Spinal anaesthesia block

Adrenaline along with local anaesthetics may be used for infiltration, nerve block and spinal anaesthesia for prolonging the action and to reduce the systemic toxicity of local anaesthetics. 

When used for spinal anaesthesia, 0.75% ropivacaine produces less intense sensory and motor block than 0.5% bupivacaine. It is suitable for regional, spinal and epidural block but not for regional intravenous anaesthesia. The addition of adrenaline (epinephrine) does not prolong the duration of anaesthesia in brachial plexus or epidural block. Ropivacaine is indistinguishable from bupivacaine when used in obstetric anaesthesia. Its direct myocardial toxicity is somewhat less than that of bupivacaine. 

Pitkanen M, Rosenberg PH. Local anaesthetics and additives for spinal anaesthesia—characteristics and factors influencing the spread and duration of the block. Best Pract Res Clin Anaesthesiol. 2003 17 ... 

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. 

Bupivacaine is long-acting 3 h) (see Table 18.1) and is used for peripheral nerve blocks, and epidural and spinal anaesthesia. Whilst onset of effect is comparable to lidocaine, peak effect occurs later (30 min). 

Casati A, Fanelli G, Beccaria P, Aldegheri G, Berti M, Senatore R, Torri G. Block distribution and cardiovascular effects of unilateral spinal anaesthesia by 0.5% hyperbaric bupivacaine. A clinical comparison with bilateral spinal block. Minerva Anestesiol 1998 64(7-8) 307-12. 

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. 

It is one of the least toxic and most commonly used local anaesthetics. The salient features for its wide popularity may be attributed due to its lack of local irritation, minimal systemic toxicity, longer duration of action, and low cost. It can be effectively used for causing anaesthesia by infiltration, nerve block, epidural block or spinal anaesthesia. In usual practice it is used in a solution containing adrenaline (1 50,000) which exerts and modifies the local anaesthetic activity through retarded absorption, and the duration of action is considerably prolonged. 

It is an all-purpose local anaesthetic drug used frequently in surface infiltration, block, caudal and spinal anaesthesia. It is reported to be 10 times more toxic and potent than procaine, whereas its duration of action is twice than that of procaine. 

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. 

Twenty patients undergoing surgery were given repeated 1-mg intravenous doses of midazolam as induction anaesthesia every 30 seconds until they failed to respond to three repeated commands to squeeze the anaesthetist s hand. This was considered as the induction end-point titrated dose. It was found that the 10 who had been given prior spinal anaesthesia with tetracaine 12 mg needed only half the dose of midazolam (7.6 mg) than the 10 other patients who had not received tetracaine (14.7 mg). The reasons are not known. The authors of this report simply advise care in this situation. In another study in which patients were given intravenous midazolam following an intramuscular injection of either bupivacaine, lidocaine or saline, it was found that both anaesthetics enhanced the effect of midazolam. This effect was dose-dependent and it was concluded that the use of lidocaine or bupivacaine for regional blocks or local infiltration could alter the effect of midazolam from sedative to hypnotic. ... 

A study involving 40 elderly patients undergoing spinal anaesthesia found that bupivacaine 9 mg, with fentanyl 20 micrograms reduced the incidence of hypotension compared with bupivacaine 11 mg alone. Respiratory rates were not depressed in either group. The rate of failed spinal block and discomfort was similar in both groups. The addition of the fentanyl allowed a reduction in the minimum dose of bupivacaine to produce an adequate block, and consequently less hypotension. ... 

No stimulant drugs are known in this class which consists mainly of the local anaesthetics, much used in dental and spinal anaesthesia. These preferentially block the smaller fibres with the result that sensory nerves are affected more than motor nerves. What local anaesthetics do is to elevate the threshold for excitation and thus they block propagation of the nervous impulse without depolarizing the fibre. 

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. 

Local anaesthetics are synergistic with intrathecal opioids and intensify sensory block without increasing sympathetic block. The combination makes it possible to achieve spinal anaesthesia with otherwise inadequate doses of local anaesthetic. 

The recent case of a parturient who developed a massive spinal block with hemi-cranial palsy after a test dose of 2.5 ml of 2% chloroprocaine, administered with the patient in the sitting position, demonstrates the dangers of giving a test dose of a hypo-baric solution with the patient in this position (21 ). One always has to bear in mind the possibility of infection after epidural and spinal anaesthesia. The recommendation has been made to place a bacterial filter between the syringe and the catheter. Five out of 101 syringes were contaminated by skin commensals, but all the catheter tips remained sterile when a bacterial filter was used. 

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. 

It is a potent and long acting local anaesthetic used for spinal, infiltration, epidural anaesthesia and nerve block. 

Lidocaine is used for all forms of infiltration anaesthesia, in addition to peripheral, regional, spinal and epidural block. Unlike bupivacaine, it is suitable for use in intravenous regional anaesthesia. Duration of anaesthesia is about 1 hour but this can be prolonged to 2 hours by the addition of adrenaline. The maximum doses are shown in Table 5.2. 

Beck GN, Griffiths AG. Failed extradural auaesthesia for caesareau sectiou. Complicatiou of subsequent spinal block. Anaesthesia 1992 47(8) 690-2. 

This is a special type of nerve block anaesthesia in which the drug is injected into the epidural space. It is technically a more difficult procedure. The roots of the spinal nerves are anaesthetized. 

Spinal and epidural techniques are shown to provide effective anaesthesia for caesarean section. Spinal block differs from an epidiual block in a number of ways ... 

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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