Michael Quintel

HYPERTONIC SALINE SOLUTION FOR CONTROL OF ELEVATED INTRACRANIAL PRESSURE IN PATIENTS WITH EXHAUSTED RESPONSE TO MANNITOL AND BARBITURATES

Critically elevated intracranial pressure (ICP) represents the most important cause of morbidity and mortality in patients suffering from severe traumatic brain injury (TBI) and is a serious complication after subarachnoid hemorrhage (SAH). Thus new strategies for the control of ICP are required. Based on the evidence available hypertonic saline solution (HSS) may be a promising approach. It was therefore the aim of the present study to evaluate in a prospective manner the effects of HSS on ICP and cerebral perfusion pressure (CPP) in patients with therapy-resistant elevation of ICP. A total of 48 bolus infusions of HSS (7.5%, 2 ml kg-1 b.w.; infusion rate 20 ml min-1) were given intravenously (range 1-15 per patient) to 10 patients (age 41 +/- 6 years) with TBI and SAH. Only patients with ICP > 25 mmHg not responding to standard ICP-management protocol and plasma sodium (Na+) concentration < 150 mmol l-1 were included in the study. Within the first hour after HSS application, ICP decreased from 33 +/- 9 mmHg to 19 +/- 6 mmHg (p < 0.05) and further to 18 +/- 5 mmHg at the time of maximum effect (98 +/- 11 min post bolus). Decrease of ICP was accompanied by a rise of CPP from 68 +/- 11 mmHg to 79 +/- 11 mmHg (p < 0.05) after 1 h and further to 81 +/- 11 mmHg at the time of maximum effect. Plasma Na+ concentration was 141 +/- 6 mmol l-1 before and 143 +/- 5 mmol l-1 1 h after HSS bolus. Corresponding values for plasma osmolality were 302 +/- 11 and 308 +/- 12 mOsm l-1. When the ICP lowering effect was transient, subsequent HSS bolus was necessary 163 +/- 54 min after previous dosing. The present results indicate that repeated bolus application of HSS (7.5% NaCl, 2 ml kg-1 b.w.) is an effective measure to decrease ICP which is otherwise refractory to standard therapeutic approaches. Whether or not the therapy scheme is also suited as primary measure for the control of ICP remains to be established.

Rapid active internal core cooling for induction of moderate hypothermia in head injury by use of an extracorporeal heat exchanger.

OBJECTIVE Moderate hypothermia (32 degrees C) may limit postischemic neuronal damage and is increasingly used clinically in head injury and stroke. For the use of hypothermia as a neuroprotective agent in the prevention of ischemic damage, it is necessary to induce it as soon as possible after the insult and to keep it at the lowest safe level. Active core cooling using an extracorporeal heat exchanger may circumvent the rather slow induction speed and temperature drifts experienced with surface cooling techniques. METHODS In eight patients with severe head injuries (Glasgow Coma Scale score, 4-5), a venovenous extracorporeal circulation was established via a percutaneously introduced double-lumen cannula in the femoral vein. A heat exchanger was connected via a pressure-controlled roller pump. In addition to standard parameters, brain white matter temperature was continuously recorded as the target temperature. Cooling was initiated as early as possible with an extracorporeal temperature of 30 degrees C and maintained at a 32 degrees C brain temperature for 48 hours, and then gradual rewarming for 24 hours. RESULTS Cooling was able to be initiated within 6 hours and 48 minutes +/- 3 hours and 47 minutes (mean +/- standard deviation) after trauma. A brain temperature of 32 degrees C was reached within 1 hour and 53 minutes +/- 1 hour and 21 minutes after induction of cooling with a cooling speed of 3.5 degrees C per hour. Brain temperature was able to be controlled within 0.1 degrees C intervals, which was especially helpful in gradual rewarming. No cardiac abnormalities or statistically significant changes in coagulation parameters occurred. Mean platelet count decreased to 89,614+/-42,090 on Day 3 after treatment. No clinical bleeding complications or problems resulting from extracorporeal circulation occurred. Moderate hypothermia was a helpful tool for managing increased intracranial pressure; however, five patients of this series died either of their intracranial abnormalities (n = 4) or of a delayed septic shock after pneumonia (n = 1) at various points in time during therapy. The three survivors experienced either an excellent or a good recovery. CONCLUSION The results of this investigation suggest that the use of an extracorporeal heat exchanger to achieve active core cooling is suitable for fast and accurately controllable induction, maintenance, and reversal of moderate hypothermia in emergency situations with reliable control of temperature. In this small series of highly selected patients with severe head injuries, we did not note a beneficial effect of hypothermic therapy on outcome.

Effects of end-inspiratory and end-expiratory pressures on alveolar recruitment and derecruitment in saline-washout-induced lung injury – a computed tomography study

Background:  Lung protective ventilation using low end‐inspiratory pressures and tidal volumes (VT) has been shown to impair alveolar recruitment and to promote derecruitment in acute lung injury. The aim of the present study was to compare the effects of two different end‐inspiratory pressure levels on alveolar recruitment, alveolar derecruitment and potential overdistention at incremental levels of positive end‐expiratory pressure.

Pulmonary gas distribution during ventilation with different inspiratory flow patterns in experimental lung injury – a computed tomography study

Background:  There is still controversy about the optimal inspiratory flow pattern for ventilation of patients with acute lung injury. The aim of this study was to compare the effects of pressure‐controlled ventilation (PCV) with a decelerating inspiratory flow with volume‐controlled ventilation (VCV) with constant inspiratory flow on pulmonary gas distribution (PGD) in experimentally induced ARDS.

Comparison of Static Airway Pressures during Total Liquid Ventilation while Applying Different Expiratory Modes and Time Patterns

To compare pump driven (active) and gravity-siphon (passive) expiration modes during perfluorocarbon total liquid ventilation (TLV), a liquid ventilator was developed capable of providing either expiration mode. In a prospective, controlled laboratory study, 90 rabbits (3.2 ± 0.1 kg) were anesthetized, tracheotomized, killed. After prefill with 12 ml/kg perflubron and TLV for 90 minutes (tidal volume 12 ml/kg, I:E ratio 1:2), randomly using passive (height 40 or 80 cm) or active expiration, respiratory rates were 4, 8, or 12/min. Static peak inspiratory and end-expiratory intratracheal pressures were measured at 5 minute intervals. Peak inspiratory and end-expiratory were constant in active groups, and increases in all 40 cm and 80 cm passive groups were significant. Differences between groups were significant for expiratory mode but not for respiratory rates. Only passive groups showed significant increases in body weight after TLV. Percentage of fluorothoraces was 10% using active and 85% using passive expiration. Based upon the stability of intrapulmonary pressures and volumes and a reduced rate of fluorothoraces, active expiration is more efficient than passive drainage during TLV.

Clinical evaluation of electrostimulation anaesthesia for hysterectomy

A prospective randomized study was undertaken to evaluate the efficacy of electrostimulation anaesthesia (ESA) when compared with neurolept anaesthesia (NLA). One hundred patients scheduled for hysterectomy received either ESA or NLA. Higher levels of mean arterial pressure and heart rate in the ESA group make this technique less suitable for patients with a history of arterial hypertension. A higher dose of muscle relaxants was used in the ESA group. Measured stress variables like plasma glucose, cortisol, and iron indicate maintenance of the stress response during ESA. The postoperative questionnaire revealed intraoperative recall in 12% of ESA patients. We conclude that “pure” ESA based on a N2O regimen should be avoided.

Extrakorporale Membranoxygenierung (ECMO) im Erwachsenenalter

Trotz anhaltender Diskussion ist die extrakorporale Membranoxygenierung (extracorporeal membrane oxygenation, ECMO) auch bei erwachsenen Patienten zu einem festen Bestandteil der therapeutischen Optionen in der Behandlung des akuten Lungenversagens (ARDS, acute respiratory distress syndrome) geworden. Die beiden bislang durchgefuhrten randomisierten Vergleichsstudien konnten allerdings keinen Vorteil im Hinblick auf die Letalitat verglichen mit konventioneller Beatmungstherapie belegen. In der Konsequenz resultierte aus beiden Studien keine Empfehlung fur die ECMO-Therapie (1–3). Mittlerweile liegen weitreichende weltweite Erfahrungen (Gesamtzahl der therapierten erwachsenen Patienten Ende 2001 ca. 1000) vor. Wachsende Erfahrung und verbesserte Technik haben die Rate technischer Komplikationen der extrakorporalen Lungenersatztherapie deutlich reduziert. Aus einer Reihe von Grunden ist in der jungsten Zeit die Inzidenz des Einsatzes von ECMO dennoch deutlich rucklaufig. Einzelne Ein- und Ausschlusskriterien variieren zwischen den verschiedenen ECMO-Zentren. Potentielle Reversibilitat der aktuellen Lungenschadigung und bei ausgeschopfter konventioneller Therapie Fortbestand einer lebensbedrohlichen Gasaustauschstorung stellen jedoch ubereinstimmende Grundvoraussetzung fur die Durchfuhrung einer ECMO-Therapie dar. Gebrauchliche Kriterien sind ein Murray lung injury score >3,5 (Rontgen-Befund, PaO2/FiO2 Ratio, statische Compliance=Cstat, PEEP) eine Morel-Klassifikation >3 (Rontgen-Befund, AaDO2/FiO2-Index, Cstat, PEEP), eine AaDO2 >600mmHg, ein intrapulmonaler Shunt QS/QT >30% und eine Erhohung des extravaskularen Lungenwassers auf >15ml/kg KG. In manchen Zentren stellt daruber hinaus die Dauer der maschinellen Beatmung ( 2 Erythrozytenkonzentrate pro h), Alter >60 Jahre und – besonders in den USA – die Dauer der vorausgehenden invasiven Beatmung. Nach unserer Erfahrung optimiert ein fruhzeitiger Kontakt zu einem ECMO-Referenzzentrum die Identifikation von Patienten die von einer ECMO-Therapie profitieren, die Gesamttherapie, den Transport und das Outcome. Auf Grund der hohen apparativen und personellen Anforderungen bei gleichzeitig sinkender Inzidenz sollte ECMO im Erwachsenensektor auf eine kleine Zahl Referenzzentren mit groser Erfahrung begrenzt bleiben. Damit lasst sich gleichzeitig eine ausreichende Routine aufrechterhalten. In Zeiten sich wandelnder okonomischer Rahmenbedingungen kommt einer kritischen Indikationsstellung und hochqualifizierten Durchfuhrung der ECMO-Therapie eine besondere Bedeutung zu.

Methods for the Determination of the Activity of Phospholipases and their Clinical Application

Many assays for the determination of phospholipase A2 activity [for review: 1] have been developed. The choice of a detection method depends partly on the purpose of a particular experiment. For example, some assays can be used on purified enzymes but are incompatible with crude systems, some methods provide a continuous assay and generate a time course while others do not, and some methods are amenable to automation while others are not. However, the most important consideration in the choice of the detection method is the sensitivity required for the particular enzyme which depends on the quantity of enzyme available and on its specific activity. This point is especially important for the assay of phospholipases A2 in human plasma, which are found in lower quantities and are, in general, less active than their counterparts from venom.