Abstract:
A method and apparatus for administering large quantities of blood which has been stored at less than ambient temperatures continuously and rapidly to a patient at physiologically acceptable temperatures and pressures in a short time wherein the blood is continuously directed through a plurality of discrete capillary paths in heat-exchange relationship with a warming medium, the number of said paths being such that the pressure of the blood is not substantially increased, and the blood is rapidly administered directly to a patient.

Description:
This application is a continuation of application Ser. No. 415,817, filed Sept. 8, 1982, now abandoned. 
    
    
     This invention relates to blood transfusions and particularly to a method and apparatus for rapidly raising the temperature of blood in order that large quantities can be administered in a short time. 
     BACKGROUND AND SUMMARY OF THE INVENTION 
     In traumatically injured patients, hemorrhagic patients, and surgery patients, it is known that large quantities of blood should preferably be administered in a short time at body temperature. Inasmuch as whole blood is normally stored at lower temperatures such as 4° C., it is difficult to warm such blood in sufficient quantities as required. In one prior method, blood is dripped into patients by gravity and forced by pressure through blood warming coils placed in a reservoir of water warmed with a heating element. In this technique, the infusion rate is not greater than 25 ml/min. This method requires about 30 minutes to administer a single unit of whole blood. 
     In another method that has been proposed, microwave heaters are provided which may cause red cell destruction. Efforts to increase the rate of heating in the method of warming through coils also causes red cell destruction and possible rupture of the coils. 
     In accordance with the invention, the method and apparatus for administering large quantities of blood which has been stored at less than ambient temperatures continuously and rapidly to a patient at physiologically acceptable temperatures and pressures in a short time comprises directing blood through a plurality of discrete capillary paths in heat-exchange relationship with a warming medium, the number of said paths being such that the pressure of the blood is not substantially increased, and the blood is rapidly administered directly to a patient. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic diagram of the method and apparatus embodying the invention. 
     FIG. 2 is a fragmentary view on an enlarged scale showing a portion of the apparatus. 
     FIG. 3 is a fragmentary view taken along the line 3--3 on an enlarged scale. 
     FIG. 4 is a fragmentary sectional view taken along the line 4--4 in FIG. 3. 
     FIG. 5 is a perspective view of a portion of the appartus. 
     FIG. 6 is a hydraulic diagram of the warming medium portion of the apparatus showing the flow during priming. 
     FIG. 7 is a hydraulic diagram similar to FIG. 6 showing the flow during operation. 
    
    
     DESCRIPTION 
     Referring to FIG. 1, the method and apparatus embodying the invention comprises directing the stored blood which is at a lower refrigeration temperature (i.e. 4° C.) having been refrigerated from a plurality of sources 10 by a pump 11 to a drip chamber 12 and then, in turn, to a heat exchanger device 13 to a drip chamber 14 and then through a line 15 at venous pressure directly and rapidly to the patient. An air bubble detector 15 is provided in line 15, in accordance with common practice and functions to shut off flow if air bubbles or foam are present. A line extends from a saline source 10a through a valve 10b for purging the system prior to passage of the blood. 
     Referring to FIG. 5, the heat exchanging apparatus 13 comprises a generally rectangular housing having a top wall 16, a bottom wall 17, side walls 18, 19, a front wall 20, and a rear wall 21. The housing further includes a first inlet 22 for introducing a warming medium such as a saline or water solution and a first outlet 23 for removing the saline solution. The housing further includes a second inlet 24 for blood and a second outlet 25 for blood. Means are provided within the medium to direct the blood in a plurality of discrete capillary paths in heat exchange relationship with the warming medium. This comprises spaced manifolds or headers 26, 27 and a plurality of discrete tubes 28 connected to the manifolds 26, 27. The tubes are made of inert, non-toxic plastic such as silicone rubber, made and sold by Dow Chemical Company under the trademark Silastic. The manifolds are both preferably made of plastic similar to tubes 28 and are connected to one another by fusing the tubes into the headers in the manner shown in FIGS. 2 and 3. 
     The tubes have ultra thin walls. The cross section of the passage through the tubes preferably ranges between 0.05 and 0.06 inch and the wall thickness ranges between 0.025 and 0.030 inch. In a preferred arrangement, the tubes have an internal diameter of 0.062 inch and an external diameter of 0.095 inch. 
     The length of the tubes is substantially greater than the distance between the two headers 26, 27 and an internal wall 28 is provided dividing the housing into two parts, the wall having an opening 29. The tubes are arranged in a figure-8 pattern passing through the opening 29. The wall with the opening 29 insures a good circulation of the warming medium from the first inlet 22 to the second outlet 23. 
     The term capillary as used herein means thin walled tubing having a small internal diameter to define a film of blood flowing in laminar fashion in heat-exchange relation to the warming medium. 
     Inlets 22, 23 are connected by tubes to a warming device 30 which functions to provide a medium such as a saline or water solution. The device 30 controls the saline bath temperature at the desired temperature, preferably 40° and delivers it to the heat exchanging apparatus 13. 
     Referring to FIG. 7, the warming device 30 comprises a closed loop system including a pump 31 that pumps the warming medium such as the saline solution through a heater 32 that is controlled by a thermocouple 33 and delivers the medium to a line 34 to the linet 22 of the heat exchanging apparatus 13 and then from the outlet 23 the saline solution is returned to a line 35 and through a three-way solenoid valve 36 to the inlet of the pump 31. 
     Referring to FIG. 6, in order to prime the circuit, the three-way valve 36 is opened permitting additional fluid to be provided and pumped through the heat exchanging apparatus 13 and then through a two-way solenoid valve 37 in a bypass line 38 to drain unitl the system is filled. 
     Pressure relief valves 39, 40 and associated lines 41, 42 are provided upstream and downstream of the valve 37 and function to relieve the pressure to drain if it exceeds a predetermined value or if kinking of lines 41, 42 occurs. 
     It has been found that in use substantial quantities of blood can be heated without adverse effect on the blood and delivered directly and rapidly at low pressure to the patient. For example, blood can be supplied at normal physiological temperature of 37.2° C. after being heated from 4° C. and at a rate of flow of 200 ml/min. 
     In order to control the flow and rate of temperature exchange, pressure sensors and temperature sensors are provided at the inlet and outlet to heat exchanging apparatus 13 as shown in FIG. 1. 
     Typical experimental results that have been achieved with the method and apparatus are as follows: 
     
         ______________________________________TRIAL  T IN   T OUT    BFL  T OF WARMING FLUID______________________________________1      25.5   37.0     100  38.52      16.3   36.0     150  38.53      21.0   35.8     100  38.54      22.0   35.8     100  38.55      16.0   36.8     100  39.06      10.2   36.8     200  40.07      10.2   37.0     200  40.0______________________________________ Where T = temperature in degrees Centigrade BFL = flow of blood out of heatexchanging apparatus in ml/min. 
    
     Laboratory tests on some of the blood trials indicated the following: 
     
         __________________________________________________________________________TRIALWBC RBC       HGB HCT              MCV MCH MCHC                          PLT                             NA K__________________________________________________________________________PRE 33.60    3.80       11.8           33.6              87.8                  30.8                      35.1                          94.                             153                                4.69POST 34.30    4.34       13.2           38.2              87.9                  30.5                      34.7                          106                             152                                5.51PRE 49.00    3.83       12.7           38.3              100.                  33.3                      33.2                          298                             XXX                                XXXXPOST 49.00    3.95       13.3           39.7              100.                  33.7                      33.0                          271                             145                                8.46PRE 53.20    3.38       10.3           32.3              94.0                  30.6                      32.3                          N.D.                             152                                3.08POST 54.00    4.27       13.2           40.7              94.0                  31.0                      32.7                          N.D.                             153                                1.60PRE 64.80    3.22       9.10           28.0              87.0                  28.1                      32.6                          N.D.                             143                                20.1POST 66.40    4.27       12.3           37.2              87.0                  28.8                      33.4                          N.D.                             140                                19.9PRE 72.40    4.60       13.2           40.3              87.6                  28.7                      32.8                          123                             137                                22.0POST 72.10    4.63       13.4           40.7              87.7                  29.1                      33.1                          96.                             137                                22.0__________________________________________________________________________ Wherein: PRE = before entering the heatexchange apparatus POST = after leaving the heatexchanging apparatus WBC = white blood cell count RBC = red blood cell count HGB = hemoglobin count  HCT = hematocrit MCV = mean corpuscular volume MCH = mean corpuscular hemoglobin MCHC = mean corpuscular hemoglobin concentration PLT = platelets NA = sodium K = potassium