Showing papers by "Bruno Bissonnette published in 2002"
TL;DR: CCO2R is preserved in healthy children anaesthetized with 1.0 MAC sevoflurane and air in 30% oxygen delivered through an Ayre's T piece by intermittent positive-pressure ventilation, while maintaining ventilation variables constant.
Abstract: Background To determine the effects of sevoflurane on cerebrovascular carbon dioxide reactivity (CCO2R), middle cerebral artery blood flow velocity (CBFV) was measured at different levels of P e ′CO2 by transcranial Doppler sonography in 16 ASA I or II children, aged 18 months to 7 yr undergoing elective urological surgery. Methods Anaesthesia comprised 1.0 MAC sevoflurane and air in 30% oxygen delivered through an Ayre's T piece by intermittent positive-pressure ventilation, and a caudal epidural block with 0.25% bupivacaine 1.0 ml kg−1 without epinephrine. P e ′CO2 was randomly adjusted to 25, 35, 45 and 55 mm Hg (3.3, 4.6, 5.9 and 7.2 kPa) with an exogenous source of CO2, while maintaining ventilation variables constant. Results CBFV increased as P e ′CO2 increased from 25 to 35, and to 45 mm Hg (P e ′CO2 from 45 to 55 mm Hg. Mean heart rate and arterial pressure remained constant. Conclusion CCO2R is preserved in healthy children anaesthetized with 1.0 MAC sevoflurane.
37 citations
TL;DR: This study shows that a higher rate of prop ofol infusion is associated with lower CBFV and MAP values in children, and propofol’s cerebral vasoconstrictive properties may be responsible for this finding.
Abstract: Purpose
Propofol, by virtue of its favourable pharmacokinetic profile, is suitable for maintenance of anesthesia by continuous infusion during neurosurgical procedures in adults. It is gaining popularity for use in pediatric patients. To determine the effects of propofol on cerebral blood flow in children, middle cerebral artery blood flow velocity (Vmca) was measured at different levels of propofol administration by transcranial Doppler (TCD) sonography.
37 citations
TL;DR: There is an important heat exchange within the tubing, which is aggravated at low flow rates, and at infusion rates appropriate for pediatric anesthesia the clinical and economic value of fluid warming without the use of heated extension tubing is questionable.
Abstract: To determine the effect of infusion rate, tubing length and fluid composition on the temperature of the infusate reaching the distal end of an infusion tubing with and without active fluid warming. Warmed normal saline (W-NS) and packed red blood cells (W-PRBC), were infused with a fluid warmer through a modified infusion set. The fluids were delivered at eight infusion rates from 50 to 999 mL·hr−1. The infusate temperature was monitored at 20 cm intervals on theiv tubing. The same temperature monitoring protocol was applied to PRBC without warmer (NoW-PRBC). In W-NS and W-PRBC groups, there was a decrease in the infusate temperature, at each flow rate, from the drip chamber to the distal end of tubing (P < 0.001). In NoW-PRBC group, there was a rapid increase in the infusate temperature from the bag to the drip chamber (P < 0.001). Thereafter, there was no change in temperature, except at the 999 mL·hr−1 infusion rate, where a slight increase in the infusate temperature throughout the tubing was shown. In W-NS and W-PRBC groups increasing the flow rate produced a significant increase in the infusate temperature, at each measurement point (P < 0.001). In the NoW-PRBC group, increasing the flow rate did not alter the infusate temperature. The fluid composition did not influence the infusate temperature. There is an important heat exchange within the tubing, which is aggravated at low flow rates. At infusion rates appropriate for pediatric anesthesia the clinical and economic value of fluid warming without the use of heated extension tubing is questionable.
27 citations
TL;DR: Fentanyl was more effective than remifentanil at preventing increases in CBFV during and immediately following laryngoscopy and tracheal intubation in children undergoing sevoflurane anesthesia.
Abstract: Controlling the cerebral and systemic hemodynamic responses to laryngoscopy and tracheal intubation may play a role in determining clinical outcome in pediatric neurosurgical patients. This study compared the effects of remifentanil and fentanyl on cerebral blood flow velocity (CBFV) and hemodynamic profile during laryngoscopy and tracheal intubation in children under sevoflurane anesthesia. Sixty healthy children aged two to six years undergoing dental surgery under general anesthesia were enrolled. Each child was randomly assigned to receive a remifentanil or fentanyl infusion, at a rate of 0.75, 1.0, or 1.5 μg·kg−1·min−1 after induction of anesthesia with 2% sevoflurane. Middle cerebral artery blood flow velocity was measured by transcranial Doppler (TCD) sonography Once a baseline set of hemodynamic variables and TCD measurements were recorded, the opioid infusion was started. Measurements were taken at two-minute intervals, starting four minutes prior to laryngoscopy until four minutes following naso-tracheal intubation. Remifentanil caused a more significant decrease in mean arterial pressure and CBFV prior to tracheal intubation than did fentanyl (P < 0.001). During laryngoscopy and for two minutes following tracheal intubation, CBFV increased in all remifentanil groups (P < 0.05), whereas it remained stable in all fentanyl groups. This study suggests that fentanyl was more effective than remifentanil at preventing increases in CBFV during and immediately following laryngoscopy and tracheal intubation in children undergoing sevoflurane anesthesia. Fentanyl also seemed to provide a more stable hemodynamic profile prior to laryngoscopy and tracheal intubation when compared to remifentanil.
22 citations
TL;DR: In fixed diameter vessels with laminar flow, the linear relationship between flow and velocity is not affected by changes in temperature and Hct in clinical ranges, supporting the use of transcranial Doppler sonography to estimate cerebral blood flow in infants who may have large variations of Hct and/or temperature during bypass.
Abstract: Background To determine whether temperature and haematocrit (Hct) alter the relationship between blood flow (BF) and blood flow velocity (BFV). Methods Using a transcranial Doppler apparatus, we measured the peak velocity of whole blood cells pumped by a cardiopulmonary bypass (CPB) circuit, through a 0.15-cm internal diameter segment of rigid tubing. BF and BFV relationships were obtained at temperatures of 19, 28, and 37°C and at Hct of 0.05, 0.22, 0.39, and 0.54, by altering CPB flow over a range from 10 to 100 cc/min. Linear regression analysis was performed. Results The relationship between velocity and flow for the pooled Hct data was y=(0.43)x+0.86, r2=0.998 and 95% CI (0.999–1) whereas the association for the temperature data was y=(0.42)x+0.02, r2=0.9998 and 95% CI (0.999–0.9997). Changes of blood viscosity had no effect on velocity at a given flow rate. The combined effect of Hct and temperature on velocity for the relationship with flow is expressed by: y=1.3+2.4x. Conclusions In fixed diameter vessels with laminar flow, the linear relationship between flow and velocity is not affected by changes in temperature and Hct in clinical ranges. These results are explained by the Fahraeus–Lindquist effect. They support the use of transcranial Doppler sonography to estimate cerebral blood flow in infants who may have large variations of Hct and/or temperature during bypass.
20 citations
2 citations