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TOPICS TO REVIEW!!!
● Special problems/issues in anesthesia ● ASRA anticoagulation guidelines ● OR safety (Dr. Hong lecture), line isolation monitors, etc ● Antibiotic prophylaxis ● Histamine release ● Electrolyte disturbances ● ABG calculations for compensation ● Inhaled agent values: partition coefficients ● PACU Criteria/Modified Alderete Scoring system ● Anticoagulant review ● Vaporizers: desflurane, output equations ======================================================== CONFIRMED: ● Fasting guidelines: ○ 8h-fried/fatty food, ○ 6h-formula/cow/light meal ○ 4h-breast milk ○ 2h-clear liquids ● CHOLINESTERASES
- Acetylcholinesterase : a) ACh
- Psuedocholinesterase aka Butylcholinesterase aka Plasma Cholinesterase : a) Succinylcholine b) Ester local anesthetics (2-chloroprocaine, tetracaine, procaine) c) Mivacurium (short acting NDNMD) d) Cocaine e) Heroin
- RBC esterases : a) Esmolol (also inhibits AChE!)
- Non-specific plasma/tissue esterases : a) Remifentanil b) Atracurium (non-specific esterases + Hoffman) ● Breathing circuits ○ Maplesons: ■ A: FGF “A”t the wall ■ B: FGF “B”y the pt ■ C: “C”ut the tube (shorter) ■ D: “D”a valve moves- APL by the wall
○ “Dead babies can’t assist in MV” ■ D>B>C>A for MV ○ “All dogs can bite spontaneously” ■ A>D>C>B in SV ● Bellows are classified according to their movement during EXPIRATION ○ Ascending bellows rise during expiration and descending bellows fall during expiration. Most modern anesthesia machines have ascending bellows because they are thought to be safer. Ascending bellows are safer because if a circuit disconnection occurs, the bellows will not fill. If there is a complete circuit disconnect with descending bellows, the bellows will continue to rise and fall and the disconnection can go unrecognized. ● E-cylinders ○ Oxygen: 2000-2200PSI = 600-660L ■ Quick estimate: Volume=pressure/3 (900psi=300L) ○ N20: ■ mix gas/liquid, weight to measure fullness ■ Full tank: 1600L at 745 psig ■ PSI will not fall until 25% remains (400L) ● Gas Laws: Boyles, Charles, Dalton, Gay-Lussac ○ Daltons Law of Partial Pressures ■ Ptot=P1+P2+P ● Ex: Arterial hypoxemia due to hypoventilation ○ Alveolar Gas Equation: ■ PAO2= FiO2(Pb-Ph2O) - PaCO2/R ○ Boyles Law ■ P1V1=P2V2 at constant temperature ○ Charles Law: V1/T1=V2/T ○ Gay Lussacs: P1/T1=P2/T ○ Laplace Law ■ Wall Tension= (pressure x radius)/ 2(thickness) ○ Pouiselles Law (Laminar flow) ■ Laminar Resistance = (8Lengthviscosity)/(Pi)radius^ ■ Laminar Flow=(piPressureradius^4)/(8lengthviscosity) ● V=IR, I=V/R ○ Static Compliance: ■ dV/dP= TV/(Plateau-PEEP) ○ Dynamic Compliance: ■ dV/dP= TV/(Peak-PEEP) ○ HendersonHasselbach ■ pH=pKA + log[HCO3/0.03PaCO2] ○ Cardiac Perfusion Pressure: ■ CoronaryPP= aDBP-LVEDP ○ Cerebral Perfusion Pressure
○ Malignant Hyperthermia ■ Halogenated gases, succinylcholine ■ 1.) Increase EtCO2, tachy, masseter spasm (esp Peds) ■ 2.) hypertherm, acidosis, muscle rigidity, CV disorders, rhabdo ■ Mixed metabolic & respiratory acidosis ■ Tx: discontinue, dantrolene (CCB) 2.5mg/kg bolus/infusion, clear gases ■ Dx associations: Central Core, Multi-Mini-Core myopathy, King-Denborough syndrome, Evans myopathy, Native American myopathy ■ ***Duchennes/Becker muscular dystrophy NOT associated with MH, but increase risk of anesthesia-induced rhabdo ○ Neuroleptic Malignant Syndrome ■ Neuroleptics/antipsychotics ■ High fever, confusion, muscle rigidity, HDuS, sweating, tachy ■ Slower in onset, gradual over 1-3days ○ Thyrotoxicosis ● Classic triad of TURP syndrome: HTN (wide PP), bradycardia, AMS ● Delays following cardiac interventions before elective surgery ○ 2 weeks : Balloon angioplasty: 2 weeks ○ 1 month : BMS: 1 month (DAPT x1month) ○ 2 months : ACS/MI w/o intervention: 2 months before elective ○ 3 months DES: 3 months if surgical delay > thrombosis risk, ○ 6 months DES: preferably 6 months (DAPT x6mo) to 1 year ● Active Cardiac Conditions:
○ Unstable coronary syndromes
■ unstable angina (CCS class III or IV), severe angina, and recent MI
○ Decompensated heart failure
■ NYHA functional class IV and worsening of new-onset heart failure
○ Significant arrhythmias
■ high-grade AV block,
■ Mobitz type II AV block,
■ third-degree AV block,
■ symptomatic ventricular arrhythmias,
■ supraventricular arrhythmias (including Afib) with RVR
■ symptomatic bradycardia
■ newly recognized ventricular tachycardia
○ Severe valvular disease
■ severe aortic stenosis
● mean pressure gradient > 40 mmHg, aortic valve < 1.
cm^2, or symptomatic
■ symptomatic mitral stenosis
● progressive dyspnea on exertion, exertional presyncope, or
heart failure
Revised Cardiac Risk Index Variables:
1) History of ischemic heart disease
2) History of congestive heart failure
3) History of cerebrovascular disease
4) Insulin therapy for diabetes
5) Preoperative serum creatinine > 2.0 mg/dL
6) High-risk type of surgery
● Nitrous oxide causes an acute increase in plasma homocysteine by irreversibly oxidizing the cobalt in Vitamin B12, resulting in decreased methionine and resulting hematologic and neurologic effects ● pH stat vs. Alpha stat ○ Relevant to cardiac surgery ABG analysis on bypass ○ Concept: as a pt gets COLDER: ■ More CO2 dissolves in blood, DECREASING paCO ■ pH INCREASES (increased ALKALOSIS) ○ Fact: ABG analyzer will always report results at 37degC ■ If pt COLDER, machine will warm, increasing reported paCO ○ Why do I care? pCO2 effects on CBF, risk of embolic load in adults vs. peds ○ pH stat: (aka “Temperature corrected”) ■ Reverse calculates results for ACTUAL patient temperature, THEN ADDS CO2 to (pt blood via bypass machine?) to normalize pH to 7. ■ Effectively increases pCO2 (resp acidosis) to increase CBF ■ Used in PEDIATRICS in order to increase CBF! ○ Alpha stat: lets just use the results reported at 37deg ■ Used in ADULTS ■ Effectively maintains hypothermia induces resp alkalosis ■ Preferred to limit CBF and risk of stroke and embolic load ● H’s & T’s ○ Hypoxia, hypo/hyperK, hypo/hypertherm, H+, hypovol, hypotension, hypogly ○ Tension ptx, tamponade, toxins, thromboembolism, thromboses(MI), trauma
● ED95 of a neuromuscular blocking drug
○ Dose required to achieve 95% block of a single twitch in 50% of
individuals
○ effective relaxation during intubation, one to two times the ED95 is
typically administered.
● Age >59, BMI >32, chronic liver disease, COPD w/ chronic bronchodil, PVD, high risk/emergency surgery Alderete PACU Discharge criteria:
- Extremity activity
- Breathing
- Circulation (BP)
- Consciousness
- Oxygen saturation O2/CO2 Dissociation Effects ● Bohr [B(O2)hr] Effect: release of CO2 at lungs facilitates O2 binding Hgb
○ ???describes the binding effect of H+ to Hb chains and the oxygen
release and dissociation that occurs thereafter
● Haldane Effect: at tissues, release of O2 facilitates CO2 binding to Hgb
○ illustrates that the oxygenation of hemoglobin lowers the affinity of
hemoglobin for carbon dioxide.
Difficult MASK VENTILATION: ● Facial hair ● Edentulous ● Over-/underbite ● Facial deformity ● Large tongue/tonsils Difficult INTUBATION: ● Tongue size (Mallampatti) ● Thyromental distance ● Atlantoaxial joint extension ● Neck circumference >48cm ASA Classifications: ● 1: healthy ● 2: mild systemic disease ● 3: uncontrolled systemic disease ● 4: constant threat to life ● 5: not expected to survive without operation ● 6: brain-dead, organ harvest NMBs in Disease ● Renal Failure a. Prolonged: Pancuronium (“starts with P, excreted in Pee”)
b. Intermed: Vecuronium/Rocuronium c. Unaffected: cisatracurium/atracurium (Hoff), mivacurium/SCh (pseudochol) d. Succinylcholine not contraindicated assuming normal K+ ● Liver Failure a. Pseudocholinesterase synthesis may be decreased → slight SCh prolongation, not cotraindicated b. Increased volume of distribution → may need increased initial dose but reduced maintenance dose given decreased clearance Volatiles effect on Neuromonitors:
● Brainstem potentials are Barely affected, Sensory potentials are Somewhat
affected, Motor potentials are Mostly affected, and Visual potentials are Very
affected.
Pharmaco- D -ynamics = what a drug “ Does ” Pharmaco- K -inetics = “ Klearance ” and metabolism Duration of monitoring following neuraxial opioids ● Epidural morphine (hydrophilics): ○ Hourly x12 hours, then q2hrs x12 hours (24hrs total) ● Epidural fentanyl (lipophilics): ○ Continuous x20minutes post admin, then hourly x2hours Chemo Toxicities ● Cisplatin, Carboplatin: acoustic nerve damage, nephrotoxicity ● Vincristine : peripheral neuropathy ● Bleomycin , Busulfan: pulmonary fibrosis (avoid hyperoxia?) ● Doxo rubicin : cardiotoxicity ● Trastuzumab : cardiotoxicity ● Cyclophosphamide: hemorrhagic cystitis ● 5-FU, 6-MP, methotrexate: myelosuppression Dantrolene: ● Unique muscle relaxant 2/2 site of action: INTRACELLULAR on the sarcoplasmic reticulum of the skeletal muscle cells (not NMJ--> DNMB/NDNMB) ● Rx: initial IV bolus ( 2.5 mg/kg ) followed by repeat boluses every 5-10 minutes prn; also infusions or administer dantrolene 1 mg/kg every 6 hours for 24-72 hours in order to prevent recrudescence Intralipid:
● Maintain platelet count at 50-60; in high-risk surgery, maintain >
● Keep fibrinogen >
● Transfuse to maintain Hgb > 7
● Do not give FFP prophylactically or chase INR levels
○ Increased INR in these patients does not necessarily reflect risk of
bleeding
○ If FFP is to be given, dose is 20-40 mL/kg
Arterial oxygen content (CaO2) = (Hgb * 1.36 * SaO2) + ( 0.003 * PaO2)
High Risk Extravasation medications (severe tissue necrosis, gangrene, or amputation)
● Diazepam
● Phenytoin
● Promethazine
● Thiopental
● NOT PROPOFOL (minimal local tissue injury)
Medications causing HYPERKALEMIA:
● ACE-I/ARBs
● Non-selective Beta-blockers
● NSAIDS
● Digoxin
● Succinylcholine
● K-sparing diuretics
● Heparin
● Mannitol
● Pentamindine
● Triamterene
● Trimethoprim
Adverse Effects of Sodium Bicarbonate administration
● increased preload
● decreased left ventricular contractility
● increased hemoglobin affinity for oxygen (left shift)
● associated with intracranial hemorrhage, especially rapid admin in infants
● increased lactate production
Volatile Vapor Pressures & MAC
● “Double HI-SEE”: halothane/isoflurane>sevoflurane/enflurane
1. Desflurane: 680 (MAC: 6.0)
2. Halothane: 243 (MAC: 0.75)
3. Isoflurane: 240 (MAC: 1.2)
4. Sevoflurane: 160 (MAC: 2.0)
5. Enflurane
Complications of Lithotomy position:
● Stretch injury to sciatic nerve- lower leg/foot
● Compression injury to nerves under inguinal ligament
○ Obturator n. - medial thigh
○ Lateral femoral cutaneous n.- lateral thigh
Fluoride Ion Production
● Methoxyflurane (+tox) > sevoflurane > enflurane(+tox) > isoflurane > desflurane
Order of non-depolarizing muscle relaxant potentiation:
● desflurane > sevoflurane > isoflurane > halothane > TIVA (e.g. propofol)
Citrate toxicity
● occurs with any blood product that uses citrate as an anticoagulant
○ highest during fresh frozen plasma administration
○ can occur with any blood transfusion
● Risk factors:
○ pediatric patient populations
○ significant liver disease or undergoing liver transplantation
○ hyperventilated
○ Hypothermia
Characteristics shared by substance abusing anesthesiologists:
1) 50% are < 35 years old
2) Residents are overrepresented
3) Many are Alpha Omega Alpha members
4) 33-50% are polydrug abusers
5) For 76-90%, opioids (e.g., fentanyl and sufentanil ) are the abuse drug class of
choice
6) 33% have a family history of addiction
7) 65% are associated with academic departments
● hypokalemia,
● hypomagnesemia,
● hyponatremia,
● hyperuricemia,
● metabolic acidosis
● respiratory alkalosis
Spinal Anatomy:
● Newborns
○ conus medullaris at L
○ dural sac typically ends at S
● Adults
○ conus medullaris at L1-L
○ dural sac typically ends at S1-S
Large R wave in lead V1:
● 1) Right ventricular hypertrophy
● 2) Posterior wall MI
● 3) Wolff-Parkinson-White syndrome
● 4) Muscular dystrophy
● 5) Right atrial enlargement
● 6) Right ventricular strain with ST-T wave abnormalities
Polymorphisms
● Cytochrome P450 2C19 ( CYP2C19 ) is responsible for the metabolism of proton
pump inhibitors, such as omeprazole, and antidepressants which may lead to
therapeutic success or failure of these medications depending on if the enzyme
is hyperactive or underactive (A)
○ PPIs: omeprazole
○ Antidepressants
○ Clopidogrel (prodrug, testing, prasurgel alternative)
● Cytochrome P450 2C9 ( CYP2C9 ) metabolizes phenytoin, warfarin, and ibuprofen
(B). Poor warfarin metabolizes can have excessive anticoagulation
○ Phenytoin
○ Warfarin
○ Ibuprofen
● Cytochrome P450 2D6 ( CYP2D6 ) is a particularly important P450 enzyme to
anesthesiologists as it metabolizes many medications we administer such as
codeine, beta-blockers, some antiarrhythmics, diltiazem, and tramadol (C).
These medications rely on CYP2D6 for creation of active metabolites.
○ Codeine-->Morphine
■ " coDeine" 2 letters then D and 6 letters total aside from the D
(2D6)
○ Beta-blockers
○ Some antiarrhythmics
○ Diltiazem
○ Tramadol
● a polymorphism in the OPRM gene may render morphine less effective in
some patients
● melanocortin 1 receptor ( MC1R ) gene, which is also associated with red hair,
may lead to increased analgesia (D)
○ Red hair
● Cytochrome P450 3A4 ( CYP3A4 ) is responsible for the metabolism of most
anesthetics, lidocaine, and dexamethasone. For example, midazolam inhibits
CYP3A4 which can prolonged the effect of fentanyl.
○ Most anesthetics!!!
○ Lidocaine
○ Dexamethasone
○ Midazolam inhibits CYP3A4 , which can prolong effect of fentanyl
○ St. John’s wort induces CYP3A
Etomidate causes adrenal suppression of cortisol production by inhibiting
mitochondrial 11β-hydroxylase , preventing the conversion of 11-deoxycortisol to
cortisol.
The 11 non-reassuring findings for DIFFICULT INTUBATION are:
1) Relatively long incisors
2) Prominent “overbite”
3) Patient cannot bring mandibular incisors anterior to maxillary incisors
4) Less than 3 cm interincisor distance
5) Uvula is not visible when tongue is protruded with patient in sitting position
6) Highly arched or very narrow palate
7) Mandibular space that is stiff, indurated or occupied by a mass
8) Less than three ordinary finger breadth thyromental distance
9) Short neck length
10) Thick neck circumference
11) Decreased extension or flexion of the neck
During an inhalational induction, the FA/FI ratio of insoluble agents (e.g. desflurane,
nitrous oxide) rises more quickly than that of soluble agents because insoluble agents
are not readily taken up and dissolved into alveolar venous blood. Moderate changes in
cardiac output and minute ventilation do not significantly alter the rate of rise of FA/FI of
insoluble agents. The rate of induction for soluble agents with higher blood:gas partition
coefficients (e.g. isoflurane, halothane) can be increased significantly with higher minute
ventilation and a reduction in cardiac output.
● Reaction time (R) is from time zero to initial clot formation, defined as a width
(amplitude) of 2 mm. Normal range is 1-3 minutes.
○ Short R values result from aggressive factor replacement or
hypercoagulable state
○ Prolonged R values result from coagulation factor abnormalities, factor
deficiencies or heparin administration. Treatment consists of giving fresh
frozen plasma (FFP)
○ R value prolonged -> FFP
● Coagulation time (K) measures speed of clot formation and strengthening. It is
equal to the time from amplitude of 2 mm to 20 mm and relies on fibrinogen.
Note that some TEG images show varying lengths for K, but it is always
measured to 20 mm amplitude.
○ Prolonged K values suggest deficiencies of thrombin formation or
generation of fibrin from fibrinogen/inadequate fibrinogen
○ K value prolonged -> cryoprecipitate.
Functional residual capacity increases with age due to loss of elastic lung tissue which
acts as an inward force pulling the lungs closed. An increase will also be seen with
increased height secondary to the larger lungs compared to short counterparts.
