Establishing intravenous access: a study of local anesthetic efficacy.

We performed a double-blind, randomized, prospective study to determine the local anesthetic that provided the best analgesia for insertion of an 18-gauge intravenous (i.v.) catheter and to determine whether alkalinization of lidocaine decreases the pain of intradermal injection. There were 280 healthy adult patients assigned randomly to seven different groups: benzyl alcohol 0.9% in normal saline, 2-chloroprocaine 3%, lidocaine 1%, lidocaine 1% with preservative, alkalinized lidocaine 1% with preservative, normal saline, and a control group that received i.v. catheter placement without previous drug injection. A 10-cm visual analog pain scale (VAPS) was used to obtain pain scores after pre-i.v. drug injection and after iv catheter insertion. Benzyl alcohol in normal saline (0.61 +/- 0.11) and alkalinized lidocaine (0.69 +/- 0.10) had the lowest mean pain scores for drug injection and these were significantly different from other drugs (P < 0.05). Alkalinized lidocaine (0.7 +/- 0.18) had the lowest mean pain score for i.v. catheter insertion with nothing (no previous drug injected) (3.47 +/- 0.38) and normal saline (3.97 +/- 0.18) had the highest mean pain scores (P < 0.05). We conclude that alkalinized lidocaine decreased the pain associated with its injection. Alkalinized lidocaine was the best local anesthetic for i.v. catheter placement. Benzyl alcohol in normal saline was also effective.

Permeability and structure of junctional membranes at an electrotonic synapse.

The dye Procion Yellow M4RS crosses junctional membranes from cytoplasm to cytoplasm at electrotonic synapses between segments of the crayfish septate axon. The dye does not enter the cells from extracellular space. Thus permeability of junctional membranes is qualitatively different from that of nonjunctional membranes. Electron microscopy after fixation in the presence of lanthanum hydroxide indicates that these synapses are "gap junctions" and that there is a network of channels continuous with extracellular space between apposed junctional membranes. These channels must be interlaced with intercytoplasmic channels that are not open to extracellular space.

Temperature-dependence of resistance at an electrotonic synapse.

The junctional resistance at septa of the crayfish lateral giant axon is inversely related to temperature with a Q(1l), of about 3 over the range from 5 degrees to 20 degrees C. Nonjunctional axonal membrane is much less affected. Resistance changes occur rapidly with temperature changes. No correlates in ultrastructure of the synapses have been found.