title: Effect of catecholamine depletion on increased blood pressure lability upon emergence from halothane anesthesia in rats: the role of sympathetic nervous activity in postanesthetic circulatory instability.
abstract: OBJECTIVE
  Circulatory instability is often observed upon emergence from general anesthesia. The increased blood pressure (BP) lability has been associated with poor clinical outcome. However, its underlying mechanisms are not fully understood. Thus, we investigated a possible role of the sympathetic nervous system (SNS) and cardiac baroreflex in the increased pressure lability observed upon emergence from general anesthesia.
  
  
  METHODS
  Male rats (n = 16) were allocated to two groups, i.e., (1) a control group (n = 8) and (2) an alpha-methylparatyrosine (alpha-MPT; an inhibitor of tyrosine hydroxylase)-treated group (n = 8). In the alpha-MPT-treated group, in order to deplete catecholamines both in the central nervous system and in the SNS, alpha-MPT (300 mg x kg(-1)) was injected intraperitoneally (i.p.), administered twice, 4 and 2 h before halothane discontinuation (total dose, 600 mg x kg(-1) i.p.). In the control group, saline was administered at identical time-points. Systolic BP (SBP) lability was evaluated on a beat-by-beat basis, using the coefficient of variation of SBP, and the occurrence of slow and rapid rises in SBP and their amplitude, while the cardiac baroreflex slope was calculated using the "sequences" method.
  
  
  RESULTS
  In the control group, heart rate, SBP, and the three indices of BP lability (i.e., the 3 indices of BP lability are: coefficient of variation of SBP, number of slow and rapid rises in pressure, amplitude of slow and rapid rises in pressure) all increased upon emergence from anesthesia (P < 0.05). Such increases were all blunted in the alpha-MPT-treated group, with the increases in the three indices of BP lability almost entirely suppressed (P < 0.05). The cardiac baroreflex slope was similarly decreased in both groups (P < 0.05).
  
  
  CONCLUSIONS
  The postanesthetic increase in pressure lability seems largely a consequence of increased sympathetic activity, irrespective of any change in cardiac baroreflex sensitivity.
authors.affiliation: Physiology, CNRS 5123-University of Lyon 1, Lyon-Villeurbanne, Lyon, France.
authors.forename: Andrei
authors.initials: A
authors.lastname: Cividjian
authors.forename: Nicolas
authors.initials: N
authors.lastname: Rentero
authors.forename: Jean Marc
authors.initials: JM
authors.lastname: Pequignot
authors.forename: Luc
authors.initials: L
authors.lastname: Quintin
mesh_terms: D000762:Anesthesia Recovery Period; D018685:Anesthetics, Inhalation; D000818:Animals; D017704:Baroreflex / Q000187:drug effects / Q000502:physiology; D001794:Blood Pressure / Q000187:drug effects* / Q000502:physiology; D002395:Catecholamines / Q000172:deficiency*; D002985:Clinical Protocols; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006221:Halothane; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D013564:Sympathetic Nervous System / Q000187:drug effects* / Q000502:physiology; D014666:Vasomotor System / Q000187:drug effects / Q000502:physiology; D019805:alpha-Methyltyrosine / Q000494:pharmacology
chemical_list: D018685:Anesthetics, Inhalation; D002395:Catecholamines; D004791:Enzyme Inhibitors; D019805:alpha-Methyltyrosine; D006221:Halothane