Intravenous and intraosseous anesthesia

Intravenous anesthesia: principles and indications

Intravenous regional anesthesia is used exclusively for surgical interventions on the limbs. The main indications include surgical wound debridement, reduction of dislocations, reposition of bone fragments in fractures, and arthrotomy.

The fundamental principle of the method's action is the artificial isolation of a specific limb segment from the general circulation. A hemostatic tourniquet is used for this purpose. After administering the anesthetic directly into the lumen of the vein, the drug gradually begins to diffuse from the vascular bed into the surrounding soft tissues. It is precisely due to diffusion that the solution reaches the nerve endings, exerting a powerful local effect on them and ensuring reliable loss of pain sensitivity in the planned surgery zone.

Technique of intravenous anesthesia

The procedure requires strict adherence to a sequence of steps to ensure efficacy and safety.

1. Establishing access: Depending on the location of the surgery, puncture or cutdown of superficial veins is performed. On the upper limb, veins of the forearm or cubital fossa are most commonly used. On the lower limb, access is established via the great or small saphenous vein.
2. Preparation (exsanguination): Before administering the drug, the limb is necessarily elevated for 1–2 minutes. This is necessary to ensure gravitational outflow of venous blood and clear the vascular bed for the anesthetic.
3. Isolation and hemostasis: Proximal (above) to the intended surgery site, an elastic bandage or rubber tourniquet is applied. The main goal of this stage is the complete cessation of arterial blood flow. As a more controlled alternative, a blood pressure cuff can be used, inflating it until arterial pulsation stops.
4. Levels of isolation:
5. For interventions on the foot, lower leg, or knee joint, the tourniquet is applied to the lower third of the thigh.
6. For surgeries on the hand, forearm, or elbow joint, isolation is performed at the level of the lower third of the arm.
7. Drug administration: A 0.25% procaine solution is used. For upper limbs, the volume is 150–200 ml, and for lower limbs, 200–250 ml.
8. Completion of the procedure: After the surgical intervention is completed, the cuff or tourniquet must be removed slowly. This is critically important to prevent a sudden influx of a large volume of procaine into the systemic circulation and to prevent severe toxic reactions.

Intraosseous anesthesia (Bier block)

Intraosseous anesthesia is a specific variant of intravenous regional anesthesia. Its mechanism of action is similar: the anesthetic injected directly into the intraosseous space is first drained into the venous system of the isolated limb and then diffuses into the surrounding soft tissues, blocking nerve pathways.

Just like with intravenous access, an absolute prerequisite for successfully performing an intraosseous block is reliable isolation of the limb from the general circulation using a tourniquet or a pneumatic blood pressure cuff.

Points for drug administration:

• On the upper limb: epicondyles of the humerus, olecranon, and bones of the hand.
• On the lower limb: epicondyles of the femur, malleoli (lateral and medial), calcaneus.

Isolation rules and bone puncture technique

The level of tourniquet application in intraosseous anesthesia strictly depends on the location of the surgical intervention:

• For surgeries on the upper limb, the tourniquet is fixed on the arm.
• For interventions on the foot, the tourniquet is applied to the lower third of the lower leg.
• For surgeries on the lower leg, the tourniquet is placed on the lower third of the thigh.
• For surgeries on the thigh itself, isolation is performed at the level of the upper third of the thigh.

Puncture algorithm:

1. First, local anesthesia of the injection site is performed. For this, the skin, subcutaneous tissue, deeper tissues, and periosteum are infiltrated with the same needle using a 0.25% procaine solution.
2. A special sturdy needle, necessarily equipped with a stylet (an internal rod preventing bone tissue from clogging the needle lumen), is used to pierce the bone.
3. The physician punctures the skin and subcutaneous tissue, then with force and rotational movements penetrates through the dense cortical plate of the bone until the needle enters the cancellous substance.

Dosages of 0.25% procaine solution:

• For the foot, lower leg, and upper limb, 100–150 ml is required.
• For the thigh, the volume is increased to 150–200 ml.

Complications and toxicity

The main danger of both intravenous and intraosseous anesthesia is the development of a toxic-resorptive effect of the drug. This complication usually occurs after the tourniquet is released, when the procaine remaining in the tissues and vessels enters the systemic circulation like an avalanche.

The clinical picture of toxicity manifests as severe general weakness, pronounced dizziness, a drop in blood pressure (arterial hypotension), as well as nausea and vomiting.

It is extremely important to monitor the correct application of the tourniquet before starting the administration of the anesthetic. If the tourniquet is applied incorrectly and does not completely block arterial blood flow, the administered drug will immediately enter the general circulation. In such a situation, regional anesthesia will not occur at all, and the risk of developing severe systemic toxicity will increase manifold.

Class and exam questions

What else to study on this topic

• Anatomic landmarks for puncture and cutdown of superficial veins
• Structural features of cancellous bone and venous drainage pathways
• Pathophysiology of the toxic-resorptive effect of local anesthetics
• Criteria for proper arterial tourniquet application and hemostasis control
• Physiological mechanisms of solution diffusion from the vascular bed into the interstitium

Other topics in the section "CHAPTER 3. ANESTHESIA"

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.