Intra-operative use of inhaled vasodilators: are there indications?

The impact of nebulized epoprostenol and iloprost on hemoglobin oxygen affinity: an ex vivo experiment

Inhalational prostacyclins act as strong vasodilators, potentially improving oxygenation by reducing shunt fraction and ventilation-perfusion mismatch. As prostacyclin receptors are known to be present on human erythrocytes, possible direct effects on hemoglobin oxygen transport were further explored by examining the sole in vitro influence of prostacyclins on hemoglobin oxygen (Hb-O2) affinity. Venous blood samples from 20 healthy volunteers were exposed in vitro to supramaximal doses of epoprostenol, iloprost, and compared with control. By high-throughput measurements, hemoglobin oxygen dissociation curves (ODCs) were derived. Hb-O2 affinity, expressed by P50 and Hill coefficient, was determined and analyzed for three subgroups: males (n = 10), females not taking oral contraceptives (n = 4), and females taking oral contraceptives (n = 6). Epoprostenol significantly decreased P50 in all (males, females without contraceptives, and females taking oral contraceptives) [27.5 (26.4-28.6) mmHg (control) vs. 24.2 (22.7-25.3) mmHg; P < 0.001. median (interquartile range, IQR)] thereby increasing Hb-O2 affinity. Inversely, iloprost only showed significant effects in females taking oral contraceptives where P50 was markedly increased and therefore Hb-O2 affinity decreased [28.4 (27.9-28.9) mmHg (control) vs. 34.4 (32.2-36.0) mmHg; P < 0.001]. Prostacyclin-receptor stimulation and subsequent cAMP-mediated ATP release from erythrocytes are discussed as a possible underlying mechanism for the effect of epoprostenol on Hb-O2 affinity. The reason for the sex hormone-modified iloprost effect remains unclear. Being aware of potentially differing effects on Hb-O2 affinity might help select the right prostacyclin (epoprostenol vs. iloprost) depending on the patient and the underlying disease (e.g., acute respiratory distress syndrome vs. peripheral arterial disease).

Sevoflurane anesthesia during acute right ventricular ischemia in pigs preserves cardiac function better than propofol anesthesia

BACKGROUND

The intention of the present study was to evaluate possible cardioprotective properties of inhalation anesthesia with sevoflurane.

METHODS AND MATERIALS

A porcine, open-chest model of right ventricular ischemia was used in 7 pigs receiving inhalation anesthesia with sevoflurane. The model was earlier developed and published by our group, using pigs receiving intravenous anesthesia with propofol. They served as controls. The animals were observed for three hours after the induction of right ventricular ischemia by ligation of the main branches supplying the right ventricular free wall.

RESULTS

In the sevoflurane group, the cardiac output recovered 2 hours after the induction of ischemia and intact right ventricular stroke work was observed. In the propofol group, no such recovery occurred. The release of troponin T was significantly lower than in the sevoflurane group.

CONCLUSIONS

Inhalation anesthesia with sevoflurane seems superior to intravenous anesthesia with propofol in acute right ventricular ischemic dysfunction.

Anesthetic Management of Patients With Pulmonary Hypertension

Advances in the treatment of patients with chronic pulmonary hypertension have greatly improved their functional status and longevity, and increasing numbers of these complex patients are presenting for elective noncardiac surgery. In this communication we will briefly review the classification and pathophysiology of pulmonary hypertension, summarize outpatient pharmacotherapy approaches, and discuss the perioperative preparation and management of these complex patients. With an understanding of the underlying pathophysiology of the disease and pharmacology of these new therapies, combined with careful perioperative planning and care, these patients can safely undergo elective surgical procedures.