emergencyregistrar

Did my first Bier’s block yesterday. unwitnessed fall in a lady (high care nursing home patient) with significant comorbidities : COPD and newly diagnosed malignancy.

I’ve done them twice at least with senior registrars (me being the lever or the counter-traction guy) during the manipulation.

Yesterday was a first adjusting the cuff etc (but the boss still insisted on giving the drug himself)

biers_block —this is a page pdf file produced by the Gold Coast hospital which serves as a good intro and explanation including step by step about the Bier’s block. More goodies from : emergencyweb.net (you need to register – FREE)

Addit as of Dec 2012, the Gold Coast Hospital has limited the access to emergencyweb.net to only their staff.

So….drug of choice we gave was : PRILOCAINE

Let’s talk about local anaesthetics with Prilocaine as our star drug

WHAT is it ?

Local anaesthethic. Amide type

PHARMACOKINETICS

• Absorption : systemic absorption affected by :

1. dosage
2. site of injection – high vascular area e.g. trachel mucosa means rapid absorption ; peak serum level highest esp intercostal block while sciatic and femoral lowest
3. drug-tissue binding
4. local tissue blod flow
5. use of adrenaline (vasoconstrictor)

• Distribution :

1. Localised >>>
2. Systemic …2 compartment model : initial alpha phase – rapid distribution and highly perfused organs. Slower beta phase – less perfused tissue ( muscle/gut) protective effect by uptake in lungs – serves to attenuate arterial concentration.

• Metabolism

1. amides converted to water soluble metabolites in liver

PHARMACODYNAMICS

• Mechanism of Action

1. Membrane potential – blockade of voltage-gated sodium channels
2. Sodium channel isoforms
3. Channel blockade
4. Other effects :

• Structure activity characteristics of Local Anaesthetics

1. smaller + more lipophilic LAs, faster rate of interaction w sodium channel R
   —-lignocaine/procaine/mepivacaine more water soluble than tetracaine/bupivacaine/ropivacaine (more potent and have longer duration, also bind more ext to proteins)

• Neuronal factors affecting block

1. differential block

Amides vs esters. Usual questions in MCQ for the primary ?which is a amide or ester ?

local anaesthetics that are Esters :have just one ” i ” in their names eg procaine ,cocaine but …
Amides : have more than one ” i ” in their names lidocaine, bupivacaine,prilocaine