test 3 flipped classroom Flashcards
What is the typical placement of the sample port in airway gas analysis?
At the Y-piece.
What does the difference in gas concentrations during gas analysis indicate?
How much gas is being diffused into arterial blood and out of venous blood.
What does monitoring the minimum alveolar concentration (MAC) help measure?
The amount of volatile anesthetic delivered to the brain.
Name a type of anesthetic gas analyzer that is infrared-based.
Ramen Scattering Analysis.
What is a limitation of Ramen Scattering Analysis?
Can be inaccurate when using high gas flow and small tidal volumes, especially in pediatrics.
What is the major disadvantage of Mass Spectrometry as an anesthetic gas analyzer?
Not cost efficient, large, not very portable, and no longer used.
What is a key limitation of the Piezoelectric analyzer?
Unable to identify the gas being measured.
What is the advantage of the Photoacoustic analyzer?
Very portable and accurate but cannot measure oxygen.
How do anesthetic gas analyzers measure multiple gases?
Using infrared light based on Beer–Lambert law.
What does Beer–Lambert law state regarding gas analysis?
Measures the amount of infrared light absorbed by a specific gas to calculate its concentration.
Why is a separate analyzer used for oxygen?
Oxygen does not absorb infrared light.
What do pulse oximeters measure?
The amount of light absorbed by hemoglobin, which corresponds to the amount of oxygen bound to hemoglobin.
What components are found in a galvanic oxygen analyzer?
Lead anode, gold cathode, electrolyte solution, and semipermeable membrane.
What chemical reaction occurs in galvanic oxygen analyzers?
2 Pb2+ + 4 OH- -> 2 PbO + 2 H2O + 4 e-.
What is the role of the paramagnetic oxygen analyzer?
Attracts oxygen molecules using a magnetic field to measure concentration.
Define Minimum Alveolar Concentration (MAC).
The minimum alveolar concentration necessary to immobilize 50% of patients exposed to a noxious stimulant.
What is the MAC value for Sevoflurane?
2%.
What is the significance of a high value for Sevoflurane?
It indicates the concentration needed for effective anesthetic action.
What is the normal range for arterial blood pH?
7.35–7.45.
What does PaO₂ measure in arterial blood gas analysis?
Oxygen dissolved in the plasma.
What is the significance of the Bicarbonate (HCO₃⁻) in blood?
It is a key component of the body’s buffer system that regulates pH.
What is the normal range for Base Excess (BE)?
-2 to +2 mEq/L.
What does a Base Excess (BE) < 0 indicate?
Metabolic acidosis.
How does the respiratory system contribute to acid-base balance?
Removes volatile acids as CO2.
What is the primary transport mechanism for oxygen in the blood?
Bound to hemoglobin.
What is the Alveolar Gas Equation used for?
Determining PaO₂ based on FiO₂, barometric pressure, and ventilation.
What does the P/F Ratio (PaO₂/FiO₂) indicate?
Severity of ARDS.
What constitutes respiratory acidosis?
Any process leading to an elevation in PaCO₂, reducing arterial pH.
What is the normal range for PaCO₂?
35 - 45 mmHg.
What is the consequence of severe hypercapnia?
CO₂ narcosis and delayed awakening post-anesthesia.
What type of blood sample is needed for accurate lung function assessment?
Arterial blood sample.
What is the effect of temperature on PaO₂ and PaCO₂ readings?
Temperature changes affect accuracy; adjustments are necessary for patient temperature.
What is the role of chloride shift in CO₂ transport?
HCO₃⁻ leaves RBCs in exchange for Cl-.
What is the formula for calculating oxygen content (CaO2)?
CaO2 = (SaO2 x 1.39 x Hb) + (0.003 x PaO2).
What is a common cause of hypercapnia in anesthesia?
Rebreathing of CO₂ in anesthesia circuits.
What happens to the pH of blood with increased CO₂ levels?
It lowers pH, leading to acidosis.
What is the normal range for lactate in blood?
0.5–1.6 mmol/L.
What is the significance of the Haldane Effect?
Deoxygenated hemoglobin increases CO₂ carrying capacity.
What is Respiratory Acidosis?
Any process leading to an elevation in PaCO₂, reducing arterial pH.
Acute Change: A 10 mmHg increase in PaCO₂ → pH decreases by 0.08 units.
What are the ABG findings for Respiratory Acidosis?
↓ pH, ↑ PaCO₂, normal HCO₃⁻ (if uncompensated).
What causes Respiratory Acidosis?
- Hypoventilation
- Opioid overdose
- COPD
- Neuromuscular disorders
- Airway obstruction
How do kidneys compensate for Respiratory Acidosis?
Kidneys retain bicarbonate and excrete hydrogen ions (H⁺).
What is the treatment for Respiratory Acidosis?
- Increased minute ventilation
- Rebreathing
- Dead space adjustments
- Mechanical ventilation adjustments
- Bronchodilators
What is the definition of Metabolic Acidosis?
Acidosis due to decreased bicarbonate or increased fixed acid.
What are the ABG findings for Metabolic Acidosis?
↓ pH, normal PaCO₂, ↓ HCO₃⁻.
What are the causes of Metabolic Acidosis?
- Lactic acidosis
- Diabetic ketoacidosis
- Renal failure
- Poisoning (methanol, ethylene glycol)
- Diarrhea (HCO₃⁻ loss)
How do patients compensate for Metabolic Acidosis?
Hyperventilation to decrease PaCO₂.
What is the treatment for Metabolic Acidosis?
Treat underlying cause; sodium bicarbonate for pH < 7.20 used cautiously.
What is Respiratory Alkalosis?
Alveolar ventilation exceeds CO₂ production → PaCO₂ < 35 mmHg.
What are the ABG findings for Respiratory Alkalosis?
↑ pH, ↓ PaCO₂, normal HCO₃⁻.
What causes Respiratory Alkalosis?
- Hyperventilation
- Anxiety
- Pain
- CNS disorders
- Fever
- High altitude
How do kidneys compensate for Respiratory Alkalosis?
Kidneys excrete bicarbonate and retain hydrogen ions.
What is the treatment for Respiratory Alkalosis?
- Reduce hyperventilation
- Rebreathing CO₂
- Adjust tidal volume
- Treat underlying causes
What is the definition of Metabolic Alkalosis?
Excess loss of fixed acid or excess bicarbonate.
What are the ABG findings for Metabolic Alkalosis?
↑ pH, normal PaCO₂, ↑ HCO₃⁻.
What causes Metabolic Alkalosis?
- Vomiting
- Nasogastric suction
- Diuretic therapy
- Excessive bicarbonate intake
How do patients compensate for Metabolic Alkalosis?
Hypoventilation to retain CO₂.
What is Mixed Acidosis?
Combination of respiratory and metabolic acidosis.
What are the common causes of Mixed Acidosis?
- Cardiac arrest
- Severe shock
- Multiple organ failure
What is Mixed Alkalosis?
Combination of respiratory and metabolic alkalosis.
What are the common causes of Mixed Alkalosis?
- Overresuscitation
- Excessive ventilation
- Bicarbonate administration
When is ABG preferred over VBG?
When assessing oxygenation (PaO₂, SaO₂) and precise respiratory function.
What is the purpose of Mixed Venous Blood Gas (SvO₂)?
Reflects global tissue oxygen consumption and delivery.
What does a low SvO₂ indicate?
- Decreased oxygen extraction
- Sepsis
- Cyanide poisoning
- Left-to-right shunts
What are the clinical uses of Somatosensory Evoked Potentials (SSEPs)?
- Detects peripheral nerve damage
- Monitors spinal cord function during surgeries
What are the anesthesia considerations for SSEPs?
- Volatile anesthetics & nitrous oxide → ↓ Amplitude, ↑ Latency
- TIVA preferred for stable monitoring
What is the function of Motor Evoked Potentials (MEPs)?
Evaluates the corticospinal (motor) pathway responsible for voluntary movement.
What are the anesthesia considerations for MEPs?
- Highly sensitive to volatile anesthetics and nitrous oxide
- TIVA preferred for optimal monitoring
What is the clinical use of Brainstem Auditory Evoked Potentials (BAEPs)?
- Diagnoses acoustic neuromas
- Evaluates anesthesia depth in high-risk patients
What are the anesthesia considerations for BAEPs?
Least affected by anesthesia compared to SSEPs & MEPs.
What is the function of Visual Evoked Potentials (VEPs)?
Evaluates visual pathway from eyes to the occipital cortex.
What are the anesthesia considerations for VEPs?
Highly sensitive to volatile anesthetics and nitrous oxide.
What is the effect of inhalational anesthetics on evoked potentials?
↓ Amplitude, ↑ Latency – depresses EP signals.
What is the effect of intravenous anesthetics (TIVA) on evoked potentials?
Preserves amplitude & latency better than inhaled agents.
What physiological factors can mask evoked potential waveforms?
- Hypothermia
- Age
- Neurological conditions
- Sedation
What is the importance of Evoked Potentials in clinical settings?
Critical for assessing neural pathways and providing insights into sensory, motor, auditory, and visual function.
What percentage of total body oxygen does the brain normally consume?
20%
How long can irreversible brain injury occur after interrupted perfusion?
3-8 minutes
What is the normal value for Cerebral Blood Flow (CBF) in mL/100g/min?
50 mL/100g/min
What are the two factors that affect Intracranial Pressure (ICP)?
Cerebral Blood Flow (CBF) and Total Intracranial Volume
What is the formula for Cerebral Perfusion Pressure (CPP)?
CPP = MAP - ICP
What is the normal range for Cerebral Perfusion Pressure (CPP)?
80-100 mm Hg
List three pathological causes of increased ICP.
- Cerebral swelling/edema
- Tumor
- Increased cerebral blood flow
What does the Monro-Kellie Doctrine describe?
Pressure-volume equilibrium between brain, blood, and CSF
What is the compensation phase in the ICP volume relationship?
Small volume increases are initially compensated by CSF & blood displacement
What are the signs and symptoms of Intracranial Hypertension?
- Headache
- Nausea and vomiting
- Papilledema
What is Cushing’s Triad?
Hypertension, bradycardia, irregular respirations
Indicate a situation that requires ICP monitoring.
Severe Traumatic Brain Injury (TBI) with GCS ≤ 8
What is the gold standard for ICP measurement?
Intraventricular Catheter (External Ventricular Drain)
What is the infection risk associated with Ventriculostomy?
Up to 22%
Name one abnormal ICP pattern.
Plateau Waves (A Waves of Lundberg)
What is the goal of ICP management?
To promote adequate oxygenation and nutrient supply
What is the target PaCO₂ level during hyperventilation?
30-35 mmHg
Fill in the blank: The cranial vault contains the brain (80%), blood (12%), and _______ (8%).
CSF
What is the risk of using hypotonic solutions in neurosurgical patients?
Cerebral edema
What is the preferred anesthetic agent for neurosurgical cases due to minimal impact on ICP?
Sevoflurane
True or False: Nitrous Oxide should be avoided in patients with pneumocephalus.
True
What is the effect of Propofol on ICP?
It decreases ICP
What is the recommended action for fluid management in neurosurgical patients?
Maintain Euvolemia
What are the potential risks of using Mannitol for ICP control?
- Hyperosmolality
- Electrolyte imbalance
What is the effect of hypothermia therapy on CMRO₂?
Decreases CMRO₂ by 7% per °C drop in core temp
What is the main concern when rapidly correcting sodium levels in patients?
Central pontine myelinolysis
What is the most widely used osmotic agent for acute ICP control?
Mannitol (0.25-1 g/kg IV)
Mannitol draws fluid out of brain tissue and decreases ICP for up to 6 hours.
What is the target serum Na⁺ level when using hypertonic saline for ICP management?
145-155 mEq/L
Do not administer hypertonic saline if Na⁺ > 155 mEq/L.
What is the most common regimen of corticosteroids used for vasogenic cerebral edema?
Dexamethasone 4 mg IV q6h
Corticosteroids are not used in traumatic brain injury (TBI) due to potential harm.
What is the purpose of barbiturate coma in refractory ICP cases?
↓ CMRO₂, prevents seizures, reduces hyperthermia
Continuous EEG induces burst suppression, keeping ICP at its lowest achievable level.
What are the normal ICP levels?
5-15 mmHg
List the indications for ICP monitoring.
- Severe TBI with GCS ≤ 8 & abnormal CT scan
- Normal CT scan + ≥ 2 risk factors:
- Age > 40 years
- Decerebrate/decorticate posturing
- SBP < 90 mmHg
- Sedated or induced coma after severe TBI
- Multisystem injury with altered consciousness
- Treatments ↑ risk of ↑ ICP
- Postoperative monitoring after intracranial mass removal
- Abnormal non-invasive ICP monitoring
What is the gold standard for ICP management?
EVD Placement (External Ventricular Drain)
What is the preferred anesthetic agent for patients with ICP concerns?
Propofol
High-dose volatile agents should be avoided.
True or False: Isoflurane is preferred over Sevoflurane in terms of increasing CBF & ICP.
True
What does the BIS monitor measure?
Depth of anesthesia using EEG signals
What numerical value does the BIS provide to represent patient consciousness?
0-100
What is the BIS scale interpretation for general anesthesia?
40-65
Fill in the blank: The BIS can erroneously interpret older adults as being in an _______ state.
awake
How do children differ from adults in terms of BIS readings?
Children have more power across a broader range of frequency bands
This can lead to incorrect BIS readings indicating sedation rather than unconsciousness.
What is the definition of intraoperative awareness?
The patient having explicit recall of events that transpired during general anesthesia
What is the controversy surrounding the usefulness of BIS monitoring?
Its effectiveness in guiding the reduction of anesthetic dosing or contributing to fast tracking has not been demonstrated by randomized clinical trials.
