General Anesthesia
POS April 14th 2009
Outline
1.Anesthesia Drugs / Monitors.
2. Anesthesia Events in the OR.
3. Anesthesia Consults.
Am I missing something ?
• Miller - 6th ed, 3204 pages (subtract about
800 pages for regional / pain)
• Sabiston – 18th ed, 2353 pages.
Am I missing something ?
•
Miller – 6th ed. , 3204 pages.
• Sabiston – 18th ed. , 2353 pages. Takes
five years to cover the
material
Am I missing something ?
• Miller - 3204 pages. We
can cover
this in 60 to 90 minutes.
•
Sabiston – 18 ed . 2353 pages.
And the POS exam is over !
• I’ll wake you up at the end.
Biggest change for you since 2008?
Biggest change for you since 2008?
• Ask for 2 grams of Cefazolin preoperatively instead of 1 gram if the patient
is > 80 kg.
ANESTHETIC DRUGS /
MONITORS
Routine Monitors
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ECG.
BP.
Oximetry (use the ear probe in shock).
End Tidal CO2 .
Temperature (axillary vs. core).
Future : Depth of anesthesia - BIS.
(Bispectral index EEG) - scale from 0 to
100
March 2008 ,NEJM negative BIS trial.
ETCO2
• Continuous monitor in OR.
• Monitor of position of ETT (after 6 breaths).
• Monitor acute decrease - ↓ Cardiac Output,
Embolism.
• Monitor acute rise - for M.H.
Intravenous Drugs
1 .Propofol - less hangover, good anti emetic .
Very easily contaminated. Pain on injection,
2 .Pentothal and Propofol - potent anticonvulsants and ICP.
- BP
- resp depressants
3. Ketamine - maintains BP, maintains
respiration, but  ICP. IM useage.
Neuromuscular Blockers Succinylcholine
• Can cause excess K+ release in certain
conditions -ACUTE neuromuscular
disease, burns > 20%.
•  IOP.
• C / I in MH.
• 5 minutes to recover from – metabolized by
plasma cholinesterase . Cannot reverse its
effect with other drugs
Nitrous Oxide
• MAC - 104%.
• Enlarges air containing closed spaces e.g.
obstructed bowel, middle ear, eye with SF6 ,
pneumothorax, VAE.
• Negative outcomes large studies
• High FIO2 and wound infection
• Not often used - air /oxygen
Vapours
• All C / I in MH.
• Lipid solubility important so awaken
quickest from Desflurane.
• Pungency - Sevoflurane least (epiglottitis).
For inhalation induction /kids
Toxicity vapours
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Halothane hepatitis (1:10 000)
Isolated single reports with other vapors.
Sevoflurane - possible nephrotoxic Fl- ion
Nitrous Oxide - Possibly  rate of
spontaneous abortion (RR 1.3) and
congenital abnormalities (RR 1.2). ?Recall
bias,voluntary response.
Neuromuscular BlockersNondepolarizing Drugs
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Cisatracurium, Pavulon, Rocuronium.
Safe in M.H. but can cause anaphylaxis.
Longer acting - 20 mins. to 90 mins.
Monitor with nerve stimulator (train of four)
But clinical testing e.g. head lift is best.
Can reverse action with cholinergic drug
e.g. neostigmine
ANESTHETIC INTRAOPERATIVE
EVENTS
ASA Score
1 - Healthy.
2 - Mild systemic disease, no functional
limitations.
3 - Severe systemic disease that limits activity.
4 - Incapacitating disease that is a constant
threat to life.
5 - Moribund, not expected to survive 24 hrs,
with or without surgery.
E - Emergency
ASA Difficult Airway Algorithm
• Not possible to visualize any of the vocal
cords = difficult.
• Mallampati score - one of many aspects of
airway assessment.
• LMA – rescue device but does not protect
vs. aspiration (Can be used as conduit for
FFOB).
Failed Intubation
• Management depends on whether can
ventilate or not.
• Different blades and smaller tube.
• LMA , Bronchoscope , Bougie, Glidescope
• Cannot intubate , Cannot ventilate - need
surgical airway.
Aspiration
• Risk factors - Morbid obesity, Pregnancy,
Massive ascites, Diabetes, Pain esp. trauma.
• Prophylaxis – H 2 blockers, Prokinetic
agents, Sodium Citrate.
• Rapid Sequence Induction (RSI).
• Presents as desaturation or wheezing.
• Guidelines : 6 hrs for light meal (clear fluid
and toast) to 8 hrs. (meat) and 2 hours for
clear fluids.
Malignant Hyperthermia
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Triggered by vapours and Succinylcholine.
Hypermetabolic state of muscles.
 ET CO2 , tachycardia (metabolic storm).
Arrhythmias from K+ release – VT,VF
Muscle rigidity and  temp -LATE signs.
Rx- Dantrolene (2,5mg/kg up to 10mg/kg),
Airway fire
1. Ignition source — cautery, laser, flammable
ointment alcohol based prep solution.
2. Fuel – drapes , PVC ETT.
3. Oxidizer near surgical site — Oxygen or
Nitrous Oxide.
• Laser surgery, Tracheotomy.
• Disconnect patient from machine, extubate
and extinguish with saline,ventilate or
reintubate, evaluate airway damage (rigid
bronchoscopy).
Gas Embolism
• Air, Helium, CO 2 .
• Operative site above heart, low CVP.
• Presents as  ETCO2, SaO2, millwheel
murmur, BP, PA pressures.
• Rx - D/C Nitrous, Trendelenburg, flood
field, aspirate from CVP catheter, left side
down (airlock RV), consider hyperbaric
oxygen.
Latex Allergy
• Multiple procedures, health care esp. dental
workers, spina bifida, food sensitivity.
• Prevent - glass syringes, remove top of vial,
1st case of day, premed optional.
• Onset after 20 - 60 minutes.
• Airway and 100% O2.
• Volume.
• Epinephrine - 0,1 micrograms / kg boluses
Massive Transfusion
• All complications of 1 unit -TRALI,
Immunosuppression.
• Hypothermia.
• Hypocalcemia from citrate.
• K + abnormalities (> 120 ml/ min).
• Dilutional coagulopathy.
ABO Transfusion Reaction
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Minimal signs under GA.
Hypotension.
Hemoglobinuria.
DIC ( “oozy” NYD ).
Blood for re XM and hemolysis workup.
Die from DIC and ARF.
Autologous donation
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EPO and Iron supplementation.
Clerical error (1: 100 000).
Yersinia enterocolitica contamination.
May not be enough blood.
Anemia.
Hypothermia
• Core and peripheral component ,with tonic
constriction normally.
• 1st hour – rapid drop 1,5 °C – vasodilation.
• 2nd stage - slow linear decrease for 2 -4 hours of
1,5 -2,5 ºC as heat loss exceeds metabolic heat
gain . (radiation*,convection, evaporation,
conduction)
• 3rd stage - plateau after 2- 4 hours
Adverse Effect Hypothermia
• Cardiac - RCT 35.4°C vs. 36.7C in 300
patients undergoing abdo, vascular, thoracic
(JAMA April 9 1127, 1997 ).
• Postop morbid cardiac events: 1,4%vs 6,3%
• VT : 2% vs. 8%.
• Infection - RCT 200 patients undergoing
colorectal surgery 34,7° vs. 36,6°- 3 x risk
wound infection (NEJM 1996 334, 1209).
Adverse effects hypothermia
• Blood loss - 500 ml greater 35,5C vs.
36,6C in THA ( Lancet 1996 347 289)
• Coagulopathy - platelet dysfunction and
sequestration in liver, false negative normal
PTT as lab always warms blood to 37.
• 1 litre fluid or 1 unit blood  temp 0,25C.
• Forced air warming best method ($10)
Positional Injuries
• Ulnar - commonest (male, >4hrs, BMI<20
or >40). 27% used extra padding.Often
delayed onset, at day 3. Occurs in regional
anesthesia also.
• Brachial plexus- median sternotomy, steep
Trendelenburg with shoulder braces,prone
esp. head to opposite side (females)
Positioning
• Arms < 90° when supine.
• At side, neutral position.
• On arm board – supinate.
• Chest roll  risk brachial neuropathy.
DNR
• Patient or SDM. – 3 choices for OR:
1.DNR intact.
2. DNR partially rescinded .
3. DNR rescinded completely
• Discuss specifics and goals - chest compressions,
pacing, defib, vasoactive drugs, postop ventilation,
postop ICU ( time limited).
Awareness
• MAC. – 50% don’t respond in to pain in a
“grossly purposeful” manner. Use surgical
incision as stimulus.
• Sandin – 18 / 11785 ( 0,15%). Trauma, OB,
CV surgery.
B – Aware trial . 2 vs. 11 cases using BIS
(bispectral index)
Laparoscopic Physiology
• CVS - Trendelenburg or reverse
- tachycardia from  venous
return,CO2
- bradycardia from insufflation
• Resp - PCO 2 , atelectasis, subcutaneous
emphysema, pneumothorax, CO2
embolus,venous stasis
Laparoscopy
• Hypothermia
• Impaired renal flow
•  ICP
PONV
• Risk factors – female, nonsmoker, volatile
agents, nitrous oxide, opioids, laparoscopy,
middle ear, strabismus, breast surgery.
• Prophylaxis – Serotonin antagonists e.g.
Ondansetron.
- Dexamethasone 4 - 8 mg IV.
- Dimenhydrinate.
Anesthesia Consults
Risks of Anesthesia
CEPOD - Mortality rate total contribution :
1. Patient factors 1: 870.
2. Surgical factors 1: 2860.
3. Anesthesia 1: 185,056 totally.
Anesthesia partially 1: 1430.
Fleisher - 564 267 outpatient , ASC , Office. Had a
mortality of 25 -50 / 100 000.
Newland - intraop arrest – 1/14 000.( 1/10 000)
Myocardial ischemia
• Risk of surgery - High ,intermediate and
low.
• > 4 Mets.
• Beta blockade preoperatively- Atenolol, 200
patients - Noncardiac surgery. NEJM 1996
335, 1713.
• Bisoprolol in vascular patients - NEJM
1999, 341, 1789.
POISE Trial
• Beta blockers decreased myocardial
infarction , but increased stroke rate and
overall mortality likely from decreasing
blood pressure.
• Risk / Benefit now much more uncertain
AHA guidelines
• Five risk factors (Lee or RCRI):
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History CAD
History heart failure
History of CVA
Renal insufficiency
Diabetes
Stents and elective surgery
• Bare metal – minimum safe Plavix duration
before discontinuation is 30 days.
• Drug Eluting - only safe to stop Plavix after
365 days
Respiratory Disease
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GA -  FRC
GA -  Diaphragmatic function
Shapiro score
Po2 on room air <50, Pco2 45
Active wheezing
Site of surgery especially upper abdomen
and thorax
Respiratory disease
• Quit smoking > 8 weeks does  resp
complications (14.5% vs. 33% in 200 ACB)
(Prospective, Mayo Clinic Proc 1989 ,64
609).
• <48 hrs  COHB levels and  ciliary
activity.
• 1-2 Weeks to  sputum.
• PFT- only to diagnose,not prognosticate.
AJRCCM Mar 1 2005.
Respiratory disease
• Laparoscopic approach- better ABG’s, PFT.
• Epidural may be better- Meta analysis
showed less atelectasis.
• Lung expansion manoevres postop work
Herbal remedies
• CVS - Ginseng, Ephedra, St. Johns Wort,
dietary  hyperadrenergic
• Bleeding - Ginko, Vit E, Ginger
• Hepato and nephro toxic
• Natural herb CPS
• www.herbnet. com
OSA
• 3 Scoring factors:
1. Severity - AHI (6-20, 21-40, >40).
2. Invasiveness surgery.
3. Narcotic needs postoperatively.
• CPAP use or not?
• Ward, ward with 24 hr oximetry, Step-down
Summary
• Think ICU post-op especially for the
emergency list patients (sepsis).
• Consult for multiple Lee cardiac risk
factors.
• OSA – beware need for step-down bed.
• Being available and in the OR at the
beginning and end of the case is greatly
appreciated and noticed.
Sickle Disease
• Hb AS -Trait - <40% S -only sickle at
extremes of O2 and temp, not anemic
• Hb SC - 50%S -eye, hip , pregnancy
borderline anemia
• Hb SS Disease > 80 %S, anemic
• Get HBS < 40%
• Keep warm and hydrated and oxygenated
MaVs Trial
• 496 patients for vascular surgery receive
metoprolol or placebo 2 hrs preoperatively
and for 5 days.
• Blinded.
• No difference in CV deaths or nonfatal MI
• CJA 2004 51 .
Ann Int
Med Nov
2001