Processed Electroencephalogram-Based Monitoring to Guide Sedation in Critically Ill Adult Patients: Recommendations from an International Expert Panel-Based Consensus.

BACKGROUND: The use of processed electroencephalography (pEEG) for depth of sedation (DOS) monitoring is increasing in anesthesia; however, how to use of this type of monitoring for critical care adult patients within the intensive care unit (ICU) remains unclear. METHODS: A multidisciplinary panel of international experts consisting of 21 clinicians involved in monitoring DOS in ICU patients was carefully selected on the basis of their expertise in neurocritical care and neuroanesthesiology. Panelists were assigned four domains (techniques for electroencephalography [EEG] monitoring, patient selection, use of the EEG monitors, competency, and training the principles of pEEG monitoring) from which a list of questions and statements was created to be addressed. A Delphi method based on iterative approach was used to produce the final statements. Statements were classified as highly appropriate or highly inappropriate (median rating ≥ 8), appropriate (median rating ≥ 7 but < 8), or uncertain (median rating < 7) and with a strong disagreement index (DI) (DI < 0.5) or weak DI (DI ≥ 0.5 but < 1) consensus. RESULTS: According to the statements evaluated by the panel, frontal pEEG (which includes a continuous colored density spectrogram) has been considered adequate to monitor the level of sedation (strong consensus), and it is recommended by the panel that all sedated patients (paralyzed or nonparalyzed) unfit for clinical evaluation would benefit from DOS monitoring (strong consensus) after a specific training program has been performed by the ICU staff. To cover the gap between knowledge/rational and routine application, some barriers must be broken, including lack of knowledge, validation for prolonged sedation, standardization between monitors based on different EEG analysis algorithms, and economic issues. CONCLUSIONS: Evidence on using DOS monitors in ICU is still scarce, and further research is required to better define the benefits of using pEEG. This consensus highlights that some critically ill patients may benefit from this type of neuromonitoring.

Brain Aging and Anesthesia.

Herein, the authors review the neuroanatomical and the neurophysiological aspects of the normal aging evolution based on the recent literature and briefly describe the difference between physiological and pathological brain aging, with consideration of the currently recommended anesthesia management of older patients. The population of elderly patients is growing drastically with advances in medicine that have prolonged the life span. One of the direct consequence has been a significant increase in the request for anesthesia care for older patients despite the type of surgery (cardiac vs noncardiac and mainly orthopedic). Because the brain of this category of patients undergoes a specific triple influence (immune, metabolic, and inflammatory), some particular physiological, anatomical, and structural modifications must be taken into account because they expose these patients more specifically to postoperative cognitive disturbances. To prevent type of adverse outcome, a better knowledge and understanding of these neurosciences must be promoted. The strategies developed to prevent such adverse outcomes include the determination and detection of significant at-risk patients and improvement in the titration of anesthesia to reduce exposure of anesthesia to these patients through an adapted anesthesia-induced unconsciousness that avoids, as much as possible, the risk of toxic overdose with an overly deep brain depression. To accomplish this, the unprocessed electroencephalogram (EEG) and its spectrogram may represent a significant improvement in monitoring, first by allowing for the rapid recognition of repetitive or persistent EEG suppression by the on-line reading of the raw EEG trace and second by allowing for the accurate determination of the adequate anesthetic-induced state, obtained in general in this category of patients by substantially lowered doses of anesthetic agents. This represents a new methodology for anesthesia titration that is adjusted on a more case-by-case basis and is related to the physiology of individual patients. A better understanding of aging-induced brain transformations remains the key regarding the improvement of the anesthetic management of the always growing population of elderly patients. The promotion of the unprocessed EEG may represent the best method of preventing the risk of anesthetic toxicity, including postoperative cognitive dysfunctions.

Combined ultrasound and nerve stimulation-guided thoracic epidural catheter placement for analgesia following anterior spine fusion in scoliosis.

Anterior spine fusion by thoracotomy is indicated for the treatment of idiopathic scoliosis. Although epidural (EP) analgesia represents the most effective way to provide adequate analgesia after thoracotomy, scoliosis patients have substantial anatomic variations that make EP catheter placement more difficult and often contraindicated. This case report describes a safe, effective technique for placing a thoracic EP catheter in a young patient undergoing anterior spine fusion surgery by thoracotomy. The procedure was guided by both ultrasound (US) and electrical stimulation of the Tuohy needle and catheter. The combination of US and nerve stimulation in this setting may be associated with easier, potentially safer, and more accurate insertion.

Delayed Horner's syndrome during a continuous infraclavicular brachial plexus block.

Horner's syndrome is a potential, albeit rare, feature of continuous infraclavicular brachial plexus local anesthetics infusion, mainly the result of anatomical considerations. Horner's syndrome may be described as an "unpleasant side effect" because it has no clinical consequences in itself. Nevertheless, patient discomfort and anxiety may reduce acceptance of the analgesic technique. Reassurance and close clinical monitoring of the patient are essential to enhance patient's safety and acceptance of the technique.

Intraoperative somatosensory evoked potentials to facilitate peripheral nerve release.

PURPOSE: The significance of intraoperative somatosensory evoked potentials (SSEP) monitoring is well known during spinal surgery. This technology could be beneficial during peripheral nerve surgery as well. In order to illustrate potential applications, two cases of successful peripheral nerve release demonstrated by on-line, intraoperative, SSEP are reported. Clinical and technical features: The first case presents a complex brachial plexus lesion involving two mixed sensory-motor nerves: median and ulnar. The second case involved an entrapment neuropathy of the lateral femoral cutaneous nerve, a pure sensory nerve (meralgia paresthetica). For each patient we elicited specific peripheral nerve SSEP (recorded using bipolar cephalic montage) by stimulating each nerve independently. In each case, during difficult nerve dissection and after having excluded other possible factors of intraoperative SSEP variations, an increase of the SSEP amplitude was observed, and later correlated with favourable patient clinical outcome. CONCLUSIONS: Two cases demonstrate that intraoperative SSEP monitoring may provide an effective tool to guide surgical dissection during peripheral nerve release. This technique has potentially beneficial clinical applications and warrants further investigation.

Somatosensory evoked potentials as an objective assessment of the sensory median nerve blockade after infraclavicular block.

PURPOSE: Median nerve somatosensory evoked responses (MnSSER) alterations were compared to clinical tests (cold and pinprick) variations, in 20 ASA I adult patients following infraclavicular block obtained with 40 mL ropivacaine 0.5% to assess first, the difference of time course of the respective electrophysiological and clinical signs, and second, the objectivity and the reproducibility of MnSSER changes. CLINICAL FEATURES: Four MnSSER derivations (Erb's point; cutaneous projection of peripheral end of brachial plexus; posterior neck at C6 level, frontal and controlateral parietal scalp) were monitored and recorded for retrospective analysis. Continuous data acquisition were started before ropivacaine injection (baseline) and maintained for 30 min thereafter. Every three minutes after ropivacaine injection, cold and pinprick tests were performed in the hand median nerve cutaneous supply zone and were assessed using a sensory visual score (varying from 0-10). Data were compared using analysis of variance. Although MnSSER values were stable during baseline period, after ropivacaine administration, severe progressive amplitude depressions of selected MnSSER were detected in every patient. While clinical cold and pinprick tests became positive (score > 8) only 15.8 +/- 1.2 min and 20.1 +/- 1.8 min respectively after ropivacaine administration, the mean time to observe the earliest MnSSER 20% amplitude decrease at Erb's point derivation was reduced to 5.6 +/- 1.1 min (P < 0.01). CONCLUSION: Selected MnSSER amplitude reduction indicates objectively the onset of median nerve anesthesia following infraclavicular brachial plexus block before the appearance of clinical signs.

Tibial nerve block: evaluation of a novel midleg approach in 241 patients.

PURPOSE: Several techniques of tibial nerve (TN) block have been described but require mobilization of the patient. We describe a new landmark, along the internal tibial shaft edge at the midleg level, that allows to block the TN and to insert a catheter with the patient lying supine. METHODS: 241 ASA physical status I to III awake, supine patients were studied prospectively. Cutaneous projections of the internal tibial condyle and the internal malleolus were marked and the needle was inserted 45 degrees cephalad in an antero-posterior plane, midway on the line between those two points, 1 cm posterior to the tibial shaft's internal edge. The catheter was introduced in the peri-nervous space using nerve stimulation (< 0.5 mA) on both the Tuohy needle and catheter. Ten millilitres of 2% lidocaine were injected through the catheter. Cutaneous and dermatomal sensory blockade were assessed using cold and pinprick tests while motor block was assessed using a modified Bromage scale. Satisfaction and analgesia scores were noted after surgery for 48 hr. Adverse events were recorded. RESULTS: The TN was always blocked, matching the distal L5 cutaneous nerve supply. Blood reflux was present in five patients (needle or catheter). No additional adverse events were noted. During the initial postoperative 48 hr, 0.2% ropivacaine was infused through the catheter (5 mL.hr(-1)) which always provided effective pain relief. CONCLUSION: The midleg technique of TN anesthesia and catheter insertion allows patients to remain in the supine position and results in a high rate of homogeneous anesthesia, a low incidence of side effects and effective continuous analgesia.

Can electrophysiological assessments of brain function be useful to the intensive care physician in daily clinical practice?

Changes in electroencephalogram parameters and auditory event-related potentials, induced by interruption to propofol sedation in intensive care patients, provide a number of electrophysiological measures that can be used to assess neurological function accurately. Studies of electroencephalogram parameters suggest that power spectral estimation, as root mean square power, is more useful and precise than spectral edge frequency 95% in evaluating the functional integrity of the brain. When such parameters are used to evaluate neurological function, in particular the N100 and mismatch negativity components, a precise assessment of a patient's readiness to awaken from a pharmacologically induced coma (such as sedation) can be obtained. In terms of ease of use, however, it is more difficult to establish whether N100 or mismatch negativity is superior.

The anterior combined approach via a single skin injection site allows lower limb anesthesia in supine patients.

PURPOSE: Lower limb anesthesia (LLA) requires the combination of, at least, three-in-one and sciatic nerve (SCN) blocks. Anterior approaches are easier to perform with minimal discomfort in supine patients, specially for traumatology. Feasibility of a single needle entry combined approach is reported. CLINICAL FEATURES: The combined landmark was applied in 119 ASA I and II patients (32-68 yr) scheduled for surgery below the knee. Needle (nerve stimulation applied through a single 150-mm long b-bevelled insulated needle) was inserted at the midpoint between the two classical approaches. Thirty and 15 mL of 0.5% ropivacaine were injected close to the femoral and the SCN, respectively. During the following 45 min, the extent of sensory block and knee and ankle motor block were assessed. Landmarks were determined within 1.7 min (0.7-2.2 min). The entire procedure was performed within 4.2 min (2.9-7.1 min) from the determination of the landmark to the SCN infiltration. The three-in-one technique was successful in 89.9% while SCN was successful in 94.9%. Femoral and tibial nerves were always blocked. Blockade of the posterior cutaneous femoral nerve was observed in 78% of patients. The extent and the quality of the sensory block always allowed surgery. Additional iv sedation was needed in 32.6% of patients. Motor block (adapted Bromage's scale > 2) was observed in the femoral (98.3%), the obturator (84.8%), the tibial (97.4%) and the common peroneal (85.7%) nerve distributions. No important adverse effects were recorded. CONCLUSION: The anterior combined approach via a single needle entry represents a technically easy and reliable technique to perform LLA in the supine patient.

Sciatic nerve blockade in the supine position: a novel approach.

PURPOSE: Sciatic nerve block is useful for surgery below the knee both intra- and postoperatively. Several techniques to insert a catheter at the knee level or higher have been described but need mobilization (lateral decubitus) of the patient. We describe novel landmarks, using a high lateral approach, to block the sciatic nerve without moving the patient. CLINICAL FEATURES: One hundred seven ASA I, II and III ASA patients scheduled for major foot or ankle surgery were studied prospectively. With patients awake and lying in the supine position, the catheter was introduced along novel landmarks in the peri-nervous adipose space using specifically designed material and nerve stimulation (< 0.5 mA). After a negative test dose (1% lidocaine with 1/200.000 epinephrine), 10 mL of 0.5% bupivacaine and 10 mL of 2% lidocaine were injected. Thirty minutes after performance of the block, the cutaneous and dermatomal sensory blockade were assessed using cold and pinprick tests while motor block was assessed using a modified Bromage scale. Complications and incidents were recorded. The tibial and superficial peroneal nerve were always blocked, while the deep peroneal and postero-femoral cutaneous nerves were blocked in only 97% and 83% of the patients, respectively. Anesthesia, was always present in the dermatome L5 and in the S1 dermatome in 98% of the patients. No major incidents or complications were noted. Three catheters could not be inserted and the anesthestic solution was injected through the needle. CONCLUSION: The lateral technique for sciatic nerve anesthesia and catheter insertion allows patients to remain in the supine position for performance of the block and catheter insertion, and results in a high rate of homogeneous anesthesia and a low incidence of side effects.

Lumbar plexus posterior approach: a catheter placement description using electrical nerve stimulation.

IMPLICATIONS: 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.