To the Editor:- It is sometimes necessary to place an intravenous catheter and a blood pressure cuff on the same extremity. In such cases backflow of blood into the intravenous line can occur on inflation of the blood pressure cuff. Several methods to avoid this incident are available. Some commercially available intravenous tubing incorporates a one-way valve. A simple way is to close a stopcock on the intravenous line during blood pressure measurements. Placing a length of intravenous line in a blood pressure cuff, introduced by Brin et al., seems unreliable because this method does not occlude intravenous line completely.
Here we describe a method to prevent backflow using a spectacle case (Figure 1). A three-way stopcock or T-connector is placed in the air line connecting the sphygmomanometer and blood pressure cuff. The open limb of the stopcock or connector is connected to another small blood pressure cuff. The intravenous tubing is inserted between the halves of the spectacle case, and the case is then rolled up in the smaller cuff. When the blood pressure cuff on the patient's arm is inflated for a measurement, the smaller cuff is also inflated, pinching the intravenous line placed between case covers. The device completely stops flow through the line only during blood pressure measurements.
Possible problems of this device are influence on blood pressure measurement and damage to intravenous tubing, although in our experiences, connection of the device to an automatic sphygmomanometer did not change blood pressure recording, and we could not find any damage in intravenous tubing even after multiple pinches by this device.
Misuzu Kondo, M.D.
Ryoichi Nomura, M.D.
Department of Anesthesia; Otsu Red Cross Hospital; Otsu, Shiga, Japan
Taijiro Enoki, M.D.
Department of Anesthesia; Kyoto University Hospital; Kyoto, Japan