CIRCULATORY CHANGES AND PULMONARY LESIONS IN DOGS FOLLOWING INCREASED INTRACRANIAL PRESSURE, AND THE EFFECT OF ATROPINE UPON SUCH CHANGES

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Abstract
Studies were made on dogs using right and left heart catheteriza-tion to measure pulmonary arterial (PAP) and venous pressures (PVP). Cardiac output, systemic arterial pressure and heart rate were also recorded. Increased intracranial pressure (IICP) was produced by inflating a balloon inserted extradurally through a small trephine opening. On the avg., in 18 dogs the mean PVP was 8.2 mm. Hg above intrathoracic before IICP was induced. Afterward the value rose to 18.1 mm. Hg. Concomitant with IICP there was bradycardia, lowered cardiac output and an elevation of PVP and PAP. Gross examination of the lungs at necropsy revealed varying degrees of pulmonary edema, congestion and hemorrhage. Atropine (1.3-1.95 mg.) was administered intraven. to 4 dogs following IICP. The control mean PVP was 5.5 mm. Hg prior to IICP and the PVP following IICP was 13.9 mm. Hg. The IICP was maintained following the admn. of atropine, and the mean PVP fell to 6.6 mm. Hg within 3 min. Atropine produced a tachycardia, raised the cardiac output to its control level and apparently protected the animals from the more severe pulmonary edema, congestion and hemorrhage encountered in the earlier group of 18 dogs which were not given atropine. There was no correlation between systemic arterial pressure and these effects.