T. Brüssel

Mechanical ventilation in the prone position for acute respiratory failure after cardiac surgery

Ten patients with acute respiratory failure (ARF) after coronary artery bypass grafting were studied during conventional mechanical ventilation in the supine and in the prone position. Impaired gas exchange was defined as an inspired oxygen fraction (FIO2) greater than 0.5 to maintain an arterial oxygen tension (PaO2) > or = 70 mmHg, an alveolar-arterial PaO2 gradient (PA-aO2) > 200 mmHg and a venous admixture (QVA/QT) > 15% during mechanical ventilation with a tidal volume (VT) = 10 to 12 mL/kg, frequency (f) = 10 to 15 VT/min, inspiratory-expiratory (I:E) ratio = 0.5, and positive end-expiratory pressure (PEEP) of 5 to 7.5 cm H2O. In the supine position, systemic and pulmonary hemodynamics were in the normal range, but oxygenation was severely impaired. In all patients thoracic computed tomography scans were obtained and revealed crest-shaped bilateral densities in the dependent lung regions. FIO2 of 0.67 +/- 0.22 was required to maintain a PaO2 greater than 70 mmHg during mechanical ventilation in the supine position. Under these conditions PA-aO2 and QVA/QT were 362 +/- 153 mmHg and 32.5 +/- 8.3%, respectively. CO2 elimination was not severely affected. The patients were turned into the prone position after an average of 30.6 +/- 5.4 hours postoperatively and ventilated with unchanged VT, f, PEEP, and inspiratory-expiratory ratio for 26.7 +/- 11.7 hours (range, 10 to 42 hours). A second cardiopulmonary status was obtained within 2 to 5 hours of ventilation in the prone position.(ABSTRACT TRUNCATED AT 250 WORDS)

Der Einfluß von Fentanyl und endotrachealer Intubation auf die hämodynamischen Effekte der Anästhesieeinleitung mit Propofol/N2O beim Menschen

In fruheren Studien uber die hamodynamischen Effekte der Narkoseeinleitung mit Propofol, einem Phenolderivat (2,6-Diisopropylphenol) wurde uber einen signifikanten Abfall sowohl des systolischen wie des diastolischen arteriellen Blutdrucks bei stark sedierten Patienten mit KHK [2] und bei Patienten mit Veranderungen an der Aorten- und Mitralklappe [3] berichtet. In diesen Untersuchungen wurde die Zubereitung Cremophor des Propofol benutzt. Da die cremophorhaltigen Anasthetika mit signifikant haufigerem Auftreten anaphylaktoider Reaktionen einhergehen, wurde Propofol in neuer galenischer Form als wasrige Emulsion herausgebracht (1% Propofol, 10% Sojabohnenol, 2,25% Glycerol und 1,2% Phosphatid aus dem Ei; [14]. Mit der neuen Zubereitung zur Narkoseeinleitung beobachtete man einen signifikanten Abfall des arteriellen Drucks zusammen mit einer leichten Abschwachung der Herzleistung bei gesunden Personen, die normale Luft [10] oder 100%igen Sauerstoff [16] atmeten.

The Influence of Volatile Anesthetics on Cerebral Blood Flow and Cerebral Autoregulation

The intracranial space, which is surrounded by cranial bone, can be divides into several compartments; in normal adults it consists of: 700–900 ml glia, 500–700 ml neurons, 100–150 ml blood (arterial and venous), 100–150 ml cerebrospinal fluid (CSF), and >75 ml extracellular fluid (ECF).

Isoflurane in Neurosurgical Patients: Are There Advantages?

Studies of the cerebrovascular effects of halothane, particularly its vasodilating properties and the resultant impact on intracranial pressure (ICP) led in the early 1970s to a curtailment of its use during neurosurgical procedures [1, 2, 3,4, 5]. Most anaesthesio-logists chose instead to employ combinations of i. v. drugs usually in conjunction with nitrous oxide [6, 7, 8]. However, inhalation agent’s have the considerable advantage of being readily controlled in terms of overall depth of general anaesthesia, and therefore, the desire for a better volatile agent did not disappear. The report in 1974 by Morphy and co-workers at the annual meeting of the American Society of Anesthesiologists suggested that isoflurane could be such a drug [9]. These authors found that, in volunteers, cerebral blood flow (CBF) increased at low levels of enflurane and halothane anaesthesia, but did not increase at the same levels of isoflurane. All three agents increased CBF at 1.6 MAC (minimum alveolar concentration). However, this study has never been published.

Kontrollierte Hypotension mit Isofluran: Einfluß auf die zerebrale Durchblutung und zerebrale Autoregulation

Seit kurzem wird Isofluran fur die Durchfuhrung der kontrollierten Hypotension vorgeschlagen [1]. Wegen einer guten systemischen vasodilatierenden Wirkung, geringfugiger myokardialer Depression, Verminderung des zerebralen Sauerstoffverbrauchs und moglicherweise zerebral protektiver Eigenschaften konnte es eine geeignete Substanz sein. Fur die Beurteilung und Bewertung eines Pharmakons zur Durchfuhrung einer kontrollierten Hypotension ist aber auch die Kenntnis des Einflusses auf die zerebrale Durchblutung und die zerebrale Autoregulation erforderlich.

Der Einfluß volatiler Anästhetika auf die zerebrale Durchblutung und die zerebrale Autoregulation

Der intrakranielle Raum, der von Schadelknochen umgeben ist, kann in mehrere Kompartimente unterteilt werden und besteht beim normalen Erwachsenen aus: 700–900 ml Gliagewebe 500–700 ml Neuronen 100–150 ml Blut (arterielles und venoses) 100–150 ml cerebrospinaler Flussigkeit (CSF) <75 ml extrazellularer Flussigkeit (ESF).

Cardiodynamic Changes Under Isoflurane with or Without Nifedipine Pretreatment

Apart from their overall effect, anaesthetics and narcotics act on the cardiovascular system in three areas: the myocardium, the low pressure system and the peripherial arterial resistance. Separation of the effects is difficult. Even when applying invasive diagnostic means it remains difficult to distinguish between changes in inotropy and those in preload and afterload because haemodynamic obsevations including left ventricular pressure (LVP), positive and negative, dp:dt and cardiac output (CO) are poorly discriminated. Fibre tension and shortening distances may be measured in the beating heart in situ, although myocardial fibres have no definite origins or insertions [1, 2].