Anesthesia Flashcards
Inhaled induction agents
Cause respiratory depression, most have myocardial depression, increased cerebral flow, and decreased renal blood flow
MAC
minimum alveolar concentration. Smallest concentration that causes 50% of people to not move with incision.
Smaller MAC = more lipid soluble-> more potent less water soluble slower the speed
Speed of induction inversely proportional to solubility. NO is fastest but, has low lipid solubility, has high MAC, low potency
Sevoflurane
MC used. Fast, less laryngospasm. Less pungent. Good for mask induction
Desflurane
Most rapid onset/offset. Pungent, not used for induction, reserved for maintenance
Nitrous oxide NO2
minimal myocardial depression. Always used with sevoflurane or desflurane. Do not use with SBO or PTX
- Causes tremors
Halothane
highest degree of cardiac depression and arrhythmias. Least pungent→ Good for kids
Volatile anesthetic hepatitis
fever, eosinophilia, jaundice, Increase LFT
Isoflurane
Good for neurosurgery, (lowers brain o2 consumption, no increase in ICP). Pungent, not used for induction
Enflurane
can cause seizures
MCC of intra-op bradycardia
inhaled anesthetic. Tx: atropine
Inhalation induction agents
Nitrous oxide, halothane, sevoflurane, isoflurane, enflurane
Intravenous induction agents
Propofol, ketamine, etomidate
Propofol
-Not an analgesic
-Metabolized in liver
-Provides bronchodilation #1 choice to patients with asthma or airway disease
- Best one to prevent post op nausea and vomiting
- Side effects: respiratory depression, hypotension
- Propofol infusion syndrome – causes bradycardia (must have this for dx), and METABOLIC ACIDOSIS, with hyperkalemia, renal failure, rhabdomyolysis, hepatomegaly, CHF. increased risk in kids
- Can measure CPK and lactate levels daily to catch early
- Treatment: stop propofol and start hemodialysis
- Propofol contraindicated in egg allergy, pregnant, Parkinson’s
Dexmedetomidine (Precedex)
alpha 2 receptor agonist. Does not cause respiratory depression. Can decrease BP
-Anesthesia and analgesia
-sedation agent for intubated patients; not an induction agent
-Not recommended for more than 24 hours
Ketamine
-Amnesia, analgesia
-No respiratory depression, good for children, safe with head injury
– Ischemic heart disease: can cause HTN and tachycardia leading to increased myocardial oxygen consumption
-Historically contraindicated in patients with elevated ICP and intraocular P; however no longer absolute contraindications
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Etomidate
Fewest cardiac side effects
Not an analgesic
SE: adrenal insufficiency/ supression, myoclonus, stevens-johnson syndrome, trismus
…post op fever, hypotension, hypokalemia
Rapid sequence intubation
Pre-oxygenate, etomidate, succinylcholine, cricoid pressure
1st/last muscles to go down/recover
Diaphragm: last muscle to go down, 1st muscle to recover from paralytics
Neck & face muscles: 1st to go down, last to recover
Succinylcholine
*Only depolarizing agent & only one that causes fasciculations
-Metabolized by plasma pseudocholinesterase.
Atypical pseudocholinesterase causes prolonged paralysis with succinylcholine (Asians). Not reversible. Have to wait till it wears off.
-Open-angle glaucoma can become closed-angle glaucoma
Contraindicated in:
- neurologic diseases (spinal cord injury, neuromuscular disorders) Have upregulation of Ach receptors: hyperkalemia
- In head injury: increases ICP
-Severe burns, acute renal failure
Malignant hyperthermia
Malignant hyperthermia
Defect in calcium metabolism
Calcium released from sarcoplasmic reticulum causes muscle excitation- contraction syndrome (ryanodine receptor defect)
SE: 1st= increase end-tidal CO2, then fever, tachycardia, rigidity, acidosis, hyperkalemia, rhabdomyolysis
Tx= dantrolene (10 mg/kg) inhibits Ca release and decouples excitation complex; cooling blankets, HCO3, glucose
Non-depolarizing agents
inhibit neuromuscular junction by competing with acetylcholine
Cis-atracurium, rocuronium, vecuronium, pancuronium
Cisatracurium (Nimbex) – Hoffman elimination. Use this if patient has liver or kidney disease!!!!
Pancuronium – metabolized in kidney. Slow and long acting. MC SE is tachycardia. DON’T USE IN ANY ARRYTHMIA or CAD.
Rocuronium – 1 mg/kg for induction. Fastest acting. metabolized in liver. Little effect on blood pressure. Short half life
Vecuronium – Metabolized in kidney. Short half life
Reversal of non-depolarizing agent – Sugammadex is best. Also can use Neostigmine or edrophonium to block Ach-esterases. Add atropine or glycopyrrolate to counteract Ach overdose
Local anesthetics
Amides - have 2 I’s. Lidocaine, bupivacaine, mepivacaine. Rarely cause allergic reaction
Esters - tetracaine, procaine, cocaine. Has higher risk of allergic reactions due to PABA
Benzocaine: can cause methemoglobinemia
Narcotics (opioids)
Narcotics (opioids) – causes respiratory depression, NO cardiac affects. Morphine causes hypotension from histamine release
Act on mu receptor in CNS
Liver metabolism and kidney excretion
Avoid morphine and codeine in renal injury
Dilaudid is metabolized in liver but only small amount excreted in kidney. OK to use in AKI
Fentanyl and methadone = safest to use in ESRD
Demerol - meperidine
- SE→ Tremors, fasciculations, coma, seizures, avoid in patients with renal failure
- Avoid with MAOI, can cause hyperpyrexic coma→ serotonin release syndrome
- No histamine release
Fentanyl – no histamine release. Can give if pt has morphine allergy
Sufentinel – Most potent
Benzos + opioid has synergistic effects
Benzos
Metabolized in liver
Binds GABA
-Versed (midazolam): short acting; crosses placenta
-Valium(diazepam) & Ativan (lorazepam): long acting
Overdose= flumazenil
Serotonin syndrome
rigidity, tachycardia, sweating, hyperthermia, seizure
Epidural & Spinal anesthesia
Epidural – Sympathetic denervation, only affects sensory, not motor.
- Causes vasodilation
- Lowers respiratory and cardiac complications post op vs IV narcotics. No effect on mortality
- Anesthetic is placed outside the dura, In epidural space
- Avoid insertion at T5 or higher, affects cardiac nerves bradycardia
- Thoracotomy T6-T9
- Laparotomy T8-T10
- Morphine causes respiratory depression use dilaudid
- Morphine epidural does not cause hypotension
- Lidocaine causes bradycardia and hypotension Turn off epidural, give fluids, phenylephrine, and atropine if severe
- If leg numb: Turn down epidural rate
- CI to epidural – elevated intracranial pressure, hypertrophic cardiomyopathy, cyanotic heart disease, aortic stenosis, elevated ICP, systemic infection
Epidural hematoma – sudden back pain at epidural site, loss of sensation and motor in extremities. Loss of bowel bladder control. Dx: MRI, Tx: emergent laminectomy
Spinal headache – caused by CSF leak after spinal or epidural. Headache is worse with sitting up. Patients prefer to be supine. Tx: rest, fluids, caffeine. Blood patch if persists > 24 hours
Spinal anesthesia = motor and sensory blockade. Injected into subarachnoid space= intrathecal space. Must be injected below L2 to avoid spinal cord. Single shot.
Predicators of major cardiac complications
Low-risk surgeries confer < 1% risk of myocardial infarction (MI) and include cataract surgery, breast surgery, and endoscopy.
Medium-risk surgeries confer a 1-5% risk of MI and include most head and neck surgeries, thoracic surgeries, abdominal surgeries, orthopedic surgeries, and carotid endarterectomy.
High-risk surgeries confer >5% risk of MI and include emergent operations, cardiac surgeries, and major vascular surgeries except carotid endarterectomy.
Pre-operative 12-lead ECG is recommended for patients with known coronary artery disease, arrhythmia, peripheral arterial disease, cerebrovascular disease, or other significant structural heart disease undergoing surgery that is associated with a medium to high risk of peri-operative MI.
Percutaneous angioplasty only – wait 2 weeks before surgery
Bare metal stent – 4 weeks before elective surgery
DES – 6 months
Wait 6 weeks after MI before elective surgery
Mets/ cardiac evaluation
4 METs are climbing a flight of stairs, walking up a hill, walking on level ground at 4 mph, and performing moderate intensity work around the house.
Comorbidities with high risk of peri-op cardiovascular events
CHF (Highest risk), ischemic heart dz, CVA, DM, ESRD or AKI Cr > 2
If any above figure out METS
- < 4 mets slow walking, light effort on stationary bike Need pharmacologic stress test
- > 4 mets climb 1 flight of stairs without stopping, walking uphill 1-2 blocks No need for testing
Intubated and sudden rise in ETCO2
Intubated patient with sudden rise of ETCO2:
1. Hypoventilation
2. CO2 embolus
3. Malignant hypothermia
4. Capnothorax
MCC hypoventilation (tx= increase TV or RR)
Co2 embolus will cause transient rise of ETCO2 with quick fall of ETCO2
- CO2 embolus is most commonly associated with a DROP of end tidal CO2 (lack of blood flow to lungs)
-CO2 embolus associated with hypotension
-High end tidal CO2 during mediastinal dissection (EG Nissen) is most likely capnothorax (pneumothorax due to pleural tear)
-Enlarge tear to avoid tension capnothorax
-Place red rubber catheter with one end into pleural tear and other end into abdomen (equalizes pressures)
-At end of procedure bring one end outside of abdomen and place to water seal while Valsalva administered
-Can also needle decompress intra-operatively – be sure to prep lower chest
Intubated and sudden drop in ETCO2
Sudden drop of ETCO2: MC disconnected from vent
Also, PE or air embolism, or CO2 embolism; cardiac arrest (all have hypotension)
Air embolism: trendelenberg (head down) + left lateral decubitus position; hyperventilate
ASA
ASA 1 healthy. 2 mild disease Controlled HTN, diabetes, smoker, 3 severe disease, hx of MI, uncontrolled HTN or DM, Controlled COPD. 4 severe disease with threat to life, unstable angina, decompensated CHF, ESRD, cirrhosis. 5, moribound patient, ruptured AAA, saddle embolus. 6 Donor
Shoulder pain after abdominal laparoscopy
Induction of pneumoperitoneum stretches the diaphram, which irriates the phrenic nerve, which causes referred pain to the shoulder. C3-5= phrenic nerve
Brachial plexus bloc now pleuritic chest pain, breathlessness, desaturates
Iatrogenic pneumothorax: pleuritic chest pain, dyspnea, hypoxemia
PUnctured apical pleura
Perioperative Management Recommendations for Cardiac-Related Medications
-Beta-blockers: continue peri-operatively to reduce cardiac morbidity (can pause if bradycardia, hypotension)
-Aspirin: can continue throughout most elective surgical procedures
P2Y12 antagonists (clopidogrel, prasugrel, ticagrelor)
-Hold typically 1 week before elective surgery after at least 6 months of dual-antiplatelet therapy after percutaneous coronary intervention (at least 1 month if time-sensitive surgery)
-Stop clopidogrel at least 5 days before procedure (restart with loading dose)
-Stop ticagrelor 3-5 days before surgery
Warfarin: hold 5 days before procedure
Direct thrombin inhibitor (dabigatran)
-If Cr clearance >50 mL/min, stop 1 day before surgery in low risk bleeding; 2 days if high risk bleeding
-Cr 30-50: 2 days before for low risk bleeding, 5 days before for high risk bleeding
Factor Xa inhibitors (rivaroxaban, apixaban): 48 hours before surgery (24 hours if low risk bleeding); resume 24 hours after in low risk bleeding, 48-72 hours in high risk bleeding
