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

Three months before this study, susceptibility for malignant hyperther mia (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. F rom the EEG, power densities in selected frequencies and the median fr equency of the power spectrum were calculated. Therapy was started whe n severe respiratory changes were observed (Pa(CO2) > 10 kPa, mixed ve nous oxygen tension (PV(O2)BAR) < 4 kPa). At this time, heart rate exc eeded 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, administrat ion of all anaesthetics was terminated, 100% oxygen was delivered and ventilation was increased four-fold. Acidosis was treated by administr ation of sodium bicarbonate 2-4 mmol litre-1 kg-1. Animals were alloca ted randomly to one of two groups: group (control, n = 7) received no dantrolene; group (n = 8) received dantrolene 2.5 mg kg-1 iv. All vari ables were measured over a period of 60 min after therapy.- EEG, HR an d MAP were recorded continuously and blood-gas tensions, arterial pota ssium 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 min after the start of t herapy. In dantrolene-treated animals, EEG total power and median freq uency increased within 5 min. The improvement in brain electrical acti vity occurred before any significant increases in MAP, Pa(O2) and PV(O 2)BAR or decreases in all Pa(CO2) or potassium plasma concentration. O ur results indicate that dantrolene given for the treatment of a fulmi nant MH crisis helps to improve, not only haemodynamic state and metab olism, but also recovery of neuronal activity.