In the present study, the flow rate and in-line pressures were positively correlated with the catheter length. On comparing a 45-cm PICC to a 20-cm CVC with a similar diameter, the in-line pressures were lower for the 20-cm CVC at a flow rate <30 mL/min but higher for rapid infusion at a flow rate >80 mL/min. In addition, the flow rate at which the in-line pressure reached 300 mmHg, when hemolysis is expected to occur, did not differ markedly between the 45-cm PICC and 20-cm CVC.
Regarding the relationship between the flow rate and in-line pressure, longer catheters have a higher in-line pressure than shorter ones. In our previous report concerning the relationship between the flow rate and in-line pressure using a peripheral venous catheter, there was a positive correlation between the catheter length and in-line pressure with an 18-G peripheral venous catheter, which has same diameter as the lumen of the PICC used in the present study. The in-line pressure was approximately 300 mmHg at a flow rate of 150 mL/min (9000 mL/h) [8]. The length of the peripheral venous catheter was 4.8 cm in the previous study, while the lengths of the CVC and PICC with the same diameter in the present study were 13 and 20 cm and 35, 45 and 55 cm. In each catheter, the in-line pressure increased to 1745–2523 mmHg as the catheter length was increased. However, in the present study, we confirmed that repeated infusions at an in-line pressure of ≥2000 mmHg did not affect the flow rate or in-line pressure using a pressure-resistant PICC or CVC. These results suggest that there is no issue with performing repeated high-pressure infusion.
Compared with rapid infusion from a peripheral venous catheter, the flow rate was limited when rapid intravenous infusion was performed with a PICC. However, a pressure-resistant PICC can withstand rapid intravenous infusion of 150 mL/min (9000 mL/h), which is clinically sufficient. The maximum pressure of a clinical pressurized rapid infusion device is limited to 300 mmHg, and it has been reported that in-line pressure is increased to about 600 mmHg during manual rapid infusion using a piston syringe [9]. In the present study, a pressure-resistant PICC was able to withstand a higher pressure than exerted with these methods, suggesting that a pressure-resistant PICC can be safely used for rapid infusion.
On comparing a 45-cm PICC with a 20-cm CVC, which are usually used clinically, the PICC, which was longer than the CVC, was expected to have a higher in-line pressure with the same flow rate provided the catheter diameter was the same. However, in actuality, the in-line pressure of the PICC was higher than that of the CVC at a low flow rate, whereas the in-line pressure of the PICC at a high flow rate was significantly lower than that of the CVC. This is considered to be due to the lumen partition wall of the double-lumen tube used in this study. In CVCs, the luminal septum does not move, whereas in pressure-resistant PICCs, the shape of the catheter lumen changes according to the in-line pressure, which expands the effective inner diameter of the catheter.
Regarding red blood cell products, hemolysis reportedly occurs under pressures exceeding 300 mmHg [10]. Thus, rapid transfusion using a pressurized rapid transfusion device was performed at a maximum internal pressure of 300 mmHg. In the present study, the rate of saline administration that resulted in an in-line pressure of 300 mmHg did not differ between the 45-cm PICC and 20-cm CVC and was comparable to 30 mL/min (1800 mL/h). Therefore, the PICC can be used as a transfusion route as well as the CVC in case of rapid transfusion due to massive bleeding. If the flow rate is higher than this, transfusion should be performed through a larger venous route, such as a peripheral venous catheter or sheath.
Several limitations associated with the present study warrant mention. First, the data in the present study were obtained from an in vitro study. Thus, the in-line pressure may be influenced by the intravascular position and resistance of vasculature and may actually be much higher than the result shown here. Second, because the in-line pressure was not measured using red blood cells, the usefulness of a PICC in blood transfusion has not been confirmed.