ITE 1993 Flashcards
What drug aside from 3,4-DAP can also increase the release of acetylcholine and improve the symptoms of LEMS?
Guanidine hydrochloride
How are amide local anesthetics eliminated?
Via microsomal enzymes in the liver. Therefore decreased liver function or liver blood flow increases their elimination half-life.
What is the only acetylcholinesterase inhibitor that crosses the blood-brain barrier?
Physostigmine
What are the effects of an overdose of an anticholinergic agent?
CNS effects (central anticholinergic syndrome) Tachycardia Dry mouth Hyperthermia Mydriasis Cycloplegia
What is atropine fever?
Hyperthermia as a result of blockade of sweat glands and the inability to dissipate heat.
How do CO2 levels affect the oculocardiac reflex?
Hypercarbia increases the incidence of the oculocardiac reflex.
The oculocardiac reflex is most commonly seen in what surgery?
Strabismus surgery in the pediatric population. Thus avoiding hypercarbia in that population is important during that procedure.
What triggers the oculocardiac reflex?
Manipulation, pressure on, or pain of the eye or the extraocular muscles.
A retrobulbar block can trigger it for example. The reflex persists even in an enucleated (i.e., eyeball taken out) patient and can be triggered by stimulating the orbit.
What are the afferent and efferent limbs of the oculocardiac reflex?
Afferent: Impulses along Short and Long Ciliary Nerves–>Ciliary Ganglion–> Gasserian Ganglion via V1 branch
Efferent: Vagus nerve
What are the effects of the oculocardiac reflex?
Bradycardia
Dysrhythmias
Nausea
Somnolence
What does train-of-four look like in a phase I block?
Equally diminished TOF without fade.
Remember that Phase I is the commonly recognized effect of succinylcholine.
How do phase 1 and phase 2 blocks with succinylcholine differ with regards to train-of-four?
Phase I: equally diminished twitches without fade
Phase II: does have fade (looks like a non-depolarizing block)
How do phase 1 and phase 2 blocks with succinylcholine differ with regards to anticholinesterase administration?
Phase 1 is prolonged by anticholinesterases
Phase 2 is improved by anticholinesterases.
How do phase 1 and phase 2 blocks with succinylcholine differ with regards to tetanic stimulation?
Repeated tetanic stimulation has no effect on a phase I block, but phase 2 shows a reduced response with successive stimulation.
How does tetanic stimulation affect the train-of-four seen in a phase 1 block and a phase 2 block with succinylcholine?
Tetanus will increase the train-of-four ratio in a phase 2 block only.
What train-of-four ratio corresponds to a phase 2 block?
0.4
What are characteristics of a phase 2 succinylcholine block?
Fade with TOF
prolonged recovery
improves with anticholinesterase administration
fade with repeated tetanic stimulation
What are the advantages and disadvantages of closed-circuit anesthesia?
Advantages: maximal humidification maximal warming of gases less environmental pollution lower quantity of volatile anesthetic used
Disadvantages:
cannot rapidly change gas concentrations because of the low fresh gas flows
What is the TPN effect on the retina?
Linked to ROP in the newborn but not linked to any adult retinopathy despite causing hyperglycemia.
Why might diabetics as well as patients on TPN be at increased risk for infection?
Hyperglycemia depresses granulocyte function.
How does hyperglycemia affect the RQ (i.e., respiratory quotient)?
It increases it from 0.8 to approximately 1. This means more CO2 is being produced and needs to be blown off.
A patient with severe COPD is placed on TPN. The following day the patient is found obtunded and barely breathing. What may have happened?
The patient suffered respiratory failure due to excessive CO2 production as a result of excess glucose administration via TPN. Hyperglycemia increases the RQ ratio from 0.8 to 1.
When in the respiratory cycle should external defibrillation occur?
End-expiration because resistance is lowest at that time (chest diameter is smallest, thus distance to the heart is smallest).
Transthoracic resistance to DC defibrillation is increased, decreased or unchanged by repeated shocks?
Resistance is decreased with repeated shocks which increases current flow to the heart.
Why do premature babies suffer respiratory fatigue sooner?
Prior to 37 weeks GA, the diaphragm has < 10% type 1 (slow-twitch) muscle fibers (an adult has 50%!). Also the kid has a higher rate of O2 consumption.
What is the etiology of paradoxical motion of the chest wall in a neonate/infant?
The chest wall of a neonate and infant commonly displays paradoxical movement with inspiration owing to rib orientation, undeveloped muscles, incomplete calcification, higher cartilage content. It’s normal.
How does airway resistance change with age?
Small airway resistance decreases as we get older. Larger “central airway” resistance is constant throughout life.
How does the FRC/TLC ratio of an infant compare to that of an adult.
An infant has a larger FRC to TLC ratio than adult. FRC is equal between the two groups at 30cc/kg, but an infant’s TLC is 63cc/kg while the adult’s is 82cc/kg.
Describe the growth of alveoli in children.
Alveoli increase in number but not size until age 3. After that the increase is greatest until age 5. Alveolar maturation is complete at about 8 years old.
At what age is alveolar maturation complete?
Age 8
What are the side effects of methylmethacrylate cement?
The monomer itself can cause vasodilation and hypotension.
However, the cement can cause a syndrome as a result of embolized fat, marrow, cement, or air into the venous system that manifests as hypoxemia, dysrhythmia, pHTN, decreased CO.
When in the perioperative period does bone cement implantation syndrome manifest?
Arterial desaturation often occurs at the time of cementing and has been reported up to 5 days postop.
What energy levels are required for direct ventricular defibrillation?
5 - 10 Joules. Up to 60 Joules can be used but these higher values are associated with myocardial damage.
What potassium levels favor successful defibrillation?
high-normal levels.
At what level of spinal cord transection are there pulmonary sequelae and what are they?
T7 and higher due to reduction in VC, FEV1, ERV, and intercostal impairment/paralysis. These lead to potential hypoventilatory issues.
How does intraoperative epidural use affect the rate of DVT after hip surgery?
There is no difference from GA. The incidence is about 35% for both.
What effect does aspirin have on the incidence of DVT after hip surgery?
A recent meta-analysis of 17,000 patients found that ASA prophylaxis (160mg QD for up to a month after) had at least a one-third reduction of risk in PE and DVT.
How is ketamine metabolized?
Metabolized via hydroxylation and demethylation in the liver to norketamine.
Factors that reduce hepatic blood flow prolong ketamine effects.
How does CHF affect drug metabolism?
It decreases hepatic blood flow and thus increases the duration of effect of drugs metabolized by the liver.
What methods reduce the risk of airway fire? Use sublaryngeal tumor excision with laser as the example procedure.
Minimize FiO2
Non-intubation techniques such as jet ventilation
Periods of apnea and spontaneous ventilation
Conventional ETT with saline in cuff
Laser-resistant tubes
Water-based lubrication
What are the effects of hypercalcemia?
polyuria/polydipsia kidney stones muscle weakness GI symptoms Psychiatric sequelae HTN (20 - 50% of patients)
How does one treat hypercalcemia?
Normal saline administration Loop diuretic bisphosphonate administration calcitonin plicamycin corticosteroids
How does hyperventilation affect calcium levels?
Alkalosis doesn’t affect total serum calcium levels but does decrease ionized levels by promoting binding to serum proteins.
Via what mechanism(s) does normal saline administration help in hypercalcemia?
Volume expansion dilutes serum calcium concentration, and it promotes diuresis.
Sodium itself also inhibits renal tubular calcium absorption, and thus promotes calcium excretion in the urine.
A pediatrician comes on duty and notes tachypnea in a two-day old child in the nursery. A CXR had been performed by the team yesterday and shouwed perihilar markings, fluid in the fissures, and streaky linear opacities in the parenchyma. What is the diagnosis and treatment?
Transient tachypnea of the newborn is a self-limiting condition in which there is residual fluid in the lungs for the first 24 - 72 hours of life. It’s a typical benign finding.
The initial expansion of a newborns lungs at delivery require how much negative pressure?
40 - 80 cmH20!
What does the PDA close functionally and anatomically?
It closes functionally with PA pressure is less than systemic arterial pressure.
It may not close anatomically until the full-term neonate is 10 - 14 days old.
Where does the superior laryngeal nerve divide and what does it divide into?
It divides 1cm below the greater cornu of the hyoid into the external and internal branches.
What factor is associated with hemophilia B?
Factor IX deficiency
What is plasma protein fraction?
A blood product derived from plasma that has albumin plus alpha and beta globulins.
What are the components of cryoprecipitate?
Factor VIII, fibrinogen, vWf, fibronectin.
What viruses can be transmitted via albumin?
Albumin is treated at 60 degrees celsius for 10 hours so transfusion infection risk is extraordinarily low, but parvovirus B19 has been shown to be present in clotting factors and albumin.
What structure is traversed when the “pop” is felt in a correctly placed caudal block?
sacrococcygeal ligament (a distal extension of the ligamentum flavum)
Where does the dural sac terminate in infants? In adults?
Infants = S3
Adults = S1
What forms the lateral borders of the sacral hiatus?
The sacral cornua.
What physiologic changes cause the most profound effect of advanced age on lung physiology?
Reduced lung elasticity and recoil secondary to decreased lung tissue elastin. This causes premature closure of small airways on expiration.
How does elderly lung tissue compliance compare to younger lung tissue?
More compliant but exhibits decreased alveolar surface area available for gas exchange.
How does chest wall compliance in the elderly compare to a young adult?
It is decreased due to calcific chest walls. This is decreased thoracic (not lung) compliance.
How does FRC in the elderly compare to the young adult?
FRC is slightly increased in the elderly due to loww of elastic recoil that results in increased residual volume (FRC = RV + ERV)
How FVC in the healthy elderly compare to the young healthy adult?
Decreased owing to the loss of elastic recoil.
What effect does ethanol-induced enzyme induction have on MAC?
This is another way of saying chronic alcohol abuse which increases MAC. Acute alcohol intoxication on the other hand, decreases MAC.
Why is alfentanil’s clinical effect so much shorter than fentanyl’s?
Alfentanil has a smaller volume of distribution and shorter elimination half-life.
(Counterintuitively, alfentanil has a slower rate of clearance than does fentanyl. It is also more protein bound than fentanyl)
Is stored blood more likely to have a left-shift or a right-shift of the oxygen-hemoglobin dissociation curve?
Left shift due to the low levels of 2,3 DPG which apparently wins out over acidosis in this particular case.
A patient is brought to the OR on a NTG infusion for open heart surgery. What must you consider prior to going on bypass?
This patient is at risk for heparin resistance and may need higher doses of heparin to achieve the required level of anticoagulation.
How does nitroglycerine affect heparin?
It decreases heparin’s anticoagulant affect.
What are the key differences between Type 1 and Type 2 heparin-induced thrombocytopenia?
Onset:
Type 1 = after 2 - 5 days
Type 2 = after 7 - 9 days of heparin gtt
Severity:
Type 1 = mild low plt count, no thrombi
Type 2 = more serious and severe immune-mediated effect
How does prolonged heparin administration affect the reliability of ACT?
It doesn’t.
What are the landmarks for a sciatic nerve block?
Draw a line between the femur greater trochanter and PSIS.
Draw another line perpendicular and caudomedially from the center of the 1st line 4 -5 cm in length. the sciatic nerve is at the end of this 2nd line.
What effect does preeclampsia have on sensitivity to exogenously administered catecholamines?
Preeclamptic patients are MORE sensitive to catecholamines.
What is a normal aortic valve area?
3 cm squared
Symptoms of aortic stenosis appear when the valve narrows to less than what area?
0.8 cm squared
Most CDH herniations occur on what side?
Left side (90%) via the left foramen of Bachdalek.
What is the major reactant in baralyme?
calcium hydroxide (but it also containes barium hydroxide to start the reaction but it’s the calcium hydroxide responsible for most of the absorbing)
What is the major reactant in soda lime?
calcium hydroxide (but it also contains KOH, and sodium hydroxide to start the reaction)
Which CO2 absorbent contains silica?
Soda lime. Silica is used to minimize dust. Baralyme doesn’t have a dust problem.
What is the pKa of lidocaine?
7.8
If the serum pH is lower than the pKa of a drug, do you expect the drug to be in the ionized or non-ionized form?
Ionized form. The lower the serum pH is than the drug pKa the more ionized the drug will be.
What is the only device on the anesthesia machine that monitors the integrity of the low pressure circuit?
The oxygen analyzer.
What is pentazocine?
Pentazocine is an opioid agonist-antagonist (primarily kappa) that is 0.25 - 0.5 as potent as morphine.
What is buprenorphine?
opioid agonist-antagonist that is a partial mu-receptor antagonist.
What is nalbuphine?
Opioid agonist-antagonist that stimulates kappa receptors and antagonizes mu-receptors
What do organophosphates inhibit?
Most famously, acetylcholinesterases.
But they also inhibit: pseudocholinesterase, and nonspecific plasma esterases.
Organophosphates may affect function for several weeks.
How are atracurium and cis-atracurium metabolized?
Atracurium undergoes ester hydrolysis by plasma esterases and nonenzymatic degradation. The majority is via plasma esterases.
Cis-atracurium is virtually all non-enzymatic degradation (Hofmann reaction).
Does the use of volatile agents in GA c-section lower apgar scores?
No. In fact, the addition of volatine agesnt s allows for higher inhaled FiO2 for a given level of anesthesia which improves newborn condition.
At doses < 1 MAC, by how much do halogenated agents increase blood loss during GA for cesarian section, versus N20 and O2 alone?
No difference has been found in EBL for GA with low dose halogenated agents versus without low-dose halogenated agents.
Note: GA is associated with more EBL than neuraxial anesthesia.
What is miosis?
Small pupil.
What is Horner’s syndrome?
Caused by getting rid of sympathetic tone at the stellate ganglion. This results in:
Ptosis
Miosis
anhydrosis
enopthalmos
nasal congestion, scleral hyperemia (i.e., injected sclerae), increased skin temperature.
What is enopthalmos?
It is a sunken eye. Recession of the eyeball into the orbit.
What are the components of the stellate ganglion?
Inferior cervical ganglion and the 1st thoracic ganglion.
Why is a large volume of anesthetic used for a stellate ganglion block?
Because not all the sympathetic innervation of the head face and upper extremity pass through this ganglion. Spread is sought all the way down to T4 and superiorly along the prevertebral fascia.
What causes the ptosis of a successful stellate ganglion block?
Blockade of sympathetic innervation to the superior tarsal muscle (Mueller’s third).
What causes the enopthalmos of a successful stellate ganglion block?
Interruption of sympathetic tone to the orbitalis muscle (Mueller’s first), which spans the interior orbital fissure.
