Subarachnoid block anaesthesia

Lignocaine injections are indicated for production of local or regional anaesthesia by infiltration techniques such as percutaneous injection, peripheral nerve block, spinal or subarachnoid block. 

Spinal anaesthesia (spinal block or sub-arachnoid block) is used to administer the injection into the subarachnoid space. Several local anaesthetics are used for spinal anaesthesia such as procaine, lidocaine, tetracaine, and bupivacaine. Vasoconstrictors such as adrenaline (0.1-0.2 mg) and phenylephrine (0.5-2 mg) can be added to subarachnoid blocks to decrease vascular uptake and prolong diuation of action. 

Subarachnoid (intrathecal) block (spinal anaesthesia). By using a solution of appropriate specific gravity and tilting the patient the drug can be kept at an appropriate level. Sympathetic nerve blockade causes hypotension. Headache due to CSF leakage is virtually eliminated by using very narrow atraumatic penal point needles. 

Saddle block is a variation of spinal anaesthesia where the injection is made into the lower part of the subarachnoid space. The drug normally settles in the lower part of the dural space. It is used in obstetrics and for suigery in the perineal region. 

Techniques range from inhltraiion of anac-sthctic around a single nerve (e.g. dental anaesthesia) to epidural and spinal anaesthesia. In. spinal anaesthesia (intrathecal block) a drug is injected into the ccrebrospina) fluid in the subarachnoid space. In epidural anaesthesia the anaesthetic is injected outside the dura. Spinal anaesthesia is technically far easier to produce than cpidural anaesthesia, but the latter technique virtually eliminates the postanaesihetic complications such as headache. 

An epidurally placed catheter can enter the subarachnoid space in the course of a continuous epidural anaesthesia. In 2 recently reported obstetric cases, repetition of the injection caused a spinal block (19, 20 -). It is therefore advisable to aspirate each time before injecting the local anaesthetic drug. 

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