<prompt> Thiopentone is CI inAcute intermittent porphyriaBronchial asthmaShockAll the above  <response>: Barbiturates promote aminolevulinic acid synthetase, which stimulates the formation of porphyrin an intermediary in heme synthesis. This may precipitate acute intermittent porphyria or variegate porphyria in susceptible individuals. Barbiturates incompletely depress airway reflex responses to laryngoscopy and intubation, and airway instrumentation may lead to bronchospasm in asthmatic patients or laryngospasm in lightly anesthetized patients. In situations where the baroreceptor response will be blunted or absent eg, hypovolemia, congestive hea failure, b-adrenergic blockade, cardiac output and aerial blood pressure may fall dramatically due to uncompensated peripheral pooling of blood and direct myocardial depression. Ref: Morgan Mikhails clinical anesthesiology 6e 