Book 6, Case 7 emergent crani, vWD Flashcards
What is vWD?
most common inherited coagulation disorder,
caused by qualitative or quantitative defects of von Willebrand factor (vWF) in the plasma.
vWF plays an important role in both primary hemostasis and coagulation by mediating
platelet adhesion to the subendothelial surface of blood vessels (via the GPib receptor),
facilitating platelet-to-platelet aggregation (via the GPIIb/IIIa receptor), and functioning as a
carrier protein and stabilizer for factor VIII
Look over vWD types in learning issues
Okay
The family is not sure of the patient’s specific type of vWD or past treatment. How
would you evaluate her coagulation status?
I would perform a history, physical, and chart review to help identify the type
and severity of vWD; previous transfusion requirements; and episodes of abnormal bleeding,
such as easy bruising, hematomas, epistaxis, menorrhagia, and gingival, traumatic, or
perioperative bleeding. I would then order a CBC, platelet count, bleeding time, PT, and
PTT, recognizing that mild disease will likely produce near-normal studies, with severe
disease resulting in prolonged bleeding, thrombocytopenia, and a prolonged PTT, depending
on the type of disease. Given the severity of this patient’s condition and the urgency of the
case, I would not delay treatment to obtain studies designed to confirm and diagnose the type
ofvWD, such as vWF antigen, vWF activity (ristocetin cofactor or collagen binding
activity), factor VIII coagulant activity, and vWF multimer distribution by electrophoresis.
Rather, I would anticipate the possibility of significant bleeding and ensure the availability of
blood products, DDA VP, cryoprecipitate, FFP, and Humate P (a purified commercial
preparation of factor VIII-vWF concentrate containing large vWF multimers).
You giving prophylactic DDAVP to vWD pts for crane?
Ahhhhh….
Considering the significant risk of bleeding associated with this major
surgery, and assuming I have been unable to identify the patient’s specific subtype of vWD, I
would provide prophylactic vWF replacement with either cryoprecipitate or Humate P (less
risk of transfusion-related infections with Humate P). While DDA VP (desmopressin), a
synthetic analogue of vasopressin that stimulates the release of vWF from endothelial cells, is
effective first-line therapy for many patients with Type I vWD (about 80% of patients with
vWD respond well), it provides little to no response in patients with Type 2A, Type 2M, and
Type 3 vWD, and will lead to thrombocytopenia in patients with Type 2B vWD. The lack of
a consistent response, a limited duration of action ( 6-12 hours), and the potential for
tachyphylaxis, render treatment with DDA VP inadequate for surgical prophylaxis during
major surgery where it is critical to control the patient’s bleeding tendency.
Clinical Note:
• To provide prophylaxis for major surgery, it is recommended to obtain initial vWF:RCo
and factor VIII levels of 2:100 IU/dL. Subsequent dosing should maintain VWF:RCo
and factor VIII levels above a trough of 50 IU/dL for at least 7-10 days following
You lowering BP in pt with increased IcP?
Recognizing that this patient’s decreased level of consciousness, papilledema,
headache, and nausea are suggestive of severely elevated intracranial pressures and reduced
cerebral perfusion, and keeping in mind that cerebral perfusion pressure is equal to the mean
arterial pressure minus the intracranial pressure (CPP =MAP- ICP), I would be very
concerned that reducing her blood pressure may lead to worsening cerebral ischemia.
Therefore, while hypertension could potentially lead to hyperemia, increased cerebral blood
flow (CBF), and increased ICP (increased CBF -7 increased CBV -7 increased ICP), I would
not treat her hypertension at this time. My concern is that lowering the MAP of a patient
with elevated ICP and/or altered cerebral autoregulation (potentially abolished or rightward
shifted secondary to tumor affects or chronic hypertension, respectively), prior to undergoing
a procedure in the sitting position, could contribute to decreased cerebral perfusion pressure
and worsening cerebral ischemia. Rather, with this concern in mind, I would take immediate
steps to reduce her intracranial pressure prior to initiating any treatment to lower her blood
pressure.
Aren’t you concerned that her high blood pressure will result in increased intracranial
pressure (ICP), placing the patient at increased risk of brain herniation?
Yeah, but I’m also concerned that lowering the BP will cause her to be at risk for cerebral ischemia….so….Therefore, prior to lowering her blood pressure, I
would attempt to lower her ICP by one or more of the following methods: (1) hyperventilate
the patient to a PaC02 of about 30 mmHg; (2) ensure unobstructed venous drainage and
elevating the head to 30° to facilitate venous drainage; (3) administer mannitol (the increase
in osmolarity draws water from the extravascular brain tissue) and/or a diuretic (particularly
useful for hypervolemic patients or those who will not tolerate mannitol - CHF or nephrotic
syndrome); (4) administer a corticosteroid, which is thought to reduce ICP by stabilizing
capillary membranes around the brain tumor (vasogenic cerebral edema often develops
around tumors) and /or decreasing CSF production; (5) administer a cerebral vasoconstricting
anesthetic, such as propofol or thiopental (this would be done at induction); and (6) ask the
surgeon to consider performing a ventriculostomy to allow for the drainage of CSF (and
provide a means of direct ICP measurement). Moreover, I would avoid factors that could
further increase ICP or decrease cerebral perfusion, such as hypoventilation (hypercapnia),
sympathetic stimulation (light anesthesia, especially during laryngoscopy), hypotension (i.e.
induction, sitting position, excessive anesthesia), and hypervolemia. My treatment goals
throughout this period of time would be to maintain adequate cerebral perfusion pressure
while avoiding ICP-induced brain herniation.
Could you just quickly place a lumbar subarachnoid catheter to drain some CSF and
reduce her ICP? And if no, what would you rather have placed instead?
I would not do that, as I would be concerned that the pressure gradient between the
cranial and spinal compartments in a patient who already has severely elevated intracranial
pressures could result in tonsillar herniation. Since the pressure measurements of a lumbar
subarachnoid catheter are less reliable, and recognizing that patients with a posterior fossa
tumor are at increased risk for noncommunication hydrocephalus (obstruction of the CSF
outflow through the 4th ventricle), I would prefer a ventricular catheter to a lumbar
subarachnoid catheter, if possible.
How does hyperventilation decrease ICP? What would be your target PaC02? and what are some bad things about hyperventilation to bring down CO2?
The decrease in PaC02 that occurs with hyperventilation leads to a higher
CSF pH around the walls of arterioles, which in tum leads to arteriolar vasoconstriction,
reduced CBF, reduced CBV, and, finally, lower ICP
the abrupt discontinuation of profound
hyperventilation could potentially lead to a rebound increase in ICP.
Therefore, when employing hyperventilation as a treatment modality, I would attempt to
lower the patient’s PaC02 to around 30 mmHg (possibly 25 mmHg ifl believed that cerebral
herniation was imminent). Further reductions in PaC02 may provide little benefit while, at
the same time, placing the patient at increased risk of cerebral ischemia (this is a theoretical risk) and other complications associated with respiratory alkalosis
What does MVP with MR look like on EKG and sound wise? And would you require a work up in this emergent crane?
The auscultatory findings of midsystolic click and late systolic murmur along
with PVC’s on ECG are consistent with mitral valve prolapse associated with mitral valve
regurgitation.
In the absence of symptoms, such as syncope, chest pain, and fatigue, these
findings would not normally warrant further cardiac workup. However, in this case, cardiac
echocardiography would be desirable for several reasons: (1) to determine the severity of the
mitral valve prolapse and regurgitation of this patient who is unable to discuss recent
symptomatology; (2) to determine if there are any atrial thrombi present in this patient who is
most likely taking propranolol for dysrhythmia control; and (3) to rule out a patent foramen
ovale in this patient who will be at increased risk of experiencing an air embolism when
undergoing craniotomy in the sitting position. In fact, the presence of a patent foramen ovale
is a relative contraindication to the performance of a craniotomy in the sitting position, due to
the potential for paradoxical embolism to the coronary or cerebral circulations. If, however,
the emergent nature of the patient’s condition did not allow for further preoperative cardiac
evaluation, I would proceed with the case and discuss alternative patient positioning with the
surgeon
Basically, I would say that I understand the urgency of this case, and would ask the surgeon to do a different position due to risk for VAE
Who needs antibiotic prophylaxis for infective endocarditis?
(1) a prosthetic cardiac valve or prosthetic material used for valve
repair; (2) a previous occurrence oflE; (3) unrepaired cyanotic congenital heart disease; ( 4)
the 6 month postoperative period following a repaired congenital heart defect using
prosthetic material or a device; (5) repaired congenital heart disease with residual defects at
the site or adjacent to the site of a prosthetic patch or device (which inhibits
endothelialization); and (6) cardiac transplantation recipients who develop cardiac
valvulopathy.
Also, always say you would discuss with surgeon
Don’t forget to add what monitor?
TEE!!!!
Think of it in all sitting position patients, or patients who you think could benefit from a PAC.
Types of catheters (central)
Silicone catheters (Hickman, Broviac) are too flexible and are inappropriate for ICU use – polyurethane catheters are stiffer, designed for shorter use, and more appropriate. Do not use heparin-impregnated catheters: they may reduce infection by a small amount but they have not been shown to reduce thrombosis-the heparin washes off after several hours, and they can cause HIT Antimicrobial-impregnated catheters should be considered if the infection rate in your ICU is above the national average
Single lumen catheters are associated with a lower infection rate and should be used when clinically feasible
Where would you place your CVC in pt with increased ICP?
And where are you placing that tip? and what kind of catheter?
While
the subclavian approach carries a higher risk of pneumothorax, I would avoid placement in
the internal jugular vein due to the need to avoid the head-down position during placement
and the potential for obstruction of cerebral venous drainage following placement, which
could lead to increased ICP.
with the tip of a multi-orificed catheter 2 cm below the
superior vena caval-atrial junction to allow for optimal aspiration of intra-cardiac air. I
would then confirm the correct positioning using either x-ray or intravascular
electrocardiography (TEE can also be used).
If airway info isn’t given, always say…
Assuming this patient had a reassuring airway!!!
Sux in these increased ICP patients?
I think it can be okay if pt has mild signs and sxs, but with papilledema and other severe signs, I would still avoid it-even with the pre-dosing of roc.