MARCAIN SPINAL 0.5% HEAVY INJECTION

INJECTION

**DOSAGE AND ADMINISTRATION** As with all local anaesthetics, the dosage varies and depends upon the area to be anaesthetised, the vascularity of the tissues, the number of neuronal segments to be blocked, the depth of anaesthesia and degree of muscle relaxation required, individual tolerance, the technique of anaesthesia, and the physical condition of the patient. The lowest dosage that results in effective anaesthesia should be used. In general, surgical anaesthesia requires the use of higher concentrations and doses than those required for analgesia. The presentations of MARCAIN injection solutions are for use in one patient on one occasion only. Any solution remaining from an opened container should be discarded. The following dosage recommendations should be regarded as a guide only for use in normal, healthy adults: **Spinal anaesthesia for surgery** The spread of anaesthesia obtained with both MARCAIN 0.5% and MARCAIN SPINAL 0.5% HEAVY is dependent on several factors, the most important being volume of solution injected, position of patient and rate of injection. 1. **MARCAIN 0.5%** (isobaric) 3 – 4 mL MARCAIN 0.5% (15 – 20 mg bupivacaine hydrochloride). The difference in spread between 3 and 4 mL is approximately 2 segments. The larger volume gives 1/2 to 1 hour longer duration of anaesthesia in the lumbar segments and more lasting motor blockade. When injected into the L3 – L4 interspace with the patient in the supine horizontal position, 3 mL of MARCAIN 0.5% spreads to TS – T7. If the patient is placed in the sitting position the anaesthesia spreads to T4 – T5. The effects of subarachnoid injection of MARCAIN 0.5% exceeding 4.5mL have not yet been studied and can therefore not be recommended. 2. **MARCAIN SPINAL 0.5% HEAVY**(hyperbaric) 2 – 4 mL MARCAIN SPINAL 0.5% HEAVY (10 – 20 mg bupivacaine hydrochloride). When 3 mL MARCAIN SPINAL 0.5% HEAVY was injected into the L3 – L4 interspace and patients were kept in the sitting position for 2 minutes before being placed supine, blockade spread to the T7 – T10 segment. When a similar injection was made in patients in the lateral position who were then immediately placed supine, blockade spread to the T4 – T7 segment. The effects of injections of MARCAIN SPINAL 0.5% HEAVY exceeding 4 mL have not yet been studied and such volumes can therefore not be recommended. **Note:-** **Hypotension** During spinal anaesthesia, a marked fall in blood pressure and/or intercostal paralysis may be seen, possibly due to the use of excessive doses or improper positioning of the patient. Hypotension and bradycardia may occur as a result of sympathetic blockade. Standard textbooks should be consulted with respect to techniques for administration of MARCAIN for spinal anaesthesia. **Use in Children** The use of spinal anaesthesia in children requires a thorough knowledge of the differences between adults and children to enable the administration of adequate doses of the drug. Since a relatively high CSF volume is found in infants and neonates, proportionately larger doses per kg are required to produce the same level of block. In small children the nerves are less myelinated, allowing easier diffusion of the drug and a more rapid onset of anaesthesia, hence lower concentrations are needed to block nerve conduction. The hypotension usually seen following spinal block in adults is uncommon in children below the age of 8. The following doses of MARCAIN 0.5% and MARCAIN SPINAL 0.5% HEAVY are recommended for use in children: 0.4 – 0.5 mg/kg for infants up to 5 kg 0.3 – 0.4 mg/kg for children weighing between 5 and 15 kg 0.25 – 0.3 mg/kg for children weighing more than 15 kg The onset of anaesthesia is slower than with lignocaine and lasts for 60 – 120 minutes. **Use in Pregnancy** It should be noted that the dose should be reduced in patients in the late stages of pregnancy. **Use in Debilitated or Elderly Patients** The dose should be reduced in the elderly.