Intravenous anaesthesia technique

2021-05-15 12:59 PM

When local anaesthetic is injected into the vein for venous anaesthesia, the local anaesthetic is concentrated in the area below the tourniquet, the local anaesthetic is located first in the large superficial veins

Outline

Concept

Venous anaesthesia is injecting a local anaesthetic into a vein in a limb after the blood has been collected to the proximal extremity of the area to be operated on, and then a garrot is placed at the base of the extremity in the area where all the blood has been collected. The anaesthetic will follow the intravenous route to spread to the sub-gargoyle, inhibiting the nerves that supply that area.

For surgery on the hand and forearm, this technique has many advantages, that is, it is a simple technique, has a high success rate, only fails about 1%, if compared with anaesthesia of the wing plexus. hand.

In principle, to ensure the safety of the technique, only 0.5% xylocaine anaesthetic is used, a double-stage tourniquet is used, and the tourniquet is released slowly to avoid the risk of anaesthetic toxicity.

History

August Bier (Germany) was the first to describe and perform intravenous anaesthesia with procaine in 1908.

The technique of intravenous anaesthesia has only really been applied since 1963 when Holmes improved.

The technique of intravenous anaesthesia has been applied in Vietnam since the war against America.

Indications and contraindications

Point

In hand, forearm, foot or foot surgery, the operation time is less than 90 minutes.

Especially in patients at risk such as allergy to anaesthetics, muscle relaxants, patients with respiratory failure, full stomach in emergency surgery conditions.

Outpatient.

In older children with the condition that the tourniquet can be placed.

Contraindications

Absolute contraindication

History of allergy to local anaesthetic.

Malignant high fever.

Seizures due to brain stimulation.

Severe atrioventricular conduction disturbances.

Lower blood pressure.

The patient disagreed.

Relative contraindications

Liver failure.

Severe high blood pressure.

Technical contraindications

Haemolytic anaemia.

The wound is large enough to drain the anaesthetic.

Infectious and toxic lesions are at risk of spreading throughout the body.

Arteriosclerosis and occlusive disease.

Mechanism of action

The mechanism of action is still not fully understood, many hypotheses have been put forward:

The garrot causes ischemia and nerve compression resulting in an analgesic effect.

The analgesic effect of local anaesthetics, anaemia only enhances the effect of local anaesthetics and relaxes muscles due to inhibition of acetylcholine secretion, possibly also due to metabolic acidosis, hypoxia, and accumulation of metabolites such as acidosis. Lactic acid causes this condition.

Local anaesthetics act on all sensory and motor nerves, the smaller the fibres, the more easily they are inhibited.

The site of local anaesthetic action is at three levels: nerve trunks, nerve endings, and neuromuscular junctions.

When injecting local anaesthetic into a vein for venous anaesthesia, the local anaesthetic is concentrated in the area below the tourniquet, the local anaesthetic is located first in the large superficial veins, then in the muscle veins and veins. connections and deep veins.

In fact, one does not see veins located far from the injection site where the anaesthetic is delivered. The distribution of local anaesthetic is mainly in the surrounding tissues and nerves during the time the tourniquet remains the same. After removing the tourniquet, the anaesthetic will return in the opposite direction from the organization to the circulatory system, this is a type of contact anaesthesia.

In the upper extremities, the median and ulnar nerves are better perfused and thus are more strongly inhibited than the radial nerve, so pain relief usually occurs first in the anterior medial region of the forearm and in the extremities, even though local anaesthetic is not available. penetrates the distal veins.

Advantages and disadvantages of the technique

Advantage

The biggest benefit is that there is no need for expensive equipment and highly specialized people. It is essential to perform the correct technique, to use the correct dose and volume of drug, in addition, to perform emergency resuscitation techniques.

Allows early surgery because of its fast effect, allows surgery on patients with full stomach, patients with contraindications to general anaesthesia such as respiratory failure and allows this technique to be performed in outpatients.

Disadvantage

Side effects of anaesthetics.

The short duration of pain relief.

Discomfort due to tourniquet and no pain relief after surgery, sometimes not enough muscle relaxation.

Injecting local anaesthetic into the vein causes swelling at the injection site, hematoma, or insufficient pain relief.

Pain at the site of injury in the extremities during blood collection for intravenous anaesthesia.

An unintentional tourniquet can also cause complications of anaesthetic toxicity.

Techniques for intravenous anaesthesia in the upper extremities

Prepare

Prepare the patient

Prepare the patient before surgery:

Preoperative examination to detect abnormalities, explain and exchange ideas with patients so that they can be assured.

 Preparing the patient for surgery:

 There must be a good intravenous line to administer fluids and drugs.

Monitor vital parameters: pulse, temperature, blood pressure...

Have to prepare respiratory emergency equipment (ambu balloon, oxygen, endotracheal lamp, endotracheal tube) and resuscitation medicine...

Tool

The Esmarch gang.

A 2-stage tourniquet (in the absence of a tourniquet, a sphygmomanometer can be used, but the cuff must be kept tight to avoid dangerous slippage).

Needle, syringe or intravenous catheter.

The anaesthetic xylocaine 0.5% (lidocaine).

Skill

After the blood pressure is measured in the arm, under anaesthesia, a short catheter is inserted into the dorsal or forearm vein. This catheter is placed as close to the extremity as possible, the distance from the injected vein to the surgical site is not important for analgesia. But it should not be injected into a vein above the proximal limb relative to the surgical site because sometimes the one-way valve system will prevent the spread of the anaesthetic.

Raise your arms, palms facing the ceiling.

Use Esmarch bandages to gather blood. Using Esmarch bandage wrapped from the tip of the limb (fingers or toes) gradually to the base of the limb, sometimes due to pain or without the Esmarch bandage, one can collect venous blood by elevating the arm for about 10 minutes when the coil needs to observe the first tourniquet setting.

Insert the first tourniquet and inflate the tourniquet up to the maximum arterial pressure plus 100mmHg, check for no radial pulse, then remove the Esmarch bandage. The tourniquet must be placed in the limb area with many muscles, avoiding placing it on the wrist, ankle, elbow, knee, causing anaemia, lack of oxygen and easily damaging the organization at the place where the tourniquet is placed.

Perform anaesthetic injection, the injection rate of 1ml in 2 seconds. The injection pressure should not be too high to avoid the drug passing through the tourniquet into the general circulation causing anaesthetic toxicity. When the drug is injected into the vein, we will see that the skin in this limb has "goosebumps" and has alternating red and white patches. Some authors recommend that after the injection is completed, use your hands to rub the muscle of the operated limb to help the anaesthetic spread faster, but cause swelling of the limb afterwards.

Figure. Diagram of the steps involved in administering intravenous anaesthesia.

1. Place an intravenous catheter 2. Constrict the blood with an Esmarch. bandage

3. Inflatable tourniquet on the upper floor 4. Inject local anaesthetic

5. Lower grooving pump 6. Upper grooving drain

Some improved techniques have been applied

Creange and Thir-Alquist suggested that only maximal limb elevation for a minimum of 5 minutes was sufficient to induce venous blood flow to induce anaesthesia.

But Rifat only elevating the limb without using an elastic bandage will not guarantee anaesthesia and therefore cases of limb wounds that do not allow the use of elastic bandages are a relative contraindication.

Krishnan suggested that to prolong the analgesia when administering intravenous anaesthesia, the tourniquet should be discharged after 60 minutes, rested for about 5 to 10 minutes, and then raised to the extremity again, re-inflated the tourniquet, and injecting half the initial dose of the drug. head.

Bell and Harris again advise after injecting tourniquet, wait 20 minutes before injecting anaesthetic because arterial ischemia will increase the effect of local anaesthetic, reduce drug dose, side effects but the patient is uncomfortable due to gas. check and the time to operate is shortened.

Some authors think that if we operate on the wrist and hand, we can put two tourniquets in the forearm to reduce the amount of medicine used. But even with a tourniquet, there is still very strong intraosseous circulation in both forearm bones, so this technique should be used with caution.

Venous anaesthesia in the lower extremities

When administering lower extremity venous anaesthesia, the following points should be noted:

Arteritis of the lower extremities is an absolute contraindication because it aggravates the patient's illness.

In addition, when vascular sclerosis is present, the blood vessels may not collapse despite the tourniquet, so the anaesthetic can be injected directly into the general circulation.

Never place a tourniquet at the knee because it can directly compress the lateral popliteal nerve and cause irreversible paralysis.

In practice, it is necessary to place a short catheter in the instep, place a double tourniquet under the knee, uninflated, and then elevate the lower limb for some time (approximately 5 minutes). Place the Esmarch bandage to pool blood only wrap the Esmarch bandage from the foot to the level of the tourniquet. Once blood is pumped to the proximal extremities, be sure to give the upper tourniquet (first tour), then 0.6ml/kg 0.5% xylocaine (approximately 20ml/min) after the injection is complete for about 5-10 minutes later inject the bottom tourniquet (2nd tourniquet) and then drain the 1st tourniquet. Then proceed to surgery.

The process of monitoring, the time of anaesthesia and the removal of the tourniquet are performed as the technique of anaesthesia in the upper extremities.

Anaesthesia and dosage

Lidocaine is a prescribed drug; the usual dose is 2.5-3mg/kg with a concentration of 0.5%. Solutions with high concentrations or large doses have a high risk of causing local anaesthetic toxicity after the tourniquet. Conversely, low volume and concentration may cause insufficient numbness (some places lose sensation, some places still have pain).

With the anaesthetic dose introduced above, the onset of the anaesthetic effect is rapidly established:

Loss of pain sensation in the skin completely after 5-15 minutes after injection depending on the location.

Feeling of touch and autonomous movement disappear after 10-15 minutes, depending on the drug.

After removing the tourniquet, pain and muscle activity are restored after 5-10 minutes

Intravenous anaesthesia is contraindicated for the local anaesthetic bupivacaine. Because when local anaesthetics enter the general circulation (after galloping) causes cardiovascular complications, due to the release of a lot of K + and a decrease in pH to 7.0, it can cause cardiac arrest, even mepivacaine, which is a precursor of bupivacaine is also contraindicated

Procaine 0.5% has been used by A.Bier since 1908 but is no longer used because the duration of action is too short.

Chloprocaine is now rarely used, although the anaesthetic effect is good, the rate of causing thromboembolism is high (about 8%).

Prilocaine is contraindicated in patients with heart failure and anaemia because an overdose of the drug causes hypoxia and should only be used in healthy people, the dose is about 3mg/kg, the concentration is 0.5%.

Currently, only lidocaine and prilocaine are the most commonly used.

Do not add adrenaline to the anaesthetic solution because it increases anaemia during the tour and the systemic effect after the tourniquet is removed.

After 5 -10 minutes inflate the second tourniquet in the pain relief area with the same pressure as the first tourniquet. Check that the second tourer is safe, then release the first one.

Record the time of the tourniquet on the anaesthesia sheet.

Remove the tourniquet

Do not remove the tourniquet before 30 minutes even after surgery.

The danger is that local anaesthetics and metabolites enter the systemic circulation after early throttling.

Garage discharging technique:

Deflate slowly, after 10-15 seconds inflate again and hold for 30-60 seconds.

Can repeat a second time.

After discharging the tourniquet, the patient must be monitored for 10 minutes.

Keep the limb immobile for the first 30 minutes to reduce anaesthetic migration.

Anaesthesia time: Allowed about 90 minutes for upper extremities, can be extended up to 120 minutes for lower limbs.

Some problems related to anaesthesia and complications

Anaesthesia time

The duration of anaesthesia always depends on the time of tourniquet placement, usually about 90 minutes for the upper extremities, if the surgery is longer, it will cause many difficulties for both surgery and anaesthesia technique. To avoid this incompatibility, many authors recommend that continuous intravenous anaesthesia can be applied, especially when applied to the upper extremities. The technique is performed as follows:

Performing intravenous anaesthesia requires saving the catheter and when the anaesthetic time reaches 90 minutes, remove the tourniquet for 5-10 minutes, then use a sterile Esmarch bandage (made by the surgeon) to collect blood back root chi, re-injecting tourniquet, injecting anaesthetic with a concentration of 0.5% but the amount is only 50% of the first time. With this technique, enough anaesthesia is allowed to continue to prolong the surgery time from 30-60 minutes, because many studies have demonstrated that after removing the tourniquet, there is still about 50% of the fixed anaesthetic in the area. the limb is anaesthetized.

Pain relief after surgery

At the time after surgery, the analgesic effect is almost completely absent, which is a major drawback of the technique of intravenous anaesthesia. Several studies have used a combination of local anaesthetics and morphine or fentanyl to achieve postoperative pain relief but to no avail. Therefore, it is necessary to use analgesia soon after surgery, if the patient has a lot of pain, it is necessary to use systemic morphine (subcutaneous or intravenous injection).

Intraoperative pain due to tourniquet

Visitor pain can occur early, usually in the first half-hour after anaesthesia, this complication is due to the second tourniquet earlier than the required waiting time. However, in some cases, even if the technique is performed correctly, due to the poor spreading of the anaesthetic to the base of the extremities, there is still a pain due to tourniquets. In this case, if the surgical time is still long, it is necessary to switch to general anaesthesia to avoid using excessive sedation.

Complications

Loss of tourniquet

Urticaria is a dangerous complication that is rare but still needs attention. This complication happens to be the main cause of anaesthetic toxicity. In some cases, it is often detected early, but it is difficult to manage and treat, especially cardiovascular complications that result in complications. very large can be life-threatening.

Therefore, check the tourniquet before administering anaesthesia, and prepare adequate respiratory and circulatory resuscitation facilities. Closely monitor the patient during surgery.

Due to set the tourniquet

The tourniquet can cause damage to nerves and blood vessels, so the time to place the tourniquet is 90 minutes for the upper limb, 120 minutes for the lower limb.

When removing the tourniquet, there may be a mild transient headache complication. If there is a convulsion, it is because the anaesthetic returns to circulation quickly, causing an overdose of the anaesthetic.

If the tourniquet is removed too soon after the anaesthetic, it can decrease peripheral vascular resistance, cause hypotension, tachycardia, and post-throated ischemic reactive congestion that may be aggravated. this complication.

Therefore, the time allowed to release the tourniquet is after 40 minutes.

Metabolic disorders

Possible changes in blood gases: PaO2 decreased and PaCO2 increased due to hypoxia, hypercapnia.

Metabolic acidosis in an ischemic extremity increases with time, and the pH may drop below 7.0, usually transiently.

An ischemic limb also has cellular damage such as increased vascular permeability and postoperative oedema.

Therefore, to prevent this, the following measures should be taken:

After surgery, the extremities must be elevated, not to be lower than the patient's body.

The tourniquet should not be placed for longer than the allowed time and the tourniquet should be removed early to avoid the accumulation of toxins outside the cell.

There may also be coagulation disorders caused by acidosis, causing bleeding after surgery.

K+ ions are released from ischemic cells, often transiently, causing less serious cardiovascular complications.

Complications of anaesthetic toxicity

A lot of reasons:

The concentration of local anaesthetic is high in the blood.

Overdose used.

The injection rate is too fast.

How the drug is injected (injected into an unknown blood vessel or injected too quickly).

Degree of drug binding.

Complications usually occur when the tourniquet is removed or the tourniquet is released.

Systemic toxicity is caused by the rapid return of the anaesthetic to the systemic circulation. In order to limit the loss of anaesthetic through the tourniquet, an intravenous catheter should be placed to inject the drug as far as possible from the base of the extremity, with slow injection, and an appropriate tourniquet pressure.