Flashcards in Exam 2: Key Terms Deck (78):
Why do patients lose heat under anesthesia?
Anesthesia lowers thermoregulatory threshold for shivering and causes vasodilation.
What is the potential benefit of inducing deliberate hypothermia during cardiopulmonary bypass?
Improves tissue tolerance of ischemia and protects against cerebral and cardiac ischemia
CNS injury may be higher with normothermic CPB
What is the physiologic response to heat loss in adults?
Shivering followed by vasoconstriction, moving the temperature gradient toward the core.
What effect does temperature have on MAC requirements?
Decreases MAC 5% for every 1*C lost
What are some physiologic consequences of hypothermia?
-Impaired immune function
-Decreased oxygen flow to tissue
-Increased incidence of arrhythmias
-Decreased drug metabolism
-Reduced platelet function and activation of clotting cascade (more blood loss)
-Marked increase in O2 consumption (shivering)
What is a potential benefit of monitoring temperature via the auditory meatus?
Theoretically reflects brain temperature because the auditory canal's blood supply is the external carotid artery
What effect does hypothermia have on metabolic requirements?
For every 1°C below 37°C there is a 5 to 7% decrease in metabolic requirements (BMR & CMRO2)
To what temperature would you have to cool the patient in order for it to be neuroprotective?
< 35°C may be neuroprotective
How do we confirm placement of a double lumen tube?
With a flexible fiber-optic bronchoscope
When using a FFOB to look out of the Murphy Eye in a right-sided double lumen tube what should be seen?
What are some of the predictors of increased morbidity during thoracic procedures?
PPO < 40% ****
Max VO2 <10 mL/kg/min ****
Type of surgery (pneumonectomy = highest)
Post-op hemorrhage (20% mortality)
Regardless of the procedure the major anesthetic consideration for patients with esophageal disease is what?
Risk of pulmonary aspiration
How does the lateral decubitus position effect ventilation and perfusion?
Perfusion favors the dependent lung whereas ventilation favors the less perfused upper lung
What are some examples of thoracic procedures?
According to our lecture notes, what are some absolute indications for one lung ventilation?
Necessary controlled distribution of ventilation
How can we achieve one lung ventilation?
Double lumen tube
Single lumen tube with bronchial blocker
What is the difference between resectability and operability?
Resectability is determined by the anatomic stage of the tumor
Operability is dependent upon the extent of the procedure and the physiological status of the patient
What factors can inhibit HPV?
Calcium channel blockers
What are some of the ventilation goals for one lung ventilation?
Optimize oxygenation & ventilation!
6-8 mL/kg to ventilated lung
Peak pressure <25 cmH2O
Typically use PC
+/- PEEP to ventilated lung (auto peep=bad)
+/- CPAP to non-ventilated lung
What are the two special monitor placement requirements for a mediastinoscopy?
Right sided pulse ox
Left sided BP cuff
What is the most common site for cerebral aneurysms?
At the bifurcation of the large arteries at the base of the brain (Anterior circle of Willis)
What are the normal values for:
CBF = 50mL/100g/min (750mL/min)
CMRO2 = 3.5mL/100g/min (50mL/min)
CSF volume = 150mL
CPP = 80-100 mmHg
ICP = 5-10mmHg
How is intracranial hypertension defined and how does the body naturally compensate?
Sustained ICP > 15mmHg
1. Displacing CSF
2. Increasing CSF absorption
3. Decreasing CSF production
4. Decreasing CBF
What are some risks associated with intracranial hypertension?
What are the risk factors for subarachnoid hemorrhage?
Same as for freaking everything else
Familial (1st gen.)
What are the critical values for CBF and CPP?
CBF = 18mL/100g
Irreversible damage @ CPP <25 mmHg
What are some of the determinants CBF?
-CPP [= MAP-ICP (or CVP)]
-Respiratory gas tension (PaCO2 more than PaO2)
-Temperature (decrease temp, decrease CBF)
What effect do IV induction drugs have on CBF? What is the exception?
Induction drugs = decrease CBF
Ketamine = increase CBF
What can we do to lower ICP?
Treat underlying cause
Decrease CSF volume (drainage, diuretics)
Decrease brain volume (steroids, mannitol 1g/kg)
What are some anesthetic considerations for a patient with a seizure disorder?
NMB Resistance (due to chronic therapy)
Avoid: ketamine, etomidate, and N2O
What are some potential complications of subarachnoid hemorrhage?
-Rerupture (kiss of death)
-Reactive vasospasm w/ infarction
(acute=5-30min after, long-term=3-12days)
-Hydrocephalus -> 2* hyponatremia
What are some of the signs & symptoms of intracranial mass lesions?
Decline in cognitive function
Focal neurological deficits
In general, how is the prognosis for intracranial tumors related to growth?
Slow changes are better tolerated.
Acute changes and fast growth leads to a poor prognosis.
What is the most aggressive primary brain tumor?
Which neurological disease is treated with a deep brain stimulator(DBS)? How does it work?
DBS promotes dopamine release
What 2 adverse events are the 2 leading causes of morbidity and mortality in patients with intracranial aneurysms?
According to Dr. Ghani, What is the difference between slightly, moderately and severely increased ICP?
Slightly increased = 15-20 mmHg
Moderately increased = 21-40 mmHg
Severely increased = >40 mmHg
Which brain herniation site is associated with the highest mortality?
(Bonus: what congenital malformation can cause this?)
Cerebellar tonsils through the Foramen Magnum (#3 on diagram)
(Bonus: Arnold-Chiari malformation)
What is the triple H therapy of cerebral vasospasm treatment?
What is the time course of re-bleeding following subarachnoid hemorrhage?
AVM vs. Aneurysm: Matching
Compare: Blood Loss, Vasospasm, hyperperfusion, BP mgmt, BV mgmt
(AVM=massive, An.=min. unless rupture)
(AVM= no, Aneurysm= yes, problem)
(AVM = yes, Aneurysm = no)
BP Post-Op management:
(AVM = Low, Aneurysm = High)
Blood vol. Post-Op management:
(AVM = Normal, Aneurysm = High)
What are the effects of changes in cerebral perfusion pressure (CPP)?
Too high = edema
Too low = ischemia
What can cause shifts in the CBF curve?
Right = HTN
Left = hypercarbia, vasodilators, anesthetics
What is an important positioning consideration for neuroanesthesia?
Encourage venous drainage
(obstruct IJs -> increase ICP)
What are the four emergence goals for neuroanesthesia?
1. No coughing
2. No hypertension
3. Prompt - neurological fxn
4. Minimal hypercarbia
What is the most important consideration during induction for an intracranial aneurysm?
What do you do if the aneurysm ruptures?
-Keep up with blood loss
-Controlled hypotension (if surgeon needs it)
-Barbiturates: propofol (not etomidate)
How do we protect the brain during repair of a cerebral aneurysm?
Hypertension (with focal ischemia)
Drugs (barbiturates, propofol, Iso)
What is hyperperfusion phenomenon?
When areas surrounding an AVM are ischemic, sudden reperfusion is not tolerated. (Avoid HTN)
Oculocardiac reflex effects which cranial nerves?
Afferent- Trigeminal (V)
Efferent- Vagus (X)
What are some of the risks associated with a retrobulbar block?
Central retinal artery occlusion
Perforation of globe
What are the contraindications for a retrobulbar block?
Open eye injury
What are the advantages of a peribulbar block?
Avoids injection into muscle cone
Avoids need for facial nerve block
Lowers risk of globe perforation
What is the purpose of hyaluronidase with local anesthesia for ophthalmologic procedures?
It's an enzyme to breakdown orbital fat which allows for faster onset time of block
What happens if local is accidentally injected into the spatium intervaginale? Why?
After 5 to 7 minutes the patient will lose consciousness and stop breathing (lasts 10-15 mins)
Why? Spatium intervaginale is a subarachnoid space
What is the leading cause of cataracts?
What drug can you not give to strabismus patients and why?
-Interferes with forced duction testing
-Increased MH incidence with strabismus patients
What part of the eye allows you to see details?
Why is it important that a patient not move or cough during ophthalmological procedures?
-Surgeon is working in a tiny area
-Can cause increased IOP & expulsive hemorrhage
What are the two most important determinants of intraocular pressure?
Rate of formation and drainage
What is the treatment for oculocardiac reflex?
Tell surgeon & wait it out (will eventually stop)
Supportive therapy if necessary
For purposes of convention what is the definition of geriatric?
Persons over the age of 65
What are some examples of continuously replicating cells, cells Replicating in response to a challenge and non-replicating cells?
-GI, epidermal, hematopoietic
Replicating in response to challenge:
-neurons, skeletal and cardiac muscle
Why does the geriatric population in general require lower drug doses?
They have increased or exaggerated pharmacologic effects due to less efficient protein binding
How does the blood volume of an elderly patient compare to that of an average adult?
Elderly have 20 to 30% reduction in blood volume
How does the thermoregulatory setpoint in an elderly patient compare to the average adult? How does that affect their ability to thermoregulate?
Set point = 0.5°C lower in elderly
They cool faster, warm slower
What are the physiologic changes in the CNS associated with aging?
How do they present?
Decreased: neuronal mass, CBF, CMRO2
-Decreased complex learning, sleep requirement, REM sleep.
-Slower psychomotor performance
-Increased motor response time
Which lab values remain unaffected in the aging population?
What is the most important part of the preoperative assessment for the geriatric patient?
What is the best choice of anesthesia for a geriatric patient?
In general, less is more.
-local without sedation is better than regional or general
What is the main difference between anaphylactic and anaphylactoid reactions?
Anaphylactoid reactions resemble anaphylaxis but are NOT mediated by immune system
Anaphylaxis, angioedema, urticaria, and atopy are examples of what type of reaction?
Type I: immediate
What must have first happened in order for an anaphylactic reaction to occur?
Previous exposure to antigen
What is the most common drug induced allergic reaction seen in the OR?
Redman's syndrome is an example of what?
What is the only anaphylactic reaction that has a delayed onset as seen in the OR?
What is the first sign of an anaphylactic reaction?
Hypotension, but depending on cuff cycling times reflex tachycardia may be seen first