วันศุกร์ที่ 8 พฤษภาคม พ.ศ. 2569

Central Venous Access (CVC)

Central Venous Access (CVC)

Overview

Central venous access คือการใส่ catheter เข้า central vein เช่น

  • SVC
  • IJV
  • Subclavian vein
  • Femoral vein
  • Iliac vein
  • IVC

ใช้สำหรับ:

  • Infusion
  • Hemodynamic monitoring
  • Extracorporeal therapies
  • Device insertion

Types of Central Venous Catheters

ตาม duration

Short-term

  • Nontunneled CVC

Mid/Long-term

  • PICC
  • Tunneled catheter
  • Implanted port

Types by insertion site

  • Internal jugular vein (IJV)
  • Subclavian vein (SCV)
  • Femoral vein
  • Basilic/Cephalic vein (PICC)

Indications

1. Difficult peripheral access

  • Shock
  • Obesity
  • Burns
  • Chronic illness
  • Frequent blood draw

2. Infusion incompatible with peripheral vein

ได้แก่:

  • Vasopressors
  • Hyperosmolar solution
  • TPN
  • Chemotherapy
  • Irritant medications

3. Hemodynamic monitoring

ใช้วัด:

  • CVP
  • ScvO₂
  • Pulmonary artery pressures

4. Extracorporeal therapies

เช่น:

  • Hemodialysis
  • CRRT
  • ECMO
  • Plasmapheresis

5. Device insertion

เช่น:

  • Pulmonary artery catheter
  • Pacemaker
  • ICD
  • IVC filter

Site Selection

เลือกตาม:

  • Operator experience
  • Ultrasound availability
  • Anatomy
  • Coagulopathy
  • Infection risk
  • Pneumothorax risk
  • Need/duration of access

Comparison of Sites

Site

Advantages

Disadvantages

Internal jugular

Easy US guidance

Less comfortable

Subclavian

Lower infection

Pneumothorax, hard compression

Femoral

Fast, easy during CPR

Higher infection/DVT

PICC

Long-term use

Thrombosis

Internal Jugular Vein (IJV)

Advantages

  • Easily visualized with ultrasound
  • Compressible
  • Lower pneumothorax risk than SCV

Disadvantages

  • Patient discomfort
  • Infection > subclavian
  • Carotid puncture possible

Subclavian Vein

Advantages

  • Lowest infection rate
  • Comfortable
  • Stable fixation

Disadvantages

  • Pneumothorax risk
  • Difficult compression
  • Avoid in severe coagulopathy

Femoral Vein

Advantages

  • Fastest access
  • No pneumothorax
  • Useful during CPR/shock

Disadvantages

  • Highest infection/DVT risk
  • Difficult mobilization

Ultrasound Guidance

Strongly recommended

Benefits:

  • ↑ first-pass success
  • ↓ attempts
  • ↓ arterial puncture
  • ↓ hematoma
  • ↓ pneumothorax
  • ↓ procedure time

Ultrasound benefits by site

IJV

Major benefit demonstrated clearly

Arterial puncture:
ลดจาก ~9.4% → 2%

Complications:
ลดจาก ~13.5% → 3.4%

Femoral

First-pass success:
84% vs 46% (US vs landmark)

Subclavian/Axillary

ลด:

  • Arterial puncture
  • Hematoma
  • Pleural complications

General Preparation

Monitoring

ควรมี:

  • ECG monitoring
  • Pulse oximetry
  • Oxygen available

Positioning

Trendelenburg position

ช่วย:

  • Distend vein
  • ลด air embolism

แต่ระวัง:

  • Respiratory compromise
  • Obesity
  • Elevated ICP

Sterile Technique

Full maximal barrier precautions:

  • Sterile gown
  • Sterile gloves
  • Mask
  • Cap
  • Full-body drape
  • Sterile ultrasound probe cover

Skin Antisepsis

Preferred

Chlorhexidine-alcohol (>0.5% CHG)

Superior to povidone-iodine

Allow to air dry completely

No routine prophylactic antibiotics

ไม่มี role สำหรับ routine antimicrobial prophylaxis

Coagulopathy & Thrombocytopenia

Key concepts

  • Major bleeding uncommon (<1%)
  • Platelet dysfunction สำคัญกว่าค่า INR อย่างเดียว
  • Ultrasound reduces bleeding risk

Platelet threshold

ไม่มี absolute cutoff

General approach:

  • Consider platelet transfusion if <20,000/µL
  • Individualize based on:
    • Liver disease
    • Uremia
    • Sepsis
    • Concurrent coagulopathy

Avoid subclavian if severe coagulopathy

เพราะ:

  • Compress difficult
  • Bleeding monitor difficult

Anticoagulation

  • Hold anticoagulant if possible
  • Usually resume within hours if no bleeding
  • Reversal rarely needed

Seldinger Technique

Standard technique for CVC insertion

Steps:

1.       Needle puncture

2.       Venous blood aspiration

3.       Guidewire insertion

4.       Needle removal

5.       Dilator insertion

6.       Catheter advancement

7.       Wire removal

8.       Flush & secure catheter

Confirmation of Venous Placement

ก่อน dilate ควร confirm venous placement

Methods:

  • Ultrasound visualization
  • Venous waveform
  • Dark non-pulsatile blood
  • Pressure transduction

Confirming Catheter Tip Position

Methods

  • Chest X-ray
  • Fluoroscopy
  • Ultrasound
  • TEE
  • Intracavitary ECG

Chest X-ray

Still common standard after:

  • IJV
  • Subclavian CVC

Not routinely needed for uncomplicated femoral line

Intracavitary ECG

ใช้ P-wave morphology เพื่อ identify cavoatrial junction

Findings

  • Maximal P-wave = optimal tip position

Limitations:

  • AF/flutter

Optimal Tip Position

Generally:

  • Lower SVC
  • Cavoatrial junction

Avoid:

  • High SVC
  • Right atrium (risk perforation/arrhythmia)

PICC

Inserted through:

  • Basilic vein
  • Cephalic vein

Advantages:

  • Long-term access
  • Lower pneumothorax risk

Complications:

  • Upper extremity DVT
  • Malposition

Tunneled Catheters

Examples:

  • Dialysis catheter

Features:

  • Subcutaneous tunnel
  • Lower infection
  • Long-term use

Implanted Ports

Used for:

  • Chemotherapy
  • Long-term intermittent access

Advantages:

  • Lowest infection risk
  • Cosmetic

Disadvantages:

  • Requires needle access
  • Procedure room placement

Complications

Mechanical

Arterial puncture

Most common

More common:

  • Landmark technique
  • Difficult anatomy

Pneumothorax

Especially:

  • Subclavian
  • Low IJV puncture

Hemothorax

Rare but serious

Air embolism

Risk increased:

  • Upright patient
  • Hypovolemia
  • Deep inspiration

Prevention:

  • Trendelenburg
  • Occlude hub
  • Remove air

Arrhythmia

Usually from guidewire entering RV

Treatment:

  • Withdraw wire

Catheter malposition

Possible sites:

  • Contralateral vein
  • Azygos vein
  • Arterial placement

Infectious complications

Risk factors:

  • Femoral site
  • Poor asepsis
  • Prolonged duration
  • Multiple lumens

Thrombotic complications

Includes:

  • DVT
  • Catheter thrombosis
  • PE

Higher risk:

  • PICC
  • Malignancy

Prevention of Complications

Key preventive strategies

  • Ultrasound guidance
  • Full sterile barrier
  • Chlorhexidine prep
  • Experienced operator
  • Optimal tip positioning
  • Remove unnecessary lines early

Key Clinical Pearls

  • Ultrasound guidance is standard of care for most central lines
  • Subclavian has lowest infection risk but highest pneumothorax risk
  • Femoral line useful in emergencies but infection/DVT risk highest
  • Avoid subclavian in severe coagulopathy
  • Always confirm venous access before dilation
  • Trendelenburg helps prevent air embolism
  • Maximal sterile precautions significantly reduce CLABSI
  • Catheter tip ideally at lower SVC/cavoatrial junction
  • Remove central line ASAP when no longer needed
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