Anesthesia and analgesia
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Anesthesia and analgesia · Aug 2003
The bispectral index declines during neuromuscular block in fully awake persons.
Using an Aspect A-1000 BIS monitor, researchers demonstrated a drop in Bispectral Index Score in awake, paralysed volunteers to low values ranging from 9 to 64.
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Anesthesia and analgesia · Aug 2003
Randomized Controlled Trial Clinical TrialThe effect of mixing lidocaine with propofol on the dose of propofol required for induction of anesthesia.
Lidocaine is used to reduce pain associated with propofol injection, either mixed with propofol or preceding it as a separate injection. The addition of lidocaine to propofol causes destabilization of the emulsion and reduces anesthetic potency in rats and humans. We conducted a randomized double-blinded study on 67 patients to assess the effect of mixing lidocaine with propofol on the dose of propofol required for the induction of anesthesia. Patients in Group S (n = 32) received IV lidocaine 0.2 mg/kg followed by an infusion of propofol whereas those in Group M (n = 35) received IV normal saline (placebo) followed by an infusion of a freshly prepared mixture of propofol 1%/lidocaine 1% in 10:1 volume ratio. The infusion was stopped when the subjects lost consciousness, as detected by the syringe-drop method. There was no statistically significant difference between the two groups in the mean (95% confidence interval) doses of propofol required for loss of consciousness: 2.0 (1.8-2.2) mg/kg for Group S versus 1.9 (1.7-2.0) mg/kg for Group M (P = 0.206). Mixing 20 mg of lidocaine with 200 mg of propofol is unlikely to affect the dose of propofol required for the induction of anesthesia. ⋯ Adding lidocaine to propofol destabilizes the propofol emulsion. A randomized double-blinded trial found no statistically significant difference in the doses of propofol required for the induction of anesthesia whether administered as a freshly prepared propofol 1%/lidocaine 1% 10:1 mixture or as a separate injection after a dose of lidocaine.
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Anesthesia and analgesia · Aug 2003
Randomized Controlled Trial Clinical TrialThe effect of small dose fentanyl on the emergence characteristics of pediatric patients after sevoflurane anesthesia without surgery.
We designed this study to measure the effect of a small dose of IV fentanyl on the emergence characteristics of pediatric patients undergoing sevoflurane anesthesia without any surgical intervention. Thirty-two ASA physical status I or II pediatric outpatients receiving sevoflurane anesthesia for magnetic resonance imaging scans were enrolled and assigned in a random and double-blinded manner to receive either placebo (saline) or 1 micro g/kg IV fentanyl 10 min before discontinuation of their anesthetic. The primary outcome measure was the percentage of patients with emergence agitation. We also evaluated the duration of agitation and time to meet hospital discharge criteria. Patients who received fentanyl had a decreased incidence of agitation (12% versus 56%) when compared with placebo. There was no significant difference in time to meet hospital discharge criteria. We conclude that the addition of a small dose of fentanyl to inhaled sevoflurane anesthesia decreases the incidence of emergence agitation independent of pain control effects. ⋯ The addition of a small dose of fentanyl given to patients undergoing nonsurgical sevoflurane anesthesia resulted in a significant decrease in emergence agitation in a prospective, randomized, and controlled trial involving pediatric patients.
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Anesthesia and analgesia · Aug 2003
Clinical Trial Controlled Clinical TrialThe relationship between expired concentration of sevoflurane and sympathovagal tone in children.
In children, sevoflurane depresses parasympathetic tone during induction more than halothane. The effects of sevoflurane on parasympathetic activity could explain the difference in heart rate (HR) changes described between infants and children. In this study, we sought to determine the relationship between the end-tidal concentration of sevoflurane and sympathetic and parasympathetic tone in children by spectral analysis of RR intervals. Thirty-three children, ASA physical status I, who required elective surgery were studied. In 10 children (Group A), recordings were performed while gradually decreasing the inspired sevoflurane concentration from 8% to the beginning of clinical awakening. In 23 other children (Group B), recordings were performed while children were awake and at a steady-state of 1 and 2 minimum alveolar anesthetic concentration of sevoflurane. A time-varying autoregressive modeling of the interpolated RR sequences was performed, and spectral density in low-frequency (LF; 0.04-0.15 Hz) and high-frequency (HF; 0.15-0.55 Hz) bands was calculated. In Group A, HR slowing paralleled the decrease in expired sevoflurane concentration. Conversely, the decrease in expired concentration of sevoflurane led to an increase in systolic blood pressure (SBP), HF, LF, and LF/HF. The increase in LF/HF preceded the increase in HF. In Group B, the baseline HF power spectrum and normalized values HFnu (HFnu = HF/LF + HF) were significantly increased in children older than 3 yr. Changes in HR induced by sevoflurane were negatively correlated with baseline HF and HFnu (R(2) = 0.6; P < 0.001). These results demonstrate that withdrawal of parasympathetic tone is the main determinant for the change in HR induced by sevoflurane. ⋯ The effects of sevoflurane on parasympathetic activity could explain the difference in heart-rate changes described between infants and children during induction. This study describes the changes in heart rate and its variability induced by sevoflurane in children and shows that these changes are related to parasympathetic tone before the induction of anesthesia.
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Anesthesia and analgesia · Aug 2003
Randomized Controlled Trial Clinical TrialThe effect of exogenous epinephrine on the incidence of hypotensive/bradycardic events during shoulder surgery in the sitting position during interscalene block.
Sudden hypotensive and/or bradycardic events (HBE) have been reported in 13%-28% of patients undergoing shoulder surgery in the sitting position during interscalene block. The Bezold-Jarisch reflex is the most likely mechanism for these events. It has been hypothesized that exogenous epinephrine might be a key component to the occurrence of HBE. We conducted this prospective, randomized study to verify this hypothesis. Patients received a local anesthetic solution with (Group E; n = 55) or without (Group P; n = 55) epinephrine for interscalene block; no further exogenous epinephrine was administered. Blood pressure control was achieved with IV urapidil, a peripheral vasodilator, as needed. The incidence of HBE was 11% in Group P versus 29% in Group E (P = 0.015). Increased intraoperative heart rate and arterial blood pressure were recorded in Group E (P = 0.000). Urapidil was administered to 13% of Group P and to 31% of Group E patients (P = 0.018). Urapidil administration induced a HBE in 4% of Group P and in 5% of Group E patients. We conclude that exogenous epinephrine is involved in the development of HBE in this setting. ⋯ Sudden hypotensive and/or bradycardic events occur during shoulder surgery in the sitting position during interscalene block. In this study, we demonstrated that the presence of epinephrine in the local anesthetic mixture significantly increases the incidence of these events.