Article

A comparison of the transient hyperemic response test and the static autoregulation test to assess graded impairment in cerebral autoregulation during propofol, desflurane, and nitrous oxide anesthesia.

University Department of Anaesthesia and Intensive Care, Queen's Medical Centre and City Hospital NHS Trust, Nottingham, United Kingdom.
Anesthesia & Analgesia (impact factor: 3.29). 07/2001; 93(1):171-6.
Source: PubMed

ABSTRACT The transient hyperemic response (THR) test has been used to assess cerebral autoregulation in anesthesia and intensive care. To date it has not been compared with the static autoregulation test for assessing graded changes in cerebral autoregulation. We compared the two tests during propofol, desflurane, and nitrous oxide anesthesia. Seven subjects were studied. For the THR test, changes in the middle artery blood flow velocity were assessed during and after a 10-s compression of the ipsilateral common carotid artery. Two indices of autoregulation--THR ratio (THRR) and strength of autoregulation (SA)--were calculated. For the test of static autoregulation, changes in the middle cerebral artery flow velocity after a phenylephrine-induces increase in mean arterial pressure were assessed, and the static rate of regulation (sROR) was calculated. The tests were performed before induction and after equilibrium at 0.5 minimum alveolar anesthetic concentration (MAC) and then at 1.5 MAC of desflurane. THRR, SA and sROR decreased significantly (P < 0.001) at 0.5 MAC and then at 1.5 MAC desflurane. CHanges in THRR and SA reflected the changes in sROR with a sensitivity of 100%. Implications: When compared with the established test of static autoregulation, the transient hyperemic response test provides a valid method for assessing graded impairment in cerebral autoregulation.

0 0
 · 
0 Bookmarks
 · 
17 Views
  • Source
    Article: The effects of large-dose propofol on cerebrovascular pressure autoregulation in head-injured patients.
    Luzius A Steiner, Andrew J Johnston, Doris A Chatfield, Marek Czosnyka, Martin R Coleman, Jonathan P Coles, Arun K Gupta, John D Pickard, David K Menon
    [show abstract] [hide abstract]
    ABSTRACT: In healthy individuals, cerebrovascular pressure autoregulation is preserved or even improved when propofol is infused. We examined the effect of an increase in propofol plasma concentration on pressure autoregulation in 10 head-injured patients. Using target-controlled infusions, the static rate of autoregulation was determined at a moderate (2.3 +/- 0.4 microg/mL) and a large (4.3 +/- 0.04 microg/mL) plasma target concentration of propofol. Using norepinephrine to control cerebral perfusion pressure, transcranial Doppler measurements from the middle cerebral artery were made at a cerebral perfusion pressure of 70 and 85 mm Hg at each propofol concentration. Middle cerebral artery flow velocities at the large propofol concentration were significantly lower than at the moderate concentration, without any concurrent increase in arterio-jugular difference in oxygen content, a finding compatible with maintained flow-metabolism coupling. Despite this, static rate of autoregulation decreased significantly from 54% +/- 36% to 28% +/- 35% (P = 0.029). Our data suggest that after head injury, the cerebrovascular effects of propofol are different from those observed in healthy individuals. We propose that large doses of propofol should be used cautiously in head-injured patients, because there is the potential to increase the injured brain's vulnerability to secondary insults. IMPLICATIONS: Propofol is used for sedation and control of intracranial pressure in head-injured patients. In contrast to previous data from healthy individuals, we show a deterioration of cerebrovascular pressure autoregulation with fast propofol infusion rates after head injury. Large propofol doses may increase the injured brain's vulnerability to secondary insults.
    Anesthesia & Analgesia 09/2003; 97(2):572-6, table of contents. · 3.29 Impact Factor
Data provided are for informational purposes only. Although carefully collected, accuracy cannot be guaranteed. The impact factor represents a rough estimation of the journal's impact factor and does not reflect the actual current impact factor. Publisher conditions are provided by RoMEO. Differing provisions from the publisher's actual policy or licence agreement may be applicable.

Keywords

0.5 minimum alveolar anesthetic concentration
 
arterial pressure
 
cerebral autoregulation
 
graded changes
 
intensive care
 
ipsilateral common carotid artery
 
MAC desflurane
 
middle artery blood flow velocity
 
middle cerebral artery flow velocity
 
nitrous oxide anesthesia
 
phenylephrine-induces increase
 
sROR
 
static autoregulation
 
static autoregulation test
 
static rate
 
THRR
 
transient hyperemic response
 
transient hyperemic response test
 
two tests
 
valid method