title: Inhalation versus endovenous sedation in subarachnoid hemorrhage patients: effects on regional cerebral blood flow.
abstract: OBJECTIVE
  Isoflurane is a volatile anesthetic that has a vasodilating effect on cerebral vessels producing a cerebral blood flow increase. Furthermore, it has been shown in animal studies that isoflurane, when used as a preconditioning agent, has neuroprotective properties, inducing tolerance to ischemia. However, it is not routinely used in neurointensive care because of the potential increase in intracranial pressure caused by the rise in cerebral blood flow. Nevertheless, subarachnoid hemorrhage patients who are at risk for vasospasm may benefit from an increase in cerebral blood flow. We measured regional cerebral blood flow during intravenous sedation with propofol and during sedation with isoflurane in patients with severe subarachnoid hemorrhage not having intracranial hypertension.
  
  
  METHODS
  The study is a crossover, open clinical trial (NCT00830843).
  
  
  METHODS
  Neurointensive care unit of an academic hospital.
  
  
  METHODS
  Thirteen patients with severe subarachnoid hemorrhage, (median Fisher scale 4), monitored on clinical indication with intracranial pressure device and a thermal diffusion probe for the assessment of regional cerebral blood flow. An intracranial pressure>18 mm Hg was an exclusion criterion.
  
  
  METHODS
  Cerebral and hemodynamic variables were assessed at three steps. Step 1: sedation with propofol 3-4 mg/kg/hr; step 2: after 1 hr of propofol discontinuation and isoflurane 0.8%; step 3: after 1 hr of propofol at the same previous infusion rate. Cerebral perfusion pressure and arterial PCO2 were maintained constant. Mean cerebral artery flow velocity and jugular vein oxygen saturation were measured at the end of each step.
  
  
  RESULTS
  Regional cerebral blood flow increased significantly during step 2 (39.3±29 mL/100 hg/min) compared to step 1 (20.8±10.7) and step 3 (24.7±8). There was no difference in regional cerebral blood flow comparing step 1 vs. step 3. No significant difference in intracranial pressure, mean cerebral artery transcranial Doppler velocity, PaCO2, cerebral perfusion pressure between the different steps.
  
  
  CONCLUSIONS
  Isoflurane increases regional cerebral blood flow in comparison to propofol. Intracranial pressure did not change significantly in the population not affected by intracranial hypertension.
authors: Division of NeuroIntensive Care, Department of Anesthesia and Critical Care, Ospedale San Gerardo, Monza, Italy. villa.federico@fastwebnet.it
authors: Federico
authors: F
authors: Villa
authors: Cosimo
authors: C
authors: Iacca
authors: Andrea Forastieri
authors: AF
authors: Molinari
authors: Carlo
authors: C
authors: Giussani
authors: Giacomo
authors: G
authors: Aletti
authors: Antonio
authors: A
authors: Pesenti
authors: Giuseppe
authors: G
authors: Citerio
mesh_terms: D000046:Academic Medical Centers; D000328:Adult; D000368:Aged; D018685:Anesthetics, Inhalation / Q000008:administration & dosage / Q000627:therapeutic use*; D018686:Anesthetics, Intravenous / Q000008:administration & dosage / Q000627:therapeutic use*; D001783:Blood Flow Velocity; D002560:Cerebrovascular Circulation / Q000187:drug effects*; D018592:Cross-Over Studies; D005260:Female; D015600:Glasgow Coma Scale; D006801:Humans; D007362:Intensive Care Units; D007427:Intracranial Pressure / Q000187:drug effects; D007530:Isoflurane / Q000008:administration & dosage / Q000627:therapeutic use*; D008297:Male; D008875:Middle Aged; D015742:Propofol / Q000008:administration & dosage / Q000627:therapeutic use*; D013345:Subarachnoid Hemorrhage / Q000188:drug therapy*; D017585:Ultrasonography, Doppler, Transcranial
chemical_list: D018685:Anesthetics, Inhalation; D018686:Anesthetics, Intravenous; D007530:Isoflurane; D015742:Propofol