Thiopentone = Sodium Thiopental
Thiopental, a barbiturate, is used for the induction of anesthesia
First used in 1934 by Lundy' and Waters
Yellow amorphous powder.
pH 10.5 - 11 , therefore not to be given with Normal Saline & RL
Dose - 3-5mg/kg ; Route: IV
Adequate induction dose will cause loss of eyelash reflex.
Used in concentration of 2.5%
Given Commonly at outer aspect of forearm (Never in anticubital fossa)
If Concentration >2.5%
- Pain on injection
- Venous thrombosis
Mechanism of action :
- depress RAS
- binds at a distinct binding site associated with a Cl- ionopore at the GABAA receptor, increasing the duration of time for which the Cl- ionopore is open. The post-synaptic inhibitory effect of GABA in the thalamus is, therefore, prolonged.
Duration of action
- Determined by redistribution (not by elemination)
- Patient looses consciousness in 30 sec and regains in 20 min.
- With repeated doses - duration depends on elimination (Metabolized in Liver)
- Decrease BP (Compensatory increase in Heart Rate)
- Decreased response to hypoxia & hypercarbia.
- Apnea (Treat with Positive pressure resp. - IPPV)
- Decrease Tidal Volume and Respiratory Rate
- Can cause bronchospasm & laryngospasm
- Decreases Cerebral blood flow
- Decreases Cerebral O2 consumption ( Therefore Cerebroprotective ; DOC - in Head Injury )
- Lowers threshold for pain ( it is AntiAnalgesic)
- Does not cause Muscle relaxation
- Powerful anticonvulsant (refractory seizures can respond to it)
- Decreases Renal blood flow and GFR
- Crosses Placenta and has some antithyroid activity.
It is Microsomal enzyme inducer.
Induction of hepatic enzymes increase the rate of metabolism.
Acute Intermittent Porphyria and Variegate Porphyria
Can be used in Porphyria Cutaneous Tarda
In case of inadvertent intra-arterial injection (eg: if in anticubital fossa)
- pain ,
- blanching hand ,
- absent radial pulse ,
- Secondary thrombosis
- Stop injection & Leave the needle in situ (most important)
- Flush with saline
- Give Vasodialator
- Brachial or stellate ganglion block