Review of Pharmacology - 9E (2015)

Anaesthesia
trigeminal nerve, cervical plexus and phrenic nerve block), upper limbs (brachial plexus
and wrist block), thorax and abdomen (intercostal nerve, celiac plexus, lumbar sympathetic
chain, ilioinguinal nerve, iliohypogastric nerve, penile and paravertebral block) and lower
limbs (psoas compartment and perivascular block). Pneumothorax is the most common
complication of brachial plexus block.
4. Intravenous Regional Block (Bier’s Block)
Intravenous regional anaesthesia (IVRA) is indicated for any procedure on the arm below
the elbow or leg below the knee that will be completed within 40-60 minutes. An intravenous
cannula is inserted in a distal vein in the limb scheduled for surgery. The tourniquet is then
applied to the upper arm or thigh. The local anaesthetic solution is then slowly injected into
the cannula. Analgesia will occur within 3-4 minutes and surgery can then commence. The
pressure in the tourniquet must be maintained at least 50 mm Hg above the patient’s
systolic blood pressure. The drug of choice for IVRA is prilocaine as it is the least toxic local
anaesthetic and has the largest therapeutic index. If prilocaine is not available, lignocaine is an
acceptable alternative. It is essential that plain and not adrenaline-containing solutions are used.
Bupivacaine should never be employed as it is too toxic, particularly to the myocardium.
IVRA should be avoided in a
patient with sickle cell disease
The drug of choice for IVRA is
prilocaine
5. Spinal Anaesthesia
It is the injection of LA in the subarachnoid space (between pia and arachnoid; also known
as intrathecal space) in lumbar spinal cord. Spinal cord ends at lower border of L 3
vertebrae
in children and at lower border of L 1
vertebrae in adults. Thus, spinal anaesthesia can
be performed safely in L 2-3
intervertebral space in adults and L 4-5
space in children. Spinal
anaesthesia leads to creation of a zone of differential blockade in which autonomic fibres
are blocked at two segments higher and motor fibres are blocked at two levels lower than
sensory blockade. It is due to different sensitivity of various types of nerve fibres.
Structures encountered during lumbar puncture
1. Skin
2. Subcutaneous tissue
3. Supraspinous ligament
4. Interspinous ligament
5. Ligamentum flavum
6. Duramater
7. Arachnoidmater
Maximum dose of lignocaine
• With adrenaline : 7 mg/kg
• Without adrenaline : 4.5 mg/kg
• For IVRA : 4 mg/kg
General Anaesthesia Pharmacology
Drugs used for Spinal Anaesthesia
• Lignocaine – 5% in 7.5% dextrose (heavy or hyperbaric)
• Bupivacaine – 0.5% in 8% dextrose
Indications
• Orthopaedic surgery of lower limbs and pelvis.
• Surgery of lower abdomen (all pelvic and perineal surgeries, hernia, hydrocele,
appendix, testicular surgeries).
• Gynaecological and obstestrics surgeries (hysterectomy, myomyectomy, cervical
surgeries, tubectomy, tuboplasty, caesarean section).
Complications
• Hypotension is the most common intraoperative complication. It can be prevented
by preloading with crystalloids or colloids and treated by head low position (Trendlenburg
position), fluids, vasopressors and ionotropic agents. Other intraoperative
complications include bradycardia, respiratory depression, and cardiac arrest.
• Most common postoperative complication is headache, known as post dural
puncture headache (PDPH). It is mainly occipital headache that occurs after 12-24
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