Anesthesia and analgesia
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Anesthesia and analgesia · Feb 1999
Comparative StudyDynamic cerebral autoregulation during sevoflurane anesthesia: a comparison with isoflurane.
We investigated dynamic cerebral pressure autoregulation awake and during 1.5 minimum alveolar anesthetic concentration (MAC) sevoflurane or isoflurane anesthesia in 16 patients undergoing nonintracranial neurosurgical procedures. All patients received a standardized anesthetic, and their lungs were ventilated with 1.5 MAC volatile anesthetic in 100% oxygen to normocapnia. Routine monitors included electrocardiogram, pulse oximetry, end-tidal capnography, and continuous noninvasive blood pressure. In addition, middle cerebral artery blood velocity (Vmca) was measured continuously using transcranial Doppler ultrasonography. Dynamic cerebral autoregulation was tested by inducing a rapid transient decrease in mean arterial pressure by deflation of large thigh cuffs, which were placed around both thighs and inflated to 100 mm Hg above systolic pressure. The Vmca response to the decrease in blood pressure was fitted to a series of curves to determine the rate of dynamic cerebral autoregulation (dRoR). Awake dRoR values were similar in the isoflurane and sevoflurane groups, 32 +/- 2%/s and 29 +/- 2%/s, respectively. dRoR decreased to 5 +/- 1%/s during isoflurane anesthesia but to only 24 +/- 2%/s during sevoflurane anesthesia. We conclude that dynamic cerebral autoregulation is better preserved during sevoflurane than isoflurane anesthesia in humans. ⋯ We investigated the effect of sevoflurane and isoflurane on dynamic cerebral pressure autoregulation using transcranial Doppler ultrasonography. At 1.5 minimum alveolar anesthetic concentration, dynamic autoregulation was better preserved during sevoflurane than isoflurane anesthesia.
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Anesthesia and analgesia · Feb 1999
Randomized Controlled Trial Comparative Study Clinical TrialThe effects of needle bevel orientation during epidural catheter insertion in laboring parturients.
Lateral needle bevel orientation during identification of the epidural space has been recommended to reduce the risk of postdural puncture headache (PDPH). Rotation to cephalad or caudad orientation before catheter insertion is assumed necessary for analgesic success. We prospectively compared the effects of catheter insertion through lateral- and cephalad-oriented Tuohy needle bevels in laboring parturients. Anesthesiology residents were randomized to identify the epidural space with bevels oriented cephalad or lateral. Catheters were inserted without needle rotation. Outcomes compared included ease of insertion, analgesic effectiveness, and complications. We evaluated 534 catheter insertions in 500 parturients. Initial catheter insertion produced satisfactory analgesia in 80.2% of the lateral group versus 91.1% of the cephalad group (P < 0.001). Resistance preventing catheter insertion accounted for the difference. There were no differences in i.v. cannulation (5.8% vs 5.1%), dural puncture (3.8% vs 2.0%), PDPH (0.4% vs 0.7%), or asymmetric block (31% vs 27%). There was a slightly higher rate of paresthesias in the lateral group (31% vs 23%; P = 0.048). In 78% of parturients experiencing both paresthesias and asymmetric block, the side of the paresthesia and greater extent of block were the same. Analgesic effectiveness, as measured by using a visual analog scale, was not different between the groups. ⋯ Two methods of epidural catheter insertion were compared in laboring parturients. Catheter insertion with the needle orifice oriented cephalad was associated with the greatest initial success and the fewest complications.
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Anesthesia and analgesia · Feb 1999
Randomized Controlled Trial Comparative Study Clinical TrialAssessment of the level of sensory block after subarachnoid anesthesia using a pressure palpator.
In a cross-over study, we compared two methods of assessing the level of sensory block during subarachnoid anesthesia: the traditional pinprick sensation or a novel pressure palpator exerting a pressure of 650 g. Fifty patients scheduled for transurethral surgery under subarachnoid anesthesia were randomly assigned to be tested for spread of sensory block. In Group 1, the pressure palpator was followed by pinprick; in Group 2, the reverse sequence was used. Evaluation was performed 15 and 25 min after the subarachnoid injection of 2 mL of 5% lidocaine hyperbaric solution. In Group 1, the level of sensory block assessed with the pressure palpator was 1.7 +/- 3.2 cm (0.5 +/- 1.2 dermatomes) higher than that with the pinprick at 15 min, and 2.2 +/- 3.4 cm (0.6 +/- 1.0 dermatomes) higher than that with the pinprick 25 min after the block. In Group 2, the difference was accentuated. The level of sensory block assessed by pinprick 15 min after subarachnoid lidocaine was 5.7 +/- 4.8 cm (1.2 +/- 0.9 dermatomes) lower than the level with the pressure palpator, and 4.2 +/- 3.3 cm (0.9 +/- 0.6 dermatomes) lower than that with the pressure palpator at 25 min. In all instances, the pressure palpator gave a significantly higher assessment than the pinprick. We conclude that the pressure palpator, when preceded by the pinprick test, is associated with an increased threshold. This method may be useful in assessing the sensory block produced by subarachnoid anesthesia. ⋯ A novel pressure palpator that maintains the integrity of the epidermis was used to assess the level of sensory block after subarachnoid anesthesia and was compared with the standard method of the pinprick sensation. This method assessed the block consistently higher than the pinprick method, but it may have advantages as a noninvasive sensory test.