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%
The functional residual capacity is made up of what two lung volumes?
Residual Volume
Expiratory Reserve Volume
The inspiratory capacity is made up of what lung volumes?
Tidal Volume
Inspiratory Reserve Volume
What is the vital capacity made up of?
Vital capacity
Sum of ERV + TV + IRV
How does vital capacity change in pregnancy?
Vital capacity (VC, the sum of ERV + TV + IRV) is unchanged in pregnancy because the increases in IRV and TV are largely balanced by the decrease in ERV.
How does the total lung capacity change in pregnancy?
Finally, the total lung capacity (TLC, the sum of RV + ERV + TV + IRV) is slightly decreased by up to 5% during normal pregnancy.
What is the closing capacity defined as?
The CC is defined as the lung volume (or, more precisely, the sum of residual volume and closing volume) at which small, non-cartilaginous airways begin to collapse, particularly the respiratory and terminal bronchioles in the dependent areas of the lung.
Does closing capacity change in pregnancy?
No
What are the stages of labor?
Labor is divided into 3 stages.
The first stage begins with the maternal perception of regular, painful uterine contractions and ends with complete dilation of the cervix.
The second stage begins with complete dilation of the cervix and ends with the birth of the baby.
The third stage begins with the birth of the baby and ends with the delivery of the placenta
What spinal segments spinal segment coverage is required to relieve the pain of contractions and cervical dilation?
T10 to L1 spinal segment coverage is required to relieve the pain of contractions and cervical dilation
What spinal segments spinal segment coverage is required to relieve the pain of vaginal and perineal distention?
S2-S4 spinal segment coverage is required to relieve the pain of vaginal and perineal distention.
What isolated nerve block is helpful for the second stage of labor?
Pudendal nerve block helps relieve pain during the second stage of labor. The pudendal nerve includes somatic nerve fibers from S2-S4.
Why is Sodium Bicarbonatae added to local anesthetics for blocks?
Sodium bicarbonate is chiefly added to increase the rate of onset of anesthesia by increasing local pH, thus facilitating entry of uncharged local anesthetic into neurons.
Why is Epinephrine added to local anesthetics for blocks/epidurals/spinals?
- May reduce systemic absorption (and toxicity) of the local anesthetic by decreasing local blood flow through vasoconstriction.
- Epinephrine-induced vasospasm also prolongs the duration of action of the local anesthetic by maintaining its effects at the injection site. The addition of epinephrine allows for intravascular injection to be detected early through an increase in heart rate or blood pressure in response to incremental dosing.
- Finally, the quality and density of the block may be augmented by local vasoconstriction as well as the intrinsic analgesic effects of epinephrine, which hinge on its alpha2-adrenergic agonist activity
Does epinephrine affect the onset of the regional/neuraxial block?
No
What is the mcg/mL concentrations of Epinephrine for:
1: 1,000
1: 10,000
1: 100,000
1: 200,000
1: 1,000 = 1000 mcg/mL (1 mg / mL)
1: 10,000 = 100 mcg/mL
1: 100,000 = 10 mcg/mL
1: 200,000 = 5 mcg/mL
The transtracheal block, anesthetizes whta nerve?
The translaryngeal block can be used to safely anesthetize the tracheal mucosa, which draws sensory innervation from the recurrent laryngeal nerve
What nerve block is used to anesthetize the hypopharynx and larynx above the vocal cords?
Superior laryngeal nerve block is used to anesthetize the hypopharynx and larynx above the vocal cords
What nerve block can be used to anesthetize much of the oropharynx and tongue base?
Glossopharyngeal nerve block can be used to anesthetize much of the oropharynx and tongue base
The external iliac arteries become the what arteries after the groin crease?
The external iliac arteries become the common femoral artery after the groin crease.
The common femoral artery branches off into what two arteries?
The common femoral artery branches off into:
1. The deep femoral artery (profunda femoris)
2. The superficial femoral artery
The superficial femoral artery continues down the leg and becomes what artery at the knee crease?
Popliteal Artery
The popliteal artery branches off into what two arteries?
The popliteal artery branches off into the anterior tibial artery and the tibiofibular (tibioperoneal) trunk
The tibioperoneal (TP) trunk bifurcates into what two arteries?
The tibioperoneal (TP) trunk bifurcates into the posterior tibial artery and the fibular (peroneal) artery.
Phosgene creates what end organ damage?
Antidote & Treatment?
Phosgene is a chemical warfare agent that can lead to significant pulmonary damage.
There is no specific antidote
Treatment is generally centered around providing supportive care and minimizing the effects of the inflammatory mediator cascade.
What is the Liver’s blood supply?
The liver has a unique dual blood supply
Receiving blood from both the hepatic artery, which arises from the celiac trunk, as well as the portal vein, which is a confluence of the venous drainage from the splanchnic circulation
Compare hepatic artery vs. portal vein
- % of blood Flow
- % of Oxygen Supply
The hepatic artery provides 25% of the blood flow
Portal Vein provides 75% of blood flow (Think Portal = Plump and lots of blood)
Oxygen supply 50% and 50% for each
The primary means of physiologic hepatic blood flow?
The primary means of intrinsic autoregulation of hepatic blood flow is the hepatic arterial buffer response that causes adenosine-mediated vasodilation of the hepatic artery in response to decreased blood flow in the portal vein.
Think about this as a compensatory way to increase Liver blood flow
When does the HABR effect reach maximum capacity?
HABR = Hepatic Arterial Buffer Response
The HABR reaches its maximal effect when the hepatic arterial flow is doubled and will not increase blood flow in the hepatic artery past this point.
Even in this case, the oxygen supply to the liver is preserved because the hepatic arterial blood carries more oxygen compared with the partially deoxygenated blood in the portal vein.
Certain endotoxins can obliterate this response and leave the liver vulnerable to ischemic or hypoxic injury.
How does Volatile Anesthetics affect HABR?
HABR = Hepatic Artery Buffer Response
Most volatile anesthetics will tend to attenuate this response, resulting in a muted vasodilation of the hepatic artery in direct response to decreased portal venous pressures
What can happen to uterine blood flow when a mother hypoventilates?
Note that maternal hypocapnea can cause fetal hypoxia and acidosis secondary to vasoconstriction, decreased venous return (hypocapnea is usually the result of hyperventilation and increased thoracic pressure), and left shift of the maternal oxygen dissociation curve (CO2 leads to unloading of O2, hypocapnea leads to retention of O2)
What are the only procedures that warrant infective endocarditits antibiotic prophylaxis?
Dental or oral surgery procedures that “involve the manipulation of gingival tissue…periapical region of teeth, or perforation of the oral mucosa”
What are the 5 high risk cardiac conditions that warrant infective endocarditis prophylaxis?
- Prosthetic cardiac valves, including transcatheter-implanted prosthetic valves
- Patients with implanted prosthetic material, such as annuloplasty rings and artificial chordae tendineae
- Patients with a history of infectious endocarditis
- Patients with a history of unrepaired cyanotic congenital heart disease, including patients with a repair, but with a residual shunt or valvular regurgitation near an implanted patch or device
Patients with a history of cardiac transplantation who have a regurgitant valvular lesion due to a structurally abnormal valve
What is the conversion rate of mmHg –> cm H20?
Conversion rate is 1 mmHg = 1.36 cmH2O.
Are the rings of the trachea anterior or posterior?
Rings = Anterior
Trachealis muscle = Posterior (Longitudinal fibers)
What is the Bronchus Intermedius?
The bronchus intermedius is the distal portion of the right main bronchus after the takeoff of the right upper lobe and before the takeoffs of the right lower and middle lobes.
How does pH & PaCO2 tension affect Hemoglobin dissociation shift curves?
Acidosis and Increase in PaCO2 shift Right
How does temperature affect Hemoglobin dissociation shift curves?
Increase temperature = Right shift
Decrease in temperature = Left shift
How does stored PRBC affect Hemoglobin dissociation shift curves?
Left Shift
How does hypophosphatemia affect Hemoglobin dissociation shift curves?
Left Shift (Decreased DPG)
What are 6 causes of increase in 2,3 DPG that would cause a Right Shift on Hgb dissociation curve?
- Hyper-phosphatemia
- Thyroxine (Hyperthyroidism)
- Anemia
- Liver Cirrhosis
- Sleep Apnea (OSA)
- Herat Failure
- High Altitude Hypxia
The treatment of choice for type 1 vWD is desmopressin when factor VIII levels are what percent?
<50%
What is the most common congenital bleeding disorder?
von Willebrand disease is the most common congenital bleeding disorder, with a prevalence of up to 1%,
What are the Subtypes of Von Willebrand Disease?
1 = Partial Quantitative Deficiency
2 = Qualitative deficiency (Types A, B, M, N)
3 = Complete Deficiency
For Type I vWD disease, what is the cutoff for treating with desmopressin?
Typically for type 1, women do not require treatment during pregnancy when factor VIII levels are >50%. If levels are <50%, then treatment should be initiated
If you have a pregnant woman with vWD Type I and you give desmopressin, what can happen? (List 2 things)
- Tachyphylaxis
- Initiation of Uterine Contractions
If you have a patient with vWD (Type II and Type III) what should be administered?
Humate-P (Factor 8)
Alphanate (vWF)
Can you use FFP to treat for vWD?
Fresh frozen plasma does contain functional vWF and factor VIII; however, it is not the preferred method of providing these because of exposure to allogeneic blood products and the other components of plasma that are not required. If replacement is indicated, factor VII and vWF concentrates are preferred.
