Nerve injury can arise as a complication peripheral nerve block anesthesia. Of the various factors involved, the trauma caused by the injection needle may be of significance. In this experimental study the frequency of fascicular injury was investigated immediately after needling isolated rabbit sciatic nerve preparations, and after intraneural injection with the nerve in situ. Two different injection needles were used, one with a bevel angle of 14 degrees and the other with a 45 degrees bevel angle. Fascicular injury was indicated by a fluorescence microscopy technique, tracing locally applied Evans Blue Albumin, The results show that a 45 degrees-beveled needle less frequently produces fascicular damage and should therefore be recommended for use in clinical anesthesia. It is also concluded that paresthesiae, when necessary, should be elicited gently, and that intraneural injections should be avoided.

Differences in the effects of commercially available, sodium bisulfite-containing (pH 3.5-4), and freshly prepared (pH 6.5) lidocaine-adrenaline solutions on tissue pH and tissue oxygenation were studied experimentally. In rabbits, a 5 x 5 cm area under the panniculum was infiltrated with 0.9% NaCl, plain lidocaine, plain adrenaline or one of the two lidocaine-adrenaline solutions. Tissue pH was measured continuously as well as intermittently in the infiltrated area with monocrystalline antimony needle electrodes. Infiltration of the tissue with the 4 ml volume of a test solution did not seem to induce any significant tissue injury. Tissue pH was decreased for 30 min following plain lidocaine and for 90 min or more following lidocaine-adrenaline infiltration. With the exception of the first few minutes, no significant differences in the effects on tissue pH between commercial and freshly prepared lidocaine-adrenaline solutions could be seen. Tissue hypoxia occurred only following infiltration with plain adrenaline. It may thus be concluded that in spite of the low pH and the O2-reducing properties of commercial lidocaine-adrenaline solutions, a rapid buffering occurs in the tissues. The use of commercial lidocaine-adrenaline solution for local infiltration thus seems as safe as that of freshly prepared lidocaine-adrenaline solutions.

SUMMARY An objective method for testing local anaesthetic drugs in human test subjects with the Ninhydrin print technique is described. The method is reliable in ulnar, median and finger nerve blocks. It is of more limited value in other blocks or for skin wheals, where it must be used together with the subjective neurological tests. A comparison between this method and the conventional technique used in ulnar nerve blocks was made. We feel that the Ninhydrin test is superior to the pin‐prick method in testing local anaesthesia. ZUSAMMENFASSUNG Es wird eine objektive Methode zur Testung von Lokalanaestheticis an Versuchspersonen beschrieben: die Ninhydrin Fingerabdruck‐Technik. Die Methode ist verlasslich beim Ulnaris‐, Medianus‐ und beim Fingerblock. Sie hat einen etwas begrenzteren Wert bei anderen Nervblocks und bei Haut‐quaddeln. In diesen Fällen muss sie zusammen mit subjektiven neurologischen Tests angewendet werden. Es wurde ein Vergleich zwischen dieser Methode und den konventionellen Techniken beim Block des N. ulnaris angestellt. Wir haben den Eindruck, dass der Ninhydrin‐Test der Nadelstichmethode bei der Testung von Lokalanaestheticis überlegen ist.

liecently cases h a v c been reported \\>here C0,-retention, d u e to insufficient ventilation, has caused i m p a i r m e n t of consciousness (1, 2).

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