Hypoxia-hypotension decreases pressor responsiveness to exogenous catecholamines after severe traumatic brain injury in rats.
Crit Care Med
; 29(8): 1609-14, 2001 Aug.
Article
em En
| MEDLINE
| ID: mdl-11505138
ABSTRACT
OBJECTIVE:
To quantify the phenylephrine pressor responsiveness after severe brain injury combined with hypoxia-hypotension, and to study the respective roles of brain injury and hypoxia-hypotension in the observed alteration.DESIGN:
Randomized study.SETTING:
Accredited animal laboratory.SUBJECTS:
Adult Sprague Dawley rats.INTERVENTIONS:
Anesthetized animals were assigned to control, brain injury, hypoxia-hypotension, and brain injury combined with hypoxia-hypotension groups. Brain injury was induced with an impact-acceleration device. During the 15-min hypoxia-hypotension, arterial oxygen pressure was decreased to 40 torr (5.3 kPa) and mean arterial pressure to 30 mm Hg. Thirty-six of the 53 included rats were alive at the end of hypoxia-hypotension (nine animals per group). In an additional group (Hypo, n = 8), mean arterial pressure was lowered to the level observed in brain injury combined with hypoxia-hypotension with pentobarbital infusion. Sixty minutes after injuries (T60), animals received 0.1, 1, and 10 microg/kg phenylephrine in a random order. Pressor responsiveness to phenylephrine was defined as maximal postinjection minus preinjection mean arterial pressure. MEASUREMENTS AND MAINRESULTS:
During hypoxia-hypotension, mortality was higher and residual restored blood volume was lower (p <.01) in the animals with brain injury and hypoxia-hypotension compared with hypoxia-hypotension alone. At T60, mean arterial pressure (mm Hg) was lower (p <.01) in the brain injury group (83 +/- 22) compared with controls (110 +/- 10) and in brain injury combined with hypoxia-hypotension (76 +/- 18) compared with controls and hypoxia-hypotension (107 +/- 14). Pressor responsiveness (mm Hg) to 1 and 10 microg/kg phenylephrine was less (p <.05) in brain injury combined with hypoxia-hypotension (15 +/- 6 and 44 +/- 8) and hypoxia-hypotension (15 +/- 3 and 44 +/- 8) compared with controls (26 +/- 2 and 57 +/- 11). No significant difference was observed for phenylephrine pressor responsiveness between controls and the Hypo group (25 +/- 5 and 66 +/- 7).CONCLUSIONS:
Combination of brain injury and hypoxia-hypotension induces a severe hemodynamic alteration associated with a decreased pressor responsiveness to phenylephrine. Transient hypoxia-hypotension is responsible for the depressed alpha-1 adrenergic reactivity.
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Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Fenilefrina
/
Pressorreceptores
/
Lesões Encefálicas
/
Hipóxia Encefálica
/
Agonistas alfa-Adrenérgicos
/
Hipotensão
Limite:
Animals
Idioma:
En
Revista:
Crit Care Med
Ano de publicação:
2001
Tipo de documento:
Article
País de afiliação:
França