IMPROVEMENT OF BRAIN ELECTRICAL ACTIVITY DURING TREATMENT OF PORCINE MALIGNANT HYPERTHERMIA WITH DANTROLENE

Three months before this study, susceptibility for malignant hyperthermia (MH) had been tested in 15 pigs. In all pigs, MH was triggered by administration of 1% halothane. Brain electrical activity was examined during therapy of MH with and without administration of dantrolene. From the EEG, power densities in selected frequencies and the median frequency of the power spectrum were calculated. Therapy was started when severe respiratory changes were observed (Paco2 > 10 kPa, mixed venous oxygen tension ( Pv¯o2 < 4 kPa. At this time, heart rate exceeded 150 beat min−1, mean arterial pressure (MAP) was less than 60 mm Hg and median frequency was less than 2 Hz. EEG was isoelectric (n=6) or showed slow polymorphic delta-activity. For therapy, administration of all anaesthetics was terminated, 100% oxygen was delivered and ventilation was increased four-fold. Acidosis was treated by administration of sodium bicarbonate 2–4 mmol litre−1 kg−1. Animals were allocated randomly to one of two groups: group I (control, n=7) received no dantrolene; group II (n=8) received dantrolene 2.5 mg kg−1 i.v. All variables were measured over a period of 60 min after therapy: EEG, HR and MAP were recorded continuously and blood-gas tensions, arterial po tassium and glucose concentrations and pH were measured every 150 s. In group I (no dantrolene) minor, transient improvements in EEG activity were noted, but all animals died within 15–25 mm after the start of therapy. In dantrolene-treated animals, EEG total power and median frequency increased within 5 min. The improvement in brain electrical activity occurred before any significant increases in MAP, Pao2 and Pv¯o2 or decreases in all Paco2 or potassium plasma concentration. Our results in dicate that dantrolene given for the treatment of a fulminant MH crisis helps to improve, not only haemodynamic state and metabolism, but also recovery of neuronal activity. (Br. J. Anaesth. 1993; 71: 881–884)