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.