Reduction of the acquisition time needed to obtain somatosensory evoked potentials by estimation of the required averaging sweep count by an algorithm.

Somatosensory evoked potentials are frequently acquired by stimulation of the median or tibial nerves (mSEPs and tSEPs) for intraoperative monitoring of sensory pathways. Due to their low amplitudes it is common practice to average 200 or more sweeps to discern the evoked potentials from the background EEG. The aim of this study was to investigate if an algorithm designed to determine the lowest sweep count needed to obtain reproducible evoked potentials in each patient significantly reduces the median necessary sweep count to under 200. 30 patients undergoing spinal surgery at the Department of Neurosurgery were included in the study. Beginning with a sweep count of 200 an algorithm was designed to determine the lowest sweep count that yielded reproducible evoked potentials in each patient. By this algorithm the minimal sweep count was determined in 15 patients for mSEPs and in 15 patients for tSEPs. The required sweep count was below 200 in 14 of 15 patients for mSEPs (93.3%) with a mean sweep count of 56 ± 51. For tSEPs the sweep count was below 200 in 11 of 15 patients (73.3%) with a mean sweep count of 106 ± 70 (mean ± SD). The calculated mean time to average the potentials could thereby be reduced from 48.8s to 13.7s for mSEPs and from 48.8s to 25.9s for tSEPs. The proposed algorithm allowed sweep count and acquisition time reduction in roughly 90% of all patients for mSEPs and in 70% of all patients for tSEPs.

Evidence-based art in the hospital.

BACKGROUND: Evidence-based art is the investigation of art effects and art investigated for effects. In this study the evidence regarding patient preferences for art styles and effects of art in nonpsychiatric hospitals and outpatient departments was reviewed. METHODS: Results from original articles were retrieved by a scoping PubMed search and by browsing the internet using the terms "evidence based art", "evidence based design", "art and hospital" and "design and hospital", "art effect", "design effect", "landscape preference" and "abstract art figurative art". The quality of art was not operationalized as a criterion. RESULTS: Of the articles 7 original sources showed patient preference for natural scenes and figurative art, 2 studies showed no preference, 16 studies showed positive art effects on well-being and behavior and 5 studies showed a positive effect of nature pictures on measurable findings. CONCLUSION: Controversial results together with theoretical aspects suggest natural scenes in patient rooms and diverse art in public areas.

[Anaesthesia in Adult Patients with Obesity]. / Anästhesie bei Erwachsenen mit Adipositas.

The prevalence of obesity has substantially increased worldwide during the last ten years. Hence, more anaesthetic procedures will be performed in obese patients in the future and more hospitals have to be prepared for the perioperative treatment of extremely obese patients including medical, technical and organisational issues. These include not only the management of the perioperative problems of adiposity, but also of its numerous concomitant diseases. Besides hyperlipidemia, diabetes mellitus, arterial hypertension and coronary heart disease, the obstructive sleep-apnea syndrome (OSAS) challenges the available equipment and the staff involved. Airway and breathing problems are very frequent and regional anaesthesia should be preferred. If general anaesthesia is indicated, short acting drugs like desflurane or remifentanil are recommended. Preoxygenation is improved by continuous positive airway pressure (CPAP). In this educational review, a summary of the currently known facts regarding anaesthesia in obese patients is outlined together with future perspectives. Regional anaesthesia is also recommended for postoperative pain therapy.

Effect of ischemic and pharmacological preconditioning of lower limb muscle tissue on tissue oxygenation measured by near-infrared spectroscopy--a pilot study.

BACKGROUND: Ischemic or volatile anesthetic preconditioning is defined as tissue protection from impending ischemic cell damage by repetitive short periods of tissue exposure to ischemia or volatile anesthetics. Objective of this study was to elucidate, if ischemic preconditioning and pharmacological preconditioning with sevoflurane have effects on muscle tissue oxygen saturation in patients undergoing surgical revascularization of the lower limb. METHODS: In this prospective randomized pilot study ischemic and pharmacological (sevoflurane) preconditioning was performed in 40 patients with lower limb arterial occlusive disease undergoing surgical revascularization. Sevoflurane preconditioning was performed in one group (N = 20) by repetitive application of sevoflurane for six minutes interspersed by six minutes of washout. Thereafter, ischemic preconditioning was performed in all patients (N = 40) by repetitive clamping of the femoral artery for six minutes interspersed by six minutes of reperfusion. The effect of both procedures on leg muscle tissue oxygen saturation (rSO2) was measured by near-infrared spectroscopy during both procedures and during surgery and reperfusion (INVOS® 5100C Oxymeter with Small Adult SomaSensor® SAFB-SM, Somanetics, Troy, Michigan, USA). RESULTS: Repetitive clamping and reperfusion of the femoral artery resulted in significant cyclic decrease and increase of muscle rSO2 (p < 0.0001). Pharmacological preconditioning with sevoflurane resulted in a faster and higher increase of rSO2 during postoperative reperfusion (Maximal 111% baseline ± 20 versus 103% baseline ± 14, p = 0.008) consistent with an additional effect of pharmacological preconditioning on leg perfusion. CONCLUSIONS: Ischemic preconditioning of lower limb muscle tissue and pharmacological preconditioning with sevoflurane have an effect on tissue oxygenation in patients with lower limb occlusive arterial disease. TRIAL REGISTRATION: The trial has been registrated at http://www.ClinicalTrial.gov, TRIAL NUMBER: NCT02038062 at 14 January 2014.

Transcranial Doppler sonography as a potential screening tool for preanaesthetic evaluation: a prospective observational study.

CONTEXT: Intraoperative cervical spine rotation may compromise cerebral blood flow in susceptible individuals by distortion of cervical arteries. OBJECTIVE: To investigate the effect of five cervical spine positions on cerebral blood flow in the middle cerebral artery. DESIGN: Prospective observational study. SETTING: University hospital. PATIENTS: Fifty-six male and 24 female patients scheduled for general anaesthesia for routine surgery. Exclusion criteria were cranial spine pathology and cerebral vascular disease. INTERVENTIONS: Maximum rotation of the head to the left and right side with and without hyperextension, and hyperextension in the neutral position. MAIN OUTCOME MEASURES: Change of mean blood flow velocity in the middle cerebral artery measured by transcranial Doppler sonography. RESULTS: Age had a significant effect on mean blood flow velocity in the left middle cerebral artery in the neutral position (P = 0.047). There was a significant difference in mean blood flow velocity in the left middle cerebral artery between patients younger than 40 years and patients older than 59 years [61.2 (16.6) ml min(-1) vs. 47.7 (16.2) ml min(-1); P = 0.015]. There was a significant effect of head position on mean blood flow velocity in both the left and in the right middle cerebral arteries (P = 0.039 left, P = 0.025 right). Twenty patients had a decrease of more than 20% from their baseline mean blood flow velocity. CONCLUSION: Neck rotation and/or extension resulted in a significant change of blood flow in the middle cerebral artery.

Postoperative cognitive deficit after cardiopulmonary bypass with preserved cerebral oxygenation: a prospective observational pilot study.

BACKGROUND: Neurologic deficits after cardiac surgery are common complications. Aim of this prospective observational pilot study was to investigate the incidence of postoperative cognitive deficit (POCD) after cardiac surgery, provided that relevant decrease of cerebral oxygen saturation (cSO2) is avoided during cardiopulmonary bypass. METHODS: cSO2 was measured by near infrared spectroscopy in 35 patients during cardiopulmonary bypass. cSO2 was kept above 80% of baseline and above 55% during anesthesia including cardiopulmonary bypass. POCD was tested by trail making test, digit symbol substitution test, Ray's auditorial verbal learning test, digit span test and verbal fluency test the day before and 5 days after surgery. POCD was defined as a decline in test performance that exceeded - 20% from baseline in two tests or more. Correlation of POCD with lowest cSO2 and cSO2 - threshold were determined explorative. RESULTS: POCD was observed in 43% of patients. Lowest cSO2 during cardiopulmonary bypass was significantly correlated with POCD (p = 0.015, r2 = 0.44, without Bonferroni correction). A threshold of 65% for cSO2 was able to predict POCD with a sensitivity of 86.7% and a specificity of 65.0% (p = 0.03, without Bonferroni correction). CONCLUSIONS: Despite a relevant decrease of cerebral oxygen saturation was avoided in our pilot study during cardiopulmonary bypass, incidence of POCD was comparable to that reported in patients without monitoring. A higher threshold for cSO2 may be needed to reduce the incidence of POCD.

Postoperative neurocognitive function and microembolus detection in patients undergoing neck dissection: a pilot study.

BACKGROUND AND OBJECTIVE: Patients undergoing oncologic neck dissection may have many of the risk factors for carotid artery stenosis, thus predisposing them to perioperative cerebral ischaemic events. The present study was designed to investigate development of postoperative neurocognitive dysfunction in these patients. METHODS: Twenty-six patients were assessed the day before surgery and 48 h and 12 months after surgery using a comprehensive neuropsychological test battery. Cognitive performance was compared with a matched control group to account for the practise effect associated with repeated testing. Doppler ultrasonography was used to detect intraoperative cerebral microembolism. S100beta protein values were evaluated before and immediately after anaesthesia. RESULTS: On the second postoperative day, 26.9% of patients undergoing neck dissection had postoperative neurocognitive deficit (POCD), defined as a total deficit score of 2SD worse than the mean performance in the control group. Microemboli were found only in the neck dissection group. S100beta levels were significantly higher after neck dissection (Wilcoxon signed ranked test: P<0.001). After 12 months, the incidence of POCD was similar in both groups. CONCLUSION: POCD was detectable only after neck dissection in the early postoperative period accompanied by increased incidence of microembolism and protein S100beta levels, but not 12 months after surgery.

A comparison between target-controlled and manually controlled propofol infusions in patients undergoing routine surgical procedures.

BACKGROUND AND OBJECTIVE: Previous studies have shown that target-controlled infusion (TCI) was associated with increased propofol consumption as compared with manually controlled infusion (MCI). However, most studies lacked an objective measurement of anaesthetic depth. We compared TCI and MCI with regard to propofol dose requirement while monitoring depth of anaesthesia with bispectral index (BIS) and midlatency auditory-evoked potentials (MLAEPs). METHODS: Fifty ASA 1 or 2 patients undergoing elective ENT surgery were randomly allocated to the TCI group (n = 25)or the MCI group (n = 25). BIS, MLAEPs, haemodynamic parameters and propofol plasma concentration were determined at various stages before, during and after anaesthesia. During anaesthesia, BIS values were always maintained between 40 and 60. RESULTS: Anaesthesia significantly increased latency of Pa and Nb compared with when patients were awake (P < 0.01). After extubation, the latency of Pa and Nb significantly decreased and basically returned to baseline level. BIS and latency of both Pa and Nb did not differ between groups.Also, the propofol induction dose (mean WSD: TCI, 2.09 +/- 0.36 mg kg(-1); MCI, 2.06 +/- 0.16 mg kg(-1) and total dose (TCI, 5.57 +/- 0.96 mg kg(-1) h(-1); MCI, 5.79 +/- 0.87 mg kg(-1) h(-1) and measured plasma propofol concentration during anaesthesia did not differ between groups. At 15 min after intubation, the mean predicted plasma concentration (2.2 +/- 0.2 microg ml(-1)) differed significantly from the measured plasma concentration (2.8 +/- 1.2 microg ml(-1)). No correlation was observed between predicted and measured propofol plasma concentrations.

[Anesthesia in vascular surgery--monitoring of cerebral function]. / Uberwachung der zerebralen Integrität.

In vascular surgery, intraoperative monitoring of the brain is recommended when the internal carotid artery (ICA) is clamped, because brain damage by ischemia and embolism is possible. Clamping of the ICA results in embolic or ischemic brain lesions in about 7 % of all patients undergoing the procedure. Prophylactic routine insertion of an intraluminal shunt can cause brain embolism and does not reduce the occurrence of complications. Consequently, a shunt should only be inserted, if critical reduction of cerebral perfusion is evident after clamping the ICA. Measurement of carotid stump pressure is an invasive method to estimate perfusion of the brain hemisphere at the clamping side. Transcranial doppler sonography (TCD) measures the mean blood flow velocity in the ACI, but practicability is suffering from technical problems in 20% of all patients. However, TCD is useful for detecting intraoperative embolism and postoperative hyperperfusion. Changes of oxyhaemoglobine and desoxyhaemoglobine concentration in brain tissue can be measured using near-infrared spectroscopy (NIRS) with wavelengths between 700 and 1000 nm. NIRS measurement is easily performed and reacts quickly to changes of brain tissue oxygenation, but there is still lacking evidence and at present a general recommendation of its application in vascular surgery is not justified. Use of somatosensory evoked potentials (SEP) is the most widespread cerebral neuromonitoring during vascular surgery due to its high reliability and simple application. Sensitivity and specifity for ischemic lesions are 100% and 94%-99%, respectively. SEP are regarded as the gold standard for cerebral neuromonitoring in anaesthetized patients.

[Anaesthesia management of the obese patient]. / Begleiterkrankungen und perioperatives Management bei adipösen Erwachsenen.

Obesity is a global epidemic, and approximately 20 % of the German population are obese. Therefore anaesthesiologists will be increasingly involved in the care of obese and morbidly obese patients in the near future. As a prerequisite, the hospital must focus on this patient population with respect to facilities and the availability of tailored medical equipment and supplies. Comorbidities such as diabetes, hypertension, coronary heart disease and sleep apnea considerably increase the risk of obese patients. A thorough preoperative evaluation of comorbidities, an anaesthesia induction and intraoperative ventilation tailored to the pathophysiological sequelae of obesity and a sound knowledge of pharmokocinetics are necessary to ensure optimal care for obese patients.

Immobilization during anesthesia for vitrectomy using a laryngeal mask without neuromuscular blockade versus endotracheal intubation and neuromuscular blockade.

BACKGROUND: For intraocular surgery, most authors recommend general anesthesia including intubation and neuromuscular blockade to avoid complications by patient movements. However, anesthesia using a laryngeal mask and avoidance of muscle relaxants is common clinical practice. Purpose of this prospective observational study was to compare the incidence of eye movement and deviation of the eye axis during general anesthesia adjusted to minimal alveolar concentration (MAC) for pars plana-vitrectomy (PPV) using a laryngeal mask without neuromuscular blockade (LM) versus endotracheal intubation and neuromuscular blockade (INT). METHODS: The patients (N.=148) who underwent PPV for vitreoretinal disorders received MAC adjusted general anesthesia by volatile anesthetics. Seventy-four patients were subjected to LM and 74 to INT. In both groups the patient's lungs were mechanically ventilated without allowing spontaneous ventilation. Eye movements and upward deviations were judged and documented during surgery. Postoperatively quality of immobilization was assessed by a standardized questionnaire. RESULTS: Intraoperative movements were not observed in either group. Upward eye deviation was observed in nine (12%) patients in the LM group, but not in patients in the INT group (0%; P=0.003). The standardized questionnaire revealed no clinically relevant difference in quality of immobilization between groups, especially eye deviations did not lead to any relevant surgical complications or difficulties. CONCLUSIONS: For PPV, MAC adjusted balanced anesthesia using a laryngeal mask without neuromuscular blockade was associated with more, but clinically irrelevant upward eye deviations and may be an alternative to intubation with neuromuscular blockade. However, adequate depth of anesthesia must be assured to avoid unwanted injuries during surgery.

The effect of the WHO Surgical Safety Checklist on complication rate and communication.

BACKGROUND: In 2009, the World Health Organisation issued a worldwide recommendation for the use of its Surgical Safety Checklist in all operative procedures. In this review, we present the available data on the implementation of this checklist and its effect on perioperative morbidity and mortality and on operating-room safety culture. We also survey the experience with the checklist to date and give some recommendations for its practical implementation. METHODS: We reviewed pertinent original publications retrieved by a selective search in the PubMed and Medline databases on the search term "Surgical Safety Checklist". All papers published before February 2012 were analyzed. RESULTS: The 20 studies that we analyzed included a single prospective randomized trial concerning the effect of the WHO checklist on safety-related behavior in the operating room. The two surgical outcome studies documented a relative improvement of perioperative mortality by 47% in one study (from 56 in 3733 cases [1.5%] to 32 in 3955 cases [0.8%]) and by 62% in the other (from 31 in 842 cases [3.7%] to 13 in 908 cases [1.4%]), as well as a relative improvement of perioperative morbidity by 36% in one study (from 411 in 3733 cases [11.0%] to 288 in 3,955 cases [7.3%]) and by 37% in the other (from 151 in 842 cases [17.9%] to 102 in 908 cases [11.2%]). Improved interdisciplinary communication was also found. Factors that aided effective use of the checklist included exemplary implementation by team leaders and structured training. CONCLUSION: These results support the WHO's recommendation to use the Surgical Safety Checklist in all operative procedures. The checklist should be understood not merely as a list of items to be checked off, but as an instrument for the improvement of communication, teamwork, and safety culture in the operating room, and it should be implemented accordingly.

A comparison of auditory evoked potentials derived from a monitor integrated module versus standard technique.

PURPOSE: Measurement of brain stem auditory evoked potentials (BAEP) and midlatency auditory evoked potentials (MLAEP) using a new monitor integrated module was compared with an established device. The aim of this study was to evaluate if the new system could replace the more inconvenient established technique. MATERIAL AND METHODS: MLAEP and BAEP were obtained from 19 anesthetized male patients using the AEP-Module for Monitor S/5 [GE, Helsinki, Finland (S/5)] and Neuropack 4 mini [Nihon Kohden, Tokyo, Japan (Neuropack)]. Significance of different results was calculated by paired t test. Bias was estimated by Bland-Altman statistics. RESULTS: Latencies of BAEP were significantly shorter and amplitudes of BAEP were significantly higher for Neuropack. Mean latencies of MLAEP (Pa and Nb) were not significantly different (Pa 44.1+/-4.4 ms vs. 41.9+/-5.4 ms/Nb 66.4+/-5.6 ms vs. 62.8+/-6.5 ms), but methods are not interchangeable owing to great variability (Pa -13.16 to 8.94 ms, Nb -19.15 to 11.79 ms). CONCLUSIONS: BAEP recorded by S/5 cannot be used for diagnostic interpretation using generally accepted normal values, but can be used for examining changes during the monitoring period. Mean values of Pa and Nb were not significantly different, but values of the S/5 varied above and below the values of Neuropack such that the measurements could not be used for diagnostic interpretation. However, this did not reduce their usefulness for determining adequate hypnosis.

Propofol infusion syndrome in anaesthesia and intensive care medicine.

PURPOSE OF REVIEW: Propofol infusion syndrome is a rare but often fatal syndrome, characterized by lactacidosis, lipaemic plasma and cardiac failure, associated with propofol infusion over prolonged periods of time. As propofol is used worldwide, knowledge of propofol infusion syndrome is essential for all anaesthesiologists and intensive care physicians. This review will provide an update on reported cases, and describe recent findings relevant to the pathophysiology and clinical presentation of propofol infusion syndrome. RECENT FINDINGS: Case reports of propofol infusion syndrome have contributed new pathophysiological evidence. Reported cases of similar syndromes may represent initial propofol infusion syndrome, and may help to identify further risk factors such as low carbohydrate supply and early warning signs such as lactacidosis. Newly identified gene defects mimicking propofol infusion syndrome may elicit the underlying genetic susceptibility. Recommendations for the limitation of propofol use have been devised by various institutions. SUMMARY: Propofol infusion syndrome must be kept in mind as a rare but highly lethal complication of propofol use, not necessarily confined to the prolonged use of propofol. Dose limitations must be adhered to, and early warning signs such as lactacidosis should lead to the immediate cessation of propofol infusion.