Blood Pressure Goals in Neurocritical Care

Subarachnoid Hemorrhage (Take home:  target SBP <140mm Hg)

Optimal blood pressure target unknown.  2012 American Stroke Association guidelines suggests that a systolic BP goal <160mm Hg is reasonable.  Avoid nitroprusside or NTG (increases cerebral blood volume / ICP). Use labetalol, nicardipine, enalapril.

Lowering BP decreases risk of rebleeding in unsecured aneurysm, but may increase risk of infarction.  CPP = MAP – ICP.  Increased ICP necessitates an elevated MAP to keep CPP.  CPP threshold may be 70mm Hg.

In the absence of ICP measurement, clinical findings (i.e. alertness) may guide therapy, Uptodate recommends keep SBP <140mm Hg in these instances.

 

Traumatic Brain Injury (Take home:  target CPP 50-70mm Hg)

Cerebral autoregulation is disrupted in about a third of patients with severe TBI, these patients are described as “pressure-passive.”  In these patients, rise in MAP leads to elevated ICP due to increased cerebral blood volume, while drops in MAP may be associated with hypoperfusion and ischemia.

Bedside measurement of cerebral blood flow is not easily obtained.  CPP = MAP – ICP, is a surrogate measure.  Low MAP, high ICP or low CPP are associated with secondary brain injury and worse outcomes.

Old strategy to induce hypertension to CPP >70mm Hg (using saline boluses or vasopressors) does not improve outcome, and increases risks of other complications s.a. ARDS.  2007 Guidelines from BTF recommend CPP target of 60 mm Hg, avoid <50 and >70 mm Hg.  In children, lower thresholds are recommended (40-65 mm Hg).  Target ICP first before MAP.

 

Post-neurosurgical Procedure

[coming soon]  Our practice is to keep SBP within 100-150mm Hg during the immediate post-operative period.

 

Cerebrovascular Accident (Take home:  tPA <185/110 then <180/105; no tPA treat if >220/120)

After stroke, CPP distal to obstructed vessel is low and distal vessels are dilated.  Blood flow depends on systemic blood pressure.  Elevated BP is necessary to maintain perfusion in ischemic penumbra.  BP rises spontaneously after stroke, this is transient and BP falls by as much as 20/10 within 10 days.

Analysis from International Stroke Trial showed a U-shaped relationship between SBP and outcomes.  SBP >200mm Hg is associated with risk of recurrent stroke while SBP <120mm Hg was associated with excess number of deaths from coronary heart disease.

Lowering BP within 24 hours of acute stroke has been associated with clinical deterioration.  Some may even benefit from pharmacologic increases in BP (studies show improvement in aphasia or perfusion imaging). [Induced HTN currently not recommended except in the setting of a clinical trial.]  Severe increase in BP can also cause hypertensive encephalopathy.

No good RCTs to guide BP management in hyperacute phase (<12hours) of stroke.

For patients eligible for tPA:  Blood pressure goal  ≤185/110 mmHg is recommended prior to starting lytic therapy.  Maintain BP ≤180/105 mmHg x 24 hours after tPA.

For patients not treated with tPA:  most guidelines recommend no treatment for BP unless hypertension is extreme (SBP >220mm Hg or diastolic >120m Hg) or patient has active ischemic coronary disease, heart failure, aortic dissection, hypertensive encephalopathy, acute renal failure, or pre-eclampsia / eclampsia.  If so, lower BP by ~15% during first 24 hours.

Restart antihypertensive medications ~24 hours after stroke in patients with pre-existing HTN who are neurologically stable.  Patients with large artery stenosis may require a slower reduction in BP (over 7-10 days after stroke)

Guidelines suggest IV labetalol and nicardipine as first-line antihypertensives.

 

 

Intracerebral Hemorrhage

Elevations in BP may cause hemorrhage to expand, but increased MAP may be necessary to maintain cerebral perfusion.  INTERACT2 trial compared intensive BP lowering (<140mm Hg within 1 hour) vs traditional management (<180mm Hg) in patients with acute ICH (within 6 hours).  Intensive BP lowering improved modified Rankin scores, with similar adverse events.  INTERACT study suggested that more aggressive BP lowering is associated iwth reduced hematoma growth.  ATACH II is in progress.

  • SBP >200 or MAP >150aggressively reduce BP   [aggressive lowering is safe based on INTERACT2]
  • SBP >180 or MAP >130 + high ICP – insert ICP bolt, keep CPP 61-80 mm Hg
  • SBP >180 or MAP >130 + no ICP issues – reduce BP modestly (MAP 110 or BP 160/90)

Useful IV antihypertensives include: labetalol, nicardipine, esmolol, enalapril, hydralazine, nitroprusside, and nitroglycerin.

The results of INTERACT2 trial was published in NEJM (June, 2013).  In this trial, early intensive lowering of BP compared with a more conservative BP control did not result in reduced rates of death or major disability.  However, there were significantly better functional outcomes among patients assigned to intensive treatment, as well as better physical and psychological well-being. [5]

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Spinal Surgery

[coming soon]  Some neurosurgeons routinely keep MAP goals >85 mm Hg in spinal surgeries where perfusion of the spinal cord is critical.  Evidence for this practice is lacking, whereas the harms from induced hypertension and prolonged ICU stay is real.

 

References

[1] Uptodate.  “Treatment of Aneurysmal Subarachnoid Hemorrhage.”  Accessed 07/07/2016.

[2] Uptodate.  “Initial assessment and management of acute stroke.”  Accessed 07/07/2016.

[3] Uptodate.  “Management of acute severe traumatic brain injury.”  Accessed 07/07/2016.

[4] Uptodate.  “Spontaneous intracerebral hemorrhage: Treatment and prognosis.”  Accessed 07/07/2016.

[5] Anderson, Craig S. et al. “Rapid Blood-Pressure Lowering In Patients With Acute Intracerebral Hemorrhage”. New England Journal of Medicine 368.25 (2013): 2355-2365.

 

 

 

 

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