Anesthesia_Review

7/29/2019 Anesthesia_Review

1/42

Anesthesia Review

Vic V. Vernenkar, D.O.

St. Barnabas HospitalDept. of Surgery


2/42

The Anesthesiologist


3/42

Initial Assessment

ASA classification is part of the physical

examination of the patient.

Is graded classes 1-6 in order of increasingrisk of mortality.


4/42

ASA Classification

Class 1 Healthy

Class 2 Mild systemic disease, no func limitations

Class 3 Moderate to severe systemic disease,functional limitations

Class 4 Severe systemic disease, constantly life

threatening, functionally incapacitating

Class 5 Not expected to survive with or without

surgery 24h

Class 6 Organ Donor

Class E Emergency


5/42

Monitoring

Noninvasive BP monitoring with

appropriate cuff size.

Invasive BP monitoring (A-line) for electivehypotension, anticipation of wide variations

in BP, need for frequent blood sampling.

Common sites are femoral and radial sites.Dont use Brachial artery.


6/42

Monitoring

EKG for detection of dysrhythmias, myocardialischemia, electrolyte abnormalities.

Leads V2 and V5 together detect 95% of

intraoperative ischemia, allowing for earlyintervention.

Pulse oximetry estimates level of oxygen bindingby hemoglobin

SaO2 of 70%, 80%, and 90% correlates to PaO2of 40, 50, 60.


7/42

Monitoring

Temperature- Axilla, esophagus, pharynx, bladder.

Urine output- a measure of end-organ perfusion;

Foley for all cases over 2 hrs,to decompress

bladder (lap procedures).

Swan-Ganz- for LVEDP, CO, SVR.

Capnography- confirms adequacy of ventilation,

ETT placement, estimates PaCO2.

Unexpected rise in CO2: Malignant hyperthermia.


8/42

Induction of Anesthesia

IV or mask induction of general anesthesia.

Combination of agents based on patient

characteristics, and procedure.Includes an amnestic, analgesic, hypnotic,

muscle relaxant, and a volatile agent.

Rapid sequence induction.


9/42

Rapid Sequence Induction

Pre-oxygenate with 100% allows de-nitrogenation of patients FRV, extra time.

Indications include recent oral intake,GERD, delayed emptying, pregnancy,bowel obstruction.

Lidocaine, Atropine, Etomidate,

Rocuronium (when Succinylcholine iscontraindicated), Versed.


10/42

Analgesic Agents

In boluses at induction and before incision, thenmaintenance as needed.

Additional doses based upon sympathetic response

to pain, like increased HR, BP.Fentanyl, a synthetic narcotic, onset 2min, peak5min. Metabolized by liver.

Gag is blunted, minimal cardiac depression, can

induce respiratory arrest.

40 times potency of morphine, no cross allergythough.


11/42

Analgesics

Morphine- 5min onset, peak at 20min.

Metabolites cleared by kidney

Histamine release with hypotensionpossible.

Ketamine- PCP analog, intense analgesia,

amnesia, dissociative anesthesia.


12/42

Analgesics

Ketamine increases HR, BP,bronchodilator, maintains spontaneousventilation. Increased CBF.

Illusions, dysphoria.

Not a respiratory depressant, can be soleanesthetic agent.

One of several induction agents, good forchildren, contraindicated in head injury.


13/42


14/42

Sedative-Hypnotic Agents

Sodium thiopental, a barbiturate, induces

unconsciousness within 30 seconds without

analgesia.Excellent anticonvulsant.

After single dose drug redistribution into

muscle may result in rapid awakening.


15/42


Side effects: hypotension (in hypovolemia),heart

failure, beta blockade, resp. arrest, decreases CBF,

metabolic rate.

Propafol, fast acting, no hangover (great for

outpatients) antipyretic, antiemetic.

Rapid metabolism by liver.

Side effects: hypotension, blunting of airwayreflexes helping in intubation, resp. arrest.


16/42


Used for maintaining anesthesia, sedation in

ICU.

1.1kCal/mL!Etomidate, fast acting, minimal

hypotension, great for induction.


17/42


Rapid metabolism by liver, avoid

continuous infusions as can cause

adrenocortical suppression.Can cause myoclonus.

Benzodiazapines, provide anxiolysis,

hypnosis, amnesia, anticonvulsant, skeletalmuscle relaxant properties.


18/42


No analgesic properties here.

Versed most common, short acting, liver

metab, so watch it.crosses placenta.Ativan long acting.

Flumazenil is a benzodiazapine

antagonistassociated with seizures!


19/42


20/42

Muscle Relaxants

Used to facilitate intubation.

During abdominal surgery.

When movement can be devastating.Paralyzed but still feel and remember

everything!

No analgesia, hypnosis, or amnesia.

Diaphragm last to go down, first to recover.

Neck Muscles first to go down, last to recover.


21/42

Muscle Relaxants

Depolarizing and non-depolarizing.

Depolarizing agents cause an initial

transient muscle fiber activation beforerelaxation occurs.


22/42

Muscle Relaxants(Depolarizing)

Succinylcholine, provides rapid

depolarizing blockade. Mimics

acetylcholine, 30 seconds, short duration 5-10 min.

Rapidly metabolized by plasma

pseudocholinesterase.

The only one!


23/42

Muscle Relaxants(Depolarizing)

1in 3000 homozygous for trait where it isabnormalprolonged paralysis.

Increase in serum potassium.cardiac arrest in

some.Contraindicated in stroke, burns, trauma,myopathy,bedridden, renal failure.

Malignant hyperthermia rare complication of

succinylcholine.An autosomal dominant disorderof skeletal muscle calcium metabolism.


24/42

Malignant Hyperthermia

Combo of volatile anesthetic plus succs.

First Sign is Increased end-tidal CO2.

Acidosis, muscle spasm.

Hypertension, arrhythmias.

Hypoxemia, hyperkalemia

Tachycardia, pyrexia.

Myoglobinuria.Tx: IV Dantrolene 10mg/kg, cool, D/c volatileagent.


25/42


26/42

Non-Depolarizing

Rocuronium

Pancuronium

VecuroniumAtracurium

Mivacurium

All inhibit acetylcholine at NMJ.

No fasciculation, or increase in potassium.


27/42

Non-Depolarizing

Rocuronium, fast, used when succscontraindicated.

Pancuronium, inexpensive, used for prolonged

paralysis, tachy, prolonged in renal.Mivacurium dependent on pseudocholinesterase.

All potentiated by hypokalemia, calcemia,hypermagnesemia.

Monitored by peripheral nerve stimulation.

To reverse, use Neostigmine (blocks acetylcholinesterase) plus anticholinergic agent (tocounteract brady) at end of surgery.


28/42

Airway

Mask ventilation used at time of induction.

Can be sole means of airway in patients withminimal risk of aspiration.

Ventilation also facilitated by oral or nasalairway (tongue, awake patient).

LMA lodges in hypopharynx superior to larynxpreventing soft tissue obstruction of airway.

Contraindicated in aspirators, paralyzed, need forcontrolled ventilation.


29/42

LMA


30/42

Airway

Endotracheal Intubation allows for ventsupport, oxygenation, relative protection ofairway.

Confirm position by checking bilateral chestrising, condensation in ETT, End-tidal CO2,bilateral breath sounds.

Fiberoptic laryngoscopy in difficultintubations.


31/42

Inhalation Anesthetic

Afterinduction anesthesia is maintained

with a volatile anesthetic.

Provides hypnosis, amnesia, some degree ofanalgesia and muscle relaxation.

Differ in blood solubility, potency, side

effect profiles.


32/42

Inhalation Anesthetic

Minimum Alveolar Conc. (MAC) is the

smallest concentration at which 50% of

patients will not move in response to

surgical incision.

Solubility of agents correlates with speed of

induction, so insoluble agents provide

quickest onset.


33/42

Inhalation Anesthetic Agents


34/42

Volatile Agents

Halothane

Isoflurane

SevofluraneDesflurane


35/42

Side Effects of Volatile Agents

Hypotension via cardiac depression

(halothane) or vasodilitation.

Arrythmogenic (halothane) potentiated byepinephrine.

Isoflurane least cardiac depressant, most

coronary artery dilation.


36/42

Side Effects of Volatile Agents

Rapid, shallow breathing resulting in decreased

minute ventilation, bronchodilation.

Blunts hypoxic drive

Impair cerebral auto regulation, or ability of brain

to maintain cerebral blood flow over a wide range

of BPs.

Isoflurane used in ICP patientsHalothane rarely causes Hepatitis.


37/42

Nitrous Oxide

Not potent, requires large inhalationconcentrations.

Insoluble in blood

Minimal cardiac depression, BP changes little. Nomuscle relaxant properties like volatile agents.

Not bronchodilator, increases PVR.

May expand air cavities by diffusing in faster thandiffuses out.ba-boom. Avoid in PTX, SBO,middle ear occlusion.


38/42

Regional Anesthesia

Spinal Anesthesia, L3-L4 interspace. Free flowof CSF confirms subarachnoid placement wherelocal is injected.

Anesthesia occurs in minutes, lasting up to 2 hrsdepending on agent and dose.

Level of sympathetic block higher than sensoryblock, this in turn above level of motor block.

Sympathetic block results in hypotension.High spinal results in respiratory depression.

Motor recovers before sensory.


39/42

Spinal


40/42

Regional Anesthesia

In Epidural anesthesia, a catheter is placed

in epidural space allowing for continuous

infusion to relieve postoperative pain.

Final level of sensory blockade depends on

volume injected not dose.

Onset slower than spinal.


41/42


42/42

Date post:	04-Apr-2018
Category:	Documents
Upload:	mukhtar-khan
View:	220 times
Download:	0 times

Anesthesia_Review

Documents