2025 Intro to Clinical Anesthesia Exam 1 Flashcards
Basic Equipment, Perioperative/Induction
Goals of Perioperative Period
Ascertain risk of patient and procedure
Sort out of patient is/needs to be/can be optimized before surgery
Develop Anesthetic Plan to care for patient that respects patient wishes, surgical expectations and, your skillset.
General vs regional
Airway choice
Surgical Positioning
Steps for Taking a Solid Patient History
Obstacles to Talking with Patient
Poor Historian
Anxious or emotional
Overly Talkative
Language Barriers
Hearing/visual impairment
Angry/disruptive
Preoperative Period (Chart Review)
Chart review- Why are they here?
Chief Complaint
HPI- History of present illness
PMH- Past medical history
PSH- Past surgical history
Previous anesthetic experiences
Allergies and Medications
Physical exam
Chief Complaint and HPI
Why is the patient here today?
What’s been going on and for how long?
Can be found in surgeon’s history and physical (H&P)
Past Medical History (PMH) and Review of Systems
Pulmonary- OSA, smoking, Asthma, SOB, COPD, Home oxygen, recent URI
Cardiac- HTN, Angina, CAD, Arrythmia, orthopnea
ROS: Cardiovascular Review Questions
History of:
High BP?
Chest pain?- can be cardiac, pulmonary, or GI based
Heart ever skip a beat?
Funny noises when they listen to your heart?
Stenotic lesion vs leaky valve murmur
Heart attack?
Swollen hands/feet?
Can indicate congestive heart failure (CHF) or renal impairment
Sleep on multiple pillows?
Orthopnea can have cardiac or GI roots
Ever randomly have vision loss, limb weakness or dysphasia (trouble speaking and comprehending)?
Carotid artery disease/vasospasm
ROS: Coronary Artery Disease (CAD)
CV complications account for 25-50% of deaths following noncardiac surgery.
MI
Pulmonary edema
CHF
Thromboembolism
~10,000,000 Americans w/ CAD
750,000 w/ significant disease will undergo anesthesia/surgery for non-cardiac operations
5 to 7% will have perioperative MI
Mortality of intraoperative MI: 38-70%
ROS: Risk for Cardiac Event Under Anesthesia
Recent MI (surgery must wait 6-8 weeks)
Valvular Heart Disease
CHF
Unstable Angina (chest pain at rest)
Diabetes (associated with neuropathy can cause silent MI)
ROS: Metabolic Equivalent of Task (METS)
<4 METS associated with great increase in risk under anesthesia
ROS: Perioperative Cardiac Risk Management
Monitor for perioperative ischemia (ST Depression, cardiac markers ie troponin trending)
Repair before if able
Severe Aortic stenosis
Coronary Revascularization
Optimize CHF
Correct anemia, volume status, nutritional status, medication adjustments
ROS: Neurological
Stroke (CVA)/mini stroke (TIA)
Seizure hx
Parkinson’s
Paraplegia
Gross motor function difficulty
ROS: Tubes and Filters
Gastrointestinal (GI)
Acid Reflux
GERD
GI bleeding/Ulcerations
Hx weight loss surgery
Liver Disease- cirrhosis, hepatitis
Acute abdomen
Genitourinary (GU)
Kidney function
ESRD (dialysis schedule PD/HD)
Nephrolithiasis
BPH
Prostate Cancer
Recent UTI
ROS: Infections/Isolations
COVID
Sepsis
Methicillin resistant staph aureus (MRSA)
Clostridium difficile (C Diff)
TB
ROS: Musculoskeletal and Pain
Musculoskeletal
Implanted hardware
DJD (joint)/DDD (disk)
OA/RA
Muscular dystrophy
Pain
Acute v Chronic
Location
Daily opiate use
ROS: Endocrine and Hematologic
Endocrine
Diabetes (Type I v II)
Thyroid disease (want to worry about Hyperthyroid, Hypothyroid does not have any big complications with Anesthesia)
Chronic Steroids
Anti-inflammatory or immunosuppressive effects
Hematologic- Do you bleed or clot easy?
Hemophilia
Thrombocytopenia
Sickle Cell Disease
Anticoagulant therapy
Liver disease
Why Care About Periop Glucose So Much?
Hyperglycemia (GLU >200) is a risk factor
Postoperative sepsis- bacteria like sugar too
Endothelial disfunction- permeability and fluid shifts, NO production
Cerebral ischemia
Pro oxidation/inflammation/coagulant lead to higher lactic acid in ischemic tissues
Impaired wound healing
Poor perfusion
ROS: Obstetric and Gynecologic History
Preop HCG pregnancy test offered to all premenopausal woman
Cannot force or coerce a patient into a pregnancy test, as this violated patient autonomy
Current literature is inconclusive as to whether exposure to anesthesia causes unknown harmful effects in early pregnancy.
G: Gravity – total number of pregnancies
T: number of term pregnancies
P: number of preterm pregnancies
A: number of abortions, spontaneous or induced
L: number of living children
Generally abbreviated to G2P1
A patient that is G2P1 is pregnant and has one living child
Weeks and days gestation. 39 weeks and 4 days abbrev 39.4 weeks.
Is baby vertex or breech?
Previous C-section/hemorrhage?
Pregnancy complicated by PIH/GDM?
High Quantities - Recreational Drug Use and Anesthesia
Affect anesthetic requirements
Reactive airway d/t inhalation
Difficult IV access
Propofol cross-tolerance
If the patient was in a car accident, were they given fentanyl already… will affect how much you can give
Psychiatric Considerations
Anxiety- baseline benzodiazepine use may increase anesthetic requirements
Depression- Very small risk of serotonin syndrome
PTSD- can affect induction/emergence
Bipolar/schizophrenia- Lithium can prolong NMB and decrease anesthetic requirements
NPO Status
Commonly are told from midnight and on…
Family History of Anesthesia
Screening for Malignant hyperthermia- “Mom had a fever under anesthesia”
Can be fatal, triggering agents succinylcholine and halogenated inhalation agents (ie Deflurane, Sevoflurane,)
Screening for pseudocholinesterase deficiency- “Dad had to stay intubated longer than they planned” or “Mom wouldn’t breathe on her own”
Can’t break down muscle relaxants
Body Mass Index (BMI)
BMI = (Weight in kg)/(Height in meters)^2
Underweight < 18.5
Normal Weight 18.5-24.9
Overweight 25-29.9
Obese >30
Airway Evaluation
Smoking- copious secretions, cough, laryngospasm
Beards and facial hair- difficult mask
Nasogastric tube present- difficult to seal mask
TMJ Disease/Rheumatoid Arthirits- difficulty opening jaw (passive vs active)
Ankylosing Spondylitis- Fusion of cervical spine
Acute burn- Edema
Appearance Suggesting Difficult Airway
ASA Physical Status
ASA Physical Status (More Detail)
ASA Classification Emergency
Emergency surgical procedure where delay could mean significant increase in threat to life or body part.
Crash C-section
Open Fracture with vascular compromise
Ruptured AAA
Closed head injury with decompensation
NPO status waved
Should I Take My Meds
Beta Blockers- Continue, supplement IV if discontinued
Decreased myocardial oxygen demand, chance of arrythmias, pre & post-op M&M
CA Channel blockers- Continue
ACE Inhibitors/ARB- Discontinue unless indicated for heart failure
Continue inhalers bronchodilators- Albuterol prior to GA etc
Discontinue blood thinners per recommendations
Generally hold oral hypoglycemics, halve SQ insulin night before
PreOp Testing: ECG (When to Based off ASA)
Resting echocardiography- Not routinely offered before surgery except when
Patient has a heart murmur or new onset cardiac symptom (breathlessness, pre-syncope, syncope, chest pain)
Signs or symptoms of heart failure
Fatigue/weakness
Swelling in legs/ankles/feet
SOB with activity or laying down
Carryout resting ECG and review before delaying surgery/ordering echo
PreOp Testing: Chest X-Ray, Lung Function
Chest X-Ray- Do not routinely order preop chest X-ray
Low yield in absence of active pulmonary symptoms, exposure to radiation
Lung function tests- Do not routinely order unless
ASA 3 or 4 with known or suspected respiratory disease having major or complex surgery.
Candidate for lung resection
ROS: Pulmonary Risks of Anesthesia
Hypoventilation Atelectasis
Pneumonia
Can result in post-operative mechanical ventilation
Patient at risk
Smokers
COPD
Age>70
Thoracic or Upper Abdominal Surgery
Anesthesia > 2 hours
ROS: Pulmonary Risk Management
Smoking cessation
Bronchodilator therapy
Early treatment bronchitis
Early mobilization
PreOp Testing: Complete Blood Count (CBC)
Ordered routinely for those with suspected active bleeding
GI Bleed, fracture of pelvis/femur, trauma
PreOp Testing: Coagulation Testing
Coagulation testing (PT/PTT/INR) and Hematology
Coagulation labs not routinely ordered outside of
Those currently anticoagulated ie coronary stents, atrial fibrillation, DVT
Those with Liver disease
Transfusion therapy
Consider preop transfusion in symptomatic patients with Hb <7mg/dl
One unit of PRBC should raise Hb 1mg/ml or HCT by 3%
Consider platelet transfusion to >50,000 (generally accepted)
1 6 pack of platelets will increase count 30-60,000
Informed Consent
Anesthesia without consent in a non emergent situation could be construed as assault, so make sure to get that paper signed.
Explain anesthetic options with pros and cons
Decision-making capacity
Minors cannot sign for themselves
No benzo admin before consent
Power of Attorney signs as proxy if patient is unable to sign/make healthcare decision
Emergency consent- if surgeon deems procedure emergent and delaying would result is loss of life or limb in a patient unable to consent themselves, and without proxy- informed consent is waived
Premedication Goals to Anesthesia
Decrease anxiety
Decrease post op pain requirements/Anesthetic requirements
Prevent Post operative Nausea and Vomiting
Early Recovery After Surgery (ERAS)
… Surgery and Surgeon Specific
Decreasing Anxiety
ANXIETY BEGONE
Midazolam- Benzodiazepine, most given anxiolytic/peri procedural sedation medication. IV/PO, anterograde amnesia
RELATIVE CONTRAIDICATIONS
Newborn (<1 year )- Won’t remember anyway
Elderly (>65 years old)- May increase POCD (post operative cognitive dysfunction)
Decreased baseline consciousness
Intracranial pathology-Increased CO2 = bad
Severe pulmonary disease- increased CO2 = bad
Hypovolemia- chance of hypotension
Decrease Post-op pain/anesthetic requirements
Acetaminophen-1 gram if no contraindications
Celecoxib ( Celebrex ) - oral COX-2 receptor inhibitor 200-400 mg dose
No increased bleeding risk, unlike non-specific COX meds (aspirin etc)
Gabapentin/Pregabalin-
Gabapentinoid meds 300-1200 mg Gabapentin (Neurontin).
75-150 mg Pregabalin (Lyrica)
Avoid in >65 years of age, OSA
Oxycontin- Extended-release oxycodone 5-20 mg for major surgery in the absence of regional anesthesia
PONV Prophylaxis- combo of meds = greater efficacy
Most Patient will routinely receive
Dexamethasone (Decadron) 4-10 mg after induction of anesthesia
Ondansetron (Zofran) 4 mg as premed/intraop/or end of surgery
Hx of PONV
Scopolamine 1.5 mg Transdermal patch
Avoid in patients over 65- confusion, sedation, dementia
EDUCATE patient on touching the patch and washing hands
Early Recovery After Surgery
Minimize narcotics when available, opt for regional or neuraxial anesthesia
Intraoperative measures to be discussed in next lecture!
Where Does the IV Go?
Non-surgical side, non-dominant side
Flat-non-moving surfaces
Back of hand, forearm
What gauge IV?
20g for most outpatient surgeries
18g for surgeries with significant expected blood loss (EBL)
Tough Stick?
Even a lowly 22 is enough to induce anesthesia, vasodilation of anesthetic agents allow for larger IV post-induction
May need to consider Ultrasound in morbidly obese patients, or those with IVDA history
Types of Anesthetics/Anesthesia… “What is the Plan?”
General anesthesia
Regional Anesthesia
Peripheral nerve blocks
Monitored Anesthesia Care (MAC)
When To Use What
ANESTHETIC CHOICE IS BASED ON SEVERAL CRITERIA
Surgeon preference and patient safety
Surgical positioning
Patient comfort/choice
Post-operative requirements
Patient age and coexisting disease
NPO status
Procedure duration
Elective and Emergency
Airway evaluation
When is a Tube Used?
Positioning- Prone and often beach chair position
Full-stomach- trauma, gastroparesis, high aspiration risk
Long surgical time, laparoscopy
Does my patient need to be paralyzed?
Open abdominal and thoracic cases, laparoscopic and robot assisted cases
Will relaxation facilitate surgical conditions, or keep patient safe?
Exposure in spine surgery, Mayfield pins for neurosurgery
Regional or Neuraxial Anesthesia
Subarachnoid block (SAB or Spinal) anesthesia- common for C-section, knee and hip replacement, some urological procedure
Epidural anesthesia- laboring parturient, thoracotomy, open abdomen
Peripheral nerve blocks (PNB) and regional anesthesia- block surgical stimulus from anesthetized area
…Far more to come on all of these
Induction - Putting them to Sleep
IV induction is gold standard, but peripheral IV access may be difficult, traumatic, or impossible preinduction
Kiddos, those with mental handicaps consider inhalational induction
IM Ketamine- 5mg/kg in patient that will not tolerate PIV placement or mask induction… KETAMINE DART
Big Questions Determining Anesthesia Plan
What meds will be used for maintenance of anesthesia? Pain Control? Inpatient vs Outpatient
Is paralysis needed? How much/when do I reverse?
How will I maintain CV homeostasis (+/- 20% of baseline BP, HR etc)
Bolus medication vs drip
How does my patient’s history affect my plan?
Cardiac/pulmonary and reactive airway disease/kidney disease etc.
Post-Op Considerations
Is patient heading home, to a hospital bed, or the ICU?
How will I meet the patient’s post-op oxygen requirements?
Nasal cannula v face mask, oral airway/nasal airway
How am I covering the patient’s pain?
Outpatient vs inpatient
How painful was the surgery?
Does patient have underlying tolerance of pain medication?
What meds are onboard?
Monitored Anesthesia Care (MAC)
Sedation without ventilatory support- breathing on your own
Full monitoring (ASA monitors) and generally End tidal CO2
Response to verbal commands or more profound stimulation unless contraindicated
Rescue equipment available, supplemental oxygen
”Twilight sleep”
Common agents- versed/fentanyl/propofol/precedex/ketamine
Preoperative Planning
Positioning- can determine ET vs LMA
Monitoring/lines/IV access- Is an arterial line indicated? Pre/post induction? Second IV? Central line? Neuro-monitoring, TEE
Post-op destination and care transition
Plan for intraoperative events
Hypothermia, bleeding, anticoagulation, tourniquet use, positioning, redosing antibiotics etc
To Sleepy Town Process
Preoxygenation
Cases where preoxygenation is particularly important:
During RSI and intubation- trauma, full stomach
If difficult airway management is predicted
In patients who are expected to desaturate quickly (Desat curve- Obese, pregnant, pediatric, hypermetaboilic)
Goals of Preoxygenation
Prolong safe apnea time without desaturation- reduces time pressure to secure an airway
Oxygen storage in lungs primarily resides in
Functional Residual Capacity (FRC )
FRC = Expiratory Reserve Volume + Residual volume and is around 3L
TV usually around 500 ml
O2 Facts
21% O2 in the air we breath
Alveolar gas makeup in healthy patient breathing room air
14% O2, 5% CO2, 6% H2O vapor, 75% Nitrogen
After onset of Apnea O2 consumption is ~250 ml/minute
Precipitous drop after 90% Sat
8 deep breaths with good mask seal, high flow O2
May require 3-5 minutes in case of severe lung disease
Common Induction Medications
Oxygen
Fentanyl- Narcotic to blunt response to airway management
Lidocaine- Decrease pain on propofol infusion/decrease airway reflexes
Propofol – Induction agent of choice for most anesthetics
Rocuronium/Succinylcholine- Muscle relaxant to maximize conditions for intubation
Stages of General Anesthesia
Considerations When Planning for Emergence from Anesthesia
Timing is Everything
Analgesia
Hemodynamic Management
Destination and Transition of Care
Airway
Cases
1
65 y/o male patient 5’7” 187lbs
NKDA
Home medications Aspirin, Metoprolol, Lisinopril, omeprazole
History of coronary stents x2 10 years ago, HTN, GERD
ROS- RUQ pain for 1 week with N/V
Scheduled for laparoscopic cholecystectomy estimate duration 1.5 hours
ASA? What’s your plan? Premeds? Airway choice? Perioperative concerns?
2
34 y/o woman 5’3”
Allergies listed to PCN and Sulfa
Home Meds- Mirena BC, multivitamin, albuterol PRN
ROS- L Breast mass, asthma
Scheduled for L Breast lumpectomy, exceptionally nervous in preoperative area
What’s the plan? Premeds? Airway?
3
55 y/o male here for screening colonoscopy
Home meds include fish oil, ibuprofen prn, Ambien
ROS- abdominal pain, pre-diabetic diet controlled, insomnia
GETA vs LMA vs MAC?
4
36 y/o male 205 pounds, 6’2”
NKDA Home medications: MVI
ROS- Negative except for torn Left ACL
Surgery- Left ACL reconstruction with patellar tendon graft
ASA? General with Et tube/LMA or MAC?
5
68 y/o female 5’6” 185 lbs
Allergic to bananas
ROS- History of CAD with CABG 7 years ago, smoker, HTN, anxiety and depression presenting with active stroke with right sided weakness in emergency room
Home medications include- Aspirin, Sublingual nitroglycerin, losartan, metoprolol, Lipitor, Xanax
Scheduled case- Thrombectomy
Patient aphasic in preop
ASA? Consent? Anesthetic Choice?
Gas Supply
Anesthesia Machines have inlets for both E-cylinder gases and pipeline gases coming from the wall (hospital source)
Pipeline inlets
Air, Nitrous Oxide, and Oxygen
Color coded tubing
Attached using a noninterchangeable Diameter-index safety System (DISS)
Approximate pipeline pressure of the gases delivered to the anes. machine is 50pisg (pounds per square inch gauge)
O2 Flush delivers 50psig directly to the pt!!!!! Bypasses vaporizers. Fig 4-3 page 53
Oxygen Cylinders
Nitrous Oxide
Normal capacity is 1590L
Normal E-cylinder tank pressure is 745psig
The volume of N20 is not proportional to its cylinder pressure
The pressure in the tank will not change until the vol. is at or around 400L
Only reliable way to measure how much is by weighing the cylinder
Anesthesia Machine Basic Components with Air
Flow valves and meters
Vaporizers
Common fresh gas outlet
Oxygen analyzers
Adjustable Pressure-Limiting Valve (APL)
Humidifiers
Ventilators
Waste gas scavengers
Flow Sequences
Surgical Fires/Thermal Injuries
Very Rare, but good to know what to do in case one happens
Prevention includes
If possible lowering the FiO2 to 30% or lower
Avoid draping that allows for the build up of O2
Using a Laser ETT if needed
Avoiding N2O use
Airway Fire
First step is to DISCONTINUE THE FLOW OF OXYGEN!!!!
This can be done a couple different ways.
Next Steps include
Removing the current ETT and flushing the airway with sterile water or saline.
Re-establish a secure airway.
Exam the burnt ETT for missing pieces and possible perform a bronchoscopy on the patient.
Anesthetic Gas Analysis
Very vital and essential part in the delivery of Anesthesia
Measured by infrared absorption analysis
Based on the BEER-LAMBERT law
Beer-Lambert Law
Formula for measuring an unknown gas within inspired gas because the absorption of infrared light passing through a solvent (inspired or expired) is proportional to the amount of that unknown gas.
Oxygen and Nitrogen do not absorb infrared light.
Oxygen Analysis
Various technologies have been used to accomplish this.
Galvanic Cell
Paramagnetic analysis (most common used)
Polarographic Electrode
In our newer machines the method used is Paramagnetic analysis.
Paramagnetic Analysis
Oxygen is a nonpolar gas, but it is Paramagnetic.
When placed in a Magnetic field it will expand and it will contract when that magnet is turned off.
If you compare the resulting change in volume (or pressure or flow) to a known standard you can measure the amount of Oxygen that is being expired or Inspired
ASA Standards for Monitoring
Non-Invasive Blood pressure Cuff (Circulation)
Pulse Oximetry monitoring (Oxygenation)
Electrocardiography (ECG) monitoring (Circulation)
Capnography (Ventilation)
Temperature
BP: Non-Invasive
Most common method used to monitor Blood Pressure
Utilizes Oscillometry to determine SBP, DBP, and MAP
MAP = SBP + 2(DBP) /3
Different Sizes Available
Can be placed in multiple locations
Actual BP can be different depending on where the cuff is located.
1cm ( 1cm H2O) is equal to 0.74mmHg
If the cuff is on a patients forearm and that is 20cm below the patients Head then we know that the Cerebral BP is 14.7mmHg lower than what the cuff is showing
Systolic and Diastolic
Pulse Oximetry
Factors that can affect your reading or give a false reading
Methemoglobinemia (rare blood disorder affecting hemoglobin)
Carboxyhemoglobin (what happens to RBC when carbon monoxide is inhaled)
Malposition of probe
Ambient light
Low perfusion to extremities
ETC,ETC
ECG
Recording of the electrical potentials generated by myocardial cells
What makes up our cardiac rhythm
“P” wave is the contraction of both Atria
”QRS” complex is the Ventricular Systole
“T” wave represents the repolarization of the Heart as it awaits the next cardiac cycle.
Two most important leads to monitor
Lead 2 (best at detecting Inferior wall Ischemia)
Lead V5 ( best at detecting Anterior and Lateral wall Ischemia)
Capnography
Capnography Visuals
Temperature
Drawing Up Medication
Medication Expiration
Infusion Lines and Medication/Fluid Bags
Standard Contact Precautions
Enhanced Contact Precautions
Multi-Drug Resistant Organisms
MRSA (Methicillin-resistant staphylococcus aureus)
VRE (Vancomycin-resistant enterococci)
Enhanced Contact Precautions
Droplet Precautions
Airbourne Precautions
Wear mask at all times in hospital unless eating/drinking.
N95 for Covid/TB positive patients or those at high risk
Chickenpox (varicella)
Measles (rubella)
Disseminated zoster (shingles)
Covid 19
TB
Current personal vaccinations
Bloodborne Pathogens
Hepatitis-B (HBV)
Hepatitis-C (HCV)
HIV (very low sero-conversion rate)
Practice standard precautions (gloves, hand washing, needle safety and eye protection)
Key Concepts: Chapter 2 - Operating Room Environment
A pressure of 1000 pounds per square inch (psig) indicates an E-cylinder that is approximately half full and represents 330 L of oxygen.
The only reliable way to determine the residual volume of nitrous oxide is to weigh the cylinder.
To discourage incorrect cylinder attachments, cylinder manufacturers have adopted a pin index safety system.
A basic principle of radiation safety is to keep exposure “as low as reasonably practical” (ALARP). The principles of ALARP optimize protection from radiation exposure by the use of time, distance, and shielding.
The magnitude of a leakage current is normally imperceptible to touch (<1 milliampere [mA] and well below the fibrillation threshold of 100 mA). If the current bypasses the high resistance offered by skin, however, and is applied directly to the heart (microshock), current as low as 100 microamperes (μA) may be fatal. The maximum leakage allowed in operating room equipment is 10 μA.
To reduce the chance of two coexisting electrical faults, a line isolation monitor measures the potential for current flow from the isolated power supply to the ground. Basically, the line isolation monitor determines the degree of isolation
between the two power wires and the ground and predicts the amount of current that could flow if a second short circuit were to develop.
Almost all surgical fires can be prevented. Unlike medical complications, fires are a product of simple physical and chemical properties. Occurrence is guaranteed given the proper combination of factors but can be almost entirely eliminated by understanding the basic principles of fire risk.
The most common risk factor for surgical fire relates to the open delivery of oxygen.
Administration of oxygen in concentrations of greater than 30% should be guided by the clinical presentation of the patient and not by protocols or habits.
The sequence of stopping gas flow and removal of the endotracheal tube when a fire occurs in the airway is not as important as ensuring that both actions are performed immediately.
Before laser surgery is begun, the laser device should be in the operating room, warning signs should be posted on the doors, and protective eyewear should be issued. The anesthesia provider should ensure that the warning signs and eyewear match the labeling on the device because laser protection is specific to the type of laser.
Key Concepts: Chapter 4 - The Anesthesia Workstation
Equipment-related adverse outcomes are rarely due to device malfunction or failure; rather, misuse of anesthesia gas delivery systems is three times more prevalent among closed claims. An operator’s lack of familiarity with the
equipment, an operator’s failure to verify machine function prior to use, or both are the most frequent causes. Such mishaps accounted for about 1% of cases in the ASA Closed Claims Project database from 1990 to 2011.
The anesthesia machine receives medical gases from a gas supply, controls the flow and reduces the pressure of desired gases to a safe level, vaporizes volatile anesthetics into the final gas mixture, and delivers the gases to a
breathing circuit that is connected to the patient’s airway. A mechanical ventilator attaches to the breathing circuit but can be excluded with a switch during spontaneous or manual (bag) ventilation.
Whereas the oxygen supply can pass directly to its flow control valve, nitrous oxide, air, and other gases must first pass through safety devices before reaching their respective flow control valves. These devices permit the flow of other gases only if there is sufficient oxygen pressure in the safety device and help prevent accidental delivery of a hypoxic mixture in the event of oxygen supply failure.
Another safety feature of anesthesia machines is a linkage of the nitrous oxide gas flow to the oxygen gas flow; this arrangement helps ensure a minimum oxygen concentration of 25%.
All modern vaporizers are agent specific and temperature corrected, capable of delivering a constant concentration of agent regardless of temperature changes or flow through the vaporizer.
A rise in airway pressure may signal worsening pulmonary compliance, an increase in tidal volume, or an obstruction in the breathing circuit, endotracheal tube, or the patient’s airway. A drop in pressure may indicate an improvement in compliance, a decrease in tidal volume, or a leak in the circuit.
Traditionally ventilators on anesthesia machines have a double-circuit system design and are pneumatically powered and electronically controlled. Newer machines also incorporate microprocessor controls and sophisticated
pressure and flow sensors. Some anesthesia machines have ventilators that use a single-circuit piston design.
The major advantage of a piston ventilator is its ability to deliver accurate tidal volumes to patients with very poor lung compliance and to very small patients.
Whenever a ventilator is used, “disconnect alarms” must be passively activated. Anesthesia workstations should have at least three disconnect alarms: low peak inspiratory pressure, low exhaled tidal volume, and low exhaled carbon dioxide.
Because the ventilator’s spill valve is closed during inspiration, fresh gas flow from the machine’s common gas outlet normally contributes to the tidal volume delivered to the patient.
Use of the oxygen flush valve during the inspiratory cycle of a ventilator must be avoided because the ventilator spill valve will be closed and the adjustable pressure-limiting (APL) valve is excluded; the surge of oxygen (600–1200 mL/s) and circuit pressure will be transferred to the patient’s lungs.
Large discrepancies between the set and actual tidal volume are often observed in the operating room during volume-controlled ventilation. Causes include breathing circuit compliance, gas compression, ventilator–fresh gas flow
coupling, a preset ventilator peak airway pressure limit, and leaks in the anesthesia machine, the breathing circuit, or the patient’s airway.
Waste-gas scavengers dispose of gases that have been vented from the breathing circuit by the APL valve and ventilator spill valve. Pollution of the operating room environment with anesthetic gases may pose a health hazard to surgical personnel.
A routine inspection of anesthesia equipment before each use increases operator familiarity and confirms proper functioning. The U.S. Food and Drug Administration has made available a generic checkout procedure for anesthesia gas machines and breathing systems.
Key Concepts: Chapter 5 - Cardiovascular Monitoring
The tip of the central venous pressure catheter should not be allowed to migrate into the heart chambers.
Although the pulmonary artery (PA) catheter can be used to guide goal-directed hemodynamic therapy to ensure organ perfusion in shock states, other less invasive methods to determine hemodynamic performance are available, including transpulmonary thermodilution cardiac output (CO) measurements, pulse contour analyses of the arterial pressure waveform, and methods based on bioimpedance measurements across the chest.
Relative contraindications to PA catheterization include left bundle-branch block (because of the concern about complete heart block) and conditions associated with a greatly increased risk of arrhythmias.
Pulmonary artery pressure should be continuously monitored to detect an over wedged position indicative of catheter migration.
Accurate measurements of CO depend on rapid and smooth injection, precisely known injectant temperature and volume, correct entry of the calibration factors for the specific type of PA catheter into the CO computer, and avoidance of measurements during electrocautery.
Key Concepts: Chapter 6 - NonCardiovascular Monitoring
Capnographs rapidly and reliably detect esophageal intubation—a cause of anesthetic catastrophe—but do not reliably detect mainstem bronchial intubation.
Postoperative residual paralysis remains a problem in postanesthesia care, producing potentially injurious airway and respiratory function compromise and increasing length of stay and cost in the postanesthesia care unit (PACU).
Key Concepts: Chapter 18 - Preoperative Assessment, Premedication & Perioperative Documentation
The cornerstones of an effective preoperative or preprocedure evaluation are the history and physical examination, which should include a complete and up-to date listing of all medications taken by the patient in the recent past, all pertinent allergies, and responses and reactions to previous anesthetics.
The anesthesiologist should not be expected to provide the risk-versus-benefit discussion for the proposed surgery or procedure; this is the responsibility and purview of the responsible surgeon or “proceduralist.”
By convention, physicians in many countries use the American Society of Anesthesiologists’ classification to identify relative risk prior to conscious sedation and surgical anesthesia.
In general, the indications for cardiovascular investigations are the same in elective surgical patients as in any other patient with a similar medical condition.
Adequacy of long-term blood glucose control can be easily and rapidly assessed by measurement of hemoglobin A1c.
In patients deemed at high risk for thrombosis (eg, those with certain mechanical heart valve implants or with atrial fibrillation and a prior thromboembolic stroke), chronic anticoagulants should be replaced by intramuscular low molecular- weight heparins or by intravenous unfractionated heparin.
Current guidelines recommend postponing all but mandatory emergency surgery until at least 1 month after any coronary intervention and suggest that treatment
options other than a drug-eluting stent (which will require prolonged dual antiplatelet therapy) be used in patients expected to undergo a surgical procedure within 12 months after the intervention.
There are no good data to support restricting fluid intake (of any kind or any amount) more than 2 h before induction of general anesthesia in healthy patients undergoing elective procedures; moreover, there is strong evidence that
nondiabetic patients who drink fluids containing carbohydrates and protein up to 2 h before induction of anesthesia experience less perioperative nausea and dehydration than those who are fasted longer.
To be valuable, preoperative testing must discriminate: There must be an avoidable increased perioperative risk when the results are abnormal (and the risk will remain unknown if the test is not performed), and when testing fails to detect the abnormality (or it has been corrected), there must be reduced risk.
The utility of a test depends on its sensitivity and specificity. Sensitive tests have a low rate of false-negative results and rarely fail to identify an abnormality when one is present, whereas specific tests have a low rate of false-positive
results and rarely identify an abnormality when one is not present.
Premedication should be given purposefully, not as a mindless routine.
Incomplete, inaccurate, or illegible records unnecessarily complicate defending a physician against otherwise unjustified allegations of malpractice.
Gradient Difference Between PaCO2 and ETCO2
normally 2-5 mmHG, reflects alveolar dead space
Carboxyhemoglobin (COHb) and HbO2
Reviewed from Test 1 - Tough Airway for Intubation
Edentulous is not a sign of hard airway
Neck radiation
Pregnancy
Short Neck
Reviewed from Test 1 - Drugs
Know your drugs always for test
Reviewed from Test 1 - House Fire
Carboxyhemoglobin - falsely elevated Pulse Ox
Methemoglobinemia - falsely low
Look at more!!!
Reviewed from Test 1 - Normal gradient for
ETCO2 will be 2-5mmHg higher than PaCO2
