Monthly Archives: January 2016

How much hypertonic solution?

To determine how much hypertonic solution to give a patient with hyponatremia:

  1.  calculate sodium deficit (mEq) = weight (kg) x 0.6 x (desired Na – actual Na)
    1. use 0.5 for females
    2. desired sodium in mEq/L
  2. calculate the safe rate of sodium correction for the patient in mEq/hr (0.5-1 mEq/L/hr) = weight (Kg) x 0.6 x 1.0 (rate of correction desired)
  3. 3% hypertonic saline contains 513 mEq/L; 2% contains 342 mEq/L; 1.5% contains 256 mEq/L and 0.9% contains 154 mEq/L
  4. desired rate = (safe rate of correction / 513) x 1000
  5. infusion time (hrs) = sodium deficit (mEq) / safe rate of correction (mEq/hr)

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References

Globalrph.com,. “Sodium Chloride 3% –  Intravenous (IV) Dilution”. N.p., 2016. Web. 30 Jan. 2016.

Leukoaraiosis

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Leukoaraiosis:  

  • ischemic damage to the subcortical white matter
  • frequent complication of hypertension-related microvascular disease
  • contributes to the risk of stroke and vascular dementia
  • at greater risk of sICH and have a worse functional outcome after tPA treatment for acute ischemic stroke
  • Side Note:  other risk factors for sICH post-tPA:  age, stroke severity, DM, cardiac disease, elevated pre-treatment mean BP

 

Why is leukoaraiosis associated with greater risk of sICH after tPA?

Leukoaraiosis is a radiological marker for chronic ischemic damage of cerebral microcirculation, which worsens effects of acute ischemia and tPA at the BBB.

Pre-existing damage of cerebral microcirculation (including the endothelium) increases risk of vessel rupture and subsequent hemorrhage.   Stroke damages endothelium and astrocytes, weakening the BBB.  With tPA, further damage to BBB occurs.

Leukoaraiosis is likely a marker of increased susceptibility to hemorrhagic treatment complications, rather than a condition indicating a specific risk of thrombolytic treatment.

How is leukoaraiosis assessed?

For assessment of leukoaraiosis, studies used MRI with high-resolution T2-weighted sequence.

Sseverity of leukoaraiosis is rated using a visual rating scale proposed by Fazekas and Schmidt, with scores ranging from 0 to 3.  FLAIR sequence or high-resolution T2-weighted sequence for deep WM and periventricular WM was used to determine extent of leukoaraiosis.

Deep white matter lesions were scored as follows:

  • 0, no lesion
  • 1, punctuate foci
  • 2, beginning confluent foci
  • 3, confluent changes

Periventricular white matter lesions were scored as follows:

  • 0, no changes
  • 1, caps or a pencil-thin lining
  • 2, smooth halo
  • 3, irregular changes extending into deep white matter

 

See figure below for examples illustrating different degrees of leukoaraiosis in deep white matter (arrow) and periventricular areas (with identical scores for deep and periventricular changes).

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References

Ariës, M. J. H. et al. “Tpa Treatment For Acute Ischaemic Stroke In Patients With Leukoaraiosis”.European Journal of Neurology 17.6 (2010): 866-870. Web.

Neumann-Haefelin, T. et al. “Leukoaraiosis Is A Risk Factor For Symptomatic Intracerebral Hemorrhage After Thrombolysis For Acute Stroke”. Stroke 37.10 (2006): 2463-2466. Web.

Sph.umich.edu,. “Genetic Architecture Of Leukoaraiosis – Research – Kardia Lab – Genetic Epidemiology – Epidemiology – Faculty Research Projects – Faculty & Research – UM SPH”. N.p., 2016. Web. 29 Jan. 2016.

Debette, S. and Markus, H. The clinical importance of white matter hyperintensities on brain magnetic resonance imaging: systematic review and meta-analysis. BMJ 2010; 341:c3666.

Ictal-Interictal Continuum

Which EEG patterns warrant treatment in the critically ill?

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The IIC graph modified by Struck, et al.

 

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Modification uses current ACNS terminology, with the addition of PET metabolism from hypometabolic (blue) to hypermetabolic (red).  X-axis = spectrum of cerebral dysfunction and Y-axis = neuronal damage

*SB suppression burst, RDA rhythmic delta activity, LPD lateralized periodic discharges, SW spike wave, GPD generalized periodic discharges, SIRPIDs stimulus-induced rhythmic, periodic, or ictal discharges, NCS non-convulsive seizures, GCSE generalized convulsive status epilepticus, NCSE nonconvulsive electrographic status epilepticus, EPC epilepsia partialis continua

 

 

  • strong correlation between PDs on the IIC and subsequent NCSZs or non-convulsive status epilepticus (NCSE)
  • link between PDs on the IIC and functional outcome remains less certain
  • link between interictal periodic patterns and secondary brain injury (as inferred by increased vasogenic or cytotoxic edema [8, 9] or increase in lactate-pyruvate ratio [10]), seen as similar sequelae to those resulting from NCSZs

References

Chong, Derek J., and Lawrence J. Hirsch. “Which EEG Patterns Warrant Treatment In The Critically Ill? Reviewing The Evidence For Treatment Of Periodic Epileptiform Discharges And Related Patterns”. Journal of Clinical Neurophysiology 22.2 (2005): 79-91.

 

Struck, Aaron F. et al. “Metabolic Correlates Of The Ictal-Interictal Continuum: FDG-PET During Continuous EEG”. Neurocritical Care 24.3 (2016): 324-331.

Risk of Rupture in SAH

Handy data for prognostication in SAH.

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SAH Prognosis

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References

Bhardwaj, Anish, and Marek Alexander Z Mirski. Handbook Of Neurocritical Care. New York: Springer, 2010. Print.

Wiebers, David O. “Unruptured Intracranial Aneurysms: Natural History, Clinical Outcome, And Risks Of Surgical And Endovascular Treatment”. The Lancet 362.9378 (2003): 103-110. Web.

The 3-7 Rule

This rule is useful in estimating the age of blood in MRI images of intracerebral heomrrhages.  Mnemonic:  It Be IdDy BiDdy BaBy DooDoo. 

The 3-7 Rule pertains to the timeframe of the bleed:  {<7h-3d-7d->3w}Capture

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Reference

Bhardwaj, Anish, and Marek Alexander Z Mirski. Handbook Of Neurocritical Care. New York: Springer, 2010. Print.

How to: Transthoracic Echo

The ultrasound machine is now becoming an indispensable tool for the (non-radiologist) doctor, providing real-time, clinically-relevant information at the bedside.  While this machine may not replace the reliable stethoscope any time soon, the ultrasound has certainly proven its utility, adding to the armamentarium of the modern physician.

Interpretation of ultrasound, just like interpretation of any radiologic modality, involves a certain learning curve.  It takes time and practice to be able to superimpose the anatomy of body organs on the low-resolution images, and derive some clinical information on the function of the insonated organ.  

The transthoracic echo in particular may be more challenging to interpret, because different views are used to slice the chambers of the heart in different planes.  The method of transthoracic echo is hard taught with words and pictures, but rather, time should be spent by the sonologist visualizing the ultrasound probe and the waves that emanate from the probe slicing through the cardiac chambers. 

Here are five videos from youtube, each one a little over a minute, that wonderfully illustrates how a picture (or in this case, a video) is worth a thousand words.  A novice would very well consider watching the videos over and over, until the the images are  ingrained in his memory.
Parasternal short axis – https://m.youtube.com/watch?v=_6Ltla3NL1k

Subcostal view – https://m.youtube.com/watch?v=oMwgUo6sbyY

Apical 4-chamber view – https://m.youtube.com/watch?v=5czv-c1uUnw

Parasternal long axis – https://m.youtube.com/watch?v=CIJewMLUQkU

IVC view – https://m.youtube.com/watch?v=McUUFvnFuJU

References

YouTube,. “How To Obtain: Apical 4 (Four) Chamber Ultrasound View- Training And Techniques – ICU”. N.p., 2016. Web. 25 Jan. 2016.

YouTube,. “How To Obtain: Inferior Vena Cava Ultrasound View- Training And Techniques – ICU”. N.p., 2016. Web. 25 Jan. 2016.

YouTube,. “How To Obtain: Parasternal Long Axis Ultrasound View – Training And Techniques – ICU”. N.p., 2016. Web. 25 Jan. 2016.

YouTube,. “How To Obtain: Parasternal Short Axis Ultrasound View – Training And Techniques – ICU”. N.p., 2016. Web. 25 Jan. 2016.

YouTube,. “How To Obtain: Subcostal Cardiac Ultrasound View – Training And Techniques – ICU”. N.p., 2016. Web. 25 Jan. 2016.

VASOGRADE

Patients are classically at risk of delayed cerebral ischemia (DCI) after aneurysmal subarachnoid hemorrhage. We validated a grading scale—the VASOGRADE—for prediction of DCI.

 

vasograde

 

 

References

de Oliveira Manoel, Airton Leonardo et al. “The VASOGRADE”. Stroke 46.7 (2015): 1826-1831. Web.