J Clin Monit Comput DOI 10.1007/s10877-014-9605-3
ORIGINAL RESEARCH
In-line pressure within a HOTLINEÒ Fluid Warmer, under various flow conditions Midoriko Higashi • Ken Yamaura • Yukie Matsubara Takuya Fukudome • Sumio Hoka
•
Received: 5 February 2014 / Accepted: 26 July 2014 Ó Springer Science+Business Media New York 2014
Abstract Roller pump infusion devices are widely used for rapid infusion, and may be combined with separate warming devices. There may be instances however, where the pressures generated by the roller pump may not be compatible with the warming device. We assessed a commonly used roller pump in combination with a HOTLINEÒ Fluid Warmer, and found that it could generate pressures exceeding the HOTLINEÒ manufacturers specifications. This was of concern because the HOTLINEÒ manufacturer guideline states that not for use with pressure devices generating over 300 mmHg. Pressure greater than 300 mmHg may compromise the integrity of the HOTLINEÒ Fluid Warming Set. The aim of this study was to compare in-line pressure within a HOTLINEÒ Fluid Warmer at different infusion rates of a roller pump using various sizes of intravenous cannulae. The rapid infusion system comprised a 500 mL-normal saline bag, roller pump type infusion device, HOTLINEÒ Fluid Warmer (blood and fluid warmer system), and six different sizes of intravenous cannulae. In-line pressure was measured proximal to the HOTLINEÒ (pre-warmer) and proximal to the cannula (post-warmer), at flow rate of 50–160 mL/min. The in-line pressures increased significantly with increasing flow rate. The pre-warmer pressures exceeded 300 mmHg when the flow rate was C120 mL/min with 20-gauge, 48 mm length cannula, 130 with 20-gauge,
M. Higashi (&) K. Yamaura Operating Rooms, Kyushu University Hospital, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan e-mail: [email protected] Y. Matsubara T. Fukudome S. Hoka Department of Anesthesiology and Critical Care Medicine, Kyushu University Hospital, Fukuoka, Japan
25 mm cannula, and 160 mL/min with 18-gauge, 48 mm cannula. However, they were \300 mmHg at any flow rates with 18-gauge, 30 mm cannula and 16-gauge cannulae. The post-warmer pressures exceeded 300 mmHg at the flow rate of 140 mL/min with 20-gauge, 48 mm cannula, and 160 mL/min with 20-gauge, 25 mm cannula, while they were\300 mmHg at any flow rates with 18 and 16-gauge cannulae. The in-line pressure within a HOTLINEÒ could exceed 300 mmHg, depending on the flow rate and size and length of cannula. It is important to pay attention to the size and length of cannulae and flow rate to keep the maximum in-line pressure \300 mmHg when a roller pump type infusion device is used. Keywords In-line pressure Rapid infusion Roller pump Fluid warmer
1 Introduction Acute massive hemorrhage is one of the most challenging problems for clinicians involved in critical care medicine. Hemodynamic collapse, hypotension, and shock often develop due to intravascular hypovolemia. Treatment for hypovolemia is accomplished through rapid administration of crystalloid and colloid solutions and/or allogeneic blood products. The rapid infusion of large volumes of fluid and/ or refrigerated blood products can cause hypothermia, which may result in a decrease in tissue oxygen partial pressure [1], blood loss due to coagulopathy [2], a higher incidence of surgical-wound infections [1, 3], and cardiac events [4]. Therefore, maintenance of normothermia (37 °C) is priority. Roller pump infusion devices may be combined with fluid warmers in such circumstances to deliver normothermic
123
J Clin Monit Comput Fig. 1 The system used in the present study to infuse 500-ml normal saline. The setup included a transfusing filter set (SQ40s, Kawasumi Kagaku Kogyo, Tokyo, Japan), disposable infusion set (SureflowÒN, NIPRO, Osaka, Japan) designed for the roller pump, HOTLINEÒ Fluid Warmer (LEVEL1Ò HL-90, Smiths Medical, MA) set with HOTLINEÒ Fluid Warming Set and Gas Vent (LEVEL1Ò L-70 and L-10, Smiths Medical), and an extension line (Safe AccessTM, three-way-tap with 83 cm extension, COVIDIENTM, Shizuoka, Japan)
fluid rapidly. A frequent combination in our clinical practice is a roller pump, combined with a HOTLINEÒ Fluid Warmer. The roller pump allows the administration of large volumes of fluid over a short period of time, although high flow rates can increase the pressure in the infusion tubing. The HOTLINEÒ manufacturer guideline states that not for use with pressure devices generating over 300 mmHg. Pressure greater than 300 mmHg may compromise the integrity of the HOTLINEÒ Fluid Warming Set [5]. The HOTLINEÒ Fluid Warming Set has two circulating fluids running in parallel. One of these fluids is sterile (the IV infusion fluid) and certified for IV injection, the other fluid (the warming fluid) is non sterile, and hypotonic. Therefore, a breach in the integrity may result in the two fluids intermingling, and infusing unsterile/hypotonic fluid into the patient. The HOTLINEÒ has no pressure alarm to warn 300 mmHg has been exceeded, nor has it any means of detecting an integrity breach. Therefore operator vigilance in the selection of a safe operating pressure is important for clinical safety. The aim of this study was to compare the in-line pressures of a rapid infusion system, comprising a roller pump type infusion device with a HOTLINEÒ Fluid Warmer, at different infusion speeds using various sizes of intravenous cannulae.
123
Table 1 Specifications of the intravenous cannulae Gauge
ID (mm)
Length (mm)
Flow rate (mL/min)
20
1.1
25 48
55
18
1.3
30
105
16
1.7
48 30
95 220
45
205
65
BD InsyteTM AutoguardTM, Shielded I.V. Catheter, Sandy, Utah
2 Methods The devices evaluated in this study were the roller pump type infusion device (MP-301, NIPRO, Osaka, Japan) and the HOTLINEÒ Fluid Warmer (Smiths Medical, MA). An administrating filter set (SQ40s, Kawasumi Kagaku Kogyo, Tokyo, Japan), a disposable infusion set (SureflowÒN, NIPRO, Osaka, Japan) designed for the roller pump, HOTLINEÒ Fluid Warmer (LEVEL1Ò HL-90, Smiths Medical) set with HOTLINEÒ Fluid Warming Set and Gas Vent (LEVEL1Ò L-70 and L-10, Smiths Medical), and an extension line (Safe AccessTM, three-way-tap with 83 cm extension, COVIDIENTM, Shizuoka, Japan) were
J Clin Monit Comput Table 2 In-line pressure under gravity flow and Roller pump flow rate at which the in-line pressure exceeded 300 mmHg Intravenous cannula
In-line pressure (mmHg)}
Roller pump flow rate (mL/min)§
Prewarmer
Prewarmer
Postwarmer
Postwarmer
20-Gauge Length 25 mm
40.0 ± 4.3
30.0 ± 0*
130
160
Length 48 mm
42.5 ± 8.7
30.0 ± 0*
120
140
Length 30 mm
40.0 ± 4.3
22.5 ± 0
([160)
([160)
Length 48 mm
40.0 ± 4.3
22.5 ± 0
160
([160)
18-Gauge
16-Gauge Length 30 mm
37.5 ± 7.5
7.5 ± 0
([160)
([160)
Length 45 mm
37.5 ± 7.5
7.5 ± 0
([160)
([160)
Data are mean ± SD of three measurements each }
In-line pressures under gravity flow
* P \ 0.01 vs 16-gauge 30 mm and 45 mm §
Flow rate at which the in-line pressure exceeded 300 mmHg
Pre-warmer: between the roller pump and the HOTLINEÒ, just proximal to the HOTLINEÒ, post-warmer: between the extension line and the intravenous cannula, just proximal to the intravenous cannula
connected to a 500-ml bag of normal saline (Fig. 1). The extension line was connected to an intravenous cannula (InsyteTMAutoguardTM, BD, UT) at the ‘patient’ end. All bags were elevated one meter from the end of the catheter to the top of the fluid level. Six different sizes of cannulae were examined (Table 1). In-line pressure was measured using two pressure gauges (PG-200, COPAL Electronics Co., Tokyo) placed at two sites: between the roller pump and the HOTLINEÒ, just proximal to the HOTLINEÒ (pre-warmer), and pressure immediately proximal to the intravenous cannula (post-warmer) (Fig. 1). The pressure gauges were connected to the side port of three-way-taps. Normal saline was infused at atmospheric pressure with the roller clamp wide open (gravity flow) at first, and then infused via the roller pump at a flow rate of 50–160 mL/min with stepwise increase by 10 mL/min. Data were expressed as mean ± SD, analyzed using repeated measure ANOVA with Scheffe test. A P value less than 0.05 was considered statistically significant.
3 Results There were no significant differences in the pre-warmer inline pressures using the six different sizes cannulae under gravity flow (Table 2). The post-warmer in-line pressures
with 20-gauge cannulae were significantly greater than those with 16-gauge under gravity flow (Table 2). The pre-warmer and post-warmer in-line pressures increased significantly and proportionally with the increase in flow rate of the roller pump (Fig. 2a, b). The pre-warmer pressures with 18 and 20-gauge cannulae were significantly higher than those with 16-gauge cannula (P \ 0.01, Fig. 2). They exceeded 300 mmHg with the 20-gauge, 48 mm length cannula at a roller pump flow rate of more than 120 mL/min, with 20-gauge, 25 mm cannula more than 130 mL/min, and with 18-gauge, 48 mm cannula at 160 mL/min (Table 2; Fig. 2a). However, they were less than 300 mmHg with 18-gauge, 30 mm cannula and 16-gauge, 30 and 45 mm cannulae at any flow rate measured. The post-warmer pressures using 18 and 20-gauge cannulae were also significantly higher than the 16-gauge cannula (P \ 0.01, Fig. 2b), and exceeded 300 mmHg with 20-gauge, 48 mm cannula at roller pump flow rates of more than 140 mL/mL and with 20-gauge, 25 mm cannula at 160 mL/min (Table 2, Fig. 2b). However, they did not exceed 300 mmHg with 18 and 16-gauge cannulae at any flow rate.
4 Discussion The HOTLINEÒ Warming Set is designed to warm blood and intravenous fluids and deliver them to the patient’s intravenous access site at normothermic temperatures under gravity flow conditions. It employs a temperature controlled recirculating solution heating system to warm blood and intravenous fluid actively in the patient line. The recirculating solution flows through separate channels which surround the intravenous pathway. Fluid is warmed to normothermic temperatures at gravity flow rates between 50 and 5,000 mL/h (0.83–83 mL/min). The HOTLINEÒ manufacture states not for use with pressure devices generating over 300 mmHg. Pressure greater than 300 mmHg may compromise the integrity of the HOTLINEÒ Fluid Warming Set [5]. In this study, the pressure at immediately proximal to the HOTLINEÒ (pre-warmer) exceeded 300 mmHg when normal saline was infused via the roller pump at a flow rate of C120 mL/min with 20-gauge cannulae, and C160 mL/ min with 18-gauge cannulae. These results suggest that the flow rate of the roller pump should not be increased over 120 and 160 mL/min when 20-gauge and 18-gauge intravenous cannulae are used, respectively. Intravenous cannulae of C16-gauge should be used if fluids are infused rapidly using the roller pump with the HOTLINEÒ Fluid Warmer.
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J Clin Monit Comput
Fig. 2 a The in-line pressure before HOTLINEÒ. The pressure increased significantly with increased flow rate of the roller pump. With 18 and 20-gauge cannulae, it was significantly higher than with 16-gauge cannula (P \ 0.01), and exceeded 300 mmHg with 20-gauge, 48 mm cannula over a roller pump flow rate of 120 mL/ min, with 20-gauge, 25 mm cannula over 130 mL/min, and with 18-gauge, 48 mm cannula at 160 mL/min. b The in-line pressure after
HOTLINEÒ. The pressure increased significantly with increased flow rate of the roller pump. With 18 and 20-gauge cannulae, it was significantly higher than with 16-gauge cannulae (P \ 0.01), and exceeded 300 mmHg with 20-gauge, 48 mm cannula over a roller pump flow rate of 140 ml/mL and with 20-gauge, 25 mm cannula at 160 mL/min
The HOTLINEÒ manufacturer claims that the unique design of the HOTLINEÒ Fluid Warming Set allows blood and intravenous fluid to be delivered to the patient at normothermic temperature at gravity flow rates to 50–5,000 mL/h (0.83–83 mL/min). It has been reported that HOTLINEÒ adequately warms fluids at moderate flow (13–25 mL/min lactated Ringer’s solution) [6]. On the other hand, it is also demonstrated that HOTLINEÒ, at flow rates of more than 4 L/h (67 mL/min), which is less than the manufacturer’s recommended flow rate, exceeds its ability to adequately warm RBCs and saline to maintain normothermic temperature [7]. When we use the roller pump at the flow rates of less than 120 mL/min, at which rates the in-line pressure within the HOTLINEÒ may not exceed over 300 mmHg, blood or intravenous fluid might not be adequately warmed through the HOTLINEÒ. Although we found that the safe pressures were exceeded using smaller cannulae at flow rates exceeding 120 mL/ min, these flow rates, in any case, overwhelm the ability of the HOTLINEÒ to adequately warm the fluids, suggesting other warming devices may be more appropriate in these conditions. Even at flows generating safe pressures (less than 120 mL/min), warming, rather than pressure may be the rate limiting factor. There are multiple infusion pumps currently on the market. These deliver volumetric control, but may lead to unregulated in-line pressures, and even intravenous pressures. These pumps are often relatively slow compared to simple techniques such as inflatable
pressure bags/IV syringing [8], which most people would resort to in a real emergency. The present study has certain limitations. First, intravenous cannulae were not inserted in human veins. In clinical settings, fluids and blood products are infused against venous pressure that is affected by intravenous volume, cardiac function, and intra-thoracic pressure, as well as the size and site of the vein. Therefore, the in-line pressure of the HOTLINEÒ with rapid infusion device could be greater than the present results when it is used in vivo. Further studies are needed to determine whether consistently high flow rates that can be generated by these devices are safe for large human veins. The figure of 300 mmHg is usually used for maximum operating pressures for IV injections, without clear justification for that figure being chosen. Goodie et al. [9] reported that a traumatised vein starts to extravasate at luminal pressures above 300 mmHg, and this may be a reason why this pressure seems to have been arbitrarily selected by manufactures. However, 300 mmHg, in the IV tubing upstream of the cannula is not the same as 300 mmHg in the patient’s vein. As long as that vein has run-off, the pressure will be vastly diminished by the resistance of the IV cannula. Second, we evaluated the in-line pressure of the HOTLINEÒ with rapid infusion device using normal saline as the infusion fluid. However, rapid infusion is often needed to manage massive bleeding; therefore colloids and blood products are usually used as volume replacement
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J Clin Monit Comput
fluids. The viscosity of the colloids and blood products are more than normal saline, therefore the pressure measured in this study might be underestimated compared with clinical settings. It has been demonstrated that a flow rate of 198 mL/min obtained for Ringer’s lactate with gravity flow through 16-gauge catheter is reduced to 114 mL/min for blood (hematocrit of 45 %) without a blood warmer, and a significant reduction in flow rates occurred with the blood warmer [10]. In conclusion, we demonstrated in the present study that the in-line pressures within the HOTLINEÒ exceeded 300 mmHg when normal saline was infused using the roller pump at flow rates of 120 mL/min with 20-gauge and 160 mL/min with 18-gauge intravenous cannulae, although the manufacturer of the HOTLINEÒ warns against the use of pressure devices that can generate more than 300 mmHg. When a roller pump type infusion device and a warmer are used for rapid infusion, it is necessary to pay careful attention to the size and length of the cannulae and flow rates in order to keep the maximum in-line pressure less than 300 mmHg. Acknowledgments The authors thank Mrs. Kondo and F. G. Issa, MD, PhD (www.word-medox.com.au) for the careful reading and editing of the manuscript. This study was supported by departmental funding only. Conflict of interest
There is no relevant conflict of interest.
References 1. Buggy D. Can anaesthetic management influence surgical wound healing? Lancet. 2000;356:355–7. 2. Schmied H, Kurz A, Sessler DI, Kozek S, Reiter A. Mild hypothermia increases blood loss and transfusion requirements during total hip arthroplasty. Lancet. 1996;347:289–92. 3. Kurz A, Sessler DI, Lenhardt R. Perioperative normothermia to reduce the incidence of surgical-wound infection and shorten hostpitalization. Study of Wound Infection and Temperature Group. N Engl J Med. 1996;334:1209–15. 4. Frank SM, Fleisher LA, Breslow MJ, Higgins MS, Olson KF, Kelly S, Beattie C. Perioperative maintenance of normothermia reduces the incidence of morbid cardiac events. A randomized clinical trial. JAMA. 1997;277:1127–34. 5. HotlineÒ Fluid Warming Set: REF L-70 [package insert] Smiths Medical ASD, Inc., MA, USA. 6. Patel N, Knapke DM, Smith CE, Napora TE, Pinchak AC, Hagen JF. Simulated clinical evaluation of conventional and newer fluidwarming devices. Anesth Analg. 1996;82:517–24. 7. Horowitz PE, Delagarza MA, Pulaski JJ, Smith RA. Flow rates and warming efficacy with Hotline and Ranger blood/fluid warmers. Anesth Analg. 2004;99:788–92. 8. Smart CM, Primrose CW, Peters AL, Speirits EJ. The properties of an improvised piston pump for the rapid delivery of intravenous fluids. Anaesthesia. 2014;69:110–7. 9. Goodie DB. The effect of manual bulb pump infusion systems on venous luminal pressure and vein wall integrity. Anesth Analg. 1995;80:552–6. 10. Mateer JR, Perry BW, Thompson BM, Tucker JF, Aprahamian CA. Effects of rapid infusion with high pressure and large-bore IV tubing on red blood cell lysis and warming. Ann Emerg Med. 1985;14:966–9.
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ORIGINAL RESEARCH
In-line pressure within a HOTLINEÒ Fluid Warmer, under various flow conditions Midoriko Higashi • Ken Yamaura • Yukie Matsubara Takuya Fukudome • Sumio Hoka
•
Received: 5 February 2014 / Accepted: 26 July 2014 Ó Springer Science+Business Media New York 2014
Abstract Roller pump infusion devices are widely used for rapid infusion, and may be combined with separate warming devices. There may be instances however, where the pressures generated by the roller pump may not be compatible with the warming device. We assessed a commonly used roller pump in combination with a HOTLINEÒ Fluid Warmer, and found that it could generate pressures exceeding the HOTLINEÒ manufacturers specifications. This was of concern because the HOTLINEÒ manufacturer guideline states that not for use with pressure devices generating over 300 mmHg. Pressure greater than 300 mmHg may compromise the integrity of the HOTLINEÒ Fluid Warming Set. The aim of this study was to compare in-line pressure within a HOTLINEÒ Fluid Warmer at different infusion rates of a roller pump using various sizes of intravenous cannulae. The rapid infusion system comprised a 500 mL-normal saline bag, roller pump type infusion device, HOTLINEÒ Fluid Warmer (blood and fluid warmer system), and six different sizes of intravenous cannulae. In-line pressure was measured proximal to the HOTLINEÒ (pre-warmer) and proximal to the cannula (post-warmer), at flow rate of 50–160 mL/min. The in-line pressures increased significantly with increasing flow rate. The pre-warmer pressures exceeded 300 mmHg when the flow rate was C120 mL/min with 20-gauge, 48 mm length cannula, 130 with 20-gauge,
M. Higashi (&) K. Yamaura Operating Rooms, Kyushu University Hospital, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan e-mail: [email protected] Y. Matsubara T. Fukudome S. Hoka Department of Anesthesiology and Critical Care Medicine, Kyushu University Hospital, Fukuoka, Japan
25 mm cannula, and 160 mL/min with 18-gauge, 48 mm cannula. However, they were \300 mmHg at any flow rates with 18-gauge, 30 mm cannula and 16-gauge cannulae. The post-warmer pressures exceeded 300 mmHg at the flow rate of 140 mL/min with 20-gauge, 48 mm cannula, and 160 mL/min with 20-gauge, 25 mm cannula, while they were\300 mmHg at any flow rates with 18 and 16-gauge cannulae. The in-line pressure within a HOTLINEÒ could exceed 300 mmHg, depending on the flow rate and size and length of cannula. It is important to pay attention to the size and length of cannulae and flow rate to keep the maximum in-line pressure \300 mmHg when a roller pump type infusion device is used. Keywords In-line pressure Rapid infusion Roller pump Fluid warmer
1 Introduction Acute massive hemorrhage is one of the most challenging problems for clinicians involved in critical care medicine. Hemodynamic collapse, hypotension, and shock often develop due to intravascular hypovolemia. Treatment for hypovolemia is accomplished through rapid administration of crystalloid and colloid solutions and/or allogeneic blood products. The rapid infusion of large volumes of fluid and/ or refrigerated blood products can cause hypothermia, which may result in a decrease in tissue oxygen partial pressure [1], blood loss due to coagulopathy [2], a higher incidence of surgical-wound infections [1, 3], and cardiac events [4]. Therefore, maintenance of normothermia (37 °C) is priority. Roller pump infusion devices may be combined with fluid warmers in such circumstances to deliver normothermic
123
J Clin Monit Comput Fig. 1 The system used in the present study to infuse 500-ml normal saline. The setup included a transfusing filter set (SQ40s, Kawasumi Kagaku Kogyo, Tokyo, Japan), disposable infusion set (SureflowÒN, NIPRO, Osaka, Japan) designed for the roller pump, HOTLINEÒ Fluid Warmer (LEVEL1Ò HL-90, Smiths Medical, MA) set with HOTLINEÒ Fluid Warming Set and Gas Vent (LEVEL1Ò L-70 and L-10, Smiths Medical), and an extension line (Safe AccessTM, three-way-tap with 83 cm extension, COVIDIENTM, Shizuoka, Japan)
fluid rapidly. A frequent combination in our clinical practice is a roller pump, combined with a HOTLINEÒ Fluid Warmer. The roller pump allows the administration of large volumes of fluid over a short period of time, although high flow rates can increase the pressure in the infusion tubing. The HOTLINEÒ manufacturer guideline states that not for use with pressure devices generating over 300 mmHg. Pressure greater than 300 mmHg may compromise the integrity of the HOTLINEÒ Fluid Warming Set [5]. The HOTLINEÒ Fluid Warming Set has two circulating fluids running in parallel. One of these fluids is sterile (the IV infusion fluid) and certified for IV injection, the other fluid (the warming fluid) is non sterile, and hypotonic. Therefore, a breach in the integrity may result in the two fluids intermingling, and infusing unsterile/hypotonic fluid into the patient. The HOTLINEÒ has no pressure alarm to warn 300 mmHg has been exceeded, nor has it any means of detecting an integrity breach. Therefore operator vigilance in the selection of a safe operating pressure is important for clinical safety. The aim of this study was to compare the in-line pressures of a rapid infusion system, comprising a roller pump type infusion device with a HOTLINEÒ Fluid Warmer, at different infusion speeds using various sizes of intravenous cannulae.
123
Table 1 Specifications of the intravenous cannulae Gauge
ID (mm)
Length (mm)
Flow rate (mL/min)
20
1.1
25 48
55
18
1.3
30
105
16
1.7
48 30
95 220
45
205
65
BD InsyteTM AutoguardTM, Shielded I.V. Catheter, Sandy, Utah
2 Methods The devices evaluated in this study were the roller pump type infusion device (MP-301, NIPRO, Osaka, Japan) and the HOTLINEÒ Fluid Warmer (Smiths Medical, MA). An administrating filter set (SQ40s, Kawasumi Kagaku Kogyo, Tokyo, Japan), a disposable infusion set (SureflowÒN, NIPRO, Osaka, Japan) designed for the roller pump, HOTLINEÒ Fluid Warmer (LEVEL1Ò HL-90, Smiths Medical) set with HOTLINEÒ Fluid Warming Set and Gas Vent (LEVEL1Ò L-70 and L-10, Smiths Medical), and an extension line (Safe AccessTM, three-way-tap with 83 cm extension, COVIDIENTM, Shizuoka, Japan) were
J Clin Monit Comput Table 2 In-line pressure under gravity flow and Roller pump flow rate at which the in-line pressure exceeded 300 mmHg Intravenous cannula
In-line pressure (mmHg)}
Roller pump flow rate (mL/min)§
Prewarmer
Prewarmer
Postwarmer
Postwarmer
20-Gauge Length 25 mm
40.0 ± 4.3
30.0 ± 0*
130
160
Length 48 mm
42.5 ± 8.7
30.0 ± 0*
120
140
Length 30 mm
40.0 ± 4.3
22.5 ± 0
([160)
([160)
Length 48 mm
40.0 ± 4.3
22.5 ± 0
160
([160)
18-Gauge
16-Gauge Length 30 mm
37.5 ± 7.5
7.5 ± 0
([160)
([160)
Length 45 mm
37.5 ± 7.5
7.5 ± 0
([160)
([160)
Data are mean ± SD of three measurements each }
In-line pressures under gravity flow
* P \ 0.01 vs 16-gauge 30 mm and 45 mm §
Flow rate at which the in-line pressure exceeded 300 mmHg
Pre-warmer: between the roller pump and the HOTLINEÒ, just proximal to the HOTLINEÒ, post-warmer: between the extension line and the intravenous cannula, just proximal to the intravenous cannula
connected to a 500-ml bag of normal saline (Fig. 1). The extension line was connected to an intravenous cannula (InsyteTMAutoguardTM, BD, UT) at the ‘patient’ end. All bags were elevated one meter from the end of the catheter to the top of the fluid level. Six different sizes of cannulae were examined (Table 1). In-line pressure was measured using two pressure gauges (PG-200, COPAL Electronics Co., Tokyo) placed at two sites: between the roller pump and the HOTLINEÒ, just proximal to the HOTLINEÒ (pre-warmer), and pressure immediately proximal to the intravenous cannula (post-warmer) (Fig. 1). The pressure gauges were connected to the side port of three-way-taps. Normal saline was infused at atmospheric pressure with the roller clamp wide open (gravity flow) at first, and then infused via the roller pump at a flow rate of 50–160 mL/min with stepwise increase by 10 mL/min. Data were expressed as mean ± SD, analyzed using repeated measure ANOVA with Scheffe test. A P value less than 0.05 was considered statistically significant.
3 Results There were no significant differences in the pre-warmer inline pressures using the six different sizes cannulae under gravity flow (Table 2). The post-warmer in-line pressures
with 20-gauge cannulae were significantly greater than those with 16-gauge under gravity flow (Table 2). The pre-warmer and post-warmer in-line pressures increased significantly and proportionally with the increase in flow rate of the roller pump (Fig. 2a, b). The pre-warmer pressures with 18 and 20-gauge cannulae were significantly higher than those with 16-gauge cannula (P \ 0.01, Fig. 2). They exceeded 300 mmHg with the 20-gauge, 48 mm length cannula at a roller pump flow rate of more than 120 mL/min, with 20-gauge, 25 mm cannula more than 130 mL/min, and with 18-gauge, 48 mm cannula at 160 mL/min (Table 2; Fig. 2a). However, they were less than 300 mmHg with 18-gauge, 30 mm cannula and 16-gauge, 30 and 45 mm cannulae at any flow rate measured. The post-warmer pressures using 18 and 20-gauge cannulae were also significantly higher than the 16-gauge cannula (P \ 0.01, Fig. 2b), and exceeded 300 mmHg with 20-gauge, 48 mm cannula at roller pump flow rates of more than 140 mL/mL and with 20-gauge, 25 mm cannula at 160 mL/min (Table 2, Fig. 2b). However, they did not exceed 300 mmHg with 18 and 16-gauge cannulae at any flow rate.
4 Discussion The HOTLINEÒ Warming Set is designed to warm blood and intravenous fluids and deliver them to the patient’s intravenous access site at normothermic temperatures under gravity flow conditions. It employs a temperature controlled recirculating solution heating system to warm blood and intravenous fluid actively in the patient line. The recirculating solution flows through separate channels which surround the intravenous pathway. Fluid is warmed to normothermic temperatures at gravity flow rates between 50 and 5,000 mL/h (0.83–83 mL/min). The HOTLINEÒ manufacture states not for use with pressure devices generating over 300 mmHg. Pressure greater than 300 mmHg may compromise the integrity of the HOTLINEÒ Fluid Warming Set [5]. In this study, the pressure at immediately proximal to the HOTLINEÒ (pre-warmer) exceeded 300 mmHg when normal saline was infused via the roller pump at a flow rate of C120 mL/min with 20-gauge cannulae, and C160 mL/ min with 18-gauge cannulae. These results suggest that the flow rate of the roller pump should not be increased over 120 and 160 mL/min when 20-gauge and 18-gauge intravenous cannulae are used, respectively. Intravenous cannulae of C16-gauge should be used if fluids are infused rapidly using the roller pump with the HOTLINEÒ Fluid Warmer.
123
J Clin Monit Comput
Fig. 2 a The in-line pressure before HOTLINEÒ. The pressure increased significantly with increased flow rate of the roller pump. With 18 and 20-gauge cannulae, it was significantly higher than with 16-gauge cannula (P \ 0.01), and exceeded 300 mmHg with 20-gauge, 48 mm cannula over a roller pump flow rate of 120 mL/ min, with 20-gauge, 25 mm cannula over 130 mL/min, and with 18-gauge, 48 mm cannula at 160 mL/min. b The in-line pressure after
HOTLINEÒ. The pressure increased significantly with increased flow rate of the roller pump. With 18 and 20-gauge cannulae, it was significantly higher than with 16-gauge cannulae (P \ 0.01), and exceeded 300 mmHg with 20-gauge, 48 mm cannula over a roller pump flow rate of 140 ml/mL and with 20-gauge, 25 mm cannula at 160 mL/min
The HOTLINEÒ manufacturer claims that the unique design of the HOTLINEÒ Fluid Warming Set allows blood and intravenous fluid to be delivered to the patient at normothermic temperature at gravity flow rates to 50–5,000 mL/h (0.83–83 mL/min). It has been reported that HOTLINEÒ adequately warms fluids at moderate flow (13–25 mL/min lactated Ringer’s solution) [6]. On the other hand, it is also demonstrated that HOTLINEÒ, at flow rates of more than 4 L/h (67 mL/min), which is less than the manufacturer’s recommended flow rate, exceeds its ability to adequately warm RBCs and saline to maintain normothermic temperature [7]. When we use the roller pump at the flow rates of less than 120 mL/min, at which rates the in-line pressure within the HOTLINEÒ may not exceed over 300 mmHg, blood or intravenous fluid might not be adequately warmed through the HOTLINEÒ. Although we found that the safe pressures were exceeded using smaller cannulae at flow rates exceeding 120 mL/ min, these flow rates, in any case, overwhelm the ability of the HOTLINEÒ to adequately warm the fluids, suggesting other warming devices may be more appropriate in these conditions. Even at flows generating safe pressures (less than 120 mL/min), warming, rather than pressure may be the rate limiting factor. There are multiple infusion pumps currently on the market. These deliver volumetric control, but may lead to unregulated in-line pressures, and even intravenous pressures. These pumps are often relatively slow compared to simple techniques such as inflatable
pressure bags/IV syringing [8], which most people would resort to in a real emergency. The present study has certain limitations. First, intravenous cannulae were not inserted in human veins. In clinical settings, fluids and blood products are infused against venous pressure that is affected by intravenous volume, cardiac function, and intra-thoracic pressure, as well as the size and site of the vein. Therefore, the in-line pressure of the HOTLINEÒ with rapid infusion device could be greater than the present results when it is used in vivo. Further studies are needed to determine whether consistently high flow rates that can be generated by these devices are safe for large human veins. The figure of 300 mmHg is usually used for maximum operating pressures for IV injections, without clear justification for that figure being chosen. Goodie et al. [9] reported that a traumatised vein starts to extravasate at luminal pressures above 300 mmHg, and this may be a reason why this pressure seems to have been arbitrarily selected by manufactures. However, 300 mmHg, in the IV tubing upstream of the cannula is not the same as 300 mmHg in the patient’s vein. As long as that vein has run-off, the pressure will be vastly diminished by the resistance of the IV cannula. Second, we evaluated the in-line pressure of the HOTLINEÒ with rapid infusion device using normal saline as the infusion fluid. However, rapid infusion is often needed to manage massive bleeding; therefore colloids and blood products are usually used as volume replacement
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fluids. The viscosity of the colloids and blood products are more than normal saline, therefore the pressure measured in this study might be underestimated compared with clinical settings. It has been demonstrated that a flow rate of 198 mL/min obtained for Ringer’s lactate with gravity flow through 16-gauge catheter is reduced to 114 mL/min for blood (hematocrit of 45 %) without a blood warmer, and a significant reduction in flow rates occurred with the blood warmer [10]. In conclusion, we demonstrated in the present study that the in-line pressures within the HOTLINEÒ exceeded 300 mmHg when normal saline was infused using the roller pump at flow rates of 120 mL/min with 20-gauge and 160 mL/min with 18-gauge intravenous cannulae, although the manufacturer of the HOTLINEÒ warns against the use of pressure devices that can generate more than 300 mmHg. When a roller pump type infusion device and a warmer are used for rapid infusion, it is necessary to pay careful attention to the size and length of the cannulae and flow rates in order to keep the maximum in-line pressure less than 300 mmHg. Acknowledgments The authors thank Mrs. Kondo and F. G. Issa, MD, PhD (www.word-medox.com.au) for the careful reading and editing of the manuscript. This study was supported by departmental funding only. Conflict of interest
There is no relevant conflict of interest.
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