The superficial cervical plexus block for postoperative pain therapy in carotid artery surgery. A prospective randomised controlled trial.

OBJECTIVES: Rapid and reliable neurological evaluation soon after carotid artery surgery is feasible with modern methods of general anesthesia, but postoperative pain therapy remains a challenge. Use of opioids can mask neurological deficits. We investigated whether superficial cervical plexus block reduced postoperative opioid consumption after carotid endarterectomy. DESIGN: Prospective, randomised, double-blinded, placebo controlled trial. METHODS: 46 patients undergoing unilateral carotid endarterectomy under general anesthesia were randomized to either superficial cervical block with ropivacaine (n=23) or placebo (n=23). A patient controlled analgesia device (PCA) delivering morphine was provided for all patients. Subjective pain levels (visual analog scale, VAS) were recorded. The primary outcome was total morphine consumption on discharge from the recovery room. Secondary outcomes included arterial pCO2 (as an indicator of central nervous effects of morphine) and patient satisfaction. RESULTS: No adverse effects of the superficial cervical plexus block were reported. Four patients in the placebo group were excluded because of other drug use post-operatively. Per protocol analysis compared 23 patients in ropivacaine group and 19 patients in the placebo group. The ropivacaine group had a significant reduction in morphine consumption (3.8+/-2.0 versus 12.9+/-4.0, p<0.001), lower maximal pain scores (2.6+/-2.0 versus 5.8+/-1.6, p<0.001), and paCO2 levels (39.0+/-2.6 versus 41.9+/-3.4, p=0.008) at discharge from the recovery room. Patient satisfaction (1=very good to 6=insufficient) was substantially higher in the ropivacaine group (1.7+/-0.7 versus 3.1+/-1.2, p<00.01). CONCLUSION: The significant and clinically relevant lower morphine consumption and pain score, as well as the substantially higher patient satisfaction demonstrate that superficial cervical plexus block provides effective pain relief for patients undergoing carotid endarterectomy.

[Fatal course after osteosynthesis in a 18-year-old male]. / Letaler Verlauf nach Osteosynthese bei einem 18-Jährigen.

A previously healthy patient became comatose 8 h after osteosynthesis of a fractured femur and humerus. After an initially normal cranial computed tomography, extended lesions were found 10 h later in the control scan as an indication of an embolization in the basilar artery. After neurosurgeons assessed the situation to be unfavorable, no other interventions were conducted and 6 days later brain death was confirmed. During the subsequent heart transplantation the suspicion of a patent foramen ovale as the reason for the paradoxical cerebral embolization was confirmed. This tragic course raises the question whether a patent foramen ovale should be excluded or closed by interventional measures in similar situations.

The bispectral index declines during neuromuscular block in fully awake persons.

UNLABELLED: Bispectral index (BIS) is an electroencephalographic variable promoted for measuring depth of anesthesia. Electromyographic activity influences surface electroencephalography and the calculation of BIS. In this study, we sought to determine the effect of spontaneous electromyographic activity on BIS. BIS was monitored in three volunteers by using an Aspect A-1000 monitor. The experiment was repeated in one volunteer. Electromyographic activity was recorded. Alcuronium and succinylcholine were administered. No other drugs were used. In parallel with spontaneous electromyographic activity of the facial muscles, BIS decreased in response to muscle relaxation to a minimum value of 33 and, in the repeated measurement, to a minimum value of 9 when total neuromuscular block was achieved. In two volunteers, no total block was achieved. BIS decreased to a minimal value of 64 and 57, respectively. In turn, recovery of BIS coincided with the reappearance of spontaneous electromyographic activity. During the entire experiment, the volunteers had full consciousness. BIS, assessed by software Version 3.31, correlates with spontaneous electromyographic activity of the facial muscles. BIS failed to detect awareness in completely paralyzed subjects. Thus, in paralyzed patients, BIS monitoring may not reliably indicate a decline in sedation and imminent awareness. IMPLICATIONS: The bispectral index (BIS) is an electroencephalographic variable intended for measuring depth of anesthesia. Electromyographic activity influences the calculation of BIS. We found that the administration of a muscle relaxant to unanesthetized volunteers decreases the bispectral index value. Thus, awareness in totally paralyzed patients cannot be excluded.

[Emergency management of an acute rupture of a perforated thoracic aortic aneurysm]. / Notfallmanagement bei akut dissezierendem und gedeckt perforiertem thorakalen Aortenaneurysma.

The emergency medical service was called to a 60-year-old woman with intensive chest pain, signs of shock, dyspnoea, intermittent paraesthesia of the right leg and disturbance of consciousness. With the diagnosis of an acute rupture of an aneurysm of the thoracic aorta, the patient was stabilised with volume, catecholamines, intubation and mechanical ventilation before being rushed to the preinformed department of cardiovascular surgery. The diagnosis was verified by transesophageal echocardiography immediately and the patient underwent surgery 2 h after onset of symptoms. Despite the rupture of the aorta and a short period of cardiac arrest, the patient recovered totally and could be discharged without any residual problems. This case shows that a ruptured thoracic aortic aneurysm can be survived although the overall mortality of this incident is more than 97%. The essentials of a good outcome are: 1. perfectly coordinated rescue operation which means an emergency medical service which includes the rupture of an aortic aneurysm in the differential diagnosis of acute chest pain, 2. an early verification of the diagnosis by means of transesophageal echocardiography which should also be carried out by anaesthesiologists due to its importance in the differential diagnosis in haemodynamic unstable patients.

Indwelling temporary retrobulbar catheter for long-lasting titratable local anesthesia.

OBJECTIVE: To evaluate an indwelling temporary retrobulbar catheter for repeatable injections of local anesthetics for long-lasting and titratable retrobulbar anesthesia in intraocular surgery. PARTICIPANTS: The prospective clinic-based study included 153 patients who underwent vitreoretinal surgery (n=111) or buckling procedures with cryocoagulation (n=34). The mean duration of surgery was 84.7 +/- 49.5 minutes (range, 25-310 minutes). Using commercially available retrobulbar needles with a diameter of 0.60 or 0.80 mm and a length of 38 mm, 5 mL of 2% mepivacaine hydrochloride was injected. Through the same needle, a 28-gauge commercially available flexible catheter was introduced into the retrobulbar space. The needle was withdrawn and the catheter was fixed. When the patients started to feel pain during surgery, 2 mL of mepivacaine hydrochloride was reinjected through the catheter. RESULTS: Ten to 240 minutes after the start of the operation, 96 patients needed an intraoperative reinjection of mepivacaine after which they felt comfortable again. Forty-two patients needed a second reinjection of mepivacaine 30 to 270 minutes after the start of the operation, and 13 patients needed a third reinjection 45 to 145 minutes after the start of surgery. Removal of the catheter after surgery was unremarkable. No infections were observed. Microbiologic examination results of the catheter tip were negative for organisms. Diplopia or other motility problems were not detected. Introduction and fixation of the catheter took less than 5 minutes in all patients. CONCLUSIONS: An indwelling temporary retrobulbar catheter for repeatable intraoperative injections of local anesthetics is simple, effective, and useful, and in comparison with general anesthesia, it is a time-saver for long-lasting and titratable local anesthesia in intraocular surgery. Arch Ophthalmol. 2000;118:996-1000

[Cerebral ischemia during carotid clamping: diagnosis and prevention]. / Zerebrale Ischämie während des Carotis-clampings. Diagnostik und Vermeidung.

A serious complication in carotid endarterectomy (CEA) is the occurrence or aggravation of neurological deficits caused by insufficient collateral cerebral blood flow during cross-clamping. At the moment, patients with failure of collateral circulation at this point cannot be identified preoperatively. Thus, intraoperative monitoring and methods to prevent clamping-related cerebral ischemia are required. To put this strategy into clinical practice there are several methods of monitoring cerebral function (e.g. surgery performed in awake patients, electroencephalography, somatosensory evoked potentials), changes of hemodynamic (e.g. carotid stump pressure, transcranial Doppler ultrasonography) or metabolic parameters (e.g. jugular bulb oximetry or transcranial oximetry). One technique that meets nearly all requirements of an ideal monitoring under general anesthesia is the use of somatosensory evoked potentials (SEPs). Registration of SEPs is simple to perform and indicates with a high sensitivity and specificity critical cerebral hypoperfusion during cross-clamping. Thus, SEPs monitoring indicates the necessity of shunt placement. As a result, the use of an indwelling shunt as the most effective method to prevent clamping ischemia can be limited to selected cases, avoiding the risks of shunting in patients with sufficient collateral flow. In addition, correct shunt function is immediately indicated by recovering potentials. Whether a combination of SEPs with transcranial Doppler measurements will be successful to provide additional information about cerebral embolisation should be determined.

Postoperative analgesia by reinjections of local anesthetic through an indwelling retrobulbar catheter.

PURPOSE: To evaluate an indwelling retrobulbar catheter for repeatable postoperative retrobulbar injections of local anesthetics for titratable analgesia after intraocular surgery. METHODS: The prospective study included all 124 patients (124 eyes) who consecutively underwent retinal or cyclocryocoagulation (n = 22), pars plana vitrectomy, or retinal detachment surgery (n = 102), and who were operated on by the same surgeon with local anesthesia within a period of 12 months. Using commercially available retrobulbar needles with a diameter of 0.60 mm or 0.80 mm and a length of 38 mm, 5 ml of mepivacaine 2% with hyaluronidase were injected. Through the same needle, a 28-gauge commercially available flexible catheter was introduced into the retrobulbar space, the needle was withdrawn, and the catheter was fixed in place. When the patients started to feel pain after surgery, 2 ml of mepivacaine 2% or 2 ml of bupivacaine 0.75% were reinjected through the catheter. The catheter was removed 24 to 72 hours after surgery. RESULTS: Because of increasing pain in the postoperative period, 93 patients (93 of 124, or 75%) received a reinjection 4.2+/-2.0 hours after the preoperative injection. Seventy patients received a second reinjection after an additional 2.7+/-1.9 hours, and 42 patients received a third reinjection 3.1+/-2.0 hours later. After each reinjection, the patients became pain free. Removal of the catheter after surgery was unremarkable. CONCLUSIONS: An indwelling retrobulbar catheter for repeatable postoperative injection of short-acting local anesthetics is useful and effective for titratable postoperative analgesia after intraocular surgery, and it allows patients to avoid the side effects of systemic analgesics and sedatives.

[Patient-oriented anesthesia] . / Patientenorientierte Anästhesie.

Goals of this study were to quantify patients' preferences for anaesthesia care and to identify what they know about various tasks of an anaesthetist. On the day before surgery, 122 patients scheduled for elective procedures were interviewed using a structured questionnaire. A reliable pain relieve and unawareness as well as stable vital functions have priority in patients' preferences. Patients are also concerned with good postoperative pain relieve and the avoidance of nausea and vomiting. Not important are short preoperative soberness, rapid awakening and initial wide awakeness. Not informed about typical tasks of an anaesthetist are 28-51% of the patients. In order to obtain maximum patient satisfaction, a thorough education plus further continuous training are the essential items for a patient orientated health care management in anaesthesia, along with good medical and technical equipment. The wide spectrum of tasks of an anaesthetist must be better represented in order to strengthen the position of anaesthesia in the competition for rare resources. A postoperative visit, which is judged of 77% of the patients as important, offers a beginning.

[Titration of intraoperative anesthesia and postoperative analgesia]. / Titrierbare intraoperative Anästhesie und postoperative Analgesie.

PURPOSE: To evaluate a temporary retrobulbar catheter for local anesthesia in intraocular surgery and for postoperative analgesia after intraocular surgery. PATIENTS AND METHODS: The study included 40 patients undergoing pars-plana vitrectomy (n = 24) or cyclocryocoagulation (n = 16). After a retrobulbar injection through a 23 G needle, a commercially available 28 G flexible catheter was inserted through the needle. As soon as the patients complained about pain during or up to 24 hours after surgery, local anesthetics were injected through the catheter. RESULTS: Repetitive injections of anesthetics were necessary in 13 patients during pars plana vitrectomy. Starting about 2 hours after surgery, 13 patients after pars-plana vitrectomy and all patients who had undergone cyclocryocoagulation received up to 6 re-injections (every 1.5-5 hours). After all re-injections, the patients became pain-free within two minutes. The catheter was removed after 24 hours. CONCLUSIONS: The results suggest that a temporary insertion of a catheter into the retrobulbar space allows repetitive application of local anesthetics thus leading to a titrable local anesthesia and postoperative analgesia in intraocular surgery.

[Detection of cerebral embolism using transcranial Doppler sonography: can artifacts be reliably recognized?]. / Zerebrale Emboliedetektion mittels transkranieller Dopplersonographie: Können Artefakte sicher erkannt werden?

A requirement for the use of TCD for the detection of emboli in the field of cardiac and vascular surgery is the reliable differentiation between true emboli and artifacts. In ten healthy volunteers we carried out a study to establish the method with which artefacts can most reliably be identified. Automatic detection of increasing signal intensity misinterpreted 14% of all artifacts as emboli; 1.7% of all artifacts sounded suspicious for embolism, and 0.6% met the classical criteria of an embolus. Using simultaneous recording of the flow signal in two sections of the middle cerebral artery, all artifacts were identified on the basis of their simultaneous manifestation. Reliable intra-operative differentiation of emboli from artifacts requires attentive, continuous acoustic and visual analysis of signals by an experienced investigator familiar with the surgical procedure. The introduction of a multiple-depth algorithm might significantly improve the automatic detection program.

The influence of the state of the vertebral arteries on the peri- and postoperative risk in carotid surgery.

OBJECTIVES: To assess the significance of the vertebral arteries (VA) as a prognostic factor within the framework of carotid surgery. DESIGN: Prospective observational study. MATERIALS: A total of 1338 operations were performed on 1182 patients. Three hundred and six of the patients had angiographically confirmed unilateral (299) or bilateral (seven) involvement of the VA. In 31 cases it was not possible to assess the VA. METHODS: Life table analysis. RESULTS: Thirty-day mortality rate was 1.6% (21 out of 1338) for all reconstructions of the internal carotid artery. In addition to three fatal strokes, 22 hemispheric events were noted (1.6%, 22/1338). Follow-up varied between 1 and 96 months (mean 34, S.E.M. 0.76, median 29) and covered a total of 3361 patient years. The cumulative 5-year survival rate was 69%. Irrespective of age, cardiac events were the leading cause of death. In patients with VA involvement, both the 30-day stroke and mortality rate (p < 0.01) and the long-term survival rate (p < 0.01) were significantly poorer. CONCLUSION: Concomitant vertebral artery disease increases the morbidity and mortality of carotid surgery, presumably due to reduced collateral perfusion during cross-clamping. However, the overall risk of surgery remains acceptable.

Comparison of near-infrared spectroscopy and somatosensory evoked potentials for the detection of cerebral ischemia during carotid endarterectomy.

BACKGROUND AND PURPOSE: We sought to assess the clinical value of regional cerebral saturation (rSO2) obtained by means of the cerebral oximeter INVOS 3100A (Somanetics) in comparison to monitoring of somatosensory evoked potentials (SEP) for the reliable detection of severe cerebral ischemia requiring shunt placement in the individual patient undergoing carotid surgery under general anesthesia. METHODS: In 317 patients undergoing reconstructive surgery on the internal carotid artery, simultaneous recordings of SEP and rSO2 were obtained throughout the operation. RESULTS: All 287 patients with preserved cortical SEP remained neurologically intact. Shunt placement was performed in 27 patients (9%) after flattening of cortical SEP during cross-clamping of the internal carotid artery. A stable rSO2 value just before cross-clamping and the lowest value after cross-clamping were registered, and the decrease was calculated. A statistically significant (P<0.01) decrease of rSO2 after cross-clamping could be found in patients without (64.9+/-8.3% to 60.9+/-9.9%) as well as in patients with consecutive loss of cortical SEP (65.8+/-9.1% to 56.1+/-13.4%). The difference of the decrease of rSO2 in both groups was highly significant (6.9+/-9.0% versus 15.6+/-14.0%; P<0.001). However, substantial interindividual variability of rSO2 and derived change of rSO2 did not allow the definition of a threshold value indicating need of shunt placement. CONCLUSIONS: The reliability of SEP for the detection of clamp-related hypoperfusion has been reaffirmed. As long as rSO2 threshold values indicating critical cerebral ischemia are not defined, therapeutic interventions based on monitoring with the cerebral oximeter INVOS 3100A are not justified.

Pharmacokinetic-pharmacodynamic modeling of the new steroid hypnotic eltanolone in healthy volunteers.

BACKGROUND: In the last 4 y, several authors have reported largely satisfactory results using the new steroid intravenous anesthetic eltanolone (pregnanolone) to induce anesthesia. Until now, however, no investigations have addressed the infusion pharmacokinetics of eltanolone or used electroencephalographic effect data for full pharmacodynamic modeling. Thus the authors conducted a study to evaluate the pharmacokinetic and pharmacodynamic properties of eltanolone after infusion in healthy volunteers. METHODS: Eltanolone emulsion was administered to 12 healthy men using a computer-controlled infusion device. Linearly increasing serum concentrations were generated for two consecutive infusions with an anticipated slope of 0.075 microgram.ml-1.min-1 and a targeted concentration of 2-2.5 micrograms/ml. During and after the infusion, electroencephalographic data were recorded as a continuous pharmacodynamic parameter to measure the hypnotic effect. In addition, blood pressure, heart rate, pulse oximetry, clinical signs of anesthesia, and any undesirable effects were recorded. The appearance of burst suppression periods in the raw electroencephalographic wave form was used as an end point for the infusion. Arterial blood samples were drawn frequently until 720 min after the cessation of the last infusion cycle. Eltanolone serum concentrations were measured using a specific gas chromatography-mass spectrometry assay. Nonlinear regression analysis was used to relate a power spectral parameter of the electroencephalograph (median frequency) to the serum concentration using a sigmoid Emax model, including an effect compartment to minimize possible hysteresis. Population pharmacokinetics were analyzed using an open three-compartment model. RESULTS: The pharmacokinetic model parameters of eltanolone were characterized by a high total clearance (1.75 +/- 0.22 l/min), small volumes of distribution (Vc = 7.65 +/- 3.40 l; Vdss = 91.6 +/- 22 l), and relatively short half-lives (t1/2 alpha = 1.5 +/- 0.6 min; t1/2 beta = 27 +/- 5 min; t1/2 gamma = 184 +/- 32 min). With regard to the pharmacodynamic model parameters, eltanolone proved to be a potent hypnotic agent (Cp50 = 0.46 +/- 0.09 microgram/ml). The hypnotic effect coincided with a remarkable hysteresis between serum concentration and biophase, determined by an equilibration half-life of 8 min (ke0 = 0.087 +/- 0.013 min-1). All volunteers breathed spontaneously during the entire observation period and showed no clinically relevant hemodynamic changes. One volunteer experienced a convulsion while awakening. CONCLUSIONS: Eltanolone is a new potent steroid-type hypnotic agent with rapid elimination characteristics. Although it is short-acting, the remarkable hysteresis limits the control and might complicate administration of eltanolone if it is used as a component of a complete intravenous anesthesia regimen. Furthermore, it involves the potential disadvantage of drug accumulation and it prolongs recovery if larger-than-necessary doses are used to induce anesthesia rapidly.

[Costs-proceeds calculation for radiotherapy; comment]. / Kosten-Erlös-Rechnung für die Strahlentherapie.

BACKGROUND: The Health Care Structure Bill (Gesundheitsstrukturgesetz) and the Federal Health Care Tariff Regulation (Bundespflegesatzverordnung) pose new challenges for the chief physician in charge, which he has to face on account of hospital management control with department-specific internal budgeting of services, expenditure and remittance. In view of the impending establishment of care-related lump sums (Fallpauschalen) and special allowances for radiation therapy (Sonderentgelte) as well as the introduction of an appropriate internal budget plan, we resolved to draw up the service-cost ratio for 11 tumor entities, implementing calculation based on process evaluation, and to match this calculation to the actual proceeds from outpatient treatment covered either by general health insurance or private care insurance. MATERIAL AND METHODS: The following 11 tumors were included in the analysis: Glioblastoma multiforme, squamous cell carcinoma of the head and neck, lung cancer, oesophageal cancer, breast cancer, rectal and prostate cancer, cancer of the anal canal and the uterine cervix, Hodgkin's disease and bone metastases. For the description of the services rendered and for the calculation of actual cost, the complex treatment regime was divided into the following steps: administration, medical radiation planning, radiation planning by physicist, workmanship, radiotherapy treatment and medical service. The calculation of costs was made either in- or excluding the cost of teatment facilities and basic investment. The proceeds were calculated according to the regulations of the EBM (dated 1. 10. 1994) for general health insurance patients (median point value 9.35 DPF) and the GOA (dated 1. 7. 1988) for private patients (point value 11 DPF). RESULTS: 1. Calculation by EBM standards: Excluding the cost of facilities and basic investment, there is a profit margin for the following tumor entities amounting to +1.6% (103.18 DM) for ENT tumors, +9.2% (671.90 DM) for carcinoma of the anal canal and +35.8% (1637.84 DM) for bone metastases. All other tumor entities cannot be treated cost-effectively. With the exception of glioblastoma, median loss comes to -20% (-14% to -27.4%, i.e. -809.48 to -1812.84 DM). Including in the calculation the cost of the facilities and investment, only bone metastases can be treated with a profit margin. For all other tumors, the mean loss amounts to -33% (-14.1% to -44.7%) or else -1308.26 to -4550.51 DM. 2. Calculation by GOA standards: Comparing cost and actual proceeds, there is a loss for all tumor entities. Excluding the cost of treatment facilities and investment, median loss amounts to -44% (-33.3% to -53.5%, or -1752.64 DM to -3488.18 DM), including both, mean loss comes to -56% (-47.8% to -53.3% or -3156.33 DM to -6332.43 DM). 3. Calculation of comprehensive cost and of the proceeds: For our own department, considering the cost-proceeds ratio for 1994, we ran up a deficit of 673,767.10 DM for outpatient care. This deficit can mainly be traced back to non-operational hours of the linear accelerator due to machine impairment, maintenance and dosimetric measurements by the physicists, leading to the loss of 53 work-days (14 hours each) amounting to 498,771.34 DM plus general costs of 271,000 DM added to the bill by hospital administration. CONCLUSIONS: As to the reviewed tumor entities, modern standard radiotherapy cannot be administrated cost-effectively. A considerable degree of under-funding is especially evident with the inclusion of cost of investment and of the facilities. The cost-proceeds ratio is most unsatisfactory as regards GOA calculation, which is obsolete as far as service description and service payment is concerned. As it in no way measures up to the required standard of modern radiotherapy, reform is therefore urgently needed.

EEG analysis and pharmacodynamic modelling after intravenous bolus injection of eltanolone (pregnanolone).

An intravenous bolus dose of 0.75 mg Kg-1 eltanolone emulsion was administered to 18 unpremedicated ASA I or II patients. In addition to clinical observation and haemodynamic monitoring, EEG power spectrum and median frequency were recorded. Venous blood was collected to establish a concentration-effect relation using the median frequency as a pharmacodynamic parameter for hypnotic effect, and with analysis of data with the sigmoidal Emax model. Emax was determined as the maximal decrease of the median frequency caused by the CNS depressant effect of eltanolone. The results of seven of 15 patients with complete serum and EEG analysis could be described by a sigmoidal curve. The calculated IC50, the serum concentration producing 50% inhibition of Emax, was 0.57 micrograms mL-1. Median frequency occasionally decreased independently of eltanolone serum concentration in seven patients because interference by natural sleep was not prevented before induction or during awakening by setting continuous stimulations. In relation to the peak serum concentration, the decrease in median frequency occurred late in one patient. Nevertheless, the present study provides a preliminary estimation of the IC50 of eltanolone. From the clinical point of view, eltanolone showed satisfactory induction characteristics which warrant further evaluation.

Changes in the EEG power spectrum after midazolam anaesthesia combined with racemic or S- (+) ketamine.

Changes in the EEG power spectrum were studied in 50 patients (ASA status I or II), receiving either 2 mg.kg-1 of racemic ketamine or 1 mg.kg-1 of S-(+) ketamine in a randomized and double-blind manner after prior administration of 0.1 mg.kg-1 of midazolam. The patients receiving intramuscular premedication with midazolam about 45 minutes prior to induction of anaesthesia showed, in a deliberately quiet environment and mostly in the early morning, a delta dominated EEG (56% delta power) with a reduced alpha peak (17% alpha power) and an average median of 4 Hz as the baseline findings of the EEG power spectrum. The intravenous administration of midazolam led to activation of the lower beta range (13-18 Hz) and the subsequent injection of ketamine caused an increase in activity in the fast beta range (21-30 Hz), both being accompanied by a reduction of delta power from 56% to 40%. Correspondingly, an increase in the median frequency was noted. Causing nearly the same changes in EEG, S-(+) ketamine was confirmed to be twice as potent as racemic ketamine.

[Neuromonitoring in carotid surgery: possibilities and limits of transcranial Doppler ultrasound]. / Neuromonitoring in der Karotischirurgie: Möglichkeiten und Grenzen der transkraniellen Doppler-Sonographie.

In order to evaluate the suitability of transcranial Doppler sonography as an intraoperative monitor in carotid surgery, we compared measurements of mean blood flow velocity in the ipsilateral middle cerebral artery with the cortical response of somatosensory evoked potentials in a prospective study of 176 carotid operations. SEP recording was readily feasible during all procedures and by means of SEP loss all patients at risk for critical cross-clamp related cerebral ischemia were reliably identified. In contrast, TCD could not be used for assessment of cerebral hemodynamics in more than 40% of patients. What is more, in high risk patients with intraoperative loss of SEP, TCD could not be performed in 74% of cases. This high rate of failure limits the usefulness of TCD as an intraoperative monitor and detracts from the additional benefit of identifying cerebral embolism and hyperperfusion as potential causes of neurological deficits. In contrast to SEP recording, TCD cannot be recommended as a routine monitor in carotid surgery.