Anesthesia and analgesia
-
Anesthesia and analgesia · Mar 2002
Comparative StudyA comparison of the INVOS 4100 and the NIRO 300 near-infrared spectrophotometers.
We determined whether two different devices for measuring near-infrared spectroscopy (NIRS)---the INVOS 4100 and the NIRO 300---produce similar cerebral oxygenation data during the CO(2) challenge test. Nineteen patients anesthetized with sevoflurane, 67% nitrous oxide in oxygen, and fentanyl were studied. A series of measurements of regional cerebral oxygen saturation (rSO(2)), measured by the INVOS 4100, and tissue oxygen index (TOI), measured by the NIRO 300, were performed in the following conditions: 1) normocapnia (PaCO(2), 35--45 mm Hg); 2) hypocapnia (PaCO(2), 25--35 mm Hg); 3) normocapnia; and 4) hypercapnia (PaCO(2), 45--55 mm Hg). Hemodynamic variables, including arterial blood gases and cerebral blood flow velocity, were measured at the same time with transcranial Doppler. The values and percentage changes of rSO(2) and TOI were compared by using regression analysis and Bland and Altman analysis. The rSO(2) showed a significant positive correlation with TOI (r = 0.58, P < 0.01). The percentage change of rSO(2) also showed a significant positive correlation with the percentage change of TOI during the CO(2) challenge (r = 0.85, P < 0.01). Bland and Altman analysis revealed a bias of -0.5% with 2 SD of 15.6% when comparing the rSO(2) value with the TOI value, and it showed a bias of -3.4% with 2 SD of 15.2% when comparing the percentage change of rSO(2) with the percentage change of TOI, indicating unacceptable disagreement of these data. These results indicate that cerebral oxygen saturation and its relative change during the CO(2) challenge may vary depending on the type of NIRS used. Because the measurement technique and algorithm were different in each device, we should carefully consider the clinical application of the values produced by NIRS. ⋯ Near-infrared spectroscopy (NIRS) has been proposed as a noninvasive clinical method for assessing cerebral oxygenation. The acceptable reliability and validity of NIRS values have not been established despite their widespread use. The INVOS 4100 and the NIRO 300 can display cerebral oxygen saturation as regional cerebral oxygen saturation and tissue oxygenation index, but they produce differing results.
-
Anesthesia and analgesia · Mar 2002
Randomized Controlled Trial Comparative Study Clinical TrialSpinal ropivacaine for cesarean delivery: a comparison of hyperbaric and plain solutions.
We compared, in this prospective, randomized, double-blinded study, the characteristics of spinal anesthesia with plain and hyperbaric ropivacaine for elective cesarean delivery. We hypothesized that the addition of glucose would change the onset, offset, and extent of motor and sensory block from intrathecal ropivacaine. Forty ASA physical status I--II women were given 25 mg of either ropivacaine (n = 20) or ropivacaine in 8.3% glucose (n = 20) intrathecally, via a combined spinal/epidural technique in the right lateral position. Sensory changes to ice and pinprick and motor block (Bromage score) were recorded at 2.5-min intervals. Adequate anesthesia for surgery was achieved in all patients in the Hyperbaric group, whereas in the Plain group, five (25%) patients required epidural top-up because of insufficient rostral spread (P < 0.05). With hyperbaric ropivacaine, we found the following: higher cephalic spread (median [range] maximum block height to pinprick, T1 [T4 to C2] versus T3 [T11 to C3], P < 0.001); lower coefficient of variation of maximum block height (17.7% vs 21.9%); faster onset to T4 dermatome (mean [SD] 7.7 [4.9] vs 16.4 [14.1] min, P = 0.015); and faster recovery to L1 (189.0 [29.6] vs 215.5 [27.0] min, P = 0.01). The onset of complete motor block (9.9 [5.3] vs 13.8 [5.4] min, P = 0.027) and complete recovery (144.8 [28.4] vs 218.5 [56.8] min, P < 0.001) was also faster. No neurologic symptoms were found at 24 h. ⋯ We compared hyperbaric and plain ropivacaine for combined spinal/epidural analgesia in the lateral position in patients undergoing elective cesarean delivery. Hyperbaric ropivacaine produced more rapid block with faster recovery and less requirement for epidural supplementation compared with plain ropivacaine.
-
The tracheas of obese patients may be more difficult to intubate than those of normal-weight patients. We studied 100 morbidly obese patients (body mass index >40 kg/m(2)) to identify which factors complicate direct laryngoscopy and tracheal intubation. Preoperative measurements (height, weight, neck circumference, width of mouth opening, sternomental distance, and thyromental distance) and Mallampati score were recorded. The view during direct laryngoscopy was graded, and the number of attempts at tracheal intubation was recorded. Neither absolute obesity nor body mass index was associated with intubation difficulties. Large neck circumference and high Mallampati score were the only predictors of potential intubation problems. Because in all but one patient the trachea was intubated successfully by direct laryngoscopy, the neck circumference that requires an intervention such as fiberoptic bronchoscopy to establish an airway remains unknown. We conclude that obesity alone is not predictive of tracheal intubation difficulties. ⋯ In 100 morbidly obese patients, neither obesity nor body mass index predicted problems with tracheal intubation. However, a high Mallampati score (greater-than-or-equal to 3) and large neck circumference may increase the potential for difficult laryngoscopy and intubation.
-
Anesthesia and analgesia · Mar 2002
Oral clonidine premedication reduces the awakening concentration of propofol.
To investigate the effects of oral clonidine premedication on emergence from propofol/fentanyl anesthesia, we studied 72 healthy male patients who were undergoing elective orthopedic surgery: the Control group, the 2.5 microg/kg Clonidine group, and the 5.0 microg/kg Clonidine group (n = 24 each). Nothing was administered to the Control group. Clonidine (2.5 or 5.0 microg/kg) was orally administered 90 min before the induction of anesthesia in the Clonidine groups. Patients were anesthetized with computer-assisted continuous infusion of propofol and fentanyl, with the three groups receiving the same concentrations of propofol (3 microg/mL) and fentanyl (1 ng/mL) starting 20 to 30 min before the end of surgery. Propofol infusion was then abruptly discontinued at the end of surgery in all patients. After propofol was discontinued, the response to verbal commands was evaluated every 30 s, and arterial blood samples for propofol and clonidine concentrations were taken when the patients opened their eyes. The time required to respond to a verbal command was 14.9 plus/minus 8.3 min for the 5.0 microg/kg Clonidine group, and this was significantly longer than the Control (8.2 plus/minus 5.0 min) and the 2.5 microg/kg Clonidine (9.0 plus/minus 3.7 min) groups (P < 0.01). Serum propofol concentration at awakening in the 5.0 microg/kg Clonidine group was 1.0 plus/minus 0.4 microg/mL, which was significantly smaller than the Control (1.6 plus/minus 0.4 microg/mL) and the 2.5 microg/kg Clonidine (1.4 plus/minus 0.3 microg/mL) groups (P < 0.01). The blood clonidine concentration was associated with a decrease in the awakening propofol concentration. In conclusion, 5 microg/kg oral clonidine premedication decreases the awakening propofol concentration and delays arousal from propofol/fentanyl anesthesia. ⋯ Preanesthetic medication with 5 microg/kg oral clonidine, but not 2.5 microg/kg clonidine, is associated with prolonged recovery from propofol/fentanyl anesthesia.