Therefore, in this study, the investigators propose to use a randomized controlled prospective open study on inpatients with difficult blood collection, by comparing the effects of the application of two types of peripheral venous catheters for blood collection via LPC and MC, with a view to improving the success rate of blood collection in difficult peripheral venous blood collection, and providing a theoretical basis for the later application of long peripheral venous catheters and midline catheters; and providing a basis for optimizing the experience of venous blood collection by nurses.

Using block randomization, patients were randomized in 1:1:1 blocks into experimental arm 1(Long peripheral venous catheter), experimental arm 2(midline catheter), and control (short peripheral venous catheter) with a block length of 6. Patients have a total of 27 blocks, import data into SPSS23, randomly group by SPSS, generate random numbers, and group according to the size of random numbers in each unit group, the largest in the group is assigned to the experimental group 1, the middle of the group is assigned to the experimental group 2, and the smallest in the group is assigned to the control group. The experimental group1 used the LPC for blood collection, the experimental group 2 used the MC for blood collection,and the control group used the Short PIVC for blood collection.

Inclusion Criteria:

• Meet the international diagnostic criteria for metabolic syndrome (such as ATP III criteria or domestic Diabetes Branch of Chinese Medical Association criteria).
• The estimated treatment time of intravenous infusion is 1-4 weeks, and the nature of the infusion drug meets the indications of LPCs and MCs.
• Blood samples should be collected more than 3 times during the hospital.

Exclusion Criteria:

• A history of radiotherapy, thrombosis, and trauma at the catheter site.
• Plan to discharge from the hospital with the tube.
• Vulnerable groups, including people with mental illness, cognitive impairment, critically ill patients, minors, pregnant women, illiterate, etc.

Not possible because of the material and characteristics of the catheter