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Effects of rapid infusion with high pressure and large-bore IV tubing on red blood cell lysis and warming
ORIGINAL CONTRIBUTION blood, infusion, effects of high pressure
Effects of Rapid Infusion with High Pressure and Large-Bore IV Tubing on Red Blood Cell Lysis and Warming A prototype large-bore intravenous tubing was developed and tested. Mean flow rates for blood (Hct 45%) and tap water were determined for several catheters at 600 m m Hg, 300 m m Hg, and gravity flow and were statistically analyzed by calculating the 95% confidence intervals. The degree of hemolysis during high pressure and flow was determined by measuring the plasma free hemoglobin using the spectrophotometric method. To determine if cold. banked blood can be adequately warmed at high flow rates, thermocouples were used to measure the blood temperature before and after rapid infusion through a bloodwarmer. Results included m a x i m u m flow rates of 1,764 mL/min for tap water, and 1,714 mL/min for blood (Hct 45%) at 600 m m Hg through the large-bore tubing and an 8.5-F catheter. Flow rates for other pressure and catheter combinations were tabulated. The plasma-free hemoglobin increased slightly compared to controls with high pressure (<~ 600 m m Hg) and flow rates. The increase correlated with less than 1% red blood cell Iysis in all trials. When 13 C blood was infused through a warmer, blood temperature increased to 25.3 C at the maximum flow rate of 732 mL/min. Slightly higher heat gain resulted with slower infusion rates. We conclude that the prototype large-bore tubing and up to 600 m m Hg pressure provide rapid flow rates without significant hemolysis. Blood warming may be inadequate at higher flow rates. [Mateer JR, Perry BW, Thompson BM, Tucker JF, Aprahamian C: Effects of rapid infusion with high pressure and large-bore IV tubing on red cell lysis and warming. Ann Emerg Med October 1985;14:966-969.]
James R Mateer, MD* Billy W Perry, PhD1Bruce M Thompson, MD* John F Tucker, MD* Charles Aprahamian, MD* Milwaukee, Wisconsin From the Section of Trauma and Emergency Medicine* and the Department of Pathology,1 Medical College of Wisconsin, Milwaukee, Wisconsin. Received for publication October 18, 1984. Revision received April 5, 1985. Accepted for publication May 30, 1985. Address for reprints: James R Mateer, MD, Section of Trauma and Emergency Medicine, 8700 West Wisconsin Avenue, Milwaukee, Wisconsin 53226.
INTRODUCTION Rapid and aggressive fluid resuscitation is an important factor for improved salvage of the hypotensive trauma victim. In recent studies, l,2 we have demonstrated that appropriate peripheral catheter selection, the use of large-bore central venous catheters (8- to 9-F), high-pressure infusion (~< 600 mm Hg), and experimental large-bore tubing (up to 6.4 m m internal diameter [ID]) can significantly improve flow rates. Based on the data in these studies, we designed a prototype large-bore IV tubing suitable for clinical use, and we tested the model to determine maximum flow rates and their effect on red blood cell lysis and warming.
METHOD To calculate flow rates, Ringer's lactate in 1,000-mL bags was replaced with tap water at room temperature after determining these liquids have identical flow rates.] All bags were elevated one meter from the end of the catheter to the top of the fluid level. Fluids were run through the prototype large-bore, 5mm-ID, 235-cm-long IV tubing (Medex Inc, Hilliard, Ohio) with inline 170-~m filter. Pressures of 300 m m Hg and 600 m m Hg were generated by compressing the solution bags with a modified 2 Infuser/1 ® (Medical Innovations, Inc, Phoenix, Arizona) and were standardized with a calibration analyzer (model RT-200, Trimeter Instrument Corporation, Lancaster, Pennsylvania}. Flow rates were calculated for the Arrow ® 8.5-F introducer sheath (Arrow International, Inc, Reading, Pennsylvania) and the Argyle ® Medicut ® 14- and 16-gauge catheters (Sherwood Medical Industries, St Louis, Missouri) by averaging the time for 100 mL in three consecutive trials. Each mean flow rate was analyzed statistically by calculating the 95% confidence interval
14:10October 1985
Annals of Emergency Medicine
966/59
EFFECTS OF RAPID INFUSION Mateer et al
Fig. 1. Degree of warming that occurs
when 13-C red blood cells (Hct 45%) are infused rapidly through a blood-
35-
warmer.
(95% CI). For the blood flow studies, outdated units (37 + 1 days) of banked packed red blood cells (PRBCs) were diluted with normal saline to a hematocrit of 45%. Flow rates through the prototype tubing and a Fenwal blood warmer (model BW-5} using a standard blood warming bag (Fenwal Laboratories, Deerfield, Illinois) were calculated for diluted PRBCs. Tubing was changed or filters were cleaned after every 600 mL of blood flow to prevent filter obstruction. The degree of hemolysis during high pressure and flow was determined by measuring the plasma-free hemoglobin using the spectrophotometric method. Aliquots of blood (15-mL) were taken from the glass collection beaker after being subjected to various high-flow rates and pressures through 3.2-mm-ID standard tubing (4C2193, Travenol Labs Inc, Deerfield, Illinois) or the prototype large-bore IV tubing, and an 8.5-F catheter. The samples were centrifuged at 4,000 g and 15 C for 30 minutes. The supematant was removed and 0.1 mL was mixed with 2 mL buffer (0.03 mol/L phosphate buffer, pH 7.4). The hemoglobin concentration (mg/dL) was calculated by measuring the absorption at 415 and 490 mm. The hemolysis trials were repeated with an inline Pall Filter (SQ405, Pall Biomedical Products Corporation, East Hills, New York). The degree of blood warming at high flow rates was measured with thermocouples and a M o n a t h e r m ® electronic thermometer (LaBarge Inc, St Louis, Missouri). The temperature of the blood bag was measured before infusion, and the blood temperature in the receiving vial was measured immediately after rapid infusion through the Fenwal ® blood warmer. Flow rates of 287 (_ 13) to 732 (_+ 16) were approximated by using various pressure/ catheter combinations. The bloodwarmer plate temperature remained at 36.7 C and all trials were at room temperature (22 C).
RESULTS Mean flow rates and 95% confidence intervals obtained for tap water 60/967
30. Blood
Temperature
(c)
25
2O
260
360
460
560
660
760
860
Flow Rate (mL/min) 1
TABLE l. Average flow rates tap water (mL/min)
Catheter 0 mm Hg 8.5-F 454 (_+ 7)* 14-gauge 319 (_+ 7) 16-gauge 198 (+ 2) *95% confidence interval.
are shown (Table 1). A maximum flow rate of 1,764 (_+ 89) mL/min was obtained with 600 m m Hg pressure through the prototype tubing and 8.5F catheter. Mean flow rates for diluted PRBCs (Hct 45%) and 95% confidence intervals are shown (Table 2). A sig0ificant reduction (P < .05) in maximum flow rates occurred with the Fenwal bloodwarmer. The IV equipment and pressure infusion device tolerated pressures up to 600 m m Hg very well. There was no rupture or leakage of blood/solution bags or IV connections. The degree of hemolysis with high pressure and flow is shown (Table 3). The cells per deciliter lysed and the percentage of cell lysis was calculated based on a mean corpuscular hemoglobin of 29 x 10 -12 g/cell and red blood cell count of 5 x 10I1 cells/dL. The hemolysis control, gravity flow through standard tubing, resulted in 2.18% calculated cell lysis. High pressure (~ 600 m m Hg) and flow rates (~< 1,714 mL/min) increased the hemolysis by less than 1% for all trials. There is no evidence that adding the inline microfilter significantly increased heAnnals of Emergency Medicine
300 mm Hg 1,333 (_+ 30) 857 (___22) 545 (+ 11)
600 mm Hg 1,764 (_+ 89) 1,176 (+ 26) 750 (_+ 21)
molysis compared to the control (Table 4). When 13 C (_+ 1 C) blood was infused through the warmer, blood temperature increased to 25.3 C at the maximum flow rate of 732 mL/min (Figure 1). Slightly higher heat gain resulted with slower infusion rates.
DISCUSSION Although the prototype tubing produced flow rates much greater than those with standard tubing, the maximum flow of 1,764 mL/min with 600 mg Hg is less than we previously measured for 5.0-mm-ID experimental tubing. 2 The model currently is being revised to increase the internal diameter of the catheter/needle adapter, which will result in maximum flow rates of approximately 2,500 mL/min with 600 m m Hg and approximately 1,700 m L / m i n with more conventional pressures of 300 m m Hg. For the hemolysis studies, the control plasma hemoglobin was measured on 37 + 1-day-old banked PRBCs that had been diluted with 100 mL to 200 mL normal saline to a hematocrit of 14:10 October 1985
TABLE 2. Average flow rates (mL/min) for blood (hct 45%) with and without bloodwarmer*
0 mm Hg Without Catheter BIoodwarmer 8.5-F 308 (+_ 16)* 14-gauge 190 (-+ 6) 16-gauge 114 (+ 3) *95% confidence interval.
300 mg Hg With Without BIoodwarmer Bloodwarmer 405 1,111 ( - 10) (-+ 36) 343 659 (-+ 9) (-+ 10) 287 419 (+ 13) (+ 13)
600 mm Hg With Without Bloodwarmer Bloodwarmer 732 1,714 (_+ 16) (_+ 83) 600 1,071 (-+ 33) (_+ 42) 461 667 (+ 8) (-+ 35)
TABLE 3. Degree of hemolysis with high pressure and flow
Tubing Size (mm ID) 3.2 3.2 3.2 5.0 5.0
Pressure (mm Hg) 0 300 600 300 600
Measured Plasma Hb (mg/dL) 315 345 383 407 362
Calculated Cells/dL Lysed 10.9 x 109 11.9 × 109 13.2 x 109 14.2 x 109 12.5 x 109
Calculated % Cell Lysis 2.18 2.38 2.64 2.80 2.50
TABLE 4. Degree of hemolysis with high pressure and flow through microfilter
Tubing Size (mm ID) 3.2 3.2 3.2 5.0 5.0
Pressure (mm Hg) 0 300 600 300 600
45%. We used slightly outdated blood cells for the study because we believed they would be more susceptible to lysis than are fresh blood cells. It has been determined that the mean plasma hemoglobin for PRBCs at the maximum usable storage time of 35 days in CPD-adenine is 658 mg/dL. 3 Considering the dilution factor, our con* trol plasma hemoglobin levels of 315 mg/dL and 260 mg/dL were consistent with the reported mean storage level at 35 days. When high pressures and 14:10 October 1985
Measured Plasma Hb (mg/dL) 260 286 299 300 333
flows were generated, the control value increased less than 100 mg/dL and the calculated percentage of cell lysis increased less than 1% for all trials. Apparently the red blood cell can withstand considerable pressure and turbulence w i t h o u t significant hemolysis. Our results support the concept of applying high pressures up to 600 mm Hg to blood/solution bags to overcome the resistance of IV tubing, filters, and blood warmers so that high Annals of Emergency Medicine
Calculated Cells/dL Lysed 9.0 x 109 9.9 x 109 10.3 x 109 10.3 x 109 11.5 x 109
Calculated % Cell Lysis 1.80 1.98 2.06 2.06 2.30
flow rates can be achieved. The question of whether or not large human veins will accept consistently the high flow rates that can be generated with these procedures has not yet been determined. It has been demonstrated, however, that canine central veins will accept 1,600 mL/min (produced with 200 mm Hg pressure, a specially designed fluid manifold, and a 14-F catheter} without evidence of significant gross or microscopic pathology.4 Adequate warming of cold banked 968/61
EFFECTS OF RAPID INFUSION Mateer et al
blood is important during rapid fluid administration. Infusion of cold blood through a central vein into the heart can precipitate myocardial dysrhythmias or paradoxical hypotension, s Infusion of multiple cold units can lead quickly to hypothermia. Our results indicate that the Fenwal ® bloodwarmer significantly limits m a x i m u m flow rates that can be achieved with large-bore tubing and provides inadequate warming of cold banked blood at these flow rates. Rapid prewarming by microwave has been studied, but was condemned due to significant increases in hemolysis. 6 Rapid prewarming of cold PRBCs can be accomplished by dilution with 150 mL to 200 mL of normal saline at physiologic temperature before infusion through the bloodwarmer. This procedure is facilitated by the design of our prototype high-flow IV tubing, which has four blood/solution connectors paired with two separate blood filter chambers (Table 2). This allows dilution of the packed cell blood bag with normal saline through one set of paired connectors while blood is being infused rapidly through the opposite filter chamber. Not only is dilution of PRBCs important from a warming standpoint, but we previously have shown that flow rates are increased threefold when PRBCs are diluted with normal saline (200 mL) to a hematocrit of approximately 45%. If cold banked whole blood is used initially instead of PRBCs, this dilutional prewarming is not feasible, and rapid infusion through the blood warmer with largebore tubing and high pressure will provide less adequate warming for safe central venous infusion. To improve flow rates and warming through the Fenwal ® blood warmer, we fir.st recommend that the internal diameter of the IV tubing leading in and out o f the blood warming bag be increased to 5.0 mm ID. Modification
62/969
!l
Fig. 2. Current design of p r o t o t y p e large-bore I V tubing. of the bloodwarming bag would not be necessary, as the channels are currently larger than 5.0 m m ID. Once this restriction to flow is corrected, adequate warming could be achieved simply by passing the blood through two or three bloodwarmers connected in a series to increase the warming plate area. Using large-bore tubing and pressure, the added length of this arrangement should not be a major limitation to maximum flow. CONCLUSIONS We have developed a p r o t o t y p e large-bore IV tubing that provides higher flow rates than does standard IV t u b i n g . M o d i f i c a t i o n of t h e catheter/needle adapter will maximize flow rates..Although red blood cells tolerate flow rates up to 1,714 mL/min and pressures <~ 600 m m Hg without significant hemolysis, warming may be inadequate at higher flow rates with currently available bloodwarming equipment. Before high pressure (> 200 m m Hg) and high flow (> 1,000 mL/min) techniques can be used clinically, they must be demonstrated to be effective and safe in animal and human trials.
The authors thank Dennis Birchall, MD, Section of Trauma and Emergency Medicine, Medical College of Wisconsin, for his preparation of Figure 2.
REFERENCES 1. Mateer JR, Thompson BM, Aprahamian C, et ah Rapid fluid resuscitation with central venous catheters. Ann Emerg Med 1983;12:149-152. 2. Mateer JR, Thompson BM, Tucker JE et ah Effects of high pressure and largebore tubing on IV flow rates (abstract). Ann Emerg Med 1984;13:405-406.
Annals of Emergency Medicine
/' ,/
2
3. Widmann FK: Technical Manual of the American Association of Blood Banks, ed 8. Philadelphia, JB Lippincott Company, 1981, pp 52-54. 4. Reeter AK, Iserson KV: A new device for rapid fluid replacement. Journal of Clinical Engineering 1984;9:37-41. 5. Committee on Trauma, American College of Surgeons: Advanced Trauma Life Support Course, Instructor Manual. Chicago, American College of Surgeons, 1981, pp 169-170. 6. Leaman P, Martyak G: Microwave warming of resuscitation fluids, abstract. Ann Emerg Med 1983;12:248.
14:10 October 1985
Effects of Rapid Infusion with High Pressure and Large-Bore IV Tubing on Red Blood Cell Lysis and Warming A prototype large-bore intravenous tubing was developed and tested. Mean flow rates for blood (Hct 45%) and tap water were determined for several catheters at 600 m m Hg, 300 m m Hg, and gravity flow and were statistically analyzed by calculating the 95% confidence intervals. The degree of hemolysis during high pressure and flow was determined by measuring the plasma free hemoglobin using the spectrophotometric method. To determine if cold. banked blood can be adequately warmed at high flow rates, thermocouples were used to measure the blood temperature before and after rapid infusion through a bloodwarmer. Results included m a x i m u m flow rates of 1,764 mL/min for tap water, and 1,714 mL/min for blood (Hct 45%) at 600 m m Hg through the large-bore tubing and an 8.5-F catheter. Flow rates for other pressure and catheter combinations were tabulated. The plasma-free hemoglobin increased slightly compared to controls with high pressure (<~ 600 m m Hg) and flow rates. The increase correlated with less than 1% red blood cell Iysis in all trials. When 13 C blood was infused through a warmer, blood temperature increased to 25.3 C at the maximum flow rate of 732 mL/min. Slightly higher heat gain resulted with slower infusion rates. We conclude that the prototype large-bore tubing and up to 600 m m Hg pressure provide rapid flow rates without significant hemolysis. Blood warming may be inadequate at higher flow rates. [Mateer JR, Perry BW, Thompson BM, Tucker JF, Aprahamian C: Effects of rapid infusion with high pressure and large-bore IV tubing on red cell lysis and warming. Ann Emerg Med October 1985;14:966-969.]
James R Mateer, MD* Billy W Perry, PhD1Bruce M Thompson, MD* John F Tucker, MD* Charles Aprahamian, MD* Milwaukee, Wisconsin From the Section of Trauma and Emergency Medicine* and the Department of Pathology,1 Medical College of Wisconsin, Milwaukee, Wisconsin. Received for publication October 18, 1984. Revision received April 5, 1985. Accepted for publication May 30, 1985. Address for reprints: James R Mateer, MD, Section of Trauma and Emergency Medicine, 8700 West Wisconsin Avenue, Milwaukee, Wisconsin 53226.
INTRODUCTION Rapid and aggressive fluid resuscitation is an important factor for improved salvage of the hypotensive trauma victim. In recent studies, l,2 we have demonstrated that appropriate peripheral catheter selection, the use of large-bore central venous catheters (8- to 9-F), high-pressure infusion (~< 600 mm Hg), and experimental large-bore tubing (up to 6.4 m m internal diameter [ID]) can significantly improve flow rates. Based on the data in these studies, we designed a prototype large-bore IV tubing suitable for clinical use, and we tested the model to determine maximum flow rates and their effect on red blood cell lysis and warming.
METHOD To calculate flow rates, Ringer's lactate in 1,000-mL bags was replaced with tap water at room temperature after determining these liquids have identical flow rates.] All bags were elevated one meter from the end of the catheter to the top of the fluid level. Fluids were run through the prototype large-bore, 5mm-ID, 235-cm-long IV tubing (Medex Inc, Hilliard, Ohio) with inline 170-~m filter. Pressures of 300 m m Hg and 600 m m Hg were generated by compressing the solution bags with a modified 2 Infuser/1 ® (Medical Innovations, Inc, Phoenix, Arizona) and were standardized with a calibration analyzer (model RT-200, Trimeter Instrument Corporation, Lancaster, Pennsylvania}. Flow rates were calculated for the Arrow ® 8.5-F introducer sheath (Arrow International, Inc, Reading, Pennsylvania) and the Argyle ® Medicut ® 14- and 16-gauge catheters (Sherwood Medical Industries, St Louis, Missouri) by averaging the time for 100 mL in three consecutive trials. Each mean flow rate was analyzed statistically by calculating the 95% confidence interval
14:10October 1985
Annals of Emergency Medicine
966/59
EFFECTS OF RAPID INFUSION Mateer et al
Fig. 1. Degree of warming that occurs
when 13-C red blood cells (Hct 45%) are infused rapidly through a blood-
35-
warmer.
(95% CI). For the blood flow studies, outdated units (37 + 1 days) of banked packed red blood cells (PRBCs) were diluted with normal saline to a hematocrit of 45%. Flow rates through the prototype tubing and a Fenwal blood warmer (model BW-5} using a standard blood warming bag (Fenwal Laboratories, Deerfield, Illinois) were calculated for diluted PRBCs. Tubing was changed or filters were cleaned after every 600 mL of blood flow to prevent filter obstruction. The degree of hemolysis during high pressure and flow was determined by measuring the plasma-free hemoglobin using the spectrophotometric method. Aliquots of blood (15-mL) were taken from the glass collection beaker after being subjected to various high-flow rates and pressures through 3.2-mm-ID standard tubing (4C2193, Travenol Labs Inc, Deerfield, Illinois) or the prototype large-bore IV tubing, and an 8.5-F catheter. The samples were centrifuged at 4,000 g and 15 C for 30 minutes. The supematant was removed and 0.1 mL was mixed with 2 mL buffer (0.03 mol/L phosphate buffer, pH 7.4). The hemoglobin concentration (mg/dL) was calculated by measuring the absorption at 415 and 490 mm. The hemolysis trials were repeated with an inline Pall Filter (SQ405, Pall Biomedical Products Corporation, East Hills, New York). The degree of blood warming at high flow rates was measured with thermocouples and a M o n a t h e r m ® electronic thermometer (LaBarge Inc, St Louis, Missouri). The temperature of the blood bag was measured before infusion, and the blood temperature in the receiving vial was measured immediately after rapid infusion through the Fenwal ® blood warmer. Flow rates of 287 (_ 13) to 732 (_+ 16) were approximated by using various pressure/ catheter combinations. The bloodwarmer plate temperature remained at 36.7 C and all trials were at room temperature (22 C).
RESULTS Mean flow rates and 95% confidence intervals obtained for tap water 60/967
30. Blood
Temperature
(c)
25
2O
260
360
460
560
660
760
860
Flow Rate (mL/min) 1
TABLE l. Average flow rates tap water (mL/min)
Catheter 0 mm Hg 8.5-F 454 (_+ 7)* 14-gauge 319 (_+ 7) 16-gauge 198 (+ 2) *95% confidence interval.
are shown (Table 1). A maximum flow rate of 1,764 (_+ 89) mL/min was obtained with 600 m m Hg pressure through the prototype tubing and 8.5F catheter. Mean flow rates for diluted PRBCs (Hct 45%) and 95% confidence intervals are shown (Table 2). A sig0ificant reduction (P < .05) in maximum flow rates occurred with the Fenwal bloodwarmer. The IV equipment and pressure infusion device tolerated pressures up to 600 m m Hg very well. There was no rupture or leakage of blood/solution bags or IV connections. The degree of hemolysis with high pressure and flow is shown (Table 3). The cells per deciliter lysed and the percentage of cell lysis was calculated based on a mean corpuscular hemoglobin of 29 x 10 -12 g/cell and red blood cell count of 5 x 10I1 cells/dL. The hemolysis control, gravity flow through standard tubing, resulted in 2.18% calculated cell lysis. High pressure (~ 600 m m Hg) and flow rates (~< 1,714 mL/min) increased the hemolysis by less than 1% for all trials. There is no evidence that adding the inline microfilter significantly increased heAnnals of Emergency Medicine
300 mm Hg 1,333 (_+ 30) 857 (___22) 545 (+ 11)
600 mm Hg 1,764 (_+ 89) 1,176 (+ 26) 750 (_+ 21)
molysis compared to the control (Table 4). When 13 C (_+ 1 C) blood was infused through the warmer, blood temperature increased to 25.3 C at the maximum flow rate of 732 mL/min (Figure 1). Slightly higher heat gain resulted with slower infusion rates.
DISCUSSION Although the prototype tubing produced flow rates much greater than those with standard tubing, the maximum flow of 1,764 mL/min with 600 mg Hg is less than we previously measured for 5.0-mm-ID experimental tubing. 2 The model currently is being revised to increase the internal diameter of the catheter/needle adapter, which will result in maximum flow rates of approximately 2,500 mL/min with 600 m m Hg and approximately 1,700 m L / m i n with more conventional pressures of 300 m m Hg. For the hemolysis studies, the control plasma hemoglobin was measured on 37 + 1-day-old banked PRBCs that had been diluted with 100 mL to 200 mL normal saline to a hematocrit of 14:10 October 1985
TABLE 2. Average flow rates (mL/min) for blood (hct 45%) with and without bloodwarmer*
0 mm Hg Without Catheter BIoodwarmer 8.5-F 308 (+_ 16)* 14-gauge 190 (-+ 6) 16-gauge 114 (+ 3) *95% confidence interval.
300 mg Hg With Without BIoodwarmer Bloodwarmer 405 1,111 ( - 10) (-+ 36) 343 659 (-+ 9) (-+ 10) 287 419 (+ 13) (+ 13)
600 mm Hg With Without Bloodwarmer Bloodwarmer 732 1,714 (_+ 16) (_+ 83) 600 1,071 (-+ 33) (_+ 42) 461 667 (+ 8) (-+ 35)
TABLE 3. Degree of hemolysis with high pressure and flow
Tubing Size (mm ID) 3.2 3.2 3.2 5.0 5.0
Pressure (mm Hg) 0 300 600 300 600
Measured Plasma Hb (mg/dL) 315 345 383 407 362
Calculated Cells/dL Lysed 10.9 x 109 11.9 × 109 13.2 x 109 14.2 x 109 12.5 x 109
Calculated % Cell Lysis 2.18 2.38 2.64 2.80 2.50
TABLE 4. Degree of hemolysis with high pressure and flow through microfilter
Tubing Size (mm ID) 3.2 3.2 3.2 5.0 5.0
Pressure (mm Hg) 0 300 600 300 600
45%. We used slightly outdated blood cells for the study because we believed they would be more susceptible to lysis than are fresh blood cells. It has been determined that the mean plasma hemoglobin for PRBCs at the maximum usable storage time of 35 days in CPD-adenine is 658 mg/dL. 3 Considering the dilution factor, our con* trol plasma hemoglobin levels of 315 mg/dL and 260 mg/dL were consistent with the reported mean storage level at 35 days. When high pressures and 14:10 October 1985
Measured Plasma Hb (mg/dL) 260 286 299 300 333
flows were generated, the control value increased less than 100 mg/dL and the calculated percentage of cell lysis increased less than 1% for all trials. Apparently the red blood cell can withstand considerable pressure and turbulence w i t h o u t significant hemolysis. Our results support the concept of applying high pressures up to 600 mm Hg to blood/solution bags to overcome the resistance of IV tubing, filters, and blood warmers so that high Annals of Emergency Medicine
Calculated Cells/dL Lysed 9.0 x 109 9.9 x 109 10.3 x 109 10.3 x 109 11.5 x 109
Calculated % Cell Lysis 1.80 1.98 2.06 2.06 2.30
flow rates can be achieved. The question of whether or not large human veins will accept consistently the high flow rates that can be generated with these procedures has not yet been determined. It has been demonstrated, however, that canine central veins will accept 1,600 mL/min (produced with 200 mm Hg pressure, a specially designed fluid manifold, and a 14-F catheter} without evidence of significant gross or microscopic pathology.4 Adequate warming of cold banked 968/61
EFFECTS OF RAPID INFUSION Mateer et al
blood is important during rapid fluid administration. Infusion of cold blood through a central vein into the heart can precipitate myocardial dysrhythmias or paradoxical hypotension, s Infusion of multiple cold units can lead quickly to hypothermia. Our results indicate that the Fenwal ® bloodwarmer significantly limits m a x i m u m flow rates that can be achieved with large-bore tubing and provides inadequate warming of cold banked blood at these flow rates. Rapid prewarming by microwave has been studied, but was condemned due to significant increases in hemolysis. 6 Rapid prewarming of cold PRBCs can be accomplished by dilution with 150 mL to 200 mL of normal saline at physiologic temperature before infusion through the bloodwarmer. This procedure is facilitated by the design of our prototype high-flow IV tubing, which has four blood/solution connectors paired with two separate blood filter chambers (Table 2). This allows dilution of the packed cell blood bag with normal saline through one set of paired connectors while blood is being infused rapidly through the opposite filter chamber. Not only is dilution of PRBCs important from a warming standpoint, but we previously have shown that flow rates are increased threefold when PRBCs are diluted with normal saline (200 mL) to a hematocrit of approximately 45%. If cold banked whole blood is used initially instead of PRBCs, this dilutional prewarming is not feasible, and rapid infusion through the blood warmer with largebore tubing and high pressure will provide less adequate warming for safe central venous infusion. To improve flow rates and warming through the Fenwal ® blood warmer, we fir.st recommend that the internal diameter of the IV tubing leading in and out o f the blood warming bag be increased to 5.0 mm ID. Modification
62/969
!l
Fig. 2. Current design of p r o t o t y p e large-bore I V tubing. of the bloodwarming bag would not be necessary, as the channels are currently larger than 5.0 m m ID. Once this restriction to flow is corrected, adequate warming could be achieved simply by passing the blood through two or three bloodwarmers connected in a series to increase the warming plate area. Using large-bore tubing and pressure, the added length of this arrangement should not be a major limitation to maximum flow. CONCLUSIONS We have developed a p r o t o t y p e large-bore IV tubing that provides higher flow rates than does standard IV t u b i n g . M o d i f i c a t i o n of t h e catheter/needle adapter will maximize flow rates..Although red blood cells tolerate flow rates up to 1,714 mL/min and pressures <~ 600 m m Hg without significant hemolysis, warming may be inadequate at higher flow rates with currently available bloodwarming equipment. Before high pressure (> 200 m m Hg) and high flow (> 1,000 mL/min) techniques can be used clinically, they must be demonstrated to be effective and safe in animal and human trials.
The authors thank Dennis Birchall, MD, Section of Trauma and Emergency Medicine, Medical College of Wisconsin, for his preparation of Figure 2.
REFERENCES 1. Mateer JR, Thompson BM, Aprahamian C, et ah Rapid fluid resuscitation with central venous catheters. Ann Emerg Med 1983;12:149-152. 2. Mateer JR, Thompson BM, Tucker JE et ah Effects of high pressure and largebore tubing on IV flow rates (abstract). Ann Emerg Med 1984;13:405-406.
Annals of Emergency Medicine
/' ,/
2
3. Widmann FK: Technical Manual of the American Association of Blood Banks, ed 8. Philadelphia, JB Lippincott Company, 1981, pp 52-54. 4. Reeter AK, Iserson KV: A new device for rapid fluid replacement. Journal of Clinical Engineering 1984;9:37-41. 5. Committee on Trauma, American College of Surgeons: Advanced Trauma Life Support Course, Instructor Manual. Chicago, American College of Surgeons, 1981, pp 169-170. 6. Leaman P, Martyak G: Microwave warming of resuscitation fluids, abstract. Ann Emerg Med 1983;12:248.
14:10 October 1985