Effect of bretylium tosylate (Darenthin) on pulmonary circulation.

BRETYLIUM tosylate (Darenthin, Burroughs Wellcome), is one of the series of benzyl quaternary ammonium compounds which blocks selectively the peripheral sympathetic nervous system without antagonizing the effects of epinephrine. This block occurs without depression of the parasympathetic or central nervous system.' Its effect on the pulmonary circulation has not hitherto been investigated. ,_ ., , ° Methods Experiments were carried out on eight sheep ranging from 40 to 45 Kg. The fasting supine animals were anesthetized with 10 to 15 mg./Kg. thiopental (Thiopentone) injected intravenously. This dose was followed by a continuous intravenous saline drip of 2.0 to 2.5 ml./min. containing 0.20 to 0.25 mg./Kg./min. thiopental and 0.15 to 0.20 mg./Kg./min. heparin. A cuffed Magill tube (no. 12) was used for intubation of the trachea and a no. 7 cardiac catheter was passed through the femoral vein and introduced into the pulmonary artery. In two animals a no. 8 double-lumen catheter was used instead with the distal end wedged into the artery to measure pulmonary "capillary" pressure. A cannula was inserted into the femoral artery and a thermometer into the rectum. Oxygen content of the systemic (Ca ) and pulmonary (Cv ) arterial blood and total hemoglobin were determined speetrophotometrically. Expired nir (VE) was collected for 1% to 2y2 minutes in Douglas bags; their composition was analyzed by the Haldane method. Carbon dioxide content and pH were measured in the arterial blood of three animals. Their arterial CO2 tension (Pa ) and alveolar ventilation (V J were calcuC02 lated as described elsewhere. Pulmonary arterial (Ppa.) and systemic arterial (Pf.a.) pressures were measured by transducers and recorded on a Sanborn multichannel directwriting oscillograph. In two animals pulmonary arterial wedge pressure (Pp.n.w.) a n d right ventricular pressure ( P r v ) were recorded simultaneously. A point 10 cm. above the back of the