A New Algorithm to Differentiate Salt-wasting Syndrome from SIADH

In cerebral salt-wasting (CSW), natriuretic factor is produced in response to a central insult.  Natriuretic factor decreases sodium transport in proximal renal tubule which leads to urinary loss of sodium (and water) and depletion of extracellular volume.  Hypovolemia then triggers secretion of ADH, renin and aldosterone, which provides a negative feedback to decrease secretion of natriuretic factor.


Differentiating CSW from syndrome of inappropriate antidiuretic hormone (SIADH) is problematic, laboratory work-up (urine and plasma sodium levels and urine and plasma osmolarity) is similar in both conditions.  CSW patients are usually volume depleted while SIADH patients are euvolemic.  The traditional approach of examining patient clinically to to determine volume status is inaccurate.

An interesting paper published in 2014 suggested a new algorithm to differentiate SIADH from CSW based on the effect of sodium correction on the fractional excretion of urate (FEUa).  FEurate is calculate using the folllowing formula:






Another formula:



Normal FEUa = 4-11%, SIADH & CSW FEUa = >11%.  FEUa determines the percent excertion of the filtered load of urate at the glomerulus.

In SIADH, FEUa normalizes after correction of hyponatremia (see graph below):


whereas in CSW, FEUa remains elevated >11% after correction of hyponatremia.  The reason is probably because natriuretic factor also decreases urate transport in the proximal tubule.



Based on this finding, the paper suggests a new algorithm for determining the etiology of hyponatremia that omits reliance of UNa (and also plasma renin, aldosterone, atrial or brain antriuretic peptide, BUN/creatinine ratio).


Based on this algorithm, a patient with hyponatremia should undergo correction of sodium by any means (water restriction or isotonic / hypertonic saline). Observing whether FEUa normalizes or remains increased would differentiate SIADH from CSW syndrome.






Maesaka, J., Imbriano, L., Mattana, J., Gallagher, D., Bade, N. and Sharif, S. (2014). Differentiating SIADH from Cerebral/Renal Salt Wasting: Failure of the Volume Approach and Need for a New Approach to Hyponatremia. Journal of Clinical Medicine, 3(4), pp.1373-1385.



CPT Codes Relevant to Neurocritical Care Practice



  • 99291 Critical care, evaluation and management of the critically ill or critically injured patient; first 30 to 74 minutes
  • 99292 each additional 30 minutes (list separately in addition to code for primary service

Document and explain why patient is critically ill.  Critically ill indicates “a high probability of imminent or life-threatening deterioration in the patient’s condition.”  Decision making and treatment must include an indication that the patient’s condition met that definition as well as considerations and plans to prevent life-threatening deterioration or organ system failure.

Code 99291 covers the initial 30 to 74 minutes on that day. Code 99292 covers the additional 30-minute time increments. Use 99292 when time totals 75 minutes or more. When using 99292, documentation should show why time was needed beyond the first hour.

Below is a list of the commonly encountered neurologic disorders that often justify use of critical care codes

  • Acute spinal cord compression or injury
  • Acute stroke
  • Coma after cardiac arrest
  • Coma of unknown etiology
  • Guillain-Barré syndrome
  • Intracerebral hemorrhage
  • Malignant intracranial pressure
  • Meningoencephalitis
  • Myasthenic crisis
  • Neuroleptic malignant syndrome
  • Paraneoplastic encephalitis
  • Status epilepticus
  • Subarachnoid hemorrhage
  • Traumatic brain injury


  • Consulting on a patient who is critically ill is not necessarily a critical care service. The use of the critical illness code is dependent on the patient’s critical illness and the neurointensivist’s actions to address the illness.
  • The patient’s location is not key. A patient may be in the emergency department or still on a floor unit and yet be critically ill.
  • Only one neurointensivist may submit critical care code 99291 on a particular calendar date. Provider must document at least 30 minutes of critical care time. Additional time may be aggregated with a second neurointensivist from the same practice group (ie, one physician may code for the sum of time of both physicians). Or, additional time may be submitted by second neurointensivist with code 99292.
  • A physician may not aggregate time with nonphysician practitioners or residents. Nonphysician practitioner’s time is counted separately from that of any physician.
  • Rules for physician assistants vary depending on hospital, carrier or state. Some combine nurse practitioners and physician assistants under the term nonphysician practitioner.

Total time for critical care services include:

  • time spent on the patient’s unit reviewing test results or imaging studies
  • time spent discussing the patient’s case with other medical staff
  • time spent documenting critical care services
  • time spent caring for the patient in the ED or in radiology department while the patient is in radiology

Total time for critical care services does not include:

  • resident’s time and teaching sessions with residents
  • providing routine updates to the family
    • Time with a surrogate decision maker can count as critical care time if the patient is unable to give a history or make decisions. Document the discussion as necessary to determine treatment decisions, preferably summarizing the conclusions or options discussed.

Procedures bundled into CPT codes 99291 and 99292 that do not require separate coding include the following:

  • Blood draw for specimens including for blood gases
  • Gastric intubation
  • Information data stored in computers (eg, ECGs)
  • Interpretation of cardiac output measurements
  • Interpretation of chest x-rays
  • Pulse oximetry
  • Temporary transcutaneous pacing
  • Ventilator management
  • Vascular access procedures


Procedures that may be coded separately include:

  • lumbar puncture
  • endotracheal intubation
  • placement of a flow-directed catheter
  • cardiopulmonary resuscitation
  • placement of a ventricular catheter
  • interpretation of an EEG
  • performance of nerve conduction studies

When performing these other procedures, use modifier 25 with the critical care codes to indicate that procedures and evaluation and management were performed on the same day.

Lumbar puncture has three different CPT codes. The three CPT codes are:

  • 62270 Spinal puncture, lumbar, diagnostic
  • 62272 Spinal puncture, therapeutic, for drainage of CSF (by needle or catheter)
  • 62273 Injection, epidural, of blood or clot patch

Neurodiagnostic and monitoring procedures for EMG, nerve conduction studies, and EEG may be coded separately.

The following monitoring and emergency procedures also are among those commonly coded separately in the critical care unit:

  • 31500 Intubation, endotracheal, emergency procedure
  • 93503 Insertion and placement of flow-directed catheter (eg, Swan-Ganz) for monitoring purposes
  • 92950 Cardiopulmonary resuscitation (eg, in cardiac arrest)


Two CPT codes allow for coding of the time spent in discussions and preparation of advance care plans.  These codes cannot be used by the same physician on the same day he or she uses CPT code 99291.  Examples of written advance directives include healthy care proxy, durable power of attorney for health care, living will and MOLST.  The two CPT codes for time spent in discussion and preparation of these forms are:

  • 99497 Advance care planning including the explanation and discussion of advance directives such as standard forms (with completion of such forms, when performed), by the physician or other qualified health care professional; first 30 minutes, face-to-face with the patient, family member(s), and/or surrogate
  • 99498 each additional 30 minutes (list separately in addition to code for primary procedure)


Prolonged services are not used with the primary codes 99291 and 99292. Subsequent day hospital management is coded as 99233, base time for this code is 35 minutes. When time spent exceeds base time by more than 30 minutes, physician may add a prolonged service code:


  • 99356 Prolonged service in the inpatient or observation setting, requiring unit/floor time beyond the usual service; first hour (list separately in addition to code for Evaluation and Management service)
  • 99357 each additional 30 minutes (list separately in addition to code for prolonged service)


Telemedicine is coded using the standard CPT codes plus a modifier. In January 2017, the modifier of choice changed from GT to 95. Modifier 95 identifies a “synchronous telemedicine service rendered via a real-time interactive audio and video telecommunications system.”

CPT specifies two codes for telehealth critical care:

  • 0188T Remote real-time interactive video-conferenced critical care, evaluation, and management of the critically ill or critically injured patient; first 30 to 74 minutes
  • 0189T each additional 30 minutes (list separately in addition to code for primary service)

When providing telehealth, use Place of Service 02, which is a new place of service code as of January 2017.

Patients covered by Medicare Part B are eligible for remote critical care only if they are hospitalized in a rural area.  Medicare uses different codes for remote critical care. Medicare also makes an exception by covering certain teleconsultations for acute stroke within 4.5 hours of symptom onset. The critical care telehealth codes for patients with Medicare are included in the Healthcare Common Procedure Coding System:

  • G0508 Telehealth consultation, critical care, initial, physicians typically spend 60 minutes communicating with the patient and providers via telehealth
  • G0509 Telehealth consultation, critical care, subsequent, physicians typically spend 50 minutes communicating with the patient and providers via telehealth


A neurointensivist might provide a telephone consultation directly with a physician who is caring for a patient at a remote hospital.  These circumstances include urgent situations where a timely face-to-face service with the consultant may not be feasible.  The codes may not be used if the consultant has or will see the patient within 14 days. This code is not to arrange for transfer of care.  The time for the service may include review of records and images if the time consulting with the primary physician is more than half of the documented time. The code may be used only once per week for the same patient by the same physician.

The CPT codes for interprofessional telephone/Internet consultations are as follows:


  • 99446 Interprofessional telephone/Internet assessment and management service provided by a consultative physician including a verbal and written report to the patient’s treating/requesting physician or other qualified health care professional; 5 to 10 minutes of medical consultative discussion and review
  • 99447 11 to 20 minutes of medical consultative discussion and review
  • 99448 21 to 30 minutes of medical consultative discussion and review
  • 99449 31 minutes or more of medical consultative discussion and review


  1. Downcoding: might happen when an attending physician’s note uses accurate language in referring to the patient as critically ill with a high probability of imminent or life-threatening deterioration, but a resident’s note on the same day makes such a statement as, “stable and may be transferred to the floor tomorrow.”
  2. Critical care may be provided on multiple days, even if no changes are made in the treatment rendered to the patient, provided that the patient’s condition continues to require the level of attention necessary in critical care. Notes that fail to change over days give the auditor the impression that the patient’s condition is stable, even if that is not true.  Details in the note should show the work accomplished and planned that day.
  3. The neurocritical care patient is at risk of imminent death due to further brain injury, which can occur unpredictably and rapidly cause multiorgan dysfunction and death.
  4. Include high-risk rationale. Emphasize specific reasons for neuroprotective strategies in critical care such as mechanical ventilation, osmolar therapy, temperature management.
  5. Document existing protocols and specific interventions in the physician’s progress notes. For example, document a 50% risk of imminent stroke or death if that is the case for that patient with new-onset vasospasm.


All CPT codes listed above are copyrighted.  CPT © 2018 American Medical Association. All rights reserved. CPT is a registered trademark of the American Medical Association.


Link to file in MS Word: CPT Codes Relevant to Neurocritical Care

Link to file in pdf:  CPT Codes Table NCC

Link to file in pdf:  CPT Codes List NCC


Nuwer, M. and Vespa, P. (2018). Neurocritical Care Coding for Neurologists. CONTINUUM: Lifelong Learning in Neurology, 24(6), pp.1800-1809.

IVH Score

This score is used for patients with intracerebral hemorrhages with intraventricular extension, and is not appropriate for pure intraventricular hemorrhages.


In this score, each lateral ventricle is graded as:

  • 0 = no blood or small amount of layering
  • 1 = up to 1/3 filled with blood
  • 2 = 1/3 to 2/3 filled with blood
  • 3 = mostly or completely filled with blood

3rd and 4th ventricles receive a score of:

  • 0 = for no blood
  • 1 = partially or completely filled with blood

Hydrocephalus was coded as

  • 0 = absent
  • 1 = present


The formula for calculating the IVH score is as follows:


Or simplified:  3(RV+LV) + III + IV + 3(H)


Once the IVH score has been computed, the IVH volume can be calculated using the following formula:



To make things simpler, here is a table showing the calculated IVH volume based on the IVH score.




Here are two examples of IVH scores calculated for you:



How to use the IVH Score?

With the IVH score, cutoff of 40 mL indicates poor outcome and 60 mL, mortality.

With the ICH score, cutoff is 25 mL and 30 mL respectively.

The total volume of hemorrhage can be calculated by adding the ICH volume (using the ABC/2 formula) and the IVH volume (using the ICH score).   Total volume predicts outcome better than ICH volume alone.



NOTE:  Be wary of using ICH score and IVH score to withdraw care.  Early limitation of care in ICH / IVH is a self-fulfilling prophecy which is, of course, associated with mortality.



Hallevi, H., Dar, N., Barreto, A., Morales, M., Martin-Schild, S., Abraham, A., Walker, K., Gonzales, N., Illoh, K., Grotta, J. and Savitz, S. (2009). The IVH Score: A novel tool for estimating intraventricular hemorrhage volume: Clinical and research implications*. Critical Care Medicine, 37(3), pp.969-e1.






Timing of Anticoagulation After Stroke with Atrial Fibrillation

Summary of National and International Guideline Recommendations on Timing of anticoagulation after ischemic stroke associated with atrial fibrillation:

  1. AHA ASA recommend starting AC within 4 to 14 days after onset (reasonable for most patients), consider later treatment for patients with hemorrhagic transformation
  2. European Society of Cardiology (ESC 2016 Recommendations) and European Heart Rhythm Association (EHRA 2018 Recommendations) endorsed by the European Stroke Organization, recommend giving AC 1 day after onset of TIA, after 3d in patients with minor stroke (NIHSS less than 8), after 6d with mild stroke (NIHSS 8 to 15), and after 12 days in those with severe stroke (NIHSS greater than 15)
  3. Canadian stroke best practice recommendations (2017) follow EHRA ESC Recommendations
  4. Australian guidelines for stroke management (2017) recommend giving AC 1d after onset of TIA, after 5 to7d in patients with moderate stroke, and after 10 to 14d in those with severe stroke. Stroke severity not defined.
  5. Middle Eastern and North African consensus statement (2017) recommends giving AC 12d after stroke onset in mod to severe ischemic stroke, and after 2 to 3 weeks in large infarct. Stroke severity and sizes not defined.
  6. European Stroke Organization and Karolinksa Stroke Update (2016) recommend giving AC 4d after stroke onset in mild stroke (undefined) and small infarct size (lesion less than or equal to 1.5 cm in ant or post circulation), after 7d in mod stroke (undefined), and med infarct size (lesion in cortical superb branch of MCA, in MCA deep branch, in internal border zone territories, in cortical superficial branch of PCA, or in cortical superb branch of ACÁ), and after 14d in severe stroke (undefined) and large infarct size (lesion involving complete MCA, the pCA or the ACÁ artery, or is in two cortical superficial branches of MCA, in a cortical superf branch of MCA associated to MCA deep branch, or in more than one arterial territory)
  7. Royal College of Physicians (UK) national clinical guideline for stroke recommends giving AC 2w after onset of disabling stroke (undefined), consider early treatment in minor, nondisabling stroke (undefined) and low risk of hemorrhagic transformation (undefined)


Seiffge, David J, David J Werring, Maurizio Paciaroni, Jesse Dawson, Steven Warach, Truman J Milling, Stefan T Engelter, Urs Fischer, and Bo Norrving. 2018. “Timing Of Anticoagulation After Recent Ischaemic Stroke In Patients With Atrial Fibrillation”. The Lancet Neurology. doi:10.1016/s1474-4422(18)30356-9.