title: Cerebral vascular effects of hypovolemia and dopamine infusions: a study in newborn piglets.
abstract: OBJECTIVE
  Despite widespread use, effects of volume boluses and dopamine in hypotensive newborn infants remain controversial. We aimed to elucidate if hypovolemia alone impairs cerebral autoregulation (CA) and if dopamine affects cerebral vasculature.
  
  
  METHODS
  In 12 piglets, cerebral perfusion (laser-Doppler flux) and oxygenation [near-infrared spectroscopy (NIRS)] were examined during dopamine (20-50 μg/kg per minute) and nonpharmacologically induced blood pressure (ABP) changes. Effect on cerebral perfusion and oxygenation was quantified as frequency gain between ABP and laser-Doppler flux (gain-LDF) and NIRS [gain-oxygenation index (OI)], respectively. Gain quantifies change in perfusion or oxygenation per ABP-change. CA was estimated as gain-LDF during nonpharmacologically induced ABP changes, that is, as degree of impairment. Dopamine's cerebrovascular effect was estimated by contrasting gain during dopamine- and nonpharmacologically induced ABP changes. Measurements were conducted during both normovolemia- and haemorrhage-induced hypovolemia.
  
  
  RESULTS
  Hypovolemia elicited hypotension (p = 0.02) as well as increasing impairment of CA (p = 0.01). However, hypovolemia without hypotension did not affect CA significantly. Dopamine increased perfusion significantly compared to nonpharmacological challenges (mean difference: 1.5%/mmHg, 95% CI: 0.5-2.6, p = 0.007). Oxygenation was, however, similar (mean difference: 0.01 μmol/L per mmHg, 95% CI: -0.03 to 0.05, p = 0.7).
  
  
  CONCLUSIONS
  Our findings do not support that hypovolemia alone impairs CA. Furthermore, dopamine seems to increase cerebral perfusion but not oxygenation.
authors.affiliation: Department of Neonatology, Copenhagen University Hospital - Rigshospitalet, Denmark. gitte.holst.hahn@gmail.com
authors.forename: Gitte H
authors.initials: GH
authors.lastname: Hahn
authors.forename: Christian
authors.initials: C
authors.lastname: Heiring
authors.forename: Ole
authors.initials: O
authors.lastname: Pryds
authors.forename: Gorm
authors.initials: G
authors.lastname: Greisen
mesh_terms: D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D001921:Brain / Q000098:blood supply / Q000187:drug effects* / Q000378:metabolism; D004195:Disease Models, Animal; D004298:Dopamine / Q000494:pharmacology*; D015259:Dopamine Agents / Q000494:pharmacology*; D006706:Homeostasis / Q000187:drug effects*; D007022:Hypotension / Q000209:etiology; D020896:Hypovolemia / Q000150:complications / Q000503:physiopathology*; D017078:Laser-Doppler Flowmetry; D010100:Oxygen / Q000378:metabolism; D011897:Random Allocation; D019265:Spectroscopy, Near-Infrared; D013552:Swine
chemical_list: D015259:Dopamine Agents; D010100:Oxygen; D004298:Dopamine