General anesthesia in "inducible" porphyrias.

To evaluate the risk of inducing acute symptoms after general anesthesia in patients with "inducible " porphyrias, the authors analyzed retrospectively the effects of 78 exposure to anesthesia in 47 patients, 33 with acute intermittent porphyria and 14 with variegate porphyria. On 62 occasions, 29 involving the use of a barbiturate, anesthesia was induced in 37 patients who had no porphyric symptoms at the time. None of these patients had an acute attack postoperatively. Anesthesia was induced 16 times in 14 patients during acute episodes; 12 of these patients also received precipitating drugs other than anesthetics. Porphyric symptoms worsened in seven in the ten patients who received thiopental and in two of the four who did not. In the latent stages of acute intermittent and variegate porphyria in this patient population, the risk of incurring symptoms after exposure to thiopental and/or other anesthetics was small. During an acute episode thiopental may aggravate porphyric symptoms.