Upload
jocelyn-mccoy
View
218
Download
1
Tags:
Embed Size (px)
Citation preview
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 pre-operatively instead of 1 gram if the patient is > 80 kg.
ANESTHETIC DRUGS / MONITORS
Routine Monitors
• 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 anti- convulsants 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
• 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 Blockers- Nondepolarizing Drugs
• 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
• 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
• Minimal signs under GA.
• Hypotension.
• Hemoglobinuria.
• DIC ( “oozy” NYD ).
• Blood for re XM and hemolysis workup.
• Die from DIC and ARF.
Autologous donation
• 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. 36.7C 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 35,5C vs. 36,6C 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 0,25C.
• 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):
- 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
• 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