Review of Pharmacology - 9E (2015)

Review of Pharmacology
Concentration (In %) of LA for
different uses:
Lignocaine Bupivacaine
Infiltration 0.5 – 2 0.25 – 0.5
Spinal 5 0.5
Epidural 2 0.5
hours. It is different from any headache previously experienced by the patient and
is initiated or made worse by the adoption of sitting or erect posture. It is relieved
by abdominal compression, which raises the venous pressure. Most common cause
of PDPH is leakage of CSF through the hole in the duramater. It can be prevented
by using small bore needle (25G). Treatment of PDPH consists of lying down for
24 hours, plenty of fluids, abdominal compression and sealing the hole by epidural
blood patch. Other post-operative complications include urinary retention, paralysis of
cranial nerves (most commonly involved nerve is abducens, sixth cranial nerve), meningitis,
arachnoiditis, paraplegia and cauda equina syndrome.
Anaesthesia
Hypotension is the most common
intraoperative complication of
spinal anaesthesia whereas
most common postoperative
complication is headache,
known as post dural puncture
headache (PDPH).
Management of LA Toxicity
(*ASRA guidelines)
1. 20% Intralipid I.V. at first sign
of toxicity
2. Benzodiazepines are DOC for
seizures. If not able to control,
give SCh. If not available, use
propofol.
3. Lignocaine and other class Ib
drugs avoided for arrhythmias.
4. NaHCo 3
for severe acidosis
* ASRA: American Society of Regional
Anesthesia
Contraindications
Absolute
• Raised intracranial tension
• Uncooperative patient
• Shock
• Bleeding disorders/coagulopathy
• Patients on anticoagulants, thrombolytic therapy
• Infection at local site
• Septicemia
6. Epidural Anaesthesia
Relative
• Aortic stenosis
• Mitral stenosis
• Recent MI, heart block
• Spinal deformity
––
Pyschiatric disorders
––
CNS disorders.
Epidural anaesthesia is given in epidural space (between duramater and bone) with Tuohy’s
needle. Epidural space extends from foramen magnum to sacral hiatus (triangular in shape)
and contains anterior and posterior nerve roots, epidural veins, spinal nerves, lymphatics
and fat.
Indications
• Mainly used for controlling postoperative pain (by continuous epidural through
a catheter).
• All surgeries which can be performed under spinal anaesthesia.
• Upper abdominal surgeries, thoracic surgeries and even neck surgeries.
• Painless labour.
• Chronic pain due to cancer and other conditions.
Spinal Versus Epidural Anaesthesia
Spinal anaesthesia is highly reliable, easier to place (because it can be confirmed by
the presence of CSF in the needle and loss of resistance) and has very quick onset.
However, it can be performed only for the surgeries of limited duration. Re-dosing cannot
be done if the procedure takes longer time than expected. PDPH is a very common
problem.
Epidural anaesthesia is difficult to perform (requires expert persons) and therefore is
less reliable. Further, onset of analgesic effect is slower. But it can be used for surgeries
of any duration by inserting an epidural catheter. Chances of PDPH is very less because
it is quite superficial procedure (no CSF leak).
Skeletal Muscle Relaxants
These drugs are used in anesthesia to relax lower limbs and abdominal wall muscles so
that operative manipulation becomes easy. These can also be used to facilitate endotracheal
intubation by relaxing laryngeal musculature. Some of these drugs are useful in the spastic
conditions also. Skeletal muscle relaxants may be divided into centrally acting and
peripherally acting agents.
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