To study the relationship between the intensity of the stimulus exerted against the base of the tongue during direct laryngoscopy and the magnitude of associated hemodynamic and catecholamine responses, a study was conducted in 40 ASA I or II patients. Laryngoscopy lasting 40 s was performed with a size 3 Macintosh blade connected to a force-displacement transducer. The intensity of the stimulus exerted during laryngoscopy is expressed by the product of its average force (N) and duration (s) and given as impulse in Ns. Highly significant relationships were found between the impulse during laryngoscopy and the maximal hemodynamic and catecholamine responses. Also, when laryngoscopy was followed by orotracheal intubation, significant relationships were found with steeper slopes of the regression lines for systolic blood pressure, heart rate and plasma epinephrine concentrations. A more rapid regression of hemodynamic data was seen in intubated patients, whereas their plasma catecholamine concentrations regressed more slowly. The mechanisms of the responses to laryngoscopy and orotracheal intubation are proposed to be by somato-visceral reflexes. Stimulation of proprioceptors at the base of the tongue during laryngoscopy induces impulse-dependent increases of systemic blood pressure, heart rate and plasma catecholamine concentrations. Subsequent orotracheal intubation recruits additional receptors that elicit augmented hemodynamic and epinephrine responses as well as some vagal inhibition of the heart.

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Equimolar doses of the investigated local anaesthetics exerted similar durations of sensory blockade in a peripheral nerve block model in the rat.

An immunoradiometric assay for tissue thromboplastin has been established. Blood levels in 6 patients undergoing total hip replacement have been determined. In 3 patients, high levels of circulating apoprotein III were found at various stages of the operation, showing a release of tissue thromboplastin chiefly during impaction of the prosthesis into the femoral bone. The other 3 patients had low or undetectable levels.

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Sixteen patients were given thoracic epidural analgesia at the T5-T6 level with 2 ml of 1.0% bupivacaine solution plain for pain relief after upper abdominal surgery. In 13 cases the analgesia was prolonged by continuous injection of 1.0% bupivacaine for 24 or 48 h. Onset time and segmental spread of the analgesia are presented as well as segmental spread, intensity of the blockade, and peak expiratory flow rates during prolongation. Signs of tachyphylaxis were noticed, and also signs of accumulation of bupivacaine in plasma. A high incidence of urinary retention occurred. The method is not considered to be ideal for pain relief after upper abdominal surgery.

The effects of addition of hyaluronic acid (sodium hyaluronate, Healon) to different local anaesthetics of the amide type on the duration of sensory or motor blocks following various regional anaesthetic procedures were studied in animal experiments. In the rat infra-orbital nerve block model, the addition of 0.1-0.5% hyaluronic acid (HA) to 2% prilocaine increased the duration of sensory block of varying degrees in a dose-dependent way by up to 500% of values obtained with plain prilocaine. The duration of degree 5 blocks produced by 0.5% etidocaine and 0.5% bupivacaine was also significantly prolonged when 0.4% HA was included to 206% and 282% of control, respectively, while blocks induced by 2% lidocaine were prolonged to 123% of control. The duration of motor block following spinal anaesthesia in the mouse was prolonged in a dose-dependent way when HA was added to prilocaine, bupivacaine and etidocaine. For solutions containing 0.4% HA, prolongations to 254%, 166% and 134% of control, respectively, were obtained. A concomitant increase of latency to onset of block and failure rate occurred with increasing concentrations of HA. The duration of corneal anaesthesia in the rabbit increased by 57% and 44% when 0.3% HA was added to prilocaine and bupivacaine, respectively. The duration of infiltration anaesthesia was not affected by the addition of HA to the local anaesthetic solutions. Addition of HA had no effect on the onset, depth and duration of prilocaine-induced block of the nervous transmission in vitro. The duration of infra-orbital nerve block and spinal anaesthesia shows a significant relation to the relative viscosity of the local anaesthetic solution.

The effects of bupivacaine-prilocaine and meperidine-lidocaine combinations (as compared with those of the agents used alone) on the duration of peripheral sensory nerve block were studied with the infraorbital nerve block model (IONB) in the rat, and those on motor block with spinal anesthesia (SA) in the mouse. The duration of bupivacaine-induced IONB was invariably prolonged when prilocaine was included in the solution. When included in 0.125% bupivacaine, 1.0% prilocaine had a slightly less pronounced enhancing effect than 0.5% prilocaine (24-57% vs. 74%-104%, respectively). The duration of IONB with 1.0% prilocaine was significantly reduced (14-37%) by inclusion of 0.125% bupivacaine. In SA, inclusion in 0.125% bupivacaine of prilocaine (0.5% or 1.0%) prolonged motor block by 128% and 192%, respectively. When included in 0.25% bupivacaine, both 0.5% and 1.0% prilocaine significantly reduced the duration of SA, by 42% and 37%, respectively. With one exception, the duration of IONB by meperidine was significantly shortened (< 44%) when lidocaine was included in the solution. In SA, inclusion of 2% lidocaine with 2% meperidine did not affect the duration of meperidine-induced motor block. The duration of SA obtained with the combination of 4% lidocaine and 4% meperidine was 45% shorter than that induced by 4% meperidine alone. The reasons for these variable effects are not clear, but may be due to interaction or antagonism at any of multiple sites.