Lecture 1 MAC, regional, GA & TIVA – Flashcards
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Pre-op anesthetic
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Interview Review of Systems Review labs EKG Old charts Discuss prior experiences with patient/family, discuss options, benefits & risks. CRNA's can order any lab test or medication that is pertinent to the anesthetic. EG: pain meds, EKG, anti-emetic, labs *Include caveat that GA may be required.
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Intra-op anesthetic
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Do what you said you would. Have back-up plans, be vigilant. Expect the worst, hope for the best. Be prepared for the unexpected.
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Post-op anesthetic
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PONV Pain control Morbidity (cut lips, damaged teeth, sore neck, limbs, nerve damage, sore throat, scratched eyes etc.) Exit interview a few days later.
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Which factors affect the absorption of inhalational anesthetics?
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CO, respiratory rate
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Advantages of Local Anesthetic
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- Don't have the risks involved with GA - If they come to OR it is monitored anesthesia care
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Disadvantages of Local Anesthetic
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-Physician can do independent of CRNA, "straight local"
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Advantages of MAC
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-Light to moderate to deep sedation similar to general - May need oral airway -Spinal, epidural or regional
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Disadvantages of MAC
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- Sometimes people are uncomfortable so they require GA anyway.
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Advantages of GA
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-A progressive depression of the CNS -Controlled passage through stage 1 and 2 to arrive in stage 3. - Patient cooperation not absolutely essential - Unconscious -Amnesia - Rapid onset of action - Titration possible
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Disadvantages of GA
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-Loss of protective airway reflexes - Depression of VS - Advanced training required - Additional personnel required - Special Equipment/setting -Need recovery room - Greater risk of intra-op complications -Post-anesthetic complications -More extensive pre-op evaluation, including lab work Indications: extreme anxiety or fear, mentally/physically disabled adults or children, poor patient cooperation, infants & children, traumatic procedures Contraindications: lack of adequate training by doctor or personnel, lack of equipment, facilities or medically compromised patient
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Mask
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-Oral airway or nasal airway -Nasal avoided, bleeding -Short-term case
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LMA
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Most common airway manipulation -Must be spontaneously breathing - LMA at induction, ventilate until propofol wears off -Reflux not a candidate
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ETT
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OETT: oral endotracheal tube NETT: nasal endotracheal tube DLT: double lumen tube (one lung ventilation- thoracic cases) Most secure airway.
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Advantages of TIVA
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-Used with allergies to gas/MH history - Quick stages of anesthesia -TIVA is a general anesthetic -used for neuro cases (rapid awakening)
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Advantages of Epidural/Neuraxial
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-Pain control 12-24 hours post surgery (duramorph) - no respiratory issues - Used with older or compromised patients
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Disadvantages of Epidural/Neuraxial
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- Urinary retention - Immobile, pad
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Advantages of Regional Block
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- Somewhat awake, will hear things - MAC cases
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Disadvantages of Regional Block
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- Need to be asleep with tourniquet because it is uncomfortable - Patient can remain awake
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Interscalene
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Indications for interscalene nerve block include the following: Shoulder surgery, such as rotator cuff repair, acromioplasty, hemiarthroplasty, and total shoulder replacement Humerus fracture Other arm surgery that does not involve the medial aspect of the forearm or hand
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Femoral
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Indications: Anterior thigh and knee surgery Landmarks: Femoral (inguinal) crease, femoral artery pulse Nerve Stimulation: Twitch of the patella (quadriceps) at 0.2-0.5 mA current Local anesthetic: 20 mL Complexity level: Basic
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Bier Block
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Indications: Surgery on the wrist, hand and fingers. Local anesthetic: 15 mL of 2% lidocaine (up to 40ml) Complexity level: Basic
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Malignant Hyperthermia Cause
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-Open ryanodine receptor allows continuous release of calcium from the sarcoplasmic reticulum. -Triggers: all anesthetic gases -Nitrous is safe.
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MH S/S and treatment
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Trigger: all halogenated anesthetics and succinylcholine (nitrous is safe) Increasing CO2, hyperthermia Treat: dantrolene 2.5 mg/kg every 5 minutes up to 10mg/kg Anesthetic plan: MAC, regional, TIVA (for general) Flush machine, new absorber, new circuit
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Stages of Anesthesia: Stage 1
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Stage 1: Analgesia Stage 2: Delerium Stage 3: Surgical Anesthesia Stage 4: Overdose (medullary paralysis) Stage 1: -Beginning of induction drug to loss of consciousness -dizzy, loses sense of reality -lessened sensitivity to touch and pain -hearing is increased, response to noise intensified
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Stage 2
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Delirium or excitement phase: loss of consciousness to onset of rhythmicity of VS into entry of surgical anesthesia -Struggling, ? muscle tone, jaw sets, eyelids closed, may breath hold and retch , nystagmus -Reflexes are hyperactive -Respiratory pattern is irregular -"Goofy" disconjugate eyes - NEVER EXTUBATE (laryngospam)
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Stage 3
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Surgical or Operative Stage: -End of stage 2 to cessation of respirations - Respirations regular, patient likely intubated or LMA There are 4 planes of anesthesia in Stage 3. -Most surgical procedures occur in plane 2.
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Stage 4
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Death... cessation of respiration to death, respiratory and circulatory arrest. Circulatory collapse. -all reflexes absent - flaccid paralysis - marked hypotension - weak irregular pulse
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IV anesthetics & pregnancy
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-Most are safe - Versed avoided but may be ok -Fentanyl & propofol frequently used
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Inhalational Anesthetics & pregnancy
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All gas anesthetics: -depress the uterus, ? risk of miscarriage - may increase blood loss during intrauterine procedures - reduced MAC required due to higher circulating blood volume hemodilution
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Benefit of continuous infusion of opioids
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-Used for maintenance of general anesthesia -Balanced technique -Morphine, fentanyl, alfentanil, sufentanil, remifentani, demerol
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Which factors lower MAC requirements?
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? age Hypothermia Depressant medications ?? agonists Acute ethanol consumption Metabolic acidosis Hypoxemia Anemia Hypotension Hyponatremia Pregnancy N?O, ketamine, lidocaine, clonidine, lithium
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Which factors raise MAC requirements?
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Kids (higher metabolism/RR) Hyperthermia Hyperthyroidism Hypernatremia Chronic alcohol consumption MAO Inhibitors Cocaine, levodopa
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What is the mechanism of action of local anesthetics?
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- Block Na channels preventing depolarization of the cells.
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Which medications reverses narcotics?
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- Narcan .04-4mg IV q 3 minutes
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Which medications reverses benzodiazepines?
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- Flumazenil -Competitive agonist at receptor binding sites. Sole benzodiazepine antagonist. - 0.2 mg doses (2ml) titrated up gradually to desired LOC, up to 1mg
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Which medications reverse paralytics?
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-Neostigmine .04-.07mg/kg up to 5mg (combine with robinul because neostigmine will increase salivation) - Endrophonium .5-1mg/kg (combine with atropine to block muscarinic cholinergic effects)
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Desflurane Advantages & Disadvantages
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Advantages: quick, rapid uptake & elimination, minimal metabolism Disadvantages: pungent, respiratory irritant, expensive, tachycardia
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Desflurane dosing & metabolism
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Dosing: 3-9% induction, 2-6% maintenance Metabolism: <0.1%
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Isoflurane Advantages & Disadvantages
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Advantages:cheap, minimal metabolism Disadvantages: pungent, respiratory irritant, slow uptake & distribution, coronary steal
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Isoflurane dosing & metabolism
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Dosing: 1-4% induction, .5-2% maintenance Metabolism: <1%
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Sevoflurane Advantages & Disadvantages
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Advantages: not respiratory irritant, rapid uptake & distribution non-pungent Disadvantages: metabolized, compound A, expensive, ? fluoride ion concentration
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Sevoflurane Dosing & Metabolism
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Dosing: 4-8% induction 1-4% maintenance Metabolism: 3-6% by liver
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What are each anesthetic agents blood/gas solubility coeffcient? What does this number tell you?
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Des:0.42 Iso:1.4 Sevo: 0.6 N?O: .47 SPEED -The proportion of the anesthetic that will be soluble in the blood. -The more soluble the drug, the slower the uptake. (The gas is "tied" up and unable to get to brain.) - Poorly soluble = rapid uptake
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What are the MAC values of each anesthetic? What does this number mean?
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Des: 5.8 Iso: 1.15 Sevo: 2 N?O: 105 DOSE
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What are the oil/gas values of each anesthetic? What does this number mean?
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Des: 18.7 Iso: 99 Sevo: 50 N?O: 105 POTENCY
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What is the second gas effect?
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Simultaneous administration of a relatively slow agent, such as iso, and a faster agent, such as N?O will speed the onset of the slower agent.
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Nitrous Oxide Advantages & Disadvantages
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Advantages: moderate analgesia, rapid uptake & elimination, non pungent, does not ?BP Disadvantages: expansion of closed air spaces, ?PONV, immune supression, teratogenic, supports combustion, weak
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Nitrous Oxide Dosing & Metabolism
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Dosing: 50-70% induction & maintenance Metabolism: <1%
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Benzodiazepines
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-Versed- quick on and off .25 mg for elderly people, 1mg-2mg for most others
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MAC of a Halogenated Anesthetic
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-The dose is expressed as minimum alveolar concentration necessary to produce anesthesia on surgical stimulation. -Faster the lung and therefore brain concentrations rise the faster the anesthesia is achieved.
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MAC defined
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-MAC -MAC awake 1/3 (amnesia) -MAC bar 1.5 (block adrenergic receptors) usually goal for start of surgery -MAC intubation 2 (ETT, very stimulating)
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Ventilation Effect
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The faster and more deeply a patient breathes or is ventilated the faster the patient loses consciousness and emerges. Ventilation/perfusion deficits or poor lung function hinders inhalation drug administration. Affects fast drugs the most.
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Uptake into the Blood
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Vessel Rich: heart, liver, kidneys, brain, to a lesser degree muscle Vessel Poor: fat ? in CO slows uptake. Pediatric uptake is faster than adults (kids have higher alveolar ventilation per weight ratio).
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Concentration Effect and Over-pressurizing
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-Concentration effect: A loading dose is given to speed initial uptake & turn up the flows ?Fi% -"Over-pressurizing" is the process of significantly increasing a volatile anesthetic delivered to a patient to increase the alveolar concentration and therefore the amount dissolved in the blood, to speed uptake. Henry's Law
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Diffusion hypoxia
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-Occurs during emergence - High concentrations of nitrous have been given - Nitrous is turned off - Nitrous exits the body quickly through the lungs and is replaced by nitrogen in the air - Results in transient dilution of oxygen and carbon dioxide - Administration of 100% FIO? for several minutes will prevent
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Placement guidelines for Epidural
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-Intercristal/Tuffier's line - Feel iliac crest, guide placement of epidural - mark L3/L4 space, have patient arch back - "heavy" on solutions mean hyperbaric, goes down -Isobaric same as CSF, hypobaric lower than CSF -Marcain .5-.75% in dextrose commonly used
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Which of the following correctly describes ketamine dose for IV induction? IM
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- 2-3 mg/kg IV - 4-6 mg/kg IM Mixed with atropine to counteract salivation.
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What is the longest acting local anesthetic?
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- Epi with tetracaine
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What is a normal dibucaine number?
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-80, 80% of the PChE inhibited by dibucaine - Dibucaine Inhibition Test
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ER, ORIF for finger reduction, ETOH
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- ETOH lowers MAC requirement with acute intoxication (already at .2-.3 MAC) - Chronic ETOH with raise MAC requirements (noticeable with propofol)
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What causes bradycardia in kids?
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-Succinylcholine -Mix with atropine to counteract bradycardia
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If eyes are midline which stage are they in?
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- Stage 1 or 3
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During what stage do you NEVER extubate?
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Stage 2 -Delirium, prone to laryngospasm
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Why are paralytics avoided in kids?
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- Want to maintain airway, respiratory drive - Succinylcholine causes MH, bradycardia - Use demerol and propofol for induction -Avoid reversals
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What do narcotics do to pupils? Atropine?
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- Pinpoint: narcotics - Dilate: atropine
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What medication can you use when a patient on ACE inhibitor is not responding to ephedrine or neosynephrine?
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- few units of vasopressin
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Most adults use which size of MAC blade?
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3
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Most adults use which size Miller blade?
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2 ( used ages 2+)
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What is the size for oral airways? Colors?
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8- green 9- yellow, most often used 10-red
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What are Mcgill forceps used for?
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-Nasal intubation
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Epiglottis hangs down so which blade works better?
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Usually Miller blade, although Mac is easier to learn with. MAC- lifts vallecula but epiglottis hanging down (in & up motion) Miller- lifts up epiglottis tougher to see, tongue obstructs
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ASA Classifications
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ASA 6: declared brain dead, organ donor ASA E: Emergency procedure, added to ASA I-VI Used for reimbursement/ report.
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Most outpatient surgical centers will not operate on a patient above which ASA class?
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ASA 3
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Narcotics
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Used for maintenance of general anesthesia "Balanced technique" -Most common fentanyl - Morphine, fentanyl, alfentanil, sufentanil, remifentanil
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Dissociative Agents
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Ketamine (only anesthetic/analgesic combo) 2mg/kg -Dissociates patient from environment - Minimal depression of protective reflexes - Hallucinations are common on emergence
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Muscle Relaxants
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-Defasciculating dose: depolarizer before succinylcholine to prevent muscle spasm/ soreness after surgery (5-10mg zemuron/rocuronium) - Succinylcholine, atracrurium, pancuronium, rocuronium, cisatracurium- (elimination PChE in blood)
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Barbituates
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-Methohexital: ECT, dental, cardioversion, lowers seizure threshold 2mg/kg -Sodium Thiopental: 2.5% solution dose 4mg
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Non-barbituates
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Propofol: Induction 1-3mg/kg
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What is the MAC of halothane?
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MAC = .74 Hepatitis, slow acting, good for inhalation
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What are some tricks you can use during long cases?
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8 hour case, anesthetics into fat, emergence on more expensive agent, maintenance on Iso, cheaper.
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5 Questions in the following format
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Laparascopic appendectomy, (regional/general/IV sedation) anesthetic. This patient (will/will not/might) recieve paralytics. This patient will be in the (supine/prone/lateral/lithotomy) position. *If it is laparascopic the patient will require paralytic.
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How can you tell when the case is nearing completion?
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Suture sizing: -small 10, big 0 - know progression of case Counting sponges/supplies towards the end of case.
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How can you tell with propofol when you can intubate or bag?
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- Eyelash reflex -Listen with precordial stethoscope
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Know brand/trade names of drugs
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Fentanyl: sublimaze Sufenta: sufentanil Alfenta: alentanil Demerol: merperidine Marcain: bubivipcaine: sensorcaine Lidocaine:xylocaine Remifentanil:ultiva Narcan:naloxone Rocuronium: zemuron Ravlon: rapacuronium (bronchospasms) Propofol: diprivan Versed: midazolam Edrophonium:reversol:enlon:tensilon Succinylcholine:anectine:quelicin Neostigmine: prostigmin
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List local anesthetics short acting to long acting.
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Lidocaine>bubivicaine>tetracaine
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Does epinephrine work well to prolong action of bubivicaine?
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Not really. Epi works well to prolong duration of lidocaine and tetracaine.
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Advantages of Continuous Opioid Infusion Box12-4
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Hemodynamic stability Decreased side effects Reduced need for opioid-reversal agents Reduced need for vasopressor drugs Suppression of cortisol and vasopressin response to Cardiopulmonary bypass Reduced total dosage of opioids Decreased recovery time
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The primary factors that influence absorption of the inhalation anesthetics are:
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Ventilation Uptake into the blood Cardiac output Solubility of the anesthetic drug in the blood Alveolar-to-venous blood partial-pressure difference (assumed to be the same as in the brain) Concentration Second gas effect
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ASA Examples
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ASA 1: normal healthy patient ASA 2: smoker, OB, thyroid, HTN, mild health issue, DM, chronic bronchitis, anemia, morbid obesity, age extremes, heart disease-slightly limits activity ASA 3: COPD, CAD-limits activity, poorly controlled HTN, DM with vascular complications, angina pectoris, previous MI ASA 4: renal or hepatic failure, CHF, persistent angina, advanced pulmonary disease ASA 5: massive trauma , AAA, uncontrolled hemorrhage "Love to give scenarios and have you pick status"
