Responses to propofol in the pulmonary vascular bed of the rat

Management of Pulmonary Hypertension in the Operating Room

Pulmonary artery hypertension is defined as persistent elevation of mean pulmonary artery pressure > 25 mm Hg with pulmonary capillary wedge pressure < 15 mm Hg or elevation of exercise mean pulmonary artery pressure > 35 mm Hg. Although mild pulmonary hypertension rarely impacts anesthetic management, severe pulmonary hypertension and exacerbation of moderate hypertension can lead to acute right ventricular failure and cardiogenic shock. Knowledge of anesthetic drug effects on the pulmonary circulation is essential for anesthesiologists. Intraoperative management should include prevention of exacerbating factors such as hypoxemia, hypercarbia, acidosis, hypothermia, hypervolemia, and increased intrathoracic pressure; monitoring and optimizing right ventricular function; and treatment with selective pulmonary vasodilators. Recent advances in pharmacology provide anesthesiologists with a wide variety of options for selective pulmonary vasodilatation. Pulmonary hypertension is a major determinant of perioperative morbidity and mortality in special situations such as heart and lung transplantation, pneumonectomy, and ventricular assist device placement.

Acute pulmonary edema associated with propofol: an unusual complication

Propofol is frequently used in the emergency department to provide procedural sedation for patients undergoing various procedures and is considered to be safe when administered by trained personnel. Pulmonary edema after administration of propofol has rarely been reported. We report a case of a 23-year-old healthy male who developed acute cough, hemoptysis and hypoxia following administration of propofol for splinting of a foot fracture. Chest radiography showed bilateral patchy infiltrates. The patient was treated successfully with supportive care. This report emphasizes the importance of this potentially fatal propofol-associated complication and discusses possible underlying mechanisms and related literature.

Acute lung injury using oleic acid in the laboratory rat: establishment of a working model and evidence against free radicals in the acute phase

OBJECTIVE

To determine the optimal model of acute respiratory distress syndrome (ARDS) using oleic acid in our laboratory and to measure the presence or absence of free radicals in this model.

DESIGN

This protocol consisted of 2 phases. During the first phase, various conditions were tested, to include different doses (30 or 50 microliters) of oleic acid, different levels of support (with and without mechanical ventilation), and different injury time periods (sacrifice 4 or 8 hours after injection). During the second phase, animals were randomly assigned to experimental (injured) and control (noninjured) groups for the measurement of free radicals by nitrotyrosine Western blot and by the conversion of hydroethidine to ethidium bromide by superoxide.

SETTING

Multidisciplinary laboratory and animal surgery suite.

PARTICIPANTS

Twenty-seven male Sprague-Dawley rats.

RESULTS

During the first phase, several animal deaths occurred in the high-dose, ventilated groups, whereas there were no deaths in the nonventilated animals. On hematoxylin and eosin stain, injury was greatest in the animals that received the higher dose of oleic acid and that were sacrificed at 8 hours. In the protocol's second phase, oxygen radical assays were negative for all experimental and control lungs.

CONCLUSIONS

During this study, we successfully established a working animal model of ARDS for our laboratory. Our findings to date suggest that free radicals do not contribute to oleic acid lung injury in the early stages.

Propofol (Diprivan-EDTA) counteracts oxidative injury and deterioration of the arterial oxygen tension during experimental septic shock

PURPOSE

Human septic shock can be replicated in the endotoxaemic pig. Endotoxaemia causes a multitude of events, including reduced PaO(2) and increased lipid peroxidation. This study was designed to evaluate the possible effects of a commonly used anaesthetic drug with known antioxidant properties (propofol) during porcine endotoxaemia.

METHODS

Ten pigs were anaesthetised and given a 6 h E. coli endotoxin infusion. The animals received, randomly, a supplementary continuous infusion of propofol emulsion (containing 0.005% EDTA) or the corresponding volume of vehicle (controls). Pathophysiologic responses were determined. Non-enzymatic (by measuring plasma 8-iso-PGF(2 alpha) and enzymatic (by measuring plasma 15-keto-dihydro-PGF(2 alpha)) lipid peroxidations were evaluated. Plasma levels of the endogenous antioxidants alpha- and gamma-tocopherols, were also analysed.

RESULTS

Endotoxaemia increased plasma levels of 8-iso-PGF(2 alpha) (1st-4th h) and 15-keto-dihydro-PGF(2 alpha) (1st-4th h) significantly more in controls than in the propofol+endotoxin group. PaO(2) was significantly less affected by endotoxin in the propofol treated animals (2nd-4th h). Mean arterial pressure (4th-6th h) and systemic vascular resistance (6th h) were reduced significantly more by endotoxin among the propofol-treated animals. Vitamin E (alpha-tocopherol) increased in all animals, significantly more in the propofol+endotoxin group (1/2-6th h) than in the control group.

CONCLUSIONS

Propofol reduced endotoxin-induced free radical mediated and cyclooxygenase catalysed lipid peroxidation significantly. The implication is that propofol counteracts endotoxin-induced deterioration of PaO(2).

Modulation of gamma-aminobutyric acid responses in the rat optic nerve

Depolarising GABA(A) receptor-mediated responses recorded from the optic nerve using a grease gap technique were modulated by classical potentiators of GABA(A) receptors. The benzodiazepine, chlordiazepoxide, the barbiturate, pentobarbitone and the widely used anaesthetic, propofol, all potentiated gamma-aminobutyric acid (GABA) responses. They did so with different maximal efficacies, propofol>pentobarbitone>chlordiazepoxide, and potencies on the basis of EC(50) estimates, chlordiazepoxide>propofol>pentobarbitone. The greater than expected GABA potentiating properties of propofol were explained by a direct hyperpolarising action that occurred in the same concentration range as its action at the GABA(A) receptor but that was unlikely to be mediated by GABA(A) receptors.