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169 Cards in this Set
- Front
- Back
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what are factors that influence EEG?
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-cerebral ischemia
-inhaled anesthetics -body temp -PaCO2 |
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what is normal voltage range of EEG?
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10-200uV
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what is voltage range during a seizure?
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750-1000uV
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what are 3 basic parameters of EEG?
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1-amplitude
2-frequency 3-Time |
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what causes EEG electrical silence?
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-barbs (coma dose)
-etomidate (high dose) -propofol (high dose) -des (2 MAC -Iso (2MAC) -Sevo (2 MAC) -hypoxia (severe) -hypothermia (<15-20degrees) -brain death |
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what occurs during delta wave on EEG?
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-deep sleep
-deep anesthesia -pathologic states (ex brain tumor, hypoxia, metabolic encephalopathy) |
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what occurs during Theta waves on EEG?
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-sleep and anesthesia in adults
-hyperventilation in awake children and young adults |
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what occurs during alpha wave on EEG?
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-resting
-awake adult w/ eyes closed |
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what occurs during beta wave on EEG?
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-mental activity
-light anesthesia |
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what is used intraop to monitor the integrity of specific sensory and motor pathways?
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Evoked potential monitoring
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when are SSEP's useful?
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-spinal cord surg
-carotids -intracranial aneurysms -aortic surg |
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what do SSEP's evaluate?
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-the functional integrity of the ascending sensory pathways
-used ot detect dorsal spinal cord and/or brain ischemia |
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what sensations do SSEP's carry?
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touch, pressure, and vibration
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where does SSEP's measure the integrity of?
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the cuneatus and gracilis tracts of dorsal-lemniscal system in the posterior (dorsal) cord
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where are SSEP' measured?
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at the scalp
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cord comprised results in what during SSEP monitoring?
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increase in latency and decrease in amplitude
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what are physiological factors that alter SSEP's?
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-temp
-systemic BP -PaCO2 -PaO2 |
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what are pharmacologic agents that alter SSEP?
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-volatile anesthetic dose dependently increase latency adn decrease amplitude
-N2O in combination w/ a volatile anesthetic produces a profound depressant on SSEP and VEP |
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what are two meds you should avoid when doing SSEP monitoring?
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-etomidate and ketamine increase the amplitude of scalp recorded waves by 200% to 600%
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what med can be used with little to no effect on SSEP's?
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dexmedetomidine
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how do opoids affect SSEP's?
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-little effect but should avoid bolus administration
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what cranial nerve do BAEP monitor?
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8th cranial nerve (acoustic nerve)
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what evoked potential are least sensitive to changes in anesthetics?
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BAEP
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how are VEP's done?
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delivering flashes of lights
-monitors 2nd cranil nerve |
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when are VEP useful?
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during pituitary tumor removal and during procedures in the vicinity of the optic tracts
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what evoked potentials are most sensitive to anesthetics?
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VEP
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what kind of sensitivity do SSEP's have to anesthetics?
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intermediate
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what do MEP evaluate?
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functiona integrity of the motor cortex and descending (efferent) motor pathways
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when are MEP's used?
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to detect loss of motor function during spinal or vascular surgery
-allows for monitoring of motor pathways w/o a "wake up" test |
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what is advantage of MEP over SSEP's?
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loss of motor function may occur without loss of SSEP's
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T oR F MEP's are more sensitive to anesthetic agents than SEP's?
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True
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what agents produce a marked effect on MEP's?
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-volatile agents
-nitrous oxide >50% -benzos -barbiturates -propofol |
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what meds have little effect on MEP's?
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-fentanyl
-etomidate -ketamine |
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what other things alter MEP's besides meds?
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-hypothermia
-hypoxia -hypotension |
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what are techniques used to monitor ICP?
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-ventricular catheters
-subdural-subarachnoid bolts/catheters -various epidural transducers -intraparenchymal fiberoptic devices |
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what does intracranial pressure monitoring allow?
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-early detection and prompt treatment of brain hemorrhage, swelling, and herniation
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what is standard method of monitoring ICP?
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ventricular catheters
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what is disadvantage of ventrics?
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-can be difficult to place d/t severe brain swelling or a large mass lesion
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what are complications of ventrics?
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-possibility of brain tissue damage
-hematoma -infection |
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what id advantage of subdural-subarachnoid bolts?
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-does not require brain tissue penetration or knowledge of ventricular position
-can be placed in any skull location that avoids major venous sinuses |
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what are disadvantages of subdural bolts?
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-cannot be used to lower ICP by CSF drainage, bolt can come loose
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what are complications of subdural bolts?
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-infections
-meningitis -osteomyelitis -epidural bleeding -focal seizures |
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what are disadvantages of various epidural transducers?
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-risk for infection to the brain is reduced
-placement is difficult and there is risk of bleeding -cannot be used to lower ICP by CSF drainage |
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what are advantages or disadvantages of intraparenchymal fiberoptic devices?
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-easily inserted, less disruptive to brain tissue, low risk of infection
-cannot be used to lower ICP by CSF drainage |
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what is transcranial doppler ultrasound used for?
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-clinical imaging of intracranl vasculature
-used to determine velocity and direction of the moving column of blood in a major artery -used to monitor for vasospasm |
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what are the four windows in the cranium to measure blood flow?
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1-transtemporal
2-transforaminal 3-Transorbital 4-transmandibular |
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where is the pituitary located?
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base of the skull in a bony cavity of the sphenoid bone called the sella turcica
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the cavernous sinus continas what cranial nerves?
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cranial nerve III, IV, V, and VI and the carotid arteries
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what connects the anterior and posterior portions of the pituitary?
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infundibular stalk
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what blood supplies the anterior pituitary?
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internal carotid: the superior hypophysial artery supplies the ant pituitary
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what supplies the posterior pituitary?
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the inferior hypophysial artery supplies the post lobe of pituitary
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what horomones does the ant pituitary secrete?
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GH, prolactin, FSH, LH, ACTH, B-lipotropin, TSH
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What horomones doe the post. pituitary secrete?
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ADH, oxytocin
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what regulates pituitary hormonal secretion?
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feedback from target organs, neuronal control, and chemical influences
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what accounts for 10-15% of intracranial neoplasms?
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pituitary tumors
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what are two types of pit. tumors?
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-nonfunctioning
-functioning |
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what type of pit. tumor is non-horomone releasing?
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Non-functioning
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when are the Non-functioning tumors usually diagnosed?
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when they cause mass effect
-see signs of increased ICP like impaired vision, HA, cranial nerve palsies, hypopituitarism |
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what is life threatening if not treated?
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Pituitary Apoplexy
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what is pituitary apoplexy?
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sudden hemorrhage or infarction of tumor characterized by acute neurologic deficits and rapid impairment of pituitary function
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what is treatment of pituitary apoplexy?
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cortiocsteroids and surgical decompression
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when is a functioning pit. tumor diagnosed?
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when a tumor is small (< 10mm)
-compression of pituitary tissue causes progressive endocrine dysfunction |
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what is the most common funcitoning pit. tumor?
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Prolactin secreting tumor
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what does GH secreting tumor cause?
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acromegaly
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what does ACTH secreting tumor cause?
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Cushing's disease
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GH increased at pubtery causes what?
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gigantism
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GH after puberty causes what?
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acromegaly
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why are people w/ acromegaly considered difficult airways?
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-overgrowth of soft tissues of the upper airway (tongue, epiglottis)
-increased length of mandible -Hoarse voice (alt. in cricoarytneoid joints and recurrent laryngeal nerve0 |
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what are some other complications of acromegaly?
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-peripheral neuropathies like carpal tunnel
-glucose intolerance or DM -osteoarthritis -HTN, CAD, cardiomyopathy -skin becomes thick and oily -skeletal muscle weakness and fatigue |
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what can coritsol do to sodium and potassium?
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enhance potassium excretion and sodium retention
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what can cortisol do to phospholipase A2?
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inhibit, phospholipase A is necessary to produce several prostaglandins responsible for vasodilation
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what are some problems from ACTH secreting tumors?
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-DM
-hyperadlosteronism w/ hypokalemia and metabolic alkalosis -HTN -CHF -obesity -buffalo hump -moonface |
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what does panhypopituitarism mean?
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most of horomones are deficient, requires replacement of horomones. Should be rendered euthyroid
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what is tx for panhypopituitarism/
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-glucocorticoids
-thyroxine therapy -synthetic vasopressin |
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what needs to be evaluated pre-op on pts w/ Cushings?
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-managment of HTN, DM electrolytes imbalances
-CV eval of ischemia heart disease and failure -Eval of CT, MRI, neuro exams for s/s of intracranial HTN -size and location of lesion |
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what lab tests should be done pre-op on pt's w/ Cushings?
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-serum and urinary levels of pituitary, thyroid, and adrenal horomones
-electrolytes Na+ and K+ -HGB, HCT, and T&S |
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when is transphenoidal approach indicated?
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for tumors < 10mm
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what are advantages of transphednoidal approach?
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-lower morbidity and mortality vs craniotomy
-less disturbance of normal tissue, no external scars -decreased incidence of transfusion -lower incidence of DI -no frontal lobe retraction -shorter length of hospitalization |
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what are disadvantages of transphenoidal approach?
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-possile CSF leakage, possible meningitis
-inability to see structures adjacent to large tumor -inaccessibiilty to extending tumors -bldg from cavernous sinuses -bldg from carotid arteries -cranial nerve damage |
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what is fluid requirment for intra-op for transphenoidal approac?
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NS/LR 4-8ml/kg/hr
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what do you need to do on emergence of pt w/ transphenoidal approach?
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-prevent vigorous coughing
-anti-emetic -thorough suctioning of blood in throat and ensure oropharyngeal packs are removed -nose will be packed-mouth breathing |
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what are complications?
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-hypopituitarism
-abnl secretion of ADH can lead to DI or SIADH |
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where is ADh synthesized?
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in the supraoptic nuclei of the hypothalamus and stored in post. lobe of pituitary
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what indictates DI?
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-onset of polyuria (4-18L/day)
-polydipsia -urine sp gravity < 1.005 -urine osmolality < 200mOsm/kg |
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what is Tx of DI?
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-hrly maint. fluid replacement+ 2/3 of the previous hours U.O
-typical fluid= D5 1/2NS -Desmopressin or vasopressin |
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when is Dx of SIADH made?
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-when free water consumption is greater than free water excretion and hyponatremia and hyperosmolar urine
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if serum sodium falls < 120meq/L what s/s may pt develop?
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-HA
-Nausea -Vomiting -Seizures -mental status changes |
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what is tx for SIADH?
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-restricting fluid intake and administration of hypertonic saline
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what are complications to pituitary surg (esp transphenoidal)?
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-permanent DI
-post-op airway obstruction -visual loss -CSF leak -meningitis -ischemic stroke -vascular injury -intracranial hemorrhage -infection -epistaxis -cranial nerve damage -septal perforation |
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what is a craniectomy?
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surgical removal of a portion of the skull
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what are some reasons a craniotomy is performed?
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-infection
-tumor -foreign body -edema -bleeding |
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what is an intracranial aneurysm?
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-a bulge at the site of the localized weakness in the muscular wall of an artery
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what are the three layers in the blood vessels?
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1-intimal layer
2-medial layer 3-adventitial layer |
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what type of aneurysma are small saccular aneurysma most often found at bifurcations of two vessels or w/in circle of willis?
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berry aneurysms
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what is most common cause of SAH?
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ruptured intracranial berry aneurysm
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where is the subarachnoid space?a
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area btwn arachnoid and pia mater
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what is used for repairing some giant aneurysms?
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circulatory arrest under CPB w/ deep hypothermia
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what are some causes of aneurysms?
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-idiopathic
-traumatic -infectious -development defect (congenital predisposition) -atherosclerosis and HTN -smoking, ETOH, cocaine or amphetamine abuse |
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what are some warning signs before the first major bleed?
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-HA
-dizziness -orbital pain -slight motor or sensory disturbances -hypovolemia |
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what are some assoc conditions with intracranial aneurysms?
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-polycystic kidney disease
-coarctation of the aorta -marfan syndrome -Ehlers-Danlos syndrome -intracranial AVM's -aortic aneurysm -sick cell disease |
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why do ECG change occur with brain bleeds?
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blood is irritating to the brain so body releases catecholamines and that release causes ECG changes
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what is used to Dx aneurysm?
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-CT scan
-cerebral angiogram -Lumbar puncture |
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the higher the WFNS score the _________the prognosis?
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worse
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what is tx for aneurysms?
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-radiologic intervention w/ coiling
-early surgical int. for ruptured aneurysm |
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what causes highest incidence of morbidity/mortality w/ aneurysms?
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re-bleeding after the initial rupture
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when is teh highest incidence of re-bleeding?
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w/in 24 hours of hemorrhage w/ no intervention
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when does the incidence of re-bleeding peak again?
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14-21 days
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minimum of how many units of blood should be available for aneurysm repairs?
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4 units
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what labs should be done pre-op on pts with aneurysm?
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-HGB, HCT, coags, t&C, anti-convulsant levels
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T or F premedicating pts w/ sedation is typically avoided w/ intracranial HTN?
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True
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what is intra-op anesthesia goal in aneurysm cases?
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-prevention of re-rupture by preventing HTN and maintaing CPP
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how do you help prevent HTN during induction?
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pretreat w/ beta blocker (esmolol) and lidocaine
-limit laryngoscopy to <15 sec -nicardipine |
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what should PaCO2 be maintained at in aneurysm cases?
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35mmHg-hyperventilation is typically avoided if no increased ICP
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what can hyperventilation do during aneurysm repair?
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can decrease ICP adn icnrease transmural pressure leading to aneurysm rupture
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what is transmural pressure?
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difference btwn arterial pressure and CSF pressure
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the pressure within an aneurysm is equal to what?
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systolic blood pressure
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a fall in ICP or an increase in MAP will do what?
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-increase transmural pressure
-wall stress -risk rupture |
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what is law of LaPlace for cylindrical vessel?
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T=(P*R)/W
T=tension P=pressure R=radius W=wall thickness |
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what is adv of temporary clips in aneurysm repair?
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-decreased blood loss and less likely to cause inadvertent rupture
-BP is often increased 20-30% to improve collateral flow |
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what can you give prior to clipping parent vessel for cerebral protection?
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thiopental
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what is first action take if aneursym ruptures?
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decrease MAP
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what is MAP maintained at during hypotensive technique?
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60-70mmHG
-rapidly decreased to 40-50mmHg if rupture occurs |
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what is temp during circ arrest?
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16-20 degrees C
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what is fluid managment for aneuyrsm repair?
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-avoid glucose containing solutions
-normovolemia until aneurysm is clipped -once aneurysm is clipped intraop fluid deficeits are replaced maintaining a high intravascular fluid volume to prevent vasopspasm |
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what is CVP maintained at after aneurysm is clipped?
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10-12mmHg
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what do you want to avoid on emergence and what can you do to try and avoid it?
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-HTN, coughing, straining, and hypercarbia
-use LITA tubes, LTA kits, IV lidocaine |
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what are the 3 main post-op complications following clipping of an aneurysm?
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-vasospasm
-hydrocephalus -re-bleeding |
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when do vasospasms most frequently occur?
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-4-14 days post-oop
-peak incidence on day 7 |
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what is leading cause of post-op morbidity and mortality after aneurysm repair?
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vasospasm
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what is the mechanism of a vasospasm?
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-causes reduction of blood flow in a large area with subsequent cerebral ischemia
-sm muscle ctx occurs along w. structural damage to the endothelium |
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what are clinical s/s of vasospasm?
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-focal deficeits and global decrease in consciousness
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what is the triple H treatment for vasospasm?
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-HTN-sys BP of 180
-Hypervolemia: goal CVP 10-12 -Hemodilution: HCT levels are stabalized at 30-34% |
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what does nimodipine do?
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-prevent sm muscle ctx
-calcium channel antagonist -dosage 60mg by mouth every 4-6 hrs for 21 days |
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what is definition of AVM?
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direct arterial-to-venous communications w/o intervening capillary circulation
-the vessels are thin and lack muscular layers |
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what are presenting s/s of AVM's?
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-seizures
-HA -progressive neuro deficeits -high output cardiac failure |
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how are AVM's tx?
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-embolization or radiation
-moderate size and lg AVM's-craniotomy |
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what are AVM's aka?
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normal perfusion pressure breakthrough
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what is tx of AVM's?
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-high dose barbiturates
-osmotic diuretics -hyperventilation -maintenance of a low-normal MAP |
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what are categories of intracranial tumors?
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-supratentorial
-infratentorial -intraaxial |
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what is number 1 tumor see?
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-astrocytoma-primarily intracranial tumors derived from astrocyte cells of the brain
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what is main fxn of astrocytes?
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formation of BBB, provision of nutrients to nervous tissue, and role in repairing and scarring process of the brain
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what is an aggressive tumor w/ small areas of necrotizing tissue that is surrounded by mighly anaplastic cells?
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gliobastoma-grade 4 astrocytoma
-most common astrocytoma |
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what is an oligodroglima?
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tumor involiving or originating from teh oligodendrocytes of the brain
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what is main fxn of oligodendrocytes?
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myelination of axons in the CNS
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what is a sterotactic surgery?
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surgery in which a system of three-dimentional coordinates is used to locate the site to be operated on
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what are indications for stereotactic surgery?
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-tx of involuntary mvts
-epilepsy -dx and tx of deeply situated brain tumors |
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what are disadvantages of stereotactic biopsy?
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limitation-tumor remains
risks: bleeding, infection risk of significant bleeding requiring craniotomy 1-2% |
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what are some causes of epilepsy?
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electrolyte imbalances
disorders of the brain metabolism infection brain tumor brain trauma hyperthermia |
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what is an intractable seizure?
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perisistent seizure activity of such severity that is prevents normal function and development
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what is a wada test?
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intracarotid inj of a barbiturate is performed to determine if the are of the resection has any speech function or cerebral dominance
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what are some SE of anticonvulsants?
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-inducement of cytochrome p450 system
-resistanct to nondepolarizing muscle relaxants |
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what does carbamazepine cause?
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-abnl liver function
-decreased plt -decreased WBC |
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what are drugs to avoid in caring for patient's with epilepsy?
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-ketamine
-methohexital -atracurium -cisatracurium -meperidine |
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what is the metabolite that cross the BBB and can cause exitement and seizure activity?
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laudanosine
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how long does normeperidine last and what can it cause?
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-half life of 15-20 hrs or more in elderly and pts w/ renal failure
-can cause dysphoria and convulsions |
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why is halothane avoided?
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d/t hepatotoxicity assoc with chronic anticonvulsant admin.
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what is recommended technique for wake up testing?
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sevo and remifentanil
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what are some possible complications of surgery for seizures?
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-an increase in seizures
-paresis/paralysis -anticonvulsant levels may increase d/t protein binding competition w/ agents used for anesthesia |
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what is communicating?
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CSF escapes from ventricular system and is not being absorbed by the arachnoid villi
-may be caused by infection or blood in CSF space |
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what is noncommunicating?
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CSF from the ventricular system is obstructed
-may be caused by blood, infection, or tumors in ventricular system |
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what is purpose of VP shunt?
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diverts CSF from ventricles to another body cavity for absorption
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there is increased morbidity w/ head trauma w/?
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-greater than 5mm midline shift
-lesion larger than 25ml -ventricular compression |
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what are signs of basilar skull fracture?
|
-blood in sinuses
-clear fluid leaking from nose and ears -racoon eyes -battles sign (caused when blood collects behind ears and causes bruising) |
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what med should you not use in head trauma pts for induction?
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ketamine
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why is STP an ideal agent for head trauma?
|
-decreases ICP, CMR, maintain cerebral autoregulation
-redistributes flow to ischem portions of the brain |
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what are 5 conditions highly correlated with spinal cord injuries?
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-paralysis
-pain -position -parasthesia -priapism |
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what are signs of spinal shock?
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-hypotension
-bradycardia -hypothermia |
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what are s/s of autonomic hyperreflexia?
|
-paroxysmal HTN
-bradycardia -cardiac dysrythmias |
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what is tx of autonomic hyperreflexia?
|
-remove the stimulus
-deepening the anesthesia -administer direct acting vasodilators -atropine or glycopyrolate |
