[Unilateral spinal anaesthesia in elderly patient for hip trauma: a pilot study]. / Rachianesthésie hypobare unilatérale chez le sujet âgé pour la chirurgie traumatique de la hanche: étude pilote.

INTRODUCTION: Fractured neck of femur is encountered more frequently as life expectancy increases. All anaesthetic techniques aim to avoid deleterious fall in arterial blood pressure. The haemodynamic effects of hypobaric unilateral spinal anaesthesia have been rarely assessed in patients over 80 year's old. This study aims to do that in a prospective manner. PATIENTS AND METHODS: Twenty-five patients were enrolled. Following a preload with HES 240/0.576 % (Hesteril) (5 ml/kg) and the administration of an iliofascial block, patients were placed in the lateral decubitus position, operative side uppermost. 3.5 ml of 0.12% hypobaric bupivacaine was administered intrathecally at a rate of 0.25 ml/second. Patients were kept in position for 15 minutes. Systolic, mean and diastolic arterial pressures, heart rate, SaO2 % and ephedrine consumption were recorded at five minutes intervals as was the rate of onset, height and duration of sensory and motor block and extent of bilateralization. Patient and surgeon satisfaction scores were also recorded. RESULTS: No significant changes in systolic, mean and diastolic pressures, or SaO2 % occurred. Median onset times of sensory and motor block were 8+/-5 and 16+/-7 minutes on the operative side and 30+/-15 and 36+/-15 minutes on the contralateral side in those with bilateralization, respectively. The maximum height of sensory block was T6 for sept patients, T8 for huit patients and T8-T10 for the remainder. Mean duration of sensory and motor block was 134+/-26 and 119+/-24 minutes on the operative side and 100+/-26 and 98+/-25 minutes on the contralateral side, respectively. In 12 patients (48%) bilateralization of their block occurred. Patients and surgeons rated the technique highly. CONCLUSION: Hypobaric unilateral spinal anaesthesia is a simple technique, produces satisfactory operative conditions and induces very little haemodynamic change in the elderly population.

Postoperative analgesia after total knee replacement: the effect of an obturator nerve block added to the femoral 3-in-1 nerve block.

Femoral nerve block (FNB) does not consistently produce anesthesia of the obturator nerve. In this single-blind, randomized, controlled study we added a selective obturator nerve block (ONB) to FNB to analyze its influence on postoperative analgesia after total knee replacement (TKR). Before general anesthesia, 90 patients undergoing TKR received FNB (Group 1), FNB and selective ONB (Group 2), or placebo FNB (Group 3). Postoperative analgesia was further provided by morphine IV via patient-controlled analgesia. Analgesic efficacy and side effects were recorded in the first 6 h after surgery. Adductor strength decreased by 18% +/- 9% in Group 1 and by 78% +/- 22% in Group 2 (P < 0.0001). Total morphine consumption was reduced in Group 2 compared with Groups 1 and 3 (P < or = 0.0001). Patients in Group 2 reported lower pain scores than those in Groups 1 and 3 (P = 0.0003). The incidence of nausea was more frequent in Groups 1 and 3 (P = 0.01). We conclude that FNB does not produce complete anesthesia of the obturator nerve. Single-shot FNB does not provide additional benefits on pain at rest over opioids alone in the early postoperative period. The addition of an ONB to FNB improves postoperative analgesia after TKR.

Propofol anesthesia and cerebral blood flow changes elicited by vibrotactile stimulation: a positron emission tomography study.

We investigated the effects of the general anesthetic agent propofol on cerebral structures involved in the processing of vibrotactile information. Using positron emission tomography (PET) and the H(2)(15)O bolus technique, we measured regional distribution of cerebral blood flow (CBF) in eight healthy human volunteers. They were scanned under five different levels of propofol anesthesia. Using a computer-controlled infusion, the following plasma levels of propofol were targeted: Level W (Waking, 0 microg/ml), Level 1 (0.5 microg/ml), Level 2 (1.5 microg/ml), Level 3 (3.5 microg/ml), and Level R (Recovery). At each level of anesthesia, two 3-min scans were acquired with vibrotactile stimulation of the right forearm either on or off. The level of consciousness was evaluated before each scan by the response of the subject to a verbal command. At Level W, all volunteers were fully awake. They reported being slightly drowsy at Level 1, they had a slurred speech and slow response at Level 2, and they were not responding at all at Level 3. The following variations in regional CBF (rCBF) were observed. During the waking state (Level W), vibrotactile stimulation induced a significant rCBF increase in the left thalamus and in several cortical regions, including the left primary somatosensory cortex and the left and right secondary somatosensory cortex. During anesthesia, propofol reduced in a dose-dependent manner rCBF in the thalamus as well as in a number of visual, parietal, and prefrontal cortical regions. At Level 1 through 3, propofol also suppressed vibration-induced increases in rCBF in the primary and secondary somatosensory cortex, whereas the thalamic rCBF response was abolished only at Level 3, when volunteers lost consciousness. We conclude that propofol interferes with the processing of vibrotactile information first at the level of the cortex before attenuating its transfer through the thalamus.

Auditory steady-state response and bispectral index for assessing level of consciousness during propofol sedation and hypnosis.

UNLABELLED: We assessed the effect of propofol on the auditory steady-state response (ASSR), bispectral (BIS) index, and level of consciousness in two experiments. In Experiment 1, propofol was infused in 11 subjects to obtain effect-site concentrations of 1, 2, 3, and 4 microg/mL. The ASSR and BIS index were recorded during baseline and at each concentration. The ASSR was evoked by monaural stimuli. Propofol caused a concentration-dependent decrease of the ASSR and BIS index values (r(2) = 0.76 and 0.93, respectively; P<0.0001). The prediction probability for loss of consciousness was 0.89, 0.96, and 0.94 for ASSR, BIS, and arterial blood concentration of propofol, respectively. In Experiment 2, we compared the effects of binaural versus monaural stimulus delivery on the ASSR in six subjects during awake baseline and propofol-induced unconsciousness. During baseline, the ASSR amplitude with binaural stimulation (0.47+/-0.13 microV, mean +/- SD) was significantly (P<0.002) larger than with monaural stimulation (0.35+/-0.11 microV). During unconsciousness, the amplitude was 0.09+/-0.09 microV with monaural and 0.06+/-0.04 microV with binaural stimulation (NS). The prediction probability for loss of consciousness was 0.97 (0.04 SE) for monaural and 1.00 (0.00 SE) for binaural delivery. We conclude that the ASSR and BIS index are attenuated in a concentration-dependent manner by propofol and provide a useful measure of its sedative and hypnotic effect. BIS was easier to use and slightly more sensitive. The ASSR should be recorded with binaural stimulation. The ASSR and BIS index are both useful for assessing the level of consciousness during sedation and hypnosis with propofol. However, the BIS index was simpler to use and provided a more sensitive measure of sedation. IMPLICATIONS: We have compared two methods for predicting whether the amount of propofol given to a human subject is sufficient to cause unconsciousness, defined as failure to respond to a simple verbal command. The two methods studied are the auditory steady-state response, which measures the electrical response of the brain to sound, and the bispectral index, which is a number derived from the electroencephalogram. The results showed that both methods are very good predictors of the level of consciousness; however, bispectral was easier to use.

Physostigmine reverses propofol-induced unconsciousness and attenuation of the auditory steady state response and bispectral index in human volunteers.

BACKGROUND: It is postulated that alteration of central cholinergic transmission plays an important role in the mechanism by which anesthetics produce unconsciousness. The authors investigated the effect of altering central cholinergic transmission, by physostigmine and scopolamine, on unconsciousness produced by propofol. METHODS: Propofol was administered to American Society of Anesthesiologists physical status 1 (n = 17) volunteers with use of a computer-controlled infusion pump at increasing concentrations until unconsciousness resulted (inability to respond to verbal commands, abolition of spontaneous movement). Central nervous system function was assessed by use of the Auditory Steady State Response (ASSR) and Bispectral Index (BIS) analysis of electrooculogram. During continuous administration of propofol, reversal of unconsciousness produced by physostigmine (28 microgram/kg) and block of this reversal by scopolamine (8.6 microgram/kg) were evaluated. RESULTS: Propofol produced unconsciousness at a plasma concentration of 3.2 +/- 0.8 (+/- SD) microgram/ml (n = 17). Unconsciousness was associated with reductions in ASSR (0.10 +/- 0.08 microV [awake baseline 0.32 +/- 0.18 microV], P < 0.001) and BIS (55.7 +/- 8.8 [awake baseline 92.4 +/- 3.9], P < 0.001). Physostigmine restored consciousness in 9 of 11 subjects, with concomitant increases in ASSR (0.38 +/- 0.17 microV, P < 0.01) and BIS (75.3 +/- 8.3, P < 0.001). In all subjects (n = 6) scopolamine blocked the physostigmine-induced reversal of unconsciousness and the increase of the ASSR and BIS (ASSR and BIS during propofol-induced unconsciousness: 0.09 +/- 0.09 microV and 58.2 +/- 7.5, respectively; ASSR and BIS after physostigmine administration: 0.08 +/- 0.06 microV and 56.8 +/- 6.7, respectively, NS). CONCLUSIONS: These findings suggest that the unconsciousness produced by propofol is mediated at least in part via interruption of central cholinergic muscarinic transmission.

Brain mechanisms of propofol-induced loss of consciousness in humans: a positron emission tomographic study.

In the present study, we used positron emission tomography to investigate changes in regional cerebral blood flow (rCBF) during a general anesthetic infusion set to produce a gradual transition from the awake state to unconsciousness. Five right-handed human volunteers participated in the study. They were given propofol with a computer-controlled infusion pump to achieve three stable levels of plasma concentrations corresponding to mild sedation, deep sedation, and unconsciousness, the latter defined as unresponsiveness to verbal commands. During awake baseline and each of the three levels of sedation, two scans were acquired after injection of an H215O bolus. Global as well as regional CBF were determined and correlated with propofol concentrations. In addition, blood flow changes in the thalamus were correlated with those of the entire scanned volume to determine areas of coordinated changes. In addition to a generalized decrease in global CBF, large regional decreases in CBF occurred bilaterally in the medial thalamus, the cuneus and precuneus, and the posterior cingulate, orbitofrontal, and right angular gyri. Furthermore, a significant covariation between the thalamic and midbrain blood flow changes was observed, suggesting a close functional relationship between the two structures. We suggest that, at the concentrations attained, propofol preferentially decreases rCBF in brain regions previously implicated in the regulation of arousal, performance of associative functions, and autonomic control. Our data support the hypothesis that anesthetics induce behavioral changes via a preferential, concentration-dependent effect on specific neuronal networks rather than through a nonspecific, generalized effect on the brain.

Postdural puncture headache after spinal anaesthesia in young orthopaedic outpatients using 27-g needles.

PURPOSE: Two large studies reported a very low rate (0.5-1.8%) of postdural puncture headache (PDPH) with the use of 27-G spinal needles. We suspected that it might be higher in young ambulatory patients. The purpose of this study was to establish the rate prospectively in such a patient population using two types of needles. METHODS: Two hundred male and female, outpatients, 18-45 yr, undergoing knee arthroscopy under spinal anaesthesia were randomly assigned to receive spinal anaesthesia with hyperbaric lidocaine 5% using either a Quincke or a Whitacre 27-G needle. Twenty patients choosing general anaesthesia formed a comparative group. Using a previously validated questionnaire, the incidence and nature of PDPH were evaluated by telephone three to five days after surgery by an anaesthetist unaware of the anaesthetic technique used. Once all data were collected, an anaesthetist not involved in the study determined in a blinded fashion which headaches were likely to be PDPH. Grading and classification of headaches were based on several criteria: postural nature, duration, intensity and confinement to bed. RESULTS: The overall incidence of PDPH in both spinal groups was 9.3%. The incidence in women, 20.4%, was higher than in men, 5.5%, (P < 0.05). Only one patient required a blood patch. Both types of needle were comparable with respect to the incidence, severity and duration of PDPH, number of dural punctures and failed spinal blocks. CONCLUSION: The rate of PDPH was higher than in large published studies with 27-G Quincke and Whitacre needles and greater in women than in men.