1 Introduction

In recent years, PICC catheterization has been favored by ICU medical staff due to its advantages, such as longer retention time, lower infection rate, ability to monitor central venous pressure, and meeting a variety of treatment needs of intravenous infusion. The PICC is inserted through the superficial peripheral vein (basilic vein, median cubital vein, cephalic vein, among others) and directed to the superior vena cava (SVC) or the junction between the SVC and right atrium (RA) [1]. This allows for safe and effective intravenous infusions for patients with various medical needs.

Patients admitted to the neurosurgical ICU(NSICU) are patients with acute cerebrovascular disease with Glasgow Coma Score (GCS) of 12 or less, patients with craniocerebral injuries and spinal cord injuries, perioperative neurosurgical intensive care patients, severe neurological infections, persistent epilepsy, and other neurological emergencies [2]. These patients are characterized by long duration of illness, increased intracranial pressure, malnutrition, postoperative pain, susceptibility to epilepsy, susceptibility to infection, and low blood volume. They have therapeutic needs such as infusion of hypertonic fluids to lower intracranial pressure, hemodynamic monitoring such as central venous pressure, parenteral nutrition, analgesia and sedation, antiepileptic, fluid management (including antishock therapy), and circulatory system management [3]. Among them, mannitol and hypertonic saline for lowering intracranial pressure, as well as parenteral nutritional fluids, are hypertonic; most of the drugs used for anti-infective, analgesic sedation and antiepileptic, and vasoactive drugs such as norepinephrine, dobutamine and mesalamine used for antishock therapy are herpetic fluids. PICC can be left in place for long periods, have a multi-access design, and monitor hemodynamics, making them a valuable tool for NSICU therapy [4].

Meanwhile, patients with severe neurological diseases impose higher requirements on the operator. On the one hand, the operators should quickly complete the catheterization operation to reduce the impact of sedative and analgesic drugs on the patient’s consciousness. On the other hand, to avoid aggravating intracranial hypertension, it is essential to prevent keeping the patient’s head low during the operation, as well as a long-term head deviation to one side and compression of the internal jugular vein, which may affect internal jugular vein reflux. More importantly, the PICC tip should be placed as precisely as possible because mispositioning of the catheter tip may obstruct the return of the internal jugular vein and lead to increased intracranial pressure [5].

Ultrasound-guided PICC catheterization can locate peripheral puncture vessels more accurately than the blind pushing technique [6]. However, ultrasound guidance cannot confirm the position of the PICC tip. Recent literature reported that ECG-guided can improve the accuracy of PICC tip positioning by allowing observation of the shape and amplitude of the P-wave [7]. Therefore, we retrospectively summarized and analyzed 308 patients with PICC placement in our department from January 2017 to January 2021. The position of the PICC tip and the catheterization process were compared between the group who received ECG-guided tip positioning combined with ultrasound guidance and those who received ultrasound-guided tip positioning without ECG guidance.

2 Methods

This was a retrospective study of adult patients admitted to the neurosurgical ICU of the First Affiliated Hospital, Sun Yat-sen University, from January 2017 to January 2021. Patients who underwent PICC placement were included in the study (Fig. 1). The hospital ethics committee approved this study (Ethics No. [2021] 370). Due to the retrospective nature of the study, informed consent was not required.

Fig. 1
figure 1

Study flow chart. NSICU neurosurgery intensive care unit, PICC peripherally-inserted central venous catheter

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Exclusion criteria were established to exclude patients with unsuccessful PICC catheterization due to peripheral vascular toughness, refusal to sign an informed consent form, patient allergy to the PICC material, pregnancy, or inability to receive X‑rays. Additionally, patients with serious cardiovascular diseases, abnormal P‑wave, severe heart blockage, a pacemaker, or implantable defibrillator were only guided by ultrasound for PICC implantation.

A total of 400 patients were finally enrolled, of which 243 cases underwent placement of the PICC under ECG-guided tip positioning combined with ultrasound guidance, and 157 cases underwent placement of the PICC under only ultrasound-guided placement.

The study authors (JX) carried out the insertion of the PICC (5 Fr single-lumen Silastic catheters or 5 Fr dual-lumen Turbo-Ject® Power-Injectable PICC, Becton, Dickinson, and Company), who had obtained the “PICC catheterization training certificate” issued by the Guangdong nursing society. The institutional sterile bundle and the PICC catheterization process for placement were strictly implemented.

The predicted length of the PICC was estimated by measuring from the puncture site to the right sternoclavicular joint and then down to the third intercostal space. Radiographic evaluation in the proximity of the junction between the VC and the RA confirmed that the tip of the catheter was in the correct position.

Ultrasound-only guidance group: Ultrasound was used to assist in the puncture and to ensure that the catheter did not accidentally enter the internal jugular vein [8]. The operator used a standard 5 to 10 MHz linear ultrasound probe to locate the appropriate vein above the elbow as the puncture point, with the PICC going through the basilic, brachial, or cephalic vein. To guide the PICC toward the SVC, the patient’s head was turned to the puncture side so that the lower jaw was close to the chest, and the internal jugular vein was compressed when the PICC was estimated to be near the armpit. After placing the predicted length, the left and right internal jugular veins were examined by ultrasound to confirm that the catheter was not malpositioned. If the catheter was detected in the internal jugular, it was retracted to the subclavian and reattempted until it could no longer be detected by ultrasound. Finally, the catheter was secured, and a bedside chest X-ray verified the position of the tip.

Combined ECG and ultrasound-guided tip positioning group (ECG-plus-ultrasound group): The PICC catheterization was performed with ultrasound guidance and intracavitary electrocardiography to verify the correct position of the PICC tip [9]. When the catheter approached the predicted length (approximately 8–10 cm remaining), the supporting guide wire was connected to the RA lead under lead II on the bedside ECG monitor using sterile forceps. The catheter was slowly delivered to obtain the intracavity electrogram, and the change in the P‑wave amplitude of the electrogram was carefully observed. As the catheter is gradually fed into the superior vena cava (SVC), the P-wave amplitude of the intracardiac electrogram gradually becomes hyperpolarized to the maximum amplitude, and the catheter continues to be fed, and the intracardiac electrogram shows that the P-wave is negative–positive and bi-directional; at this time, the operator retracts the catheter to the maximum amplitude of the P-wave and then retracts it again by 0.5 to 1.0 cm, and records the total length of the catheter, fixes the catheter with one hand, withdraws the supporting guidewire in parallel with the other hand at a slow, uniform speed, and inserts the PICC catheter.

The final PICC tip position was confirmed by bedside chest X-ray based on Infusion Nurses Society guideline [10]. The criteria for determining the PICC tip were as follows: The correct position of the PICC tip should be at the level of the T5 or below, but no more than the T8 (T5–T8) [11]. The optimal position of PICC tip was the tip should be in the middle and lower segment of the SVC, close to the junction of the SVC and the RA, approximately 2 cm above the RA, at a level within the 6th–7th thoracic intervertebral when positioned by chest X-ray (T6–T7). It was too shallow if the catheter tip was lower than the T5 (< T5). If the catheter tip was higher than T8 (> T8), it was too deep. An ectopic of the PICC tip was defined as being located in peripheral veins such as the internal jugular and axillary veins.

The primary outcome variables in this study included gender, age, arm circumference 10 cm above the elbow, preset depth catheter depth, the position of the PICC tip, and some events during catheterization such as difficult catheter delivery, blocked blood return, replace the puncture vessel.

SPSS 25.0 statistical software was used for data analysis. The measurement data are expressed in X ± standard deviation, and a t-test was adopted. The counting data were expressed as a percentage, and the Chi-square test was used. One-way analysis of variance (ANOVA) and Logistic regression analysis were used. P < 0.05 was considered statistically significant.

3 Results

3.1 Patients and Enrollment

The study included 400 patients with severe neurosurgical disease, including 353 patients with PICC tips in place and 47 patients with tips not in place, which can be further divided into 243 in the group undergoing ECG-guided tip positioning combined with ultrasound guidance and 157 in the ultrasound-only group. The primary diagnoses were brain trauma, brain tumor, and cerebrovascular disease. The punctured veins were the left and right basilic vein, left and right brachial vein, left and right cephalic vein, and median elbow vein. From high to low, the punctured vessels in the ultrasound-only group were the left and right basilic vein, left and right brachial vein, left and right elbow median vein, and right cephalic vein.

To explore the reasons that affect the position of the PICC catheter tip, we included factors such as gender, age, arm circumference, preset depth, ECG use, and selection of catheterization vessels for ANOVA and Logistic regression analysis (Tables 1, 2). ECG use improved PICC tip-in-place rates (OD, 4.541; 95CI, 2.224–9.271; p < 0.001) (Table 2).

Table 1 Single-factor analysis of the influencing factors of PICC catheterization
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Table 2 Logistic regression analysis of the influencing factors of PICC tip position
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4 PICC Tip Position

Subsequently, we investigated the effect of ECG guidance on the tip position of PICC catheters. The optimal placing rate of the PICC tip in the ECG-plus-ultrasound-guided tip positioning group was 90.73%, which was significantly higher than that in the ultrasound-only group (79.00%), χ2 was 30.69 (p < 0.001), the incidences of PICC tip shallowness rate (2.40%) and ectopic tip (1.20%) in the ECG-plus-ultrasound group were significantly lower than that in the ultrasound-only group, and the PICC tip over depth rate (4.00%) is slightly higher than that in the ultrasound-only group (Table 3).

Table 3 The tip position
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5 Catheterization Process

Regarding catheter complications, no arrhythmia or hematoma at the puncture site was observed in either group. In the ECG-guided tip positioning combined with the ultrasound guidance group, only five cases required repeated adjustments to obtain a correct P-wave. There were no incidences of blocked blood return, which was significantly better than the ultrasound group (9.55%) (2 = 14.402, p < 0.001). There was no significant difference in the incidence of difficult tube delivery and replacement of puncture vessels (Table 4).

Table 4 The PICC catheterization process
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6 Discussion

In this study, ECG-guided tip positioning combined with ultrasound for patients with severe neurological diseases can increase the correct placement rate while not aggravating the incidence of adverse events in catheterization. Bedside chest X-ray examinations, ultrasound-guided, ECG-guided, and other methods are commonly used in the ICU to assist the PICC tip positioning. The chest X-ray examination is the ‘gold standard’ for the PICC tip positioning but has delayed feedback [10]. While the ultrasound can monitor the catheter’s position, it cannot ensure the correct placement of the PICC tip. The optimal position of the catheter tip is to reach the middle and lower segment of the SVC, close to the junction between the SVC and RA, approximately 2 cm above the RA, and the length of the lower 1/3 segment of the human SVC is relatively short [12]. The patient’s postural variations, arm movement, thoracic pressure, and respiratory changes often affect the PICC tip position. Therefore, if the PICC tip is not optimal, it will float seriously [13]. For patients with severe neurological disease, especially those with intracranial hypertension, having the PICC tip in the optimal position can reduce the risks of catheter displacement or even reversal into the internal jugular vein, which will affect cerebral venous reflux. The ECG-guided tip positioning method is convenient and sensitive [14, 15]. The operator needs to connect the supporting guide wire in the catheter to an electrocardiograph or ECG monitor and can achieve real-time tip positioning in catheterization. The P-wave amplitude increases when the PICC tip reaches the middle and lower third of the SVC, which is closer to the sinoatrial node. When the PICC tip is very close to the sinoatrial node, the P-wave shows a high vertical spike and the largest peak. When the PICC enters the RA, the far-field potential affects the P-wave and presents a low negative waveform. If the PICC tube is too deep, the P-wave will be inverted. Therefore, the correct positioning of the PICC tip can be monitored in real time by the waveform of the P-wave [16].

We also found differences between the predicted length of the catheter and the actual insertion length in the group receiving ECG-plus-ultrasound-guided tip positioning, indicating that it may not be accurate enough to determine the position of the catheter tip based on calculating the insertion length of the tube using the measurement of anatomical structures. At the same time, the application of ECG tip positioning technology in the catheterization process can compensate for the above deficiency. Our research also showed that in the ultrasound-only guidance group, the method of determining the length of catheter placement by only measuring anatomical markers cannot fully ensure that the catheter tip is in place, and the incidence of tip displacement and excessive tip depth is greater than that in the combined ECG tip positioning group.

The application of ECG-guided tip positioning combined with ultrasound in PICC catheterization for patients with severe neurological illnesses can prevent the operator from pressing the internal jugular vein during the procedure. In the blind pushing technique and ultrasound guidance, pressing the internal jugular vein is a common practice to prevent the catheter from entering the internal jugular vein. However, this practice is hazardous for patients with severe neurological disease as it can increase cerebral blood volume, ultimately increasing the risk of intracranial hypertension. Additionally, patients with severe neurological diseases cannot cooperate due to neck stiffness, coma, indwelling artificial airway, and other conditions. At this time, the operator’s forced compression of the internal jugular vein will lead to agitation and severe cough, which will further increase the risk of intracranial hypertension. In the present study, under ECG-plus-ultrasound-guided tip positioning, the routine step of pressing the internal jugular vein was abandoned, which benefits patients with severe neurological disease, especially those with high intracranial pressure.

There are some limitations in this study. First, this study was a retrospective study with insufficient randomization of patient groups. Second, in this study, only the catheterization process was recorded, and long-term complications such as catheter-related thrombosis and catheter-related infection will be our next step. Nevertheless, the retrospective study provides some guidance for the PICC placement.

7 Conclusion

PICC catheterization is crucial for patients in the neurosurgery ICU who are often comatose for a long time and need to be infused with solid vascular-irritating and high-concentration drugs. PICC can prevent the complications associated with repeated puncture and catheterization while reducing the damage to peripheral blood vessels caused by infusion of stimulant drugs. However, it should be noted that improper operation during the catheterization process and poor positioning of the catheter tip may pose a risk to patient safety. In this study, the application of ECG-guided tip positioning combined with ultrasound guidance to PICC catheterization in patients with severe neurological diseases significantly improved the accuracy of placement rate without increasing the difficulty of catheterization and the incidence of catheterization complications. Therefore, using ECG-guided tip positioning combined with ultrasound guidance in PICC catheterization is feasible for NSICU patients.