The use of mesh in hernia repair, risk management and the advantages of day surgery - 
Part 2 - Hernia Repair under Local anaesthesia

AGENTS USED

There are a variety of agents and concentrations available for use but generally it is preferable to persevere with two and become completely familiar with these.

1.                  Local Anaesthetic

A combination of lignocaine (short acting) – 20 cc of 1.5% solution with adrenaline 1 in 200,000 is combined with Bupivicaine (longer acting) – 20 cc of 0.5% solution.

When using two different agents, one must consider their effects are synergistic and additive. That is, the dosage of each should be reduced by half to prevent risks of toxicity.

The aims are –

            rapid onset of action,
satisfactory anaesthesia for the duration of the surgery, and
to provide analgesia well into the post operative period.

This should be achieved without risk of any toxic reaction. Sedation reduces risk of toxicity. However, the toxic levels should not be exceeded under any circumstances. There is patient variation in absorption of the local anaesthetic and effects. This can be influenced by such factors as liver and renal function and the general state of health of the patient. Suggested maximum dosage for a 70kg healthy person is 4 mg per kg of Lignocaine plain or 7mg/12 kg adrenaline. Maximum doses of Bupivicaine are 2mg/kg.

These two agents can be mixed. A typical combination would be 20 cc of 1.5% Lignocaine with adrenaline mixed with 20 cc of  0.5% Marcaine.

Adrenaline 1 in 200,000 diluted to 1 in 400,000 is routinely used. This concentration is enough to cause vaso-constriction, decrease the absorption of the local anaesthetic and reduce the risk of toxic reaction due to the local anaesthetic. It increases the dose of local anaesthetic which may be administered. The adrenaline itself rarely causes any problem. Care with a patient with cardiac disease or sensitivity to adrenalin should be taken. The volume given at this concentration is very unlikely to have any harmful effect. Mono-amine oxidase inhibitors should be stopped two weeks prior to surgery to prevent any hypertensive crisis.

Adrenalin is theoretically a problem as it could constrict the testicular artery. However it has not been implicated as a cause of testicular atrophy and it is used routinely in both series without having any harmful effect.

1.                  I/V Sedation

Each surgeon and anaesthetist varies the dosage and depth of sedation based on the needs or anxiety of the patient.

Team work between the surgeon and anaesthetist should achieve a satisfactory combination. Sometimes inappropriate sedation results in a confused patient, which would only make surgery difficult. This problem usually only occurs when the anaesthetist and surgeon have not worked on this technique together previously.

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