Neurologic Intensive Care Flashcards
References: Continuum, Neurocritical care 2024
Monro-Kellie doctrine
ICP is a function of the volume and compliance of each component of the intracranial compartment
** Under physiologic conditions, the intracranial contents include (by volume):
●Brain parenchyma – 80 percent
●Cerebrospinal fluid – 10 percent
●Blood – 10 percent
intracranial hypertension definition
pressures ≥20 mmH2O
CSF production rate
SF is produced by the choroid plexus and elsewhere in the CNS at a rate of approximately 20 mL/hour (500 mL/day)
Causes of intracranial hypertension
intracranial hypertension clinical findings
Global symptoms of elevated ICP include
1) headache, which is probably mediated via the pain fibers of cranial nerve V in the dura and blood vessels
2) depressed consciousness due to either the local effect of mass lesions or pressure on the midbrain reticular formation
3) vomiting
Signs include
1) CN VI palsies
2) papilledema
3) spontaneous periorbital bruising
4) a triad of bradycardia, respiratory depression, and hypertension (Cushing triad)
Focal symptoms of elevated ICP may be caused by local effects in patients with mass lesions or by herniation syndromes.
Herniation results when pressure gradients develop between two regions of the cranial vault.
Most common anatomic locations affected by herniation syndromes
-
subfalcine (υποδρεπανικός)
η έλικα του προσαγωγίου πιέζεται κάτω από το δρέπανο, με αποτέλεσμα συμπίεση της πρόσθιας εγκεφαλικής αρτηρίας και επακόλουθη ετερόπλευρη πάρεση κάτω άκρου, καθώς και διαταραχές συμπεριφοράς -
central transtentorial
δυσλειτουργία στελέχους
εκδηλώνεται με κώμα, άποιο διαβήτη και σύνδρομο Parinaud (αδυναμία κατεύθυνσης βλέμματος προς τα πάνω, κόρες μέσου εύρους, σύσπαση βλεφάρου, «σημείο δύοντος ηλίου») -
uncal transtentorial (αγκιστρωτής έλικας)
συμπιέζεται το σύστοιχο κοινό κινητικό νεύρο, προκαλώντας μυδρίαση με κατάργηση του φωτοκινητικού αντανακλαστικού, καθώς και η σύστοιχη οπίσθια εγκεφαλική αρτηρία, προκαλώντας έμφρακτο στην κατανομή της
Επιπλέον, εμφανίζεται ετερόπλευρη ημιπάρεση και, μερικές φορές, ομόπλευρη ημιπάρεση λόγω παγίδευσης του ετερόπλευρου εγκεφαλικού σκέλους πάνω στο σκηνίδιο (φαινόμενο εντομής του Kernohan) -
upward cerebellar (ανάστροφος διασκηνιδιακός της παρεγκεφαλίδας)
συμπίεση του μεσεγκεφάλου
Κλινικά εκδηλώνεται με κώμα, μύση (αντιδραστική), απουσία ή ασυμμετρία οφθαλμοκεφαλικού αντανακλαστικού και κινήσεις απεγκεφαλισμού -
cerebellar tonsillar/foramen magnum
οι παρεγκεφαλιδικές αμυγδαλές παρεκτοπίζονται στο ινιακό τρήμα, με αποτέλεσμα καρδιοαναπνευστική δυσλειτουργία (άπνοια, υπέρταση) και ανακοπή -
transcalvarial (εγκεφαλοκήλη)
ο εγκέφαλος προβάλλει έξω από την κρανιακή κοιλότητα μέσω κρανιακού ελλείμματος (είτε χειρουργικού – κρανιεκτομή, είτε λόγω κατάγματος του κρανίου)
Herniation syndromes
Supratentorial lesions are associated with uncal and central herniation depending on the location of the lesion.
Infratentorial structural lesions may also cause herniation, either transtentorially upward, producing midbrain compression, or downward through the foramen magnum with distortion of the medulla by the cerebellar tonsils.
Uncal άγκιστρο
Subfalcine υποδρεπανικός
Types of ICP monitors
Intraventricular
Intraparenchymal
Subarachnoid
Epidural
standard resuscitation techniques in increased ICP
● Head elevation
● Hyperventilation to a PCO2 of 26 to 30 mmHg (contraindicated in the setting of traumatic brain injury and acute stroke)
● Intravenous mannitol (1 to 1.5 g/kg)
Increased intracranial pressure management protocol
Fluids, blood pressure and fever management in increased ICP
only isotonic fluids (such as 0.9 percent saline).
Serum osmolality should be kept >280 mOsm/L, and often is kept in the 295 to 305 mOsm/L range
BP should be sufficient to maintain CPP >60 mmHg.
Hypertension should generally only be treated when CPP >120 mmHg and ICP >20 mmHg
aggressive treatment of fever, including acetaminophen and mechanical cooling, is recommended in patients with increased ICP.
Mannitol dosing
IV (using 20% solution): 0.5 to 2 g/kg once; may repeat 0.25 to 1 g/kg per dose every 4 to 6 hours based on response and clinical status
Mannitol contraindications and warnings
1) anuria; severe hypovolemia; active intracranial bleeding except during craniotomy; preexisting severe pulmonary vascular congestion or pulmonary edema
2)
Fluid/electrolyte imbalance: May cause hypervolemia and electrolyte disturbances; monitor for new onset or worsening cardiac or pulmonary congestion. Also may cause profound diuresis with fluid and electrolyte loss; close medical supervision and dose evaluation are required. Correct electrolyte disturbances; adjust dose to avoid dehydration.
Nephrotoxicity: May cause kidney dysfunction, especially with high doses; use caution in patients taking other nephrotoxic agents, with sepsis, or preexisting kidney disease. To minimize adverse kidney effects, monitor serum osmolality or osmolar gap
When should corticosteroids be administered in increased ICP
Glucocorticoids were associated with a worse outcome in severe head injury.
They should not be used in this setting.
In addition, glucocorticoids are not considered to be useful in the management of cerebral infarction or intracranial hemorrhage
By contrast, glucocorticoids may have a role in the setting of intracranial hypertension caused by brain tumors and central nervous system infections.
Dexamethasone dosing in brain tumor edema
Initial: IV: 10 mg once followed by maintenance dosing
Maintenance: IV, Oral: 4 mg every 6 hours
Note: Consider taper after 7 days of therapy; taper slowly over several weeks