Pre-operative gastric ultrasound in patients at risk of pulmonary aspiration: a prospective observational cohort study.

Point-of-care gastric sonography offers an objective approach to assessing individual pulmonary aspiration risk before induction of general anaesthesia. We aimed to evaluate the potential impact of routine pre-operative gastric ultrasound on peri-operative management in a cohort of adult patients undergoing elective or emergency surgery at a single centre. According to pre-operative gastric ultrasound results, patients were classified as low risk (empty, gastric fluid volume ≤ 1.5 ml.kg-1 body weight) or high risk (solid, mixed or gastric fluid volume > 1.5 ml.kg-1 body weight) of aspiration. After sonography, examiners were asked to indicate changes in aspiration risk management (none; more conservative; more liberal) to their pre-defined anaesthetic plan and to adapt it if patient safety was at risk. We included 2003 patients, 1246 (62%) of which underwent elective and 757 (38%) emergency surgery. Among patients who underwent elective surgery, 1046/1246 (84%) had a low-risk and 178/1246 (14%) a high-risk stomach, with this being 587/757 (78%) vs. 158/757 (21%) among patients undergoing emergency surgery, respectively. Routine pre-operative gastric sonography enabled changes in anaesthetic management in 379/2003 (19%) of patients, with these being a more liberal approach in 303/2003 (15%). In patients undergoing elective surgery, pre-operative gastric sonography would have allowed a more liberal approach in 170/1246 (14%) and made a more conservative approach indicated in 52/1246 (4%), whereas in patients undergoing emergency surgery, 133/757 (18%) would have been managed more liberally and 24/757 (3%) more conservatively. We showed that pre-operative gastric ultrasound helps to identify high- and low-risk situations in patients at risk of aspiration and adds useful information to peri-operative management. Our data suggest that routine use of pre-operative gastric ultrasound may improve individualised care and potentially impact patient safety.

Bronchoscope-assisted Tritube® placement for resection of sequential tracheal stenosis.

Symptomatic tracheal stenosis is a rare but significant complication of long-term tracheal intubation and mechanical ventilation. Airway management for tracheal resection in severe tracheal stenosis, especially sequential stenoses, requires multidisciplinary planning. A valuable method of airway management is the insertion of a small-bore, cuffed tracheal tube (Tritube®, Ventinova Medical B.V., Eindhoven, The Netherlands) in combination with flow-controlled ventilation. In this case, a patient with tracheal stenosis following prolonged ventilation required resection of the stenosed tissue. A Tritube was placed via a J-tipped guidewire inserted through the working channel of a bronchoscope. Bronchoscopic cuff visualisation along the tube in severe stenosis is impossible because of the outer diameter of the tracheal tube. In this case, we therefore estimated the position of the tube tip based on the distance from the vocal cords to the carina measured on pre-operative computed tomography imaging. During completion of the dorsal tracheal anastomosis, cross field ventilation using a conventional tracheal tube had to be started due to impeded ventilation caused by the Tritube protruding distal to the carina. In severe sequential tracheal stenosis, a small-bore tracheal tube can safely be placed by guidance with a J-tipped guidewire. However, it is important to plan a backup method of ventilation, such as cross field ventilation, prior to commencing a critical procedure.

Arterial lactate above 2 mM is associated with increased brain lactate and decreased brain glucose in patients with severe traumatic brain injury.

BACKGROUND: Lactate fuels cerebral energy-consuming processes and it is neuroprotective. The impact of arterial lactate on brain metabolism determined by microdialysis was investigated retrospectively in patients with severe traumatic brain injury (TBI). METHODS: Cerebral microdialysis (glucose, lactate), neuromonitoring (ICP, CPP, ptiO2, SjvO2) and blood gas data collected in 20 patients during pharmacologic coma were grouped within predefined arterial lactate clusters (<1, 1-2, >2 mM). Microdialysis samples were only taken from time points characterized by normoventilation (paCO2 34.5-42 mmHg), sufficient oxygenation (paO2 >75 mmHg) and hematocrit (≥24%) to exclude confounding influences. RESULTS: Elevated arterial lactate ≥2 mM was associated with significantly increased brain lactate which coincided with markedly decreased brain glucose despite significantly increased arterial glucose levels and sufficient cerebral perfusion indirectly determined by normal SjvO2 and ptiO2 values. At elevated arterial lactate levels signs of significantly increased cerebral lactate uptake coincided with markedly decreased cerebral glucose uptake. Infused lactate above 50 mM per 24 hours was associated with significantly decreased cerebral glucose. CONCLUSION: Increased arterial lactate levels were associated with increased cerebral lactate uptake and elevated brain lactate. At the same time brain glucose uptake and brain glucose were significantly reduced. It remains unclear whether arterial lactate is the driving force for the increased cerebral lactate levels or if the reduced glucose uptake also contributed to the increased cerebral lactate levels. Further studies are required to assess the impact of lactate infusion under clinical conditions.

Insulin differentially influences brain glucose and lactate in traumatic brain injured patients.

BACKGROUND: Hypo- and hyperglycemia must be avoided to prevent additional brain damage following traumatic brain injury (TBI). However, the optimal blood glucose range requiring insulin remains unknown. Cerebral microdialysis is helpful in unmasking signs of metabolic impairment, thereby identifying deleterious blood glucose levels. METHODS: A retrospective analysis of prospectively collected cerebral microdialysis samples obtained from 20 non-diabetic patients with severe TBI treated at the trauma surgical intensive care unit at the University Hospital Zürich, Switzerland. RESULTS: The impact of different arterial blood glucose values and concomitant insulin administration on cerebral interstitial glucose and lactate levels was investigated. In addition, energetic impairment was determined by calculating lactate-to-glucose ratios. Insulin administration was associated with significantly reduced cerebral glucose concentrations and significantly increased lactate-to-glucose ratios with arterial blood glucose levels <5 mM. At arterial blood glucose levels >7 mM, insulin administration was associated with significantly increased interstitial glucose values, significantly decreased lactate concentrations, and markedly diminished lactate-to-glucose ratios. CONCLUSION: Insulin exerts differential effects that depend strongly on the underlying arterial blood glucose concentrations. To avoid energetic impairment, insulin should not be administered at arterial blood glucose levels <5 mM. However, at arterial blood glucose levels >7-8 mM, insulin administration appears to be encouraged to increase extracellular glucose concentrations and decrease energetic impairment reflected by reduced interstitial brain lactate and decreased lactate-to-glucose ratios. Nevertheless, frequent analysis is required to minimize the risk of inducing impaired brain metabolism.

[The bacteria stop system of Meierhans-Weber as room air technical alternative to laminar-air-flow and its air hygienic effectiveness]. / Das Keimstopsystem von Meierhans-Weber als raumlufttechnische Alternative zum Laminar-air-flow und seine lufthygienische Wirksamkeit.

Statistics of wound infections demonstrate the linear dependence between postoperative wound infection and the quantity of bacteria in the air of operating theatres. In the most extensive examination series we have made as yet with a special work group of DGOT the quantity of bacteria in the air of non air-conditioned operating theatres and such fitted out with different aircleaning systems was determined. Non air-conditioned operating theatres proved so extremely infected that the risk of wound infection cannot be borne any more in the future. Also air-conditioned systems according to DIN 1946/4 with an average of 190 bacteria/m3 are not sufficiently secure for bone and joint surgery. In Switzerland for such operations a value of 10/m3 at the most is admissible. Such equivalents have been attained only with LAF until today. After extensive air tests the so-called "Keimstop"-system by Meierhans and Weber is to be considered the sole system suitable to supplement air conditioning DIN 1946/4. This combination yields the same effect as the expensive LAF systems.

[Optimum utilization of the ventilation system to reduce airborne bacteria in operating rooms]. / Optimale Nuzung der Lüftung zur Reduktion des Luftkeimgehalts in Operationssälen.

In 4 operating theatres with 4 different air-conditioning equipments, the number of bacteria per m3 circulating air in the neighbourhood of the open wound has been investigated. The testing has been performed on comparable aseptic operations. The worst results were obtained in 2 conventional theatres, equipped with a modern-up-to-date air-conditioning. The number of bacteria was ranging between 230 and 270 per m3. A much better results was obtained in a theatre, equipped with a so-called germ-stop-wall, dividing the theatre into 2 sections, separating the surgical team and the open wound completely from the anaesthesist and other staff. With this arrangement, 45 germs per m3 were found. The best result with no bacteria at all is present in a vertical flow-enclosure with an exchange rate of 32 per hour. According to our 10-year experience, for aseptic surgery sterile air techniques should be adopted to improve asepsis and to decrease the risk of postoperative infection.