True Learn Questions Flashcards
A full tank of N2O contains how many liters?
A full tank of N2O contains 1590 L.
A full tank of N2O contains 1590 L at what pressure?
A full tank of N2O contains 1590 L at a pressure of ~745 psig
When will the pressure on a N2O cylinder begin to drop?
N2O is stored as a liquid and gas in a pressurized E cylinder, and the pressure within a tank of N2O will remain at ~745 psig until all liquefied gas is used up.
This occurs when the tank has ~250 L (16%) N2O remaining.
Note again that, as explained above, some textbooks state ~400 L (25%) N2O remaining before a pressure drop, but this is not backed by evidence.
There could be two answers here, know both exist.
What is the metabolism of Lorazepam?
hepatic glucuronidation is significantly impaired by hepatic dysfunction.
Less susceptible to drug/drug interactions than diazepam/midazolam
What is the metabolism of diazepam and midazolam?
oxidative metabolism via hepatic cytochrome oxidases
More susceptible to drug/drug interactions than diazepam/midazolam
What is the half life of Lorazepam?
8-25 hours
Unpredictable, 8-25 hours is also why it’s not used for preoperataive anxiolysis
When would you consider Lorazepam over Midazolam for anxiolysis?
ESRD / CKD
Because this metabolite is inactive, renal dysfunction does not impair the elimination of lorazepam or extend its duration of action.
How does ventilation affect calcium levels?
Hyperventilation?
Hypoventilation?
Hyperventilation –> Alkalemia –> Less H+ –> More calcium binds albumin –> Less free serum (Hypocalcemia)
Hypoventilation –> Acidemia –> More H+ –> Less calcium binds albumin –> Less free serum (Hypocalcemia)
How does ventilation (hyper/hypo) affect potassium levels?
Respiratory alkalosis (hyperventilataion) –> Hypokalemia
Respiratory acidosis (hypoventilation) –> Hyperkalemia
Why?
H+-K+ transporters pump H+ out of cells in the setting of alkalosis (Too few protons in the serum) to restore physiologic pH
What is the ASRA recommendation for neuraxial management for low dose subcutaneous heparin (5000 U BID or TID) administration?
The new recommendations are to hold low-dose subcutaneous heparin at least 4-6 hours prior to the performance of neuraxial anesthesia,
as well as to
hold heparin 4-6 hours before the manipulation or removal of a neuraxial catheter.
If a patient is a normal PTT but hasn’t been 4-6 hours since heparin, can you proceed with an epidural?
Yes
What is the ASRA recommendation for neuraxial management for high dose subcutaneous heparin (7500 - 10000 U BID or TID) administration?
12 hours AND normal coagulation studies
What is the ASRA recommendation for neuraxial management for therapeutic dose subcutaneous heparin (>20,000 units per day) administration?
24 hours and normal coagulataion studies
What is the ASRA recommendation for neuraxial management for prophylactic LMWH administration?
12 hours
What is the ASRA recommendation for neuraxial management for prophylactic LMWH (BID dosing) administration?
12 hours
List 8 conditions approved for hyperbaric oxygen therapy.
Gas-bubble disease (air embolism and decompression sickness)
Carbon monoxide poisoning
Infections (clostridial myonecrosis, other soft tissue necrotizing infections, refractory chronic osteomyelitis, intracranial abscess)
Acute tissue ischemia (crush injury, compromised skin flaps, central retinal artery or vein occlusion)
Chronic ischemia (radiation necrosis, ischemic ulcers)
Acute hypoxia (exceptional blood loss anemia when transfusion is unable to be given i.e. Jehovah’s witness)
Acute thermal burn injury
Idiopathic sudden sensorineural hearing loss
What is the only true contraindication to hyperbaric oxygen therapy?
Acute Untreated Pneumothorax
Patient’s can develop tension pneumothorax which can not be decompressed under hyperbaric conditions
What is the most common underlying comorbidity in patients with HFpEF?
The most common underlying comorbidity in patients with HFpEF is long-standing hypertension, which leads to concentric remodeling of the left ventricle.
What Reynolds number represents laminar flow?
What Reynolds number represents turbulent flow?
Laminar <2300
Variable flow zone (2300 - 4000)
Turbulent >4000
What does Heliox (inspired helium-oxygen mixture) do to the Reynolds number?
Heliox, an inspired helium-oxygen mixture, may be a useful intervention for patients with postoperative stridor because of the lower density of helium compared to oxygen or ambient air. The lower density decreases the Reynolds number, which favors laminar flow rather than turbulent flow.
This concept relates oxygen consumption to cardiac output and the oxygen content difference between arterial and venous blood
Fick Principle
What effect refers to the shift in the oxygen dissociation curve caused by changes in the concentration of carbon dioxide or the pH of the environment.
Bohr Effect
An integral part of the oxygen and hemoglobin interaction at the level of capillaries in tissues is the Bohr effect.
- Refers to the shift in the oxygen dissociation curve caused by changes in the concentration of carbon dioxide or the pH of the environment.
At the level of the capillaries, PCO2 is higher than in arterial blood and the pH consequently is lower. The increase in the concentration of CO2 is due to the metabolic processes of the tissues. The higher CO2 or lower pH leads to a right shift in the oxygen dissociation curve, which leads to hemoglobin offloading the oxygen to the tissues. This increases the delivery of oxygen to acidotic and hypoxic tissues.
What effect described hemoglobin’s ability to carry increased amounts of CO2 in the deoxygenated state as opposed to the oxygenated state
Haldane Effect
This is due to the fact oxygenated hemoglobin reduces the amount of CO2 bound to hemoglobin in addition to the histidine amino acid of hemoglobin being an important hydrogen ion buffer at physiologic pH.
What valvular disease is associated with rheumatoid arthritis?
Mitral Regurgitation = Most common (usaully mild)
AI = Can happen too
What are 3 reasons why rheumatoid arthritis patients can be difficult to intubate/extubate safely?
- Atlantoaxial subluxation may make intubation more difficult and cause spinal cord trauma with neck manipulation.
- Temporomandibular joint synovitis can limit mandibular motion.
- Cricoarytenoid arthritis can cause hoarseness, pain on swallowing, and possible post-extubation laryngeal obstruction.
What is the gold standard test to confirrm brain death?
Cerebral angiography
gold standard for confirmatory tests, but it is invasive.
The test will show absent blood flow at or beyond the carotid bifurcation or circle of Willis.
What tests need to be seen before performing apnea test?
● Assess for absence of the following:
○ Pupil reaction to light in both eyes
○ Corneal reflexes
○ Ocular movement with head turning (oculocephalic reflex) when no apparent cervical spine injury exists and ocular movements after caloric testing with ice water (oculovestibular reflex)
○ Bulbar function (jaw reflex)
○ Oropharyngeal reflex (gag and cough reflex)
○ Pain reflex
How does inspiratory reserve volume change in pregnancy?
Increase (0-5%)
How does tidal volume change in pregnancy?
Increase 40-45%
How does expiratory reserve volume change in pregnancy?
Decrease 20-25%
How does residual volume change in pregnancy?
Decreased 15-20%