Roman Kocian

Artificial O2 Carriers: Status in 2005

Donor blood is a limited resource and its transfusion is associated with significant adverse effects. Therefore, alternatives have been searched, the ultimate being artificial oxygen (O2) carriers. There are two main groups of artificial O2 carriers: hemoglobin based and perfluorocarbon emulsions. The hemoglobin molecule in hemoglobin based artificial O2 carriers needs to be stabilized to prevent dissociation of the alpha2beta2-hemoglobin tetramer into alphabeta-dimers in order to prolong intravascular retention and to eliminate nephrotoxicity. Other modifications serve to decrease O2 affinity in order to improve O2 off-loading to tissues. In addition, polyethylene glycol may be surface conjugated to increase molecular size. Finally, certain products are polymerized to increase the hemoglobin concentration at physiologic colloid oncotic pressure. Perfluorocarbons are carbon-fluorine compounds characterized by a high gas dissolving capacity for O2 and CO2 and chemical and biologic inertness. Perfluorocarbons are not miscible with water and therefore need to be brought into emulsion for intravenous application. Development, product specification, physiologic effects, efficacy to decrease the need for donor blood in surgery and side effects of the following products are described: Diaspirin cross-linked hemoglobin (HemAssist), human recombinant hemoglobin (rHb1.1 and rHb2.0), polymerized bovine hemoglobin-based O2 carrier (HBOC-201), human polymerized hemoglobin (PolyHeme), hemoglobin raffimer (Hemolink), maleimide-activated polyethylene glycol-modified hemoglobin (MP4) and perflubron emulsion (Oxygent). In addition, enzyme cross-linked poly-hemoglobin, hemoglobin containing vesicles (nano-dimension artificial red blood cells) and an allosteric modifier (RSR13) are discussed. The most advanced products are in clinical phase III trials but no product has achieved market approval yet in the US, Europe or Canada.

Transfusion in the cardiac patient

Transfusion guidelines in patients with coexisting cardiac diseases are similar to the ones in patients without such comorbidity, in that allogeneic blood transfusions most often are indicated at hemoglobin levels of less than 6.0 g/dL and hardly ever at hemoglobin levels greater than 10 g/dL. In the hemoglobin range of 6 to 10 g/dL, signs of impaired oxygenation should serve as transfusion indications, and such signs may be reached at higher hemoglobin values than in healthy patients. An inadequate oxygenation may become manifest globally in the form of a general hemodynamic instability with a tendency to hypotension and tachycardia despite normovolemia or an oxygen extraction of greater than 50%. An inadequate oxygenation in the form of myocardial ischemia may be manifested by new ST-segment depressions of greater than 0.1 mV, new ST-segment elevations greater than 0.2 mV, or new wall motion abnormalities in transesophageal echocardiography. Institutional guidelines also should consider local logistic characteristics such as the level of knowledge of physician and nurse staff caring for patients and the level of surveillance possible justifying eventually higher hemoglobin transfusion triggers, particularly in the postoperative period.

Bronchial aspiration in patients after weight loss due to gastric banding

Laparoscopic gastric banding is a surgical treatment of morbid obesity. There are no specific recommendations concerning anesthesia induction in patients having gastric banding. After recent experience of two bronchial aspirations during anesthetic induction in patients with gastric banding, we concluded that esophago-gastric peristalsis in these patients is altered. Such patients should consume only liquid meals the day before the operation, and we propose a rapid-sequence induction as the anesthetic technique. In patients with an expected difficult airway, an awake intubation may be considered.

Anästhesie für endoskopische Eingriffe

Die Endoskopie ist ein Eingriff in einer vorbestehenden Körperhöhle zu diagnostischen oder therapeutischen Zwecken. Der Zugang erfolgt entweder durch eine anatomische Öffnung (z. B. Mund) oder durch eine operativ angelegte Wunde (z.B. Laparoskopie). Im Rahmen dieses Artikels werden im engeren Sinne nur diejenige Eingriffe behandelt, die sich einen anatomischen Zugang zunutze machen. Die Hauptgebiete der endoskopischen Eingriffe sind die Fächer Hals-Nasen-Ohren-Heilkunde, Pneumologie, Gastroenterologie und Urologie.

Clinical Use of Artificial Oxygen Carriers

Artificial oxygen carriers aim at improving oxygen delivery (DO2). Artificial oxygen carriers, therefore, may be used as an alternative to allogeneic blood transfusions or to improve tissue oxygenation and function of organs with marginal oxygen supply [1, 2]. Modified hemoglobin solutions and perfluorocarbon (PFC) emulsions are currently undergoing clinical testing. This chapter is based on a recent review article [3] where more detailed references may be found. Current knowledge of artifical oxygen carriers is based on published data from approximately 500–1000 patients treated with these compounds and a similar number of control patients. Unfortunately, there is still a significant amount of non-published data that renders the overall assessment of these solutions difficult.

Augmented acute normovolemic hemodilution (A-ANHTM) –a new concept to minimize the need for allogeneic blood transfusion

Zusammenfassung Die augmentierte, akut normovoläme Hämodilution dient der Reduktion des Bedarfs an Fremdbluttransfusionen bei Operationen, die mit einem größeren Blutverlust verbunden sind. Die augmentierte, akut normovoläme Hämodilution läuft in 3 Phasen ab: Vor der Operation wird eine herkömmliche akut normovoläme Hämodilution durchgeführt, während der Operation wird ein künstlicher Sauerstoffträger (eine modifizierte Hämoglobinlösung oder eine Perfluorocarbon-Emulsion) verabreicht um die Periode des minimalen endogenen Hämoglobins zu überbrücken und das Eigenblut wird nach dem Eingriff zurücktransfundiert. Die Wirksamkeit im klinischen Einsatz ist noch nicht bewiesen, mathematische Modelle lassen aber eine gute Wirksamkeit erwarten.Summary Augmented Acute Normovolemic Hemodilution serves to reduce the need for allogeneic blood transfusions in patients undergoing high blood loss surgery. Augmented acute normovolemic hemodilution has 3 phases: First, acute normovolemic hemodilution prior to surgical blood loss, second, administration of an artificial O2 carrier such as a modified hemoglobin solution or perflubron emulsion during periods of low endogenous hemoglobin concentration during surgery and third, re-transfusion of autologous blood after the operation. Efficacy remains to be ultimately proven in clinical trials but mathematical modeling indicates that clinically significant reductions in allogeneic blood transfusions are likely.