Anesthesia and analgesia
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Anesthesia and analgesia · Nov 2002
Comparative StudyThe delivery rate accuracy of portable infusion pumps used for continuous regional analgesia.
Portable pumps used for local anesthetic infusion during continuous regional analgesia are gaining acceptance. These pumps are often used for ambulatory patients who are medically unsupervised throughout most of the infusion. However, the performance of these pumps, which infuse potentially toxic medication, has not been independently investigated. We investigated the flow rate accuracy, consistency, and profiles of various portable pumps often used for local anesthetic infusion during continuous regional analgesia. By using a computer/scale combination within a laboratory to record infusion rates, 6 pumps were tested with their flow regulators at expected (30 degrees-32 degrees C) and increased (34 degrees-36 degrees C) temperatures. Infusion rate accuracy differed significantly among the pumps, exhibiting flow rates within +/-15% of their expected rate for 18%-100% of their infusion duration. An increase in temperature also affected pumps to differing degrees, with infusion rates increasing from 0% to 25% for each model tested. These results suggest that factors such as flow rate accuracy and consistency, infusion profile, and temperature sensitivity should be considered when choosing and using a portable infusion pump for local anesthetic administration. ⋯ Portable pumps often used for local anesthetic infusion during continuous regional analgesia exhibit varying degrees of delivery rate accuracy and consistency. Furthermore, increases in temperature result in an increased infusion rate for various pumps investigated. These factors should be taken into consideration when choosing and using a portable infusion pump.
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Anesthesia and analgesia · Nov 2002
Comparative Study Clinical TrialNarcotrend, bispectral index, and classical electroencephalogram variables during emergence from propofol/remifentanil anesthesia.
The aim of this study was to investigate modern and classical electroencephalographic (EEG) variables in response to remifentanil and propofol infusions. We hypothesized that modern EEG variables may indicate the effects of propofol but not of remifentanil. Twenty-five patients were included in the study after the end of elective spine surgery without any surgical stimulation. Baseline values were defined with remifentanil 0.3 microg. kg(-1). min(-1) and target-controlled infusion of propofol 3.0 microg/mL. EEG changes were evaluated 1, 3, 5, 7, and 9 min after the stop of remifentanil infusion, followed by a step-by-step reduction (0.2 microg/mL) every 3 min of target-controlled infusion propofol. Narcotrend (NT; classifying EEG stages from awake to deep anesthesia), bispectral index (BIS), EEG spectral frequency bands (%), 50% (Median) and 95% percentiles (spectral edge frequency), mean arterial blood pressure, heart rate, and oxygen saturation were detected at every time point. The end of remifentanil application resulted in significant increases in %alpha, spectral edge frequency, mean arterial blood pressure, and %theta and decreases in %delta (P < 0.05). NT, BIS, Median, heart rate, and oxygen saturation were unchanged. Decreases in propofol concentration were associated with statistically significant increases in NT and BIS (P < 0.05). Thus, the sedative-hypnotic component of propofol could be estimated by modern EEG variables (NT and BIS), whereas the analgesic component provided by remifentanil was not indicated. However, during conditions without surgical stimulation, neither NT nor BIS provided an adequate assessment of the depth of anesthesia when a remifentanil infusion was used. ⋯ We investigated modern and classical electroencephalographic (EEG) variables during emergence from propofol/remifentanil anesthesia. Modern EEG variables indicate changes of infusion in propofol, but not in remifentanil. Thus, modern EEG variables did not provide an adequate assessment of depth of anesthesia when remifentanil was used.
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Anesthesia and analgesia · Nov 2002
Clinical TrialDoes the choice of electrocardiography lead affect the efficacy of the T-wave criterion for detecting intravascular injection of an epinephrine test dose?
Accidental intravascular injection of an epinephrine-containing test dose decreases the T-wave amplitude of a Lead II electrocardiogram (EKG) with 100% sensitivity and specificity on the basis of the T-wave criterion (positive if there is a > or =25% decrease in amplitude). We designed this study to test whether the choice of EKG lead would affect the efficacy of the simulated intravascular test dose in anesthetized patients. After an 8-h fast and no premedication, 35 healthy patients were anesthetized with end-tidal 2% sevoflurane and nitrous oxide after endotracheal intubation. When hemodynamic stability was obtained, all subjects received 3 mL of normal saline IV, followed 4 min later by 1.5% lidocaine 3 mL plus 15 microg of epinephrine (1:200,000) IV. Heart rate, systolic blood pressure, Leads II (n = 35) and V(5) (n = 35), and either Lead I (n = 17) or III (n = 18), whichever had the greater T-wave amplitude, were continuously recorded for 4 min after the saline and test-dose injections. An IV test dose produced significant increases in heart rate and systolic blood pressure and produced decreases in the T-wave amplitude of all EKG leads studied in all subjects, whereas IV saline elicited no changes in these variables. The maximum percentage decreases in T-wave amplitude of Leads II, I, III, and V(5) were -87% +/- 13%, -88% +/- 8%, -94% +/- 15%, and -86% +/- 16%, respectively (mean +/- SD; P > 0.05). There was no significant difference in temporal changes in T-wave amplitude among the 4 leads, and sensitivity and specificity were 100% on the basis of the T-wave criterion, irrespective of the lead examined. Our results indicate that Leads II, I, III, and V(5) of the EKG are equally effective for detecting intravascular injection of the epinephrine-containing test dose in sevoflurane-anesthetized adults. ⋯ To determine whether an epidural catheter is in a blood vessel, an epidural test dose containing 15 microg of epinephrine is used. We found that decreases in the T-wave amplitude of Leads I, II, III, and V(5) of the electrocardiogram were equally sensitive and specific for detecting intravascular injection of the test dose in sevoflurane-anesthetized adult patients.
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Anesthesia and analgesia · Nov 2002
Clinical TrialLumbar plexus posterior approach: a catheter placement description using electrical nerve stimulation.
The authors describe a modified technique of posterior approach to the lumbar plexus in the psoas compartment which allows nerve stimulation for the location of the plexus and catheter placement for extended-duration surgery and postoperative patient-controlled regional analgesia. A frequent incidence of total lumbar plexus block was observed.