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E NEUROSURGERY
ESSENTIAL INFORMATION FOR THE BUDDING NEUROSURGEON
VIVA PRACTICE

FLOSEAL: Manufactured by  Baxter. Contains bovine gelatine and human thrombin. Can swell upto 20%, usually within 10 minutes. No randomised control trials in neurosurgery.

SURGICEL:manufactured by Ethicon (Johnson & Johnson subsidiary).Oxidized regenerated cellulose
Bactericidal against a broad range of gram-positive and gram-negative organisms including various antibiotic-resistant bacteria (MRSA, VRE, PRSP and MRSE). Plant-based product with minimal tissue reaction. Fully absorbable within 7-14 days

ACTION POTENTIAL: All or none, regenerative, directionally propagated depolarising nerve impulse.

PHENYTOIN: Inhibits the generation and propagation of action potentials, most likely  by  binding to inactivated (closed) sodium channels. It also potentiates GABA-ergic neural transmission.
10-20 microgram/ml is the therapeutic level. First order pharmacokinetics at low levels. At near therapeutic levels, it becomes zero order kinetics. So a small increase near the therapeutic levels can increase the serum level substantially.
Loading dose 18mg/kg. Can be given upto 50mg/mt. In practice, put 1.2 gm phenytoin in 100ml of0.9% saline and give over 1 hour.
Side effects: Rash, ataxia, nystagmus, slurred speech, diplopia, cognitive dysfunction, megaloblastic anemia, agranulocytosis, aplastic anemia, anti Vit D effects- Rickets and osteomalacia, speeds up metabolism of other drugs like Warfarin, OCPs, corticosteroids ( Phenytoin induces liver enzymes).Neural tube defects if used in pregnancy. Should not be given in second degree heart block. Can induce acute Porphyria crisis in patients with Porphyria.

CARBAMAZEPINE: In partial and secondary generalised seizures.
Opens potassium channels and prolongs the time that sodium channels remain in the inactivated (closed) state, preventing them from returning to a resting state.
Induces hepatic enzymes, Can induce acute Porphyria crisis in patients with Porphyria, neural tube defects in pregnancy, agranulocytosis, aplastic anemia, SIADH.
Dose: start with 100-200mg daily . Increase slowly upto 2g daily. Noramally 1.2 g daily in divided doses. Therapeutic levels:4-10 microgram/ml.
Nice:if a woman who is taking carbamazepine or lamotrigine is planning a pregnancy or has an unplanned pregnancy, healthcare professionals should advise her to stop taking these drugs because of the risk of neural tube defects and other malformations in the fetus

SODIUM VALPROATE: All forms of epilepsy, but particularly generalised epilepsy, absence and myoclonic discharges.
Potentiates GABA-ergic neural transmission by increasing sensitivity to GABA receptors and inhibiting GABA transaminase(which breaks down GABA). Relative lack of side effects. But caution with liver, bleeding, porphyria disorders. Enzyme inhibitor. Displaces phenytoin from its binding sites.

Dose: I nitially 600 mg daily in two divided doses, increased every three days by 200mg/d to a maximum of 2.5g/d.
NICE:valproate should not be routinely prescribed to women of child-bearing potential

LAMOTRIGINE:Monotherapy and adjuvant treatment of partial seizures and primary and secondary generalised tonic-clonic seizures and Lennox-Gastaut syndrome. It is also used in trigeminal neuralgia.
Blocks voltage gated sodium channels and inhibits the release of excitatory aminoacids such as glutamate.
Dose; 100-200mg in 1-2 daily doses.
Nice:if a woman who is taking carbamazepine or lamotrigine is planning a pregnancy or has an unplanned pregnancy, healthcare professionals should advise her to stop taking these drugs because of the risk of neural tube defects and other malformations in the fetus

LEVETIRACETAM: Partial seizures
Inhibits burst firing without affecting neurtransmission. Lacks significant drug interactions and and can be escalated quickly.

Status Epilepticus: 4 mg lorazepam IV over 2 minutes. Repeat if necessary after 5 minutes. Load with phenytoin. If not responding, call anaesthetist to intubate.

Nimodipine (marketed by Bayer as Nimotop) is a dihydropyridine calcium channel blocker originally developed for the treatment of high blood pressure. Nimodipine binds specifically to L-type voltage-gated calcium channels.