J. F. Herrick

Experiments with calculated therapeutic and toxic doses of digitalis: III. Effects on the coronary blood flow☆

Abstract Calculated therapeutic doses of digitalis did not produce a significant change in the coronary blood flow of the dog. This confirms the results of Essex, Herrick, Baldes, and Mann. 28 Calculated toxic doses of digitalis decreased the coronary blood flow of dogs four to six hours after the drug had been administered. The diminution of flow persisted for several days after a single toxic dose of the drug. No myocardial lesions were observed after a therapeutic dose of digitalis, nor were they observed in one animal which received a toxic dose of digitalis. In the latter animal the coronary blood flow returned to the preinjection level within two days. Myocardial lesions were observed in one animal in which the coronary blood flow was kept well below the control level for twelve days by repeated injections of digitalis (toxic range). The diminution of coronary blood flow after the injection of toxic doses of digitalis could not be correlated consistently with changes in the pulse rate or systemic blood pressure. After the injection of toxic doses of digitalis the coronary blood flow returned to the control level in several experiments, and the animals recovered completely.

Studies on peripheral blood flow

Abstract Since the beginning of our work on blood flow in animals about ten years ago, we have investigated many problems concerning the peripheral circulation of the dog. In this report a number of studies have been summarized, and, in some instances, additional data only recently obtained have been included. These studies will serve to illustrate the dynamic nature of the peripheral circulation, as reflected in the blood flow in the femoral artery or vein.

A Thermostromuhr with Direct Current Heater.

From an analysis of the method of measuring blood flow by the Rein 1 2 thermostromuhr it became evident that the passage of the high frequency current through the intact blood vessel, on which a diathermy thermoelement is placed, results essentially in a localized heating of the wall of the blood vessel. Hence it was of interest to construct a thermostromuhr unit similar to the modified type introduced by Baldes, Herrick and Essex 1 in which a direct current heater replaced the platinum electrodes and likewise was spaced midway between the differential thermocouple. This arrangement of the Rein unit differs somewhat from the thermostromuhr described by Schmidt and Walker 4 in which the hot thermojunction is a silver trough interposed between a direct current heater and the blood vessel. The arrangement of the direct current heater and the thermocouple in the bakelite block is shown in Fig. 1. The heating unit is made of No. 36 or 38 B. & S. gauge nichrome wire rolled to a ribbon 0.75 mm. to 0.5 mm. wide. This unit consists of a folded loop ‘c’ soldered to copper wires ‘b’(2 strands number 38 B. & S. gauge), the resistance of the loop being at least one ohm. The unit is held in place by bakelite lacquer. The thermojunctions at ‘a’ are made by soldering copper wires (0.0016 in.) to a constantan wire (0.002 in.) which is embedded in the groove ‘d.’ The fine copper wires as well as the copper wires attached to the heater are then soldered to braided copper wires (17 strands 0.003 in. tinned copper). All grooves are filled by several applications of bakelite lacquer 3128 or Sterling varnish M-472, each application being followed by suitable air drying and baking.

THE THERMO‐STROMUHR METHOD OF MEASURING BLOOD FLOW

The purpose of the following article is to bring to the attention of the physicist, who is interested in the application of physics to physiology, a typical problem in biophysics. Rein, a physicist at the University of Freiburg, was confronted with the necessity of knowing accurately the blood supply to a certain organ. Because the various standard methods proved inadequate he developed an ingenious method which he calls the thermo‐stromuhr. This method of determining blood flow has been modified in two respects: in the method of measuring the heating energy applied to the blood vessel, and in the method of construction of the diathermy‐thermoelements. A tuned circuit is used which permits the measurement of resistance by the method of substitution. The diathermy‐thermoelements are made from transparent bakelite and the process of construction is fully described. The theory of the thermo‐stromuhr as well as the experimental application is explained in detail.

Digitalis and Coronary Blood Flow

Considerable work has been done in an effort to evaluate the effect of digitalis on coronary blood flow. A wide variety of methods have been employed and the results on the whole have been contradictory. Gilbert and Fenn 1 have reviewed the pertinent literature which preceded their report. These workers, after an extensive series of acute experiments in which they studied the effect of a number of preparations of digitalis on the outflow from the coronary sinus of the dog by use of the Morawitz cannula, concluded that digitalis preparations may exert a vasoconstrictor action on the coronary arteries. The use of the Morawitz cannula requires deep anesthesia, an open thorax and artificial respiration; consequently, the period of observation is necessarily relatively brief. For a number of years we have been studying coronary blood flow in the trained animal. 2 It has been possible to measure the blood flow in one of the coronary arteries of the dog as often as desired, and in some experiments for as long as 2 weeks. Formerly we used the thermostromuhr method of Rein, but recently we have employed the method described by Baldes and Herrick, 3 which makes use of a direct current heater. We have, therefore, been able to digitalize animals by divided doses in a manner comparable to the clinical method and at the same time observe the effect on the coronary blood flow. Seven dogs were prepared for these experiments. They were trained to lie quietly and subsequently the thermostromuhr unit was placed on the circumflex branch of the left coronary artery under general anesthesia and with sterile technic as described in a previous paper. Three of the animals fulfilled the following requirements sufficiently well to permit their use in this study: 1. The body Item perature and pulse rate of the dog must have remained within normal limits for at least 24 hours following the operation. 2. The coronary blood flow must have remained relatively constant for a like period. 3. Prior to injection of the drug the dog must have taken food without hesitation and behaved in all respects like a relatively healthy dog.

Experimental Analysis of Rein's Thermostromuhr for Small Flows

The experimental curve is determined which shows the relation between the flow of blood in cubic centimeters per minute and the deflection of the galvanometer in millimeters for a range of flows between zero and about 3 cc per minute. The curve is similar to that calculated by Burton for the Rein thermostromuhr and that experimentally obtained by Jongbloed and Noyons with their aerothermorheograph. The maximal deflection of the galvanometer occurs at a flow (Ringers solution) of about 0.08 cc per minute and for smaller or greater flows the deflection decreases. Since the deflection of the galvanometer approaches zero for very small flows and becomes zero for cessation of flow, whereas it usually decreases for increase of flow, one must be careful to distinguish between a cessation of flow and an increase. Difficulty will not arise if sufficient time is allowed for the establishment of thermal equilibrium. Certain controversies have arisen because this particular limitation of Reins thermostromuhr was di...

Visualization of Intrathoracic Vena Cava, Effect of Respiration on Diameter of the Vessel

Summary and Conclusions A method of visualizing, roentgenologically, blood vessels such as the vena cava is described. Significant changes in the diameter of the thoracic portion of the posterior vena cava were not observed when the dog was lying on its side. Slight changes in diameter occurred during the respiratory cycle when the dog was standing. The changes in diameter were too insignificant, even in the standing position, to interfere with thermal and electric contacts when the thermostromuhr method of measuring blood flow is used.