Ralph A. Epstein

The electromyogram and the mechanical response of indirectly stimulated muscle in anesthetized man following curarization.

The electromyogram (EMG) and tension evoked by single and tetanic stimuli were studied during curarization in anesthetized subjects. d-Tubocurarine depressed both evoked twitch tension and EMG, but not identically. Before curarization posttetanic potentiation (PTP) was present on tension recordings but not on EMG recordings. Small amounts of tetanic fade were present on both tension and EMG recordings before curarization. On tension recordings PTP and fade increased significantly only during profound curarization, while on EMG recordings both increased at all levels of curarization. Electromyography is more sensitive than tension recordings in the investigation or monitoring of curarization.

Ventilatory Requirements of Critically Ill Neonates

Ventilatory requirement was assessed in 15 critically ill neonates on a total of 31 occasions. All were either currently receiving mechanical ventilation or had had mechanical ventilation in the recent past. Minute ventilation, respiratory frequency, carbon dioxide production (VCO2) and arterial blood PaCO2 were measured. Dead space-to-tidal volume ratios (VD/VT were calculated. The ventilatory requirements of the infants ranged from 1.16 to 4.30 times normal. Derived parameters related the increased ventilatory requirement to pulmonary (VD/VT) and metabolic (VCO2) factors. The increased requirement was not significantly related more often to either of these two factors, although one or the other was frequently predominant in individual cases. Data presented allow specification of the minute volume range needed for ventilators designed for neonates, and the maximal compressible volume that can be tolerated when expired volume monitoring is desired.

The sensitivities and response times of ventilatory assistors.

The sensitivities and response times of six ventilators in the assist mode were measured. The withdrawal volumes necessary to cause triggering were: Bennett MA-1, 0.5 ml; Bennett PR-2, 1.5 ml; Bird Mark 8, 1.5 ml; Bourns LS 104–150, 0.1 ml; Dräger Spiromat 661, 1.0 ml; Ohio 560, 0.5 ml. The times necessary for the ventilators to respond to these withdrawals were: Bennett MA-1, 82 msec; Bennett PR-2, 226 msec; Bird Mark 8, 157 msec; Bourns, 36 msec; Dräger, 434 msec; Ohio, 123 msec. The maximal rate at which a ventilator can assist is inversely proportional to the response time.

The Metabolic Effects of Nonvolatile Anesthetics on Mammalian Hepatoma Cells in Vitro: I. Inhibition of Cell Replication

Mammalian hepatoma liver cells were grown as a suspension tissue culture to allow investigation of the effects of nonvolatile anesthetics on cell replication. Logarithmic growth of a rat hepatoma tissue culture was reversibly inhibited by thiopental, methohexital, amobarbital, phenobarbital, lidocaine, and prilocaine in a dose-dependent fashion. Barbituric acid also reversibly inhibited logarithmic growth, but only at drug concentrations greater than those necessary for inhibition by the anesthetic drugs.

The Effects of Nondepolarizing Relaxants and Anticholinesterases on the Neuromuscular Refractory Period of Anesthetized Man

Neuromuscular refractory period was determined in anesthetized patients by measuring thenar EMG and adductor pollicis tension during single and paired ulnar nerve stimulation. Non-depolarizing muscle relaxants, d-tubocurarine and gallamine, decreased the refractory period. The anticholinesterases, neostigmine and edrophonium, increased the refractory period. The effects of d-tubocurarine and gallamine occurred at doses lower than those which cause any depression of the evoked twitch tension.

The Effect of Depolarizing Relaxants on the Neuromuscular Refractory Period of Anesthetized Man

In anesthetized man decamethonium and succinylcholine, in subparatytie doses, increased the neuromuscular refractory period, as determined by observation of both the tension and the compound action potential of the indirectly stimulated adductor pollicis muscle. This is opposite to the effect previously reported for the nondepolarizing relaxants, curare and gallamine, which decrease the refractory period. Determination of changes in the refractory period allows detection of the presence of relaxant drugs in doses which fail to cause blockade.