assessment by the physician

A
  • History and physical with focus on cardiac, respiratory systems and airway
  • Labs based on findings related to procedure
  • Appropriate consultation
  • If you have a healthy patient, there is no way to do lab work to make it safer
    o Waste of time, waste of money, can get false positives
    o Lab ordering frequency was based on geographical location (unnecessary)
    o Generates money for the hospital, but there is no medical justification for this testing
  • This is what you do to EVERY patient, regardless of health status – nursing does this
    o Vital signs
    o Level of consciousness
    o Last intake of fluids or food
  • Previous heart intervention guidelines (not a lecture topic, but I’m talking about it anyway)
30
Q

When working on heart patients

A
  • If they are on long-term aspirin because of a previous procedure, you can LEAVE THEM ON ASPIRIN WHEN DOING SURGERY
  • IT WILL NOT INCREASE BLEEDING SIGNIFICANTLY = TEST QUESTION***
31
Q

Fasting guidelines

A 
Ingested Material
o	Clear Liquid = 2 Hours
o	Full Liquid = 4 Hours
o	Light Meal = 6 Hours
o	Heavy meal with fried or fatty foods will delay gastric emptying = 8 hours or longer
32
Q

Candidate for conscious sedation

A

After all of this is done, it MUST be determined whether this patient is a CANDIDATE for conscious sedation (sedation/analgesia)

33
Q

Provider qualificaiton

A
  • Determined by the facility– KNOW THE GUIDELINES
  • Understanding of pharmacology of drugs used
  • Only drugs with reversal agents should be used for conscious sedation
  • ACLS preferable for provider OR
  • Have a qualified individual immediately available
  • An individual should be available to summon help
  • Provider should be able to rescue from one level beyond the anticipated level of sedation and be able to support oxygenation, hemodynamics and ventilation
34
Q

5 classes of anesthetic agents

A
  • GABAergic agents ( benzodiazepenes )
  • Opiate receptor agonists ( fentanyl )
  • NMDA receptor antagonists ( ketamine )
  • Alpha-2 agonists ( clonidine )
  • Dopaminergic agonists ( ie: PCP –used as an anesthetic in the 1950’s )
35
Q

Medications used for conscious sedation

A
  • Sedation: Benzodiazepines
  • Analgesia: Opiates
  • Why these agents?…because they their effects can be reversed
36
Q

Benzodiazepine effects

A

NO EFFECT ON PAIN***

  • Sedation
  • Hypnosis
  • Anxiolysis
  • Muscle relaxation
  • Anticonvulsant
  • Anterograde amnesia
37
Q

Benzodiazepine characteristics

A 
Drugs
o	Diazepam (Valium)
o	Midazolam (Versed)

Half life
o Half-life
o 43 +/- 13 hours
o 1.9 +/- 0.6 hours (Range – 1 to 4 Hrs)

Metabolism
o Hepatic metabolism with active metabolite alpha-1-hydroxymidazolam
o (10 % as potent as parent drug)
o Renal or liver disease can impair it’s elimination

38
Q

Opiates effects

A 
o	Analgesia
o	Drowsiness
o	Mood changes
o	Mental clouding
o	Respiratory depression
o	Delay gastric emptying
o	Can produce nausea and sometimes vomiting
o	Interferes with urinary voiding reflex
o	Pruritis and sometimes urticaria
ALL OF THESE HAVE Mu EFFECTS = these are the receptors they act on
39
Q

Opiate drugs

A

o Morphine = 1, half-life = 2 hours, onset = 15-30 min
o Meperidine = 0.1, half-life = 3 hours, onset = 2-5 min
o Fentanyl = 100, half-life = 3-4 hours, onset = 2-5 min
o Sufentanil = 1000, half-life = 3-4 hours, onset = 2-5 min

40
Q

Opiate metabolism and dosing

A
  • Hepatic metabolism with renal excretion of active metabolites
  • Lipid soluble compounds act more quickly due to ease in crossing blood-brain barrier

MUST REMEMBER THAT WHEN GIVEN TOGETHER, THE DOSAGES OF BOTH THE OPIATE AND BENZODIAZEPINE MUST BE REDUCED!

Rules for dosing
o GO SLOW…GO LOW
o Remember…once you give it, you can’t get it back

41
Q

Monitoring

A

Oxygenation
o Pulse oximetry with appropriate alarms that must be audible and preferably variable pitch
o Supplemental oxygen recommended

Ventilation
o Direct observation
o Auscultation
o End tidal CO2 – A recent JCAHO requirement

Circulation
o Non-invasive – B.P.
o Plethesmography
o Continuous EKG (+/-) – recommend to always use if patient has cardiac history

Level of consciousness
o Continuous verbal communication
o Note response to commands, tactile stimulation sometimes necessary

42
Q

Record keeping

A
  • Pre-procedural
  • Every 5 minutes during procedure
  • Appropriate intervals – post procedure up to discharge
  • Determined by your hospital
43
Q

Reversal agents

A
  • Flumazinil (Romazicon)
  • Naloxone (Narcan)
  • Should not be used routinely
44
Q

Benzodiazepine reversal

A
  • Flumazinil – 0.1 mg/ml
  • Give 0.1 to 0.2 mg over 15 seconds
  • May repeat up to a dose of 1.0 mg.
  • Response is usually 1-2 minutes
  • Competes with benzodiazepenes at the GABA receptor
  • Do not give to patients on chronic benzodiazepine therapy due to risk of seizures
45
Q

Opiate reversal

A
  • Competes with opiate at the mu receptor to reverse respiratory depression
  • Naloxone - 0.1 to 0.2 mg IV
  • Response in 1 minute
  • May repeat
  • Do not give too much or too fast due to risk of precipitating agitation, hypertension, tachycardia and diaphoresis
46
Q

Reversal simultaneously

A
  • Encourage deep breathing
  • Give supplemental oxygen
  • Positive pressure ventilation if spontaneous breathing is inadequate
47
Q

Rescue

A
  • If reversal agents are used, keep patient a minimum of two hours to ensure that sedation and cardio-respiratory depression do not recur.
  • Keep them in the hospital and continue monitoring them – do not send them home
48
Q

Recovery care

A
  • Should be in accordance with standard recovery and discharge criteria established at your institution.
49
Q

DO NOT USE THESE DRUGS for sedation

A
  • Thiopental, Propofol, Etomidate, Ketamine should not be used unless credentialed to do so by hospital.
  • Person giving these drugs must be able to rescue from deep sedation or general anesthesia
  • Remember…anesthesia planes can change quickly and it is possible to reach deep sedation and beyond using only the drugs commonly used for conscious sedation
50
Q

Meperidine

A
  • 10 % as potent as Morphine
  • Has both anticholinergic and local anesthetic effects
  • Has short time of onset and is more euphoric making it a favorite narcotic for diversion
  • Hepatically metabolized to normeperidine which has a t1/2 5x greater than the parent drug
    o It is renally excreted
    o Toxic and hallucinogenic causing serotonin syndrome, seizures, delerium, dysphoria and tremor not reversed by Narcan
  • Do not use in pts with renal or hepatic failure
  • Not to be used in PCA analgesia
51
Q

REVIEW

A
  • Based on relative potencies

- 50 mcg Fentanyl = 5 mg Morphine = 50 mg Meperidine

52
Q

If you don’t trust these conversions

A
  • Titrate the drug to effect and go slowly – especially with Morphine due to its slower onset
53
Q

Recommendation

A
  • If Fentanyl is unavailable or in short supply, most practitioners will opt for Meperidine
  • It is a safe drug in a one-time dose of up to 100 mg
  • In patients with hepatic or renal compromise, it should not be used at all
54
Q

Automated infusion system

A
  • Controlled feedback mechanism with a machine controlling your sedation, called McSleepy

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