19.2 Intraosseous Access, Crystalloid Fluid Therapy, Pressure Infusers & Blood Products

19.2 Intraosseous Access, Crystalloid Fluid Therapy, Pressure Infusers & Blood Products

CPCF Appendix A skill #27A — Fluid and resuscitation — requires the Primary Care Paramedic to conduct intraosseous needle insertion, administer crystalloid solutions, utilize direct pressure infusion devices with IV infusions, and monitor an infusion of blood and/or blood products, alongside cardiopulmonary resuscitation and defibrillation (Section 12.1) and adapting care in the presence of a left ventricular assist device (Section 12.3).

Intraosseous Access

Why It Works

The medullary cavity of a long bone contains a rich, non-collapsible venous plexus that drains through nutrient and emissary veins directly into the central circulation. Because the sinusoids are held open by the surrounding bone, they remain accessible in shock and cardiac arrest when peripheral veins have collapsed. Onset, dosing, and drug selection are equivalent to the intravenous route — anything you may give intravenously, you may give intraosseously at the same dose.

Indications

Intraosseous access is indicated when vascular access is urgently required and peripheral intravenous access has failed or is not rapidly achievable — typically cardiac arrest, profound shock, or a critically ill patient in whom delay would cause harm. It is not a convenience route; it is an emergency route, used within the paramedic's directive and authorization.

Sites

Contraindications

• Fracture in the target bone, or a bone proximal to it in the same limb
• A previous intraosseous attempt in the same bone within roughly 48 hours — fluid extravasates from the earlier hole
• Infection, burn, or compromised skin over the site
• Prosthesis or orthopaedic hardware in the target bone
• Inability to identify the landmarks
• Osteogenesis imperfecta or osteopetrosis (relative)

Technique and the Critical Steps

1. Position and expose the limb, identify landmarks, and clean the site.
2. Insert perpendicular to the bone, avoiding the growth plate in children.
3. Advance until a distinct loss of resistance as the cortex is breached; confirm the needle stands unsupported.
4. Remove the stylet and secure the hub.
5. Aspirate for marrow if possible — helpful but its absence does not mean failure.
6. Flush forcefully with 5 to 10 mL of saline in adults (2 to 5 mL in children). This step is mandatory: it displaces marrow and opens the sinusoids, and without it flow will be poor or absent.
7. Confirm placement: the needle is firm and stands alone, the flush runs without resistance, and there is no swelling in the surrounding soft tissue or the calf compartment.
8. Use a pressure infuser or a syringe push — intraosseous infusions rarely flow adequately under gravity alone.

[!CAUTION] Extravasation into the compartment is the complication to fear. Infusing into a misplaced or dislodged needle drives fluid into the muscle compartment and can cause compartment syndrome, with limb loss in the worst cases. Check the posterior calf and the circumference of the limb after the flush and at every reassessment. Dislodgement is the commonest cause, so the needle and limb must be secured before movement.

Pain: the flush and infusion are intensely painful in a conscious patient. Slow, preservative-free lidocaine through the needle before flushing is standard practice where authorized. Never withhold analgesia simply because the access is working.

Crystalloid Fluid Therapy

Which Fluid

The examinable rule: only isotonic crystalloid is used for acute volume expansion. Hypotonic and dextrose-containing solutions redistribute out of the intravascular space and can worsen cerebral oedema in head injury.

How Much, and When to Stop

Fluid is a drug with a dose and a toxicity. The general principles:

• Give a measured bolus and reassess — the reassessment is the therapy. Look at mental status, heart rate, peripheral perfusion, and blood pressure trend after each bolus rather than running fluid continuously.
• Weight-based dosing in children, commonly 10 to 20 mL/kg per bolus per local directive, reassessing between boluses.
• Uncontrolled haemorrhage: aggressive crystalloid does not replace blood, dilutes clotting factors, raises blood pressure enough to displace a formed clot, and worsens hypothermia and acidosis — the lethal triad of hypothermia, acidosis, and coagulopathy. Contemporary practice is a restrained approach targeting a palpable radial pulse and adequate mentation rather than a normal blood pressure, within the local directive.
• Cardiogenic shock and pulmonary oedema: fluid is harmful. A patient with crackles, raised jugular venous pressure, and a history of heart failure needs a completely different approach.
• Dialysis-dependent patients (Section 14.6) have no way to excrete the volume you give.
• Warm the fluid where possible. Cold fluid worsens hypothermia, which worsens coagulopathy.

Monitoring an Infusion

Reassess the site at least every 15 minutes and after every movement; watch the volume infused against the prescribed rate; and look actively for the signs of overload — new or worsening dyspnoea, crackles, rising respiratory rate, distended neck veins, frothy sputum. Overload is iatrogenic and is caused by not watching.

Direct Pressure Infusion Devices

A pressure infuser is a sleeve inflated around a fluid bag to drive infusion faster than gravity permits.

• Purge all air from the bag before applying pressure — a pressurized bag that empties can force air into the circulation, and air embolism is the specific hazard of this device.
• Do not exceed the recommended pressure (commonly around 300 mmHg).
• Watch the bag continuously and stop before it empties.
• Pressure does not compensate for a narrow catheter — Poiseuille's law still applies.
• A pressure infuser does not make an infiltrated line work; it makes an infiltration worse, faster. Confirm the site first.
• Intraosseous infusions usually require pressure or syringe push to flow adequately.

Monitoring an Infusion of Blood or Blood Products

Skill #27A requires the PCP to monitor a blood or blood-product infusion — typically during an interfacility transfer. The paramedic is not initiating the transfusion; the competency is vigilance.

Before departure:

1. Confirm that the identity check has been completed and documented by the transferring facility: patient identifiers, blood group, unit number, and expiry, checked against the compatibility label.
2. Record the start time, the volume already infused, and the prescribed rate.
3. Confirm the fluid running alongside is 0.9% sodium chloride — not Ringer's lactate, whose calcium can cause clotting in the line, and not a dextrose solution, which causes haemolysis.
4. Note the patient's baseline observations, and know where the transfusion documentation is.

During transport: observe frequently, particularly in the first 15 minutes when severe reactions most often begin, and record observations at the intervals the transferring facility specifies.

Recognizing a reaction:

If a reaction is suspected:

1. Stop the transfusion immediately.
2. Keep the intravenous line open with 0.9% sodium chloride through new tubing — never flush the remaining blood in the existing line into the patient.
3. Support airway, breathing, and circulation, and treat within your directive.
4. Retain the unit, the tubing, and all documentation — they are required for the investigation.
5. Notify medical direction and the receiving facility immediately, and document times and observations precisely.