Help me make toppers concise notes on Cannula ij such a way that I can revise it in last 7 days before exams.
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🩺 CANNULA - Topper's Concise Notes
(Last-7-Days Revision Ready)
1. WHAT IS A CANNULA?
A cannula is a thin tube inserted into a vein (or artery) to deliver fluids, drugs, blood products, or to draw blood. The most common type is the peripheral IV cannula (over-needle type). Central venous cannulas access deep veins (internal jugular/IJ, subclavian/SV, femoral).
2. PERIPHERAL IV CANNULA
Color-Coded Size Chart (MUST memorize)
| Gauge | Color | Flow Rate | Use |
|---|---|---|---|
| 14G | Orange | ~250 mL/min | Massive hemorrhage, trauma |
| 16G | Grey | ~180 mL/min | Blood transfusion, surgery |
| 18G | Green | ~90 mL/min | General use, blood products |
| 20G | Pink | ~60 mL/min | Routine IV fluids, medications |
| 22G | Blue | ~36 mL/min | Children, elderly, small veins |
| 24G | Yellow | ~13 mL/min | Neonates, fragile veins |
Mnemonic: "Orange Gets Big Grey Pigs Blue Bunnies Yellow Chicks" → O-G-G-P-B-Y (Orange 14, Grey 16, Green 18, Pink 20, Blue 22, Yellow 24)
Key Rule: Larger gauge number = smaller bore = slower flow
Preferred Sites (proximal to distal order)
- Antecubital fossa (median cubital vein) - large, reliable
- Forearm (cephalic, basilic, median antebrachial)
- Dorsum of hand
- Foot/ankle (last resort; DVT risk)
Avoid: Joint flexures, infected/bruised areas, same side as mastectomy/lymph node dissection, dialysis fistula arm.
Procedure - Over-Needle Technique
- Tourniquet 10-15 cm above site
- Clean with alcohol swab; allow to dry
- Stabilize vein; insert bevel-up at 15-30°
- Advance until flashback of blood in chamber
- Lower angle; advance cannula off needle 1-2 mm further
- Advance cannula fully while withdrawing needle
- Release tourniquet; apply pressure; connect giving set
- Secure with transparent dressing
Dwell Time / Change
- Peripheral cannula: replace every 72-96 hours (NICE/CDC) or earlier if signs of phlebitis
3. CENTRAL VENOUS CANNULA (CVC)
Sites Comparison
| Route | Advantages | Disadvantages |
|---|---|---|
| IJ (Internal Jugular) | Good landmarks; compressible if bleeding; low pneumothorax risk; straight shot to SVC on right | Harder to secure; possibly higher infection/thrombosis risk vs. SV |
| Subclavian (SV) | Easy to secure; lower infection risk | Cannot compress if bleeding; risk of pneumothorax ~2-6%; avoid in children <2 yr |
| Femoral | Compressible; useful in coagulopathy; easy in CPR | Highest infection risk; highest DVT risk; unreliable CVP; difficult in obese |
(Source: Roberts and Hedges' Clinical Procedures in Emergency Medicine)
4. IJ CANNULATION - STEP BY STEP (Seldinger Technique)
Anatomy
- IJ vein lies lateral to the carotid artery, within the carotid sheath, lateral to the common carotid
- Enters thorax behind the medial end of the clavicle
- Joins the subclavian vein → forms brachiocephalic (innominate) vein → SVC
Landmarks (Landmark Technique - Central Approach)
- Palpate the triangle between the two heads of sternocleidomastoid (SCM)
- Insert needle at the apex of this triangle, aimed at the ipsilateral nipple at 30-45° angle
Seldinger Technique (Step by Step)
Step 1: Position patient - 15° Trendelenburg (distends IJ, prevents air embolism)
Step 2: Head turned away from insertion site (but NOT in trauma)
Step 3: Full sterile prep - gown, gloves, mask, eye protection, sterile drape
Step 4: US survey to identify IJ vs. carotid (vein = compressible; artery = pulsatile, doesn't collapse)
Step 5: Local anesthetic (lidocaine) at insertion site
Step 6: Insert finder needle + syringe; advance with gentle aspiration
Step 7: Free return of dark, non-pulsatile blood = vein located ✓
Step 8: Remove syringe; THUMB OVER HUB (prevent air embolism)
Step 9: Advance J-wire through needle (NEVER FORCE; remove wire + needle as ONE unit if resistance)
Step 10: Remove needle; maintain wire control AT ALL TIMES
Step 11: Nick skin with scalpel at wire entry site
Step 12: Advance dilator over wire → dilate tract → remove dilator
Step 13: Advance CVC over wire (wire must protrude from distal port)
Step 14: Remove wire; aspirate + flush all lumens with saline
Step 15: Suture in place; apply sterile dressing
Step 16: CXR to confirm tip in SVC + rule out pneumothorax
Maximum wire insertion depth: 18 cm from skin (SVC-atrial junction distance in IJ/SV approach) Ventricular ectopy during wire insertion = wire advanced too far → withdraw wire!
5. CONTRAINDICATIONS TO IJ CANNULATION
- Absolute: Serious allergy to antibiotic-impregnated catheter material (e.g., chlorhexidine/rifampin)
- Relative:
- Cervical trauma / distorted anatomy / cervical collar
- Known carotid artery disease (risk of plaque dislodgement)
- Previous IJ trauma (use US)
- Combative/uncooperative patient (sedate first)
- Coagulopathy (prefer US-guided; femoral if severe)
- Previous cannulation on same side (entrapment risk)
- Conditions causing central vein thrombosis/sclerosis (vasculitis, prior long-term cannulation, IV drug use)
6. COMPLICATIONS OF CENTRAL VENOUS CANNULATION
Mechanical (Early)
| Complication | Notes |
|---|---|
| Arterial puncture | Most common; dark blood + no pulsation doesn't exclude in shock |
| Hematoma | Compress; if artery lacerated → surgical repair |
| Pneumothorax | SV >IJ; up to 6% subclavian; get CXR post-procedure |
| Hemothorax | SV/subclavian artery laceration; surgical repair if large |
| Hydrothorax/Hydromediastinum | IV fluid into pleural space |
| Air embolism | Rare but fatal; prevent by thumb on hub + Trendelenburg position; treat: left lateral decubitus + head down |
| Wire embolism | Wire sheared against needle tip; never withdraw wire against resistance |
| Cardiac arrhythmias | Wire too far into RV; withdraw wire |
| Cardiac tamponade | Myocardial puncture by wire/catheter |
Infectious (Late)
- CLABSI (Central Line-Associated Bloodstream Infection) - major late complication
- Prevention: "Central Line Bundle" - hand hygiene, full barrier precautions, chlorhexidine skin prep, optimal site selection (avoid femoral), daily review of line necessity → remove ASAP
Thrombotic
- DVT/thrombosis: femoral > IJ > subclavian
7. CXR AFTER CVC PLACEMENT
Always mandatory after IJ or subclavian CVC.
Confirm:
- Tip position: distal SVC (at SVC-RA junction, ~2-3 cm above RA)
- No pneumothorax / hemothorax
Tip in RA = too far → pull back
8. ULTRASOUND GUIDANCE FOR CVC
- Now standard of care (recommended by AHRQ, NHS NICE)
- Vein vs. artery on US: Vein = compressible, thin wall, non-pulsatile; Artery = does not collapse, pulsatile, thicker wall
- If vein doesn't collapse with pressure → suspect thrombosis or misidentification
- Use sterile transducer sheath + sterile gel during procedure
- Reduces arterial puncture rate to ~1.4% for IJ (vs. ~5-10% landmark)
9. HIGH-YIELD ONE-LINERS (Exam Favorites)
| Question | Answer |
|---|---|
| Seldinger technique described for? | Percutaneous arteriography (1953) |
| Most common method for CVC? | Seldinger (guidewire) technique |
| Distinguishing vein from artery on US? | Vein collapses with pressure; artery does not |
| Wire won't advance - first action? | Reattach syringe, confirm blood return; DO NOT force |
| Wire + needle resistance on withdrawal? | Remove BOTH as a single unit (prevent wire embolism) |
| Bright red pulsatile blood → ? | Arterial puncture - remove immediately |
| Dark blood doesn't exclude artery in? | Shock states / severe desaturation |
| Max wire depth for IJ/SV? | 18 cm |
| Post-IJ/SV CVC CXR checks? | Tip in SVC + exclude pneumothorax |
| Highest infection risk CVC site? | Femoral |
| Safest site in coagulopathy? | IJ (compressible) or femoral (US-guided) |
| Subclavian contraindicated in children? | <2 years old |
| Peripheral cannula change interval? | Every 72-96 hours |
| Trendelenburg position in CVC - why? | Distends IJ + prevents air embolism |
| Largest peripheral cannula in emergencies? | 14G (Orange) |
| Treatment of air embolism? | Left lateral decubitus (Durant's position) + head-down + O2 |
10. COMPLICATIONS OF PERIPHERAL IV CANNULA
| Complication | Features | Management |
|---|---|---|
| Phlebitis | Pain, redness, warmth, cordlike vein | Remove cannula; warm compress |
| Extravasation | Non-vesicant drug outside vein; swelling, pain | Remove; elevate; cool compress |
| Infiltration | IV fluid leaks into surrounding tissue | Remove; elevate limb |
| Thrombophlebitis | Clot + inflammation | Remove; anticoagulate if needed |
| Hematoma | Cannula through posterior wall | Remove; apply pressure |
| Air embolism | Air entry during insertion | Prevention; Durant's position if occurs |
| Infection/Sepsis | CLABSI or local site infection | Strict sterile technique; remove if suspected |
REVISION CHECKLIST (tick before exam)
- Cannula gauge-color-flow chart (O-G-G-P-B-Y)
- Seldinger technique 16-step sequence
- IJ anatomy & landmark triangle
- US: vein = compressible
- CVC site comparison table (IJ vs SV vs Femoral)
- Wire rules: never force, never withdraw against resistance
- Post-CVC: always get CXR
- CLABSI bundle
- Complications + their management
- Air embolism = Durant's position
Sources: Roberts and Hedges' Clinical Procedures in Emergency Medicine; Pye's Surgical Handicraft (22nd ed.); Barash Clinical Anesthesia (9th ed.)
Here are your topper-level concise notes on Cannula - built for last-7-days exam revision. Here's what's covered:
- Peripheral IV cannula - gauge-color-flow chart, technique, dwell time, complications
- Central venous cannula - site comparison (IJ vs. Subclavian vs. Femoral)
- IJ cannulation - anatomy, landmarks, full Seldinger technique step by step
- Contraindications for IJ approach
- Complications - mechanical, infectious, thrombotic - with management
- CXR confirmation protocol
- Ultrasound guidance - how to differentiate vein from artery
- High-yield one-liners table - exactly the kind of MCQ traps that come in exams
- Revision checklist at the end
The notes are drawn from Roberts and Hedges' Clinical Procedures in Emergency Medicine, Barash Clinical Anesthesia (9th ed.), and Pye's Surgical Handicraft. Use the high-yield table for last 2 days before the exam - everything else for days 3-7.
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