Local Anesthesia

( For very old patients, we routinely try to avoid sedation as these patients develop paradoxical agitation to sedatives especially to midazolam. Fortunately for these patients, the entire procedure can be conducted alone with local anaesthesia alone – Read here for more details on pacing in elderly)

Before delving in to actual technical details, it is necessary to understand the nerve supply of the region as proper anatomic knowledge facilitates efficient administration of local anesthetic. The pectoral region is supplied by:

Supra-clavicular nerves of the cervical plexus : These fibers descend from the neck, superficial to the clavicle. These are the principle nerves which supply the skin of the operative region. As described later, adequate deep infiltration of local anesthesia along the proposed skin incision blocks these nerves and delivers a large field of anesthesia that is useful for creation of the pocket. The dermatome is C3

Lateral cutaneous nerves from the intercostal nerves : From T3 downwards, these pierce the lateral margin of the pectoralis major give branches which travel forward and backwards along the deep fascia superficial to the muscle. The anterior branches provide sensation to the infero-lateral area of our pacemaker pocket. T2’s cutaneous branch only provides the axilla via the intercostobrachial nerve. T1 has no cutaneous branches to the thorax.

Anterior cutaneous nerves from intercostal nerves : These are perforating termini of the intercostal nerves that exit at the anterior end of the intercostal space (near the sternal border). The pierce the pectoralis major muscle and reach the subcutaneous plane and provide the sensation to the medial aspect of our pacemaker pocket. The relevant dermatomes are T2 – T4

Local anesthetics act by blocking voltage gated sodium channels on the neuronal membranes. Onset and duration of action differs among various agents and toxicity from systemic absorption also varies. For all practical purposes, lignocaine is the preferred local anesthetic – it has rapid onset of action, good safety profile and provides adequate time coverage for the procedure.

Bupivacaine also can be used but caution is necessary if large amounts are used as systemic absorption may cause cardiac toxicity (but as electrophysioloigsts we should be able to manage these toxicities!). Furthermore bupivacaine has a long time of duration for onset of anesthesia. The principle advantage of bupivacaine is its long duration of action which extends well into the post operative period. However post operative pain is not a major issue in pacemaker implantation and the role of extended duration of bupivacaine must be balanced with toxic effects when large doses are used. When post operative regional anesthesia is desired – for example in an apprehensive patient or when the device is large (ICD) – supplementary bupivacaine injection to the wound edges and lateral margins of the pocket is a useful approach while having completed the procedure with lignocaine.

Local anesthesia should be used when the patient is undergoing implantation under general anesthesia as this permits lower levels of GA medications and facilitates smooth recovery and most importantly provides post operative pain relief – which may be a significant issue in children.

The decision to use Lignocaine mixed with adrenalin as a vasoconstrictor agent is at the operator’s discretion although it does provide grounds for using larger doses of lignocaine. Some operators prefer not to use adrenalin as vasoconstriction may temporarily mask bleeders that may open up later inside the pocket – especially on patients who are on antiplatelets.

The best weapon against bleeding is meticulous surgical technique (careful tissue dissection, hemostasis with diathermy/ligatures) – not to use lignocaine with adrenalin and hoping for the best.

There are two basic requirements for successful local anaesthesia in cardiac pacing : Anaesthesisa to carry out the venous puncture and anaesthesia to make the pocket.

Venous access is becomes a painful nightmare if there is inadequate anaesthesia or if the access is difficult. Furthermore in a difficult puncture, if the patient struggles with pain, there is a risk of inadvertent pneumothorax. At the outset, I followed the usual method of injecting along the potential venous access tract – but later on realized that a better method is to inject along a triangular area (as described below). This zonal anaesthesia has two benefits :

1. It pre-anathesitizes the skin incision area and proximal pocket
2. provides a wide area of anesthesia to vary the puncture if the initial attempt fails.

The fact that it  pre-anaesthetizes the future pocket incision area, enables the skin incision be made as soon as the guidewire has been placed. However the lateral pocket margins – might require some anaestheisa and therefore some additional injection is necessary before incision. – See video below

A wide area of anaesthesia on the skin helps a difficult puncture by enabling the operator chose different entry sites as necessary. This is especially true for elderly patients, who may present with difficult puncture and ironically also cannot be sedated.

However much we do emphasize on waiting for local anaesthetic to act, we have a tendency to hurry the skin incision – which may be painful. By anaesthetizing the potential skin incision before the puncture is attempted, we provide ample time for the skin to get anaesthetized when the actual incision is performed