Pulmonary Microembolism Associated with Massive Transfusion: 11. The Basic Pathophysiology of Its Pulmonary Effects JOHN BARRETT, M.B.,*t INGEMAR DAWIDSON, M.D.,t H. N. DHURANDHAR, M.B.B.S., D.C.P. (LOND.),§ EDITH MILLER, M.S., MARTIN S. LITWIN, M.D.** In animals pulmonary hypertension, a decrease in total body 02 consumption and metabolic acidosis occur after transfusion of blood with an elevated screen filtration pressure (SFP) through standard blood transfusion filters. The purpose of this study was to define in detail the pulmonary abnormalities that develop following transfusion of blood with an elevated SFP through standard blood transfusion filters. Exchange transfusions of approximately twice blood volume were administered through standard commercially available blood transfusion filters (measured pore size-200 microns) to 6 animals. SFP measurements verified the presence of large numbers of aggregates in the transfusions. Although filters reduced SFP of the stored blood somewhat, numerous microaggregates passed the filters, and post-filtration SFP remained high. After transfusion average 02 consumption decreased to 77% of normal and metabolic acidosis developed. Pulmonary arterial hypertension was associated with an increase in pulmonary shunting of blood and a decrease in pulmonary diffusing capacity. The presence of extensive numbers of microemboli in the pulmonary arteriolar and capillary bed was confirmed by microscopic examination of lung tissue.
BLOOD stored under standard blood bank conditions develops microaggregates of platelets, white blood cells and fibrin (15-18, 24-27). Determination of screen filtration pressure (SFP) allows the detection of such
microaggregates 1,2,10,11,14-16,19,21,24,26 Microaggregates may be a factor in the etiology of pulmonary insufficiency following blood transfusions.1 2 6 8 9 13 17,19,25 In animals pulmonary hypertension, a decrease in total body 02 consumption and metabolic acidosis occur after transfusion ofblood with an elevated SFPthrough standard Submitted for publication April 7, 1975. *Ainsworth Scholar from the National University of Ireland.
tSurgical Research Fellow. §Assistant Professor of Pathology. **Professor of Surgery. Supported by Contract No. DADA 17-67-C-7049, Surgical Directorate, U. S. Army Medical Research and Development Command.
From the Departments of Surgery and Pathology, Tulane University Medical School, New Orleans, Louisiana 70112
commercial blood transfusion filters.9 The purpose of this study was to define in detail the pulmonary abnormalities that develop following transfusion of blood with an elevated SFP through standard blood transfusion filters. Materials and Methods Prior to experiments canine blood was obtained for transfusion using methods previously described.11 After storage at 4 C for 5 days, the SFP of each unit ofblood was measured according to Swank's method.28 If the SFP was elevated, the blood was used in the experimental study. pH and lactic and pyruvate acid concentrations were determined in each blood bag and the blood was inspected for gross clots before being used. Mongrel dogs were anesthetized with intravenous sodium pentobarbital, 25 mg/kg. Each was ventilated with room air through an endotrachial tube using a Harvard respiratorpump set atarate of 12-14 cycles perminute and a tidal volume of 25 ± 5 cc/kg. Tidal volume was monitored using a spirometer (Wrights' Respirometer Mark 12). Muscle relaxation was maintained using small doses of pancuronium bromide given intravenously as necessary. A right jugular venous cut-down was performed, and under fluoroscopic control two catheters were passed, one into the left pulmonary artery and the other into the right atrium. The femoral artery and vein were cannulated using widebore polyvinyl catheters passed through a right femoral cut-down. The respiratory rate and tidal volume in each animal were then adjusted until femoral arterial
56
Vol. 182 NO. I ,
PULMONARY EFFECTS OF MASSIVE TRANSFUSION
oxygen and carbon dioxide tensions and pH were stabile and reproducible. Once the animal was stabilized on room air, mixed venous oxygen tension was determined on blood from the right atrium. Arterial oxygen saturation and mixed venous oxygen saturation were measured using an oximeter (American Optical Company), and oxygen consumption was determined using an oxygen consumption meter (Oxford Instrument Company, Jackson, Mississippi). Arterial blood lactate and pyruvate concentrations were determined by enzymatic procedures.18'22 Femoral artery, pulmonary artery, and right atrial pressures were recorded
continuously. Respirations were then changed from room air to 100% oxygen, care being taken to prevent any oxygen leakage in the system. The animal was allowed to restabilize on 100% oxygen and the previous determinations were repeated until reproducible results were obtained. The average time taken to achieve restabilization on 100% oxygen was 45 minutes.
57 For each unit of blood, SFP, hematocrit, and white blood cell and platelet counts were determined both before and after filtration. Each blood transfusion filter was replaced after three units (1500 cc) of blood had passed through it. The average time necessary to complete each of the exchange transfusions was 90 minutes. Once transfusion had been completed, Qs/Qt, DO2 and VA/QB were again determined. At the conclusion of the experiment, each animal was sacrificed, and the positions of the tips of the pulmonary artery and the right atrial catheters were confirmed. A sample of lung tissue was also obtained for microscopic pathological examination. Group II-Control Animals. Three animals served as controls. Each underwent the full 6½ hour protocol of the experiment as did Group I animals; however, exchange transfusions were not performed.
The anatomical shunting of blood away from the pulmonary alveolus (Qs/Qt) (per cent pulmonary shunt or direct pulmonary venous admixture) was estimated by means of the shunt equation.3 The blood at the end of the pulmonary capillary was assumed to be fully saturated since the animals were breathing 100% oxygen (FI02 = 1). The diffusing capacity ofthe lungs for oxygen (DQ) was calculated using a modification of Bohr's steady state oxygen method.5'7'20 Ventilation: perfusion ratios (VAIQB) were determined using the oxygen-carbon dioxide diagram of Rahn and
Fenn.7,21 Animals were then divided into two groups. Group I-Experimental Animals. The blood volume of each of 6 animals was assumed to be 10%o of its body weight. Each animal underwent an exchange transfusion of twice its calculated blood volume using the previously stored blood. Average pH of the infused blood was 7.02 + 0. 10, and its average lactate and pyruvate concentrations were 82.3 ± 10 mg% and 3.1 + 1.2 mg% respectively. Immmediately prior to infusion, each blood bag was warmed to 37 C in a water bath. It was then thoroughly mixed by gentle agitation and grossly inspected to insure the absence of blood clots. The blood was infused in 50 cc aliquots into the femoral vein and at the same time 50 cc aliquots were withdrawn from the femoral artery. Quantities of blood equal to that removed for the various sampling procedures were replaced during this period. All blood was filtered through standard commercial blood transfusion filters (Cutter Saftifilter blood administration set 865-08) with a measured pore size of 200 microns.
0
BEFORE INFUSION
AFTER INFUSION
FIG. 1. Exchange transfusion with blood containing microaggregates. After transfusion oxygen consumption decreased to 77% of normal. Metabolic acidosis became obvious as blood lactic acid concentration increased out of proportion to an increase in pyruvic acid concentration and average arterial blood pH dropped.
BARRETT AND OTHERS 26
Pulmonory
Artery Pressure !20
(mmHgI)
Ann. Surg. July 1975
blood cell counts before and after filtration were not
statistically significant. Representative sections of lung tissue were routinely stained with- hematoxylin and eosin (H&E), and with Periodic-acid-Schiff (PAS) and Verhoeff-Van Gieson (VVG) stains as the need arose. Lung sections in four of the six dogs showed diffuse embolization in the pulmonary microcirculation at the level of and distal to the respiratory bronchioles (Figs. 5 and 6). The pulmonary arteries, pre-capillary arterioles and capillaries were distended with homogenous to granular PAS positive emboli containing aggregated disintegrating polymorphonuclear leucocytes. The pulmonary veins
F
-O00
Femoral 2 !00 Artery Pressure I15014 ItF (mmHg) -2
I_
were free of emboli or debris. Emboli were not seen in the pulmonary microcirculation oftwo of the six dogs, but one ofthese showed an organizing thrombus in a pulmonary artery at the level of the terminal bronchiole. The other had noncaseating granulomas in the lung. Focal hemorrhages, atelectasis, alveolar capillary congestion and alveolar cell proliferation was present in the lungs of all dogs. Group Il-ControlAnimals. The only change observed in
I
ISO
T
Right Atrial Pressure
(c mH.O BEFORE INFUSION
AFTER INFUSION
FIG. 2. Exchange transfusion with blood containing microaggregates. Even though right atrial and femoral arterial pressures did not change, severe pulmonary arterial hypertension was induced.
Results Group I-Experimental Animals. During transfusion average 02 consumption on room air decreased by 23% from 80 + 16 ml/min before transfusion to 62 + 11 ml/min after transfusion (p
BLOOD stored under standard blood bank conditions develops microaggregates of platelets, white blood cells and fibrin (15-18, 24-27). Determination of screen filtration pressure (SFP) allows the detection of such
microaggregates 1,2,10,11,14-16,19,21,24,26 Microaggregates may be a factor in the etiology of pulmonary insufficiency following blood transfusions.1 2 6 8 9 13 17,19,25 In animals pulmonary hypertension, a decrease in total body 02 consumption and metabolic acidosis occur after transfusion ofblood with an elevated SFPthrough standard Submitted for publication April 7, 1975. *Ainsworth Scholar from the National University of Ireland.
tSurgical Research Fellow. §Assistant Professor of Pathology. **Professor of Surgery. Supported by Contract No. DADA 17-67-C-7049, Surgical Directorate, U. S. Army Medical Research and Development Command.
From the Departments of Surgery and Pathology, Tulane University Medical School, New Orleans, Louisiana 70112
commercial blood transfusion filters.9 The purpose of this study was to define in detail the pulmonary abnormalities that develop following transfusion of blood with an elevated SFP through standard blood transfusion filters. Materials and Methods Prior to experiments canine blood was obtained for transfusion using methods previously described.11 After storage at 4 C for 5 days, the SFP of each unit ofblood was measured according to Swank's method.28 If the SFP was elevated, the blood was used in the experimental study. pH and lactic and pyruvate acid concentrations were determined in each blood bag and the blood was inspected for gross clots before being used. Mongrel dogs were anesthetized with intravenous sodium pentobarbital, 25 mg/kg. Each was ventilated with room air through an endotrachial tube using a Harvard respiratorpump set atarate of 12-14 cycles perminute and a tidal volume of 25 ± 5 cc/kg. Tidal volume was monitored using a spirometer (Wrights' Respirometer Mark 12). Muscle relaxation was maintained using small doses of pancuronium bromide given intravenously as necessary. A right jugular venous cut-down was performed, and under fluoroscopic control two catheters were passed, one into the left pulmonary artery and the other into the right atrium. The femoral artery and vein were cannulated using widebore polyvinyl catheters passed through a right femoral cut-down. The respiratory rate and tidal volume in each animal were then adjusted until femoral arterial
56
Vol. 182 NO. I ,
PULMONARY EFFECTS OF MASSIVE TRANSFUSION
oxygen and carbon dioxide tensions and pH were stabile and reproducible. Once the animal was stabilized on room air, mixed venous oxygen tension was determined on blood from the right atrium. Arterial oxygen saturation and mixed venous oxygen saturation were measured using an oximeter (American Optical Company), and oxygen consumption was determined using an oxygen consumption meter (Oxford Instrument Company, Jackson, Mississippi). Arterial blood lactate and pyruvate concentrations were determined by enzymatic procedures.18'22 Femoral artery, pulmonary artery, and right atrial pressures were recorded
continuously. Respirations were then changed from room air to 100% oxygen, care being taken to prevent any oxygen leakage in the system. The animal was allowed to restabilize on 100% oxygen and the previous determinations were repeated until reproducible results were obtained. The average time taken to achieve restabilization on 100% oxygen was 45 minutes.
57 For each unit of blood, SFP, hematocrit, and white blood cell and platelet counts were determined both before and after filtration. Each blood transfusion filter was replaced after three units (1500 cc) of blood had passed through it. The average time necessary to complete each of the exchange transfusions was 90 minutes. Once transfusion had been completed, Qs/Qt, DO2 and VA/QB were again determined. At the conclusion of the experiment, each animal was sacrificed, and the positions of the tips of the pulmonary artery and the right atrial catheters were confirmed. A sample of lung tissue was also obtained for microscopic pathological examination. Group II-Control Animals. Three animals served as controls. Each underwent the full 6½ hour protocol of the experiment as did Group I animals; however, exchange transfusions were not performed.
The anatomical shunting of blood away from the pulmonary alveolus (Qs/Qt) (per cent pulmonary shunt or direct pulmonary venous admixture) was estimated by means of the shunt equation.3 The blood at the end of the pulmonary capillary was assumed to be fully saturated since the animals were breathing 100% oxygen (FI02 = 1). The diffusing capacity ofthe lungs for oxygen (DQ) was calculated using a modification of Bohr's steady state oxygen method.5'7'20 Ventilation: perfusion ratios (VAIQB) were determined using the oxygen-carbon dioxide diagram of Rahn and
Fenn.7,21 Animals were then divided into two groups. Group I-Experimental Animals. The blood volume of each of 6 animals was assumed to be 10%o of its body weight. Each animal underwent an exchange transfusion of twice its calculated blood volume using the previously stored blood. Average pH of the infused blood was 7.02 + 0. 10, and its average lactate and pyruvate concentrations were 82.3 ± 10 mg% and 3.1 + 1.2 mg% respectively. Immmediately prior to infusion, each blood bag was warmed to 37 C in a water bath. It was then thoroughly mixed by gentle agitation and grossly inspected to insure the absence of blood clots. The blood was infused in 50 cc aliquots into the femoral vein and at the same time 50 cc aliquots were withdrawn from the femoral artery. Quantities of blood equal to that removed for the various sampling procedures were replaced during this period. All blood was filtered through standard commercial blood transfusion filters (Cutter Saftifilter blood administration set 865-08) with a measured pore size of 200 microns.
0
BEFORE INFUSION
AFTER INFUSION
FIG. 1. Exchange transfusion with blood containing microaggregates. After transfusion oxygen consumption decreased to 77% of normal. Metabolic acidosis became obvious as blood lactic acid concentration increased out of proportion to an increase in pyruvic acid concentration and average arterial blood pH dropped.
BARRETT AND OTHERS 26
Pulmonory
Artery Pressure !20
(mmHgI)
Ann. Surg. July 1975
blood cell counts before and after filtration were not
statistically significant. Representative sections of lung tissue were routinely stained with- hematoxylin and eosin (H&E), and with Periodic-acid-Schiff (PAS) and Verhoeff-Van Gieson (VVG) stains as the need arose. Lung sections in four of the six dogs showed diffuse embolization in the pulmonary microcirculation at the level of and distal to the respiratory bronchioles (Figs. 5 and 6). The pulmonary arteries, pre-capillary arterioles and capillaries were distended with homogenous to granular PAS positive emboli containing aggregated disintegrating polymorphonuclear leucocytes. The pulmonary veins
F
-O00
Femoral 2 !00 Artery Pressure I15014 ItF (mmHg) -2
I_
were free of emboli or debris. Emboli were not seen in the pulmonary microcirculation oftwo of the six dogs, but one ofthese showed an organizing thrombus in a pulmonary artery at the level of the terminal bronchiole. The other had noncaseating granulomas in the lung. Focal hemorrhages, atelectasis, alveolar capillary congestion and alveolar cell proliferation was present in the lungs of all dogs. Group Il-ControlAnimals. The only change observed in
I
ISO
T
Right Atrial Pressure
(c mH.O BEFORE INFUSION
AFTER INFUSION
FIG. 2. Exchange transfusion with blood containing microaggregates. Even though right atrial and femoral arterial pressures did not change, severe pulmonary arterial hypertension was induced.
Results Group I-Experimental Animals. During transfusion average 02 consumption on room air decreased by 23% from 80 + 16 ml/min before transfusion to 62 + 11 ml/min after transfusion (p
