Principles I Flashcards
Cerebral blood flow determinants
- cerebral metabolic rate
- cerebral perfusion pressure (CPP)
- PaCO2
- PaO2
- Drugs
- intracranial pathology

Normal cerebral blood flow
50 mL per 100g brain tissue per minute [perfusion]
(over a CPP range of 50-150mmHg)
750mL/min
Normal cerebral metabolic rate
3.0 - 3.8 mL
(per 100g brain tissue per minute)
What can decrease cerebral metabolic rate?
decreased temperature and anesthetic agents
What can increase cerebral metabolic rate?
increased temperature and seizures
How does PaCO2 affect CBF?
CBR increases 1mL/100g/minute for every 1 mmHg increase in PaCO2
- effects of hypocapnia can last 6 hours
How does PaO2 affect CBF?
Below 50mmHg cerebral vasodilation and increased CBF
- hypoxia causes an increase in blood flow
- <50mmHg
- vessels maximally dilated - pressure dependent flow
- >150mmHg
- vessels maximally constricted - pressure dependent flow
Factors affecting autoregulation
- chronic hypertension
- shifts curve to the right
- intracranial tumors
- head trauma
- volatile agents
How do volatile agents affect cerebral blood flow?
direct vasodilators with doses greater than 0.6-1 MAC
- decrease CMRO2
- uncoupling of CBF and CMRO2
What can happen if nitrous oxide is used after dural closure?
tension pneumocephalus
Tension Pneumocephalus
increased ICP secondary to pneumocephalus
- air enters through a dural defect and is unable to escape
How does Ketamine affect the brain?
vasodilates
How do barbituates, etomidate, propofol, and opioids affect the brain?
cerebral vasoconstrictors
- decrease CBV and ICP
How does Succinylcholine affect the brain?
increases ICP temporarily
Normal Intracranial Pressure
5-15mmHg
Determinants of ICP
brain tissue and spinal cord, blood, and CSF
Intracranial Elastance Curve
depicts impact of increasing intracranial volume on ICP
- no volume increase from point 1 to 2 due to shift of CSF from cranium into spinal subarachnoid space

(6) Signs of Increased ICP
- headache
- nausea
- vomiting
- papilledema
- depressed consciousness
- coma
3 Methods of ICP measurement
- subdural bolt
- ventriculostomy
- lumbar subarachnoid catheter
(6) Methods to decrease ICP
- head elevation
- hyperventilation
- CSF drainage
- ceerebral vasoconstricting anesthetics
- surgical decompression
- hyperosmotic drugs
- mannitol
- lasix
How should mannitol be given to decrease ICP?
0.25 - 0.5 g/kg IV over 15-30 minutes
What can be given 90s before intubation and extubation?
lidocaine 1.5mg/kg IV
Foramen Ovale
hole between right and left atria
- can have a paradoxical air embolism
Diagnosis of Venous air embolism
- precordial doppler over right sternal border
- TEE
- decreased etCO2
- increase in PA catheter pressure
What drug is most commonly used for deliberate hypotension in neuro cases?
sodium nitroprusside
Side effects of Sodium Nitroprusside
- cyanide toxicity
- treat with thiosulfate
- increased ICP
- inhibition of platelet aggregation
- increased pulmonary shunting
- baroreceptor mediated tachycardia
- rebound hypertension
“Triple H Therapy” for Cerebral aneurysm
- hypervolemia
- hypertension
- hemodilution
Grading system for Cerebral Aneurysm
Hunt-Hess
- grads 1 through 5
- 1 - asymptomatic
- 5 - deep coma
Rendu-Osler-Weber Syndrome
autosomal dominant genetic disorder that leads to abnormal blood vessel formation
- common epistaxis episodes
- AVMs
What is the leading cause of death following SAH?
pulmonary embolus
What should you give to depress vasospasms?
CCB
What separates the cerebrellum from the cerebrum?
tentorium
What % of the cardiac output does the brain recieve?
15%
Equation for cerebral perfusion pressure
MAP - ICP
Pediatric Versed dose PO
0.5 - 1 mg/kg
Pediatric Versed dose IM
0.1 - 0.2 mg/kg
Pediatric Morphine dose IM
0.1 - 0.2 mg/kg
Pediatric Ketamine dose IM
3 - 5 mg/kg
Pediatric Ketamine dose IV
0.25 - 0.75 mg/kg
Metoprolol IV push
2 - 15 mg
Neosynephrine IV push
50 - 200 mcg
Neosynephrine IV infusion
0.15 - 0.75 mcg/kg/min
Mean Arterial Pressure
Diastolic pressure + 1/3(pulse pressure)
normal 80-120 mmHg
Cardiac Index
CO/BSA
2.8 - 4.2 L*min/m^2
Meperidine dose
50 - 150 mg
Morphine dose
5 - 15 mg
Atropine pre-op dose
0.4 - 0.8 mg
Scopolamine dose
0.3 - 0.6 mg
Diphenhydramine dose
25 - 50 mg
Stroke Volume
CO/HR * 100
60-90 mL/beat
Stroke Index
SV/BSA
40 - 60 mL/beat/min
Signs of Oxygen failure
hear O2 failure alarm or “low FiO2” when on 100% Oxygen
Immediate steps in Oxygen failure
- disconnect patient from the machine and ventilate with Ambu on room air
- Open O2 tank and disconnect pipeline
- or obtain E-cylinder
- connect gas sampling adaptor
- maintain anesthesia with IV drugs
Signs of Venous Air Embolism
- air on TEE or change in Doppler tone
- decrease in EtCO2
- decrease BP
- decrease SpO2
- rise in CVP
- onset of dyspnea and respiratroy in awake patient
Treatment of Venous Air Embolism
- increase to 100% oxygen
- flood surgical field with saline
- place surgical site below heart
- aspirate air from central line
- turn down or off volatile anesthetic
- Epinephrine (10-100ug) to maintain CO
- start CPR
- consider TEE, left lateral decubitus, and terminating procedure
Immediate treatment for Hypoxemia
- increase to 100% O2
- check gas analyzer to rule out low FiO2
- check vitals, PIP, pulse, and EtCO2
- hand-ventilate
- listen for breath sounds
- check tube position
- soft suction via ETT
- large recruitment breaths
- consider PEEP unless hypotensive
- bronchodilators
- increase FRC
Differential Diagnosis for Hypoxemia
- Hypoventilation
- low FiO2
- V/Q mismatch or shunt
- diffusion problem
- increased metabolic O2 demand
Copaxone
treats Multiple Sclerosis
Name (2) pathologic conditions that can lead to intracranial bleeding
aneurysm and AV malformations
Rediculopathy
pain that is localized to a specific nerve root
- usually from a pinched nerve or tumor
Multiple Sclerosis
autoimmune disease that destroys the myelin on the nerve sheath
- muscle weakness, parasthesia, and vision changes
Anesthetic concerns for Multiple Sclerosis
- avoid Succinylcholine
- may produce hyperkalemia due to denervation sensitivity by upregulation of acetylcholine receptors
- maintian lower body temperature
- epidurals are safer than spinals
- use a lower LA concentration
Side effects of long-term steroid use
(prednisone)
may cause diabetes, edema, and fragile skin
- more prone to osteoporosis
- suppresses immune system
- high risk of infection
(3) methods to improve surgical exposure during a SAH
- hyperventilate to reduce PCO2 and reduce brain size
- diuretics
- CSF drainage
AV Malformations
abnormal connection between arteries and veins that bypass the capillary system
- causes a “steal syndrome” and ischemia
- intracranial hemorrhage will cause SAH
Grading System for AV Malformations
Spetzler - Martin
- based on size, eloquence, and venous drainage
What procedures would require an awake craniotomy?
Deep-stimulation for Parkinson’s, epileptic foci, and treating depression and compulsive disorders
Deep Brain Stimulation (DBS)
high frequency electrical stimulation
- treatment for Parkinson’s
- targets subthalamic nucleus and globus pallidus interior
Dexmedetomidine for DBS
provides sedation and anxiolysis with minimal effect on respiration
- alpha agonist
Interventional Neuroradiology (IR)
endovascular neurosurgery to deliver drugs and devices
- used in aneurysms, embolization of vascular tumors, AVMs, and fistulae of the brain
ventriculoperitoneal (VP) shunt
relieves pressure on the brain from hydrocephalus
Complications of INR procedures
- hemorrhage
- occlusive complications
- contrast reactions
- contrast nephropathy
Concerns of patients with hydrocephalus undergoing neuroendoscopy
- hypovolemia
- sudden ICP changes
- avoid nitrous oxide
Cardiovascular changes with Prone
- decreased:
- cardiac index (CI)
- venous return
- left ventricular volume
- compliance
Abdominal compression in prone
increases pressure on vena cava
- increases bleeding
- due to congestion of vertebral veins
- ischemia of spinal cord
Respiratory changes in Prone
perfusion is more evenly dispersed and there is an increase in FRC
Airway management in patients with an unstable neck injury
- awake fiberoptic
- glidescope
- manual inline stabilization (MILS)
Factors in Prone Vision Loss
- retinal perfusion pressure
- arterial blood pressure
- intraocular pressure
- anemia
(4) visual defects associated with spine surgery
- ischemic optic neuropathy
- cortical blindness
- central retinal artery occlusion
- central retinal vein occlusion
Anterior Ischemic Optic Neuropathy
ischemia in the anterior part of the optic nerve where the nerve enters the globe
- can result from a low hematocrit
- first noticed upon waking up
- may present later with low-pressure glaucoma and optic atrophy
Posterior Ischemic Optic Neuropathy
(retrobulbar optic neuropathy)
infarction of the intraorbital portion of the optic nerve
- severe visual impairment
- mainly caused by hypotension, anemia, and facial edema
Cortical Blindness
damage to the occipital corte or optic radiation
- ischemic or traumatic
- may be caused by hypotension, hypoperfusion, anemia, or head position
Central Retinal Artery Occlusion
caused by embolus from ipsilateral carotid artery
- external ocular pressure with arterial hypotension
- complete vision loss that usually improves with time
Phenelzine
(nardil)
MAO inhibitor for depression
- increases catecholamines
- stop 2 weeks before surgery
-
avoid Demerol in patients using MAO inhibitors
- precipitates serotonin syndrome
Citalopram
(celexa)
SSRI for depression
(4) Types of Intracranial Hematomas
- epidural
- subdural
- subarachnoid
- intracerebral (intraparynchemal)
Epidural Hematoma
occurs when trauma causes damage to bridging arteries
- usually meningeal artery
Subdural Hematoma
between dura and arachnoid space
- bleeding from vein rather than artery
- slower bleed
- commonly seen in elderly
Subarachnoid Hematoma
commonly caused by an aneurysm rupture
Glasgow Coma Scale
measures neurological integrity
- eye opening, verbal response, and motor response
- Mild 13-15
- Severe 3-8 (3 is the lowest)
At what % of blockge in a carotid causes concern?
60-70%
What common diuretic is contraindicated in patients allergic to sulfonamide?
Loop Diuretics
(Lasix)
Symptoms of Parkinson’s
resting tremors, instability, muscle rigidity, bradykinesia, and akinesia
Anesthetic concerns in Parkinson’s Patients
- uncertain response to central neuraxial blockade
- autonomic dysfunction
- high risk of aspiration
- postoperative emergence delirium
What type of drugs should you avoid in a person using Levodopa?
MAO inhibitors
What drugs may exacerbate symptoms of Parkinson’s?
Phenothiazine, Butyrophenon, and Metoclopromide
ACC
American College of Cardiology
Risk factors for Artherosclerosis
- men > women
- family history
- overweight
- smoking
- hypertension
- diabetes
Thrombus vs. Embolus
thrombus is a stationary plaqu, embolus is moving
Most common cause of mortality in people undergoing intravascular procedures
MI
- 40-50% of patients will get an MI
High risk surgeries other than vascular
- intraperitoneal
- intrathoracic
- carotid endarterectomy
- head and neck surgery
- orthopedic
- prostate
- trauma
acute MI
7 days or less before examination
recent MI
more than 7 days but less than 1 month
How long after an MI should you wait before an elective surgery?
4-6 weeks
Which valvular diseases are considered high risk?
aortic stenosis or mitral stenosis
Types of COPD
bronchitis (blue bloaters) and emphysema (pink puffers)
Difference between asthma and COPD
asthma is somewhat reversible, COPD is chronic
Normal Creatinine
0.6 - 1.2 mg/dL
greater than 2 is significant
Chronic Kidney Disease
diminished renal function without dialysis
- based on creatinine clearance
- 1-5 classifications
Normal GFR
90 - 120 mL/min
- a rate below 60 indicates renal damage
Diagnostic Testing for Cardiac Function
- EKG
- exercise EKG
- radionuclide perfusion
- dobutamine stress test
- TEE
- coronary angiography
TEE
echo test
- show wall motion abnormalities
- chambers of the heart, ejection fraction, volume status, and valve sounds
Wait time after a bare metal stent
4 - 6 weeks
Wait timea after a PTCA
1 year
- dual anti-platelet therapy for a year after surgery
- dangerous to stop treatment because they could have acute perfusion
Benefits of shunt during a CEA
don’t have to rely on collateral flow
(but could create an embolus)
Benefits of clamping during CEA
less risk of embolus
(potential for cerebral ischemia)
If a patient develops ischemia, what would you see on a TEE
diskinetic or hypokinetic
PAD
Peripheral Arterial Disease
Peripheral Arterial Disease
intermittent claudication causing impaired blood flow during exercise
- especially present in legs
- can treat with PTA, femoral artery bypass, or aortic bi-fem bypass
PTA
Percutaneous Transluminal Angioplasty
Percutaneous Transluminal Angioplasty
opens up a bolcked vessel by using a small balloon catheter
Concens with patient undergoing surgery for PAD
- Coumadin (warfarin)
- should be taken off 4-5 days before surgery
- check PT
- may need to switch to a heparin drip while discontinuing other meds
Where does an AAA usually occur?
between renal and mesenteric arteries
What size of AAA indicates surgical removal?
greater than 5 cm
Which part of the spinal cord is at greater risk of ischemia?
anterior
(artery of adamowicz)
Bair Huggers and AAA
upper body only
- lower body may not be perfusing well and heating that area could cause burns
Physiology of Cross-Clamping during AAA
- increase in afterload
- increases more the higher the clamp is placed
- decrease in CO
- acidosis
Nipride
treatment for hypotension
1 - 10 mcg/kg/min
- light sensitive
- can develop tachyphylaxis and cyanide poisoning
- typically mixed 200mcg/mL
Nipride vs. Nitroglycerin
Nitroglycerin is more venodilating, Nipride is an arterial dilator
- Nipride is quicker on and off
- Nitroglycerin can reduce preload
Renal Toxic Drugs
non-steroidals, IV contrast, vancomycin, gentamycin
Physiology after cross-clamping during AAA
- hyperperfusion to underperfused tissues
- overal pH decreases
- PCO2 increass
- decrease in body temperature
- increase in RR
EVAR
endovascular aneurysm repair
What reverses Heparin?
protamine
Why should a patient be prepped and draped before induction?
wont have to take time while they’re asleep and risk changes in hemodynamics
What can be done to preserve renal function during aortic surgery?
- maintain blood pressure within normal range
- avoid nephrotoxic drugs
- Lasix or Mannitol questionable
What should you do in anticipation of removal of the aortic cross clamp?
- volume load
- vasoconstrictors
- Discontine nipride if using it
- request surgeon to gradually release clamp