Monthly Archives: November 2016

Equations for Phenytoin Dosing and Monitoring

#1.  loading dose for subtherapeutic phenytoin concentration:

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#2. adjust for renal disease

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#3. adjust for hypoalbuminemia

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#4. adjust in elderly and critically ill with hypoalbuminemia

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**Vd = volume of distribution (0.5-1 L/kg)

 

Reference:

Tesoro, E. P. and G. M. Brophy. “Pharmacological Management Of Seizures And Status Epilepticus In Critically Ill Patients”. Journal of Pharmacy Practice 23.5 (2010): 441-454.

**Thanks to Benjamin Wee (Clinical Pharmacist @ Lenox Hill Hospital) for giving me this resource.
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Minocycline in Moyamoya Bypass Surgery

Dosage used in the study:

  • intraoperative and postoperative IV minocycline hydrochloride (200 mg/d) until 4 days after surgery

 

Minocycline:

  • semisynthetic tetracycline
  • clinically used as an antibiotic and anti-inflammatory drug
  • Neuroprotection:
    • neuroprotective potential reported in animal models of cerebral ischemia
    • reduces infarction size in rats due to the prevention of inflammatory reactions by suppressing microglial activation, down-regulating proinflammatory cytokines, and blocking MMP expression
    • prevents reperfusion-related ICH by blocking MMP-9 in mice
    • neuroprotective role as an antiapoptotic agent and antioxidant
  • Mechanism in ischemia-reperfusion injury
    • maintains BBB? –> reducing risk of vasogenic edema and hemorrhagic convesrion?
    • Moyamoya patients have higher expression of MMP-9 –> can perioperative minocycline prevent surgical complications (cerebral hyperperfusion or ischemia)

 

 

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Proposed mechanisms:

  1. Minocycline blocks MMP-9, prevents neurological deterioration due to cerebral hyperperfusion.
  2. Minocycline compensated for deleterious effect of BP lowering by protecting contralateral and/or remote brain

 

Higher risk of reperfusion injury in Moyamoya due to

  1. poor network formation of pial arteries –> poorer hemodyamic distribution after revascularization
  2. fragile peripheral pial artery (thin media and internal elastic lamina) in Moyamoya disease
  3. increased expression of VEGF and MMP-9

 

Study conclusion:

The administration of minocycline in combination with strict blood pressure control could represent secure and effective postoperative management for the prevention of symptomatic CHP after STA-MCA anastomosis for MMD.

 

Critique:

  1. small number of patients who developed focal deficits
  2. heterogenous group
  3. no data on preoperative hemodynamic status – no SPECT stress testing
  4. CBF studies performed under different institutions
  5. did not measure MMP-9 levels

 

 

Reference:

Fujimura, Miki et al. “Minocycline Prevents Focal Neurological Deterioration Due To Cerebral Hyperperfusion After Extracranial-Intracranial Bypass For Moyamoya Disease”. Neurosurgery74.2 (2014): 163-170.

 

 

Tranexamic Acid in SAH

 

TXA Dose: tranexamic acid 1 g IV every 6 h not exceeding 48–72 h

 

Neither aminocaproic acid nor tranexamic acid is approved by the US Food and Drug Administration for prevention of aneurysm rebleeding.

AHA/ASA (2012)

For patients with an unavoidable delay in obliteration of aneurysm, a significant risk of rebleeding, and no compelling medical contraindications, shortterm (<72 hours) therapy with tranexamic acid or aminocaproic acid is reasonable to reduce the risk of early aneurysm rebleeding (Class IIa; Level of Evidence B). (Revised recommendation from previous guidelines)

NCS (2011)

An early, short course of antifibrinolytic therapy prior to early aneurysm repair (begun at diagnosis; continued up to the point at which the aneurysm is secured or at 72 h post-ictus, whichever is shorter) should be considered (Low Quality Evidence; Weak Recommendation). •

Delayed (>48 h after the ictus) or prolonged (>3 days) antifibrinolytic therapy exposes patients to side effects of therapy when the risk of rebleeding is sharply reduced and should be avoided (High Quality Evidence; Strong Recommendation). •

Antifibrinolytic therapy is relatively contraindicated in patients with risk factors for thromboembolic complications (Moderate Quality Evidence; Strong Recommendation). •

Patients treated with antifibrinolytic therapy should have close screening for deep venous thrombosis (Moderate Quality Evidence; Strong Recommendation). •

Antifibrinolytic therapy should be discontinued 2 h before planned endovascular ablation of an aneurysm (Very Low Quality Evidence; Weak Recommendation). •

 

 

References

Connolly, E. S. et al. “Guidelines For The Management Of Aneurysmal Subarachnoid Hemorrhage: A Guideline For Healthcare Professionals From The American Heart Association/American Stroke Association”. Stroke 43.6 (2012): 1711-1737.

Diringer, Michael N. et al. “Critical Care Management Of Patients Following Aneurysmal Subarachnoid Hemorrhage: Recommendations From The Neurocritical Care Society’S Multidisciplinary Consensus Conference”. Neurocritical Care 15.2 (2011): 211-240.

Sakusic, Amra and Alejandro A. Rabinstein. “Case Studies In Neurocritical Care”. Neurologic Clinics34.3 (2016): 683-697.

 

 

TCD Acoustic Windows

Two Scanning Planes: 

  1. Axial scan
    1. Mesencephalic view
      1. Probe parallel to zygomatic arch
      2. Identify midbrain (“butterfly”) at about half of the scanning plane
      3. Can identify Pcomm in 75%
    2. Diencephalic view
      1. Tilt transducer 10degrees up
      2. Identify III ventricle, then posteriorly the pineal gland (hyperechogenic) and anteriorly the thalamus and internal capsule
      3. Identify lateral ventricles
  2. Coronal scan
    1. Rotate probe 90degrees from axial position
    2. Identify III ventricle, lateral ventricles, thalamus, internal capsule
    3. Useful for assessment of midline shift

 

Four TCD Acoustic Windows:b9781437714173000127_f12-01-9781437714173

  1. Temporal window
    1. Above zygomatic arch, anterior to tragus
    2. Axial plane, mesencephalic view
    3. Divided into anterior, middle and posterior zones
    4. Identify MCA (M1, M2), A1, P2, P2, C1 of carotid siphon, Acomm and Pcomm, distal end of BAni_2014_62_5_510_144443_f4
  2. Occipital window
    1. Probe on median sub-occipital line
    2. Patient sitting or lying down with head turned to opposite direction, chin lowered toward shoulder
    3. US beam passes through foramen magnum
    4. Visualize intracranial segment of vertebral arteries and basilar trunk
    5. Y shape, with flow moving away from probe
    6. Slight lateral movements to display both AICA, PICA
  3. Orbital window
    1. Transducer perpendicular to eyelid, patient’s eyes closed, looking opposite probe
    2. Insonate ophthalmic artery, C2, C3, C4 carotid siphon
    3. Potential retinal injuries – reduce power by 10-15%
  4. Submandibular window
    1. Transducer underneath angle of mandible in front of masseter muscle, probe toward skull
    2. Allows terminal segment (C5, C6) of ICA and C1 segment of carotid siphon

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MCA: depth of 4.5-6.0cm, blood flow toward probe

Identify sphenoid bone (butterfly wing sign)

 

Reference:

D’Andrea, Antonello et al. “Transcranial Doppler Ultrasonography: From Methodology To Major Clinical Applications”. World Journal of Cardiology 8.7 (2016): 383.

TCD Arterial Segments

Schematic representation of 11 arterial segments studied by transcranial Doppler and duplex ultrasound.

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  • MCA
  • ACA
  • PCA
  • siphon ICA
  • extracranial ICA
  • vertebrobasilar artery

 

Reference:

Wong, K. S. et al. “Use Of Transcranial Doppler Ultrasound To Predict Outcome In Patients With Intracranial Large-Artery Occlusive Disease”. Stroke 31.11 (2000): 2641-2647.

ICU Checklist: FASTHUG MAIDENS

FASTHUG is a checklist developed by intensivists to ensure that key aspects of care are addressed during rounds.  The mnemonic FASTHUG stands for:

  • F = Feeding
  • A = Analgesia
  • S = Sedation
  • T = Thromboembolic prophylaxis
  • H = HOB elevation
  • U = Stress ulcer prophylaxis
  • G = Glucose control

This checklist however, does not address pharmacotherapy issues, and has been modified by clinical pharmacists to FASTHUG-MAIDENS.  FASTHUG as above, except for H which was changed to mean Hyperactive or hypoactive Delirium.  MAIDENS stands for:

  • Medication reconciliation
  • Antibiotics 
  • Indications for meds
  • Drug dosing
  • Electrolytes, Hematology and other lab tests
  • No drug interactions, allergies, duplication or side effects
  • Stop dates

 

Reference:

Masson, Sarah C et al. “Validity Evidence For FASTHUG-MAIDENS, A Mnemonic For Identifying Drug-Related Problems In The Intensive Care Unit”. The Canadian Journal of Hospital Pharmacy 66.3 (2013).

Hyponatremia Protocol

Na <133 mEq/L or a decrease of 6 mEq/L in 24 to 48 hours:

  1. NaCl tabs 3 g PO/NGT q6h
  2. Start 3%NaCl at 20 mL/h
  3. BMP q6h

Na <130:
Increase rate by 20 mL/h (max rate = 80 mL/h)
If on hold at present, initiate 3 percent NaCl infusion at 20 mL/h IV

Na = 130-135:
Increase rate by 10 mL/h (max rate = 80 mL/h)
If on hold at present, initiate 3 percent NaCl infusion at 10 mL/h IV

Na = 136-140:
No change

Na ≥140:
Hold infusion

 

Reference:

Woo, Carolyn H. et al. “Performance Characteristics Of A Sliding-Scale Hypertonic Saline Infusion Protocol For The Treatment Of Acute Neurologic Hyponatremia”. Neurocritical Care 11.2 (2009): 228-234. Web.