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
2
Q
Goals for spinal anesthesia
A
- Prevention of pain
- Adequate dermatomal level of anesthesia
- Adequate duration of anesthesia
- Skeletal muscle relaxation
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)
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
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)
6
Q
Epidural for labor
A
**Subarachnoid needle placement **
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 **
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
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)
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
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)
12
Q
Spinal local anesthetics
A
Bupivacaine is used mostly now for spinals
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
14
Q
Spinal additive drugs
A
- You can add narcotics to blocks
- Fentanyl, morphine
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
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
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
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)
19
Q
Definitions
A
- Minimal sedation
- Moderate sedation/analgesia = Conscious Sedation - What we are talking about today
- Deep sedation/analgesia
- General anesthesia
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
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
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
REMEMBER
EVERYONE RESPONDS DIFFERENTLY TO ANESTHESIA – hard to predict
- Can’t know in every case
- What are some predictors of drug requirements – Risk Factors
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Predictors of how you will respond to anesthesia
- 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
Positioning for conscious sedation
- 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
Lung volume chart
- 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
Pre-procedural assessment by the physician
- 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
***When working on heart patients***
- 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
Fasting guidelines
```
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
Candidate for conscious sedation
After all of this is done, it MUST be determined whether this patient is a CANDIDATE for conscious sedation (sedation/analgesia)
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Provider qualificaiton
- 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
5 classes of anesthetic agents
- 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
Medications used for conscious sedation
- Sedation: Benzodiazepines
- Analgesia: Opiates
- Why these agents?...because they their effects can be reversed
36
Benzodiazepine effects
NO EFFECT ON PAIN***
- Sedation
- Hypnosis
- Anxiolysis
- Muscle relaxation
- Anticonvulsant
- Anterograde amnesia
37
Benzodiazepine characteristics
```
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
Opiates effects
```
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
Opiate drugs
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
Opiate metabolism and dosing
- 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
Monitoring
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
Record keeping
- Pre-procedural
- Every 5 minutes during procedure
- Appropriate intervals – post procedure up to discharge
- Determined by your hospital
43
Reversal agents
- Flumazinil (Romazicon)
- Naloxone (Narcan)
- Should not be used routinely
44
Benzodiazepine reversal
- 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
Opiate reversal
- 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
Reversal simultaneously
- Encourage deep breathing
- Give supplemental oxygen
- Positive pressure ventilation if spontaneous breathing is inadequate
47
Rescue
- 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
Recovery care
- Should be in accordance with standard recovery and discharge criteria established at your institution.
49
DO NOT USE THESE DRUGS for sedation
- 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
Meperidine
- 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
REVIEW
- Based on relative potencies
| - 50 mcg Fentanyl = 5 mg Morphine = 50 mg Meperidine
52
If you don't trust these conversions
- Titrate the drug to effect and go slowly – especially with Morphine due to its slower onset
53
Recommendation
- 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
Automated infusion system
- Controlled feedback mechanism with a machine controlling your sedation, called McSleepy
