Abstract
Intravenous pressure may be estimated clinically either by direct or indirect methods. Direct methods, while more accurate, have certain disadvantages—impossibility of frequent determinations in the same patient, the necessary prerequisite of strict asepsis, the possibility of clot formation in the needle, the difficulty sometimes encountered in puncturing a vein in obese persons, and occasionally apprehension of patients which results in an elevated venous pressure.
The indirect or bloodless methods are free from most of these objections but the prevailing procedures have other disadvantages. The most serious objections are that the end-point is not sharp and correct estimations are therefore difficult, that the impossibility of applying such methods to obese persons in whom the veins are not visible above the surface of the skin, and that the end-point must be determined quickly.
The method we have developed is based on the principle that the superficial veins on the dorsum of the hand can be visualized easily in a darkened room by placing a small light, such as an ordinary pocket flashlight, against the palmar surface, preferably in the interosseous spaces. By this transillumination the superficial veins appear as black bands which can be obliterated by moderate pressure, thus distinguishing them from shadows cast by ligaments or bone. The mouth of a small glass funnel is covered by thin rubber dam held securely in place by thread tied tightly in a previously prepared groove near the rim. A small hole is then cut in the center of the rubber dam through which the vein to be examined is visualized.
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