Low dose perioperative intravenous lidocaine after total hip arthroplasty offers no beneficial effect on postoperative analgesia and does not modify pressure and tactile pain thresholds.

Sympathetic nervous system stimulation, which releases noradrenaline, influences the nociceptor activity which develops after tissue injury. The alpha 2-adrenergic agonist, clonidine, produces analgesia through a central mechanism but also inhibits noradrenaline release at terminal nerve fibre endings. Clonidine may induce analgesia when administered at peripheral sites. This study assesses the potential analgesic effect of clonidine after intra-articular administration. Forty ASA I-III patients, scheduled for arthroscopic knee surgery under general anaesthesia were allocated randomly in 4 groups of 10 patients each, at the end of the surgical procedure. In the control group (group 1), the patients received 20 ml of intra-articular isotonic saline. In group 2, the patients received 150 micrograms of clonidine diluted in 20 ml of isotonic saline injected into the knee joint. In group 3, the patients were given 20 ml of intra-articular isotonic saline and clonidine 150 micrograms was injected subcutaneously. In group 4, morphine 1 mg, diluted in 20 ml of isotonic saline, was injected into the knee joint. Postoperative pain was assessed in a double-blind fashion using a visual analogue scale (VAS) at 1, 2, 3, 6 and 24 h after the end of surgery. VAS scores were significantly lower in groups 2 and 4, compared to groups 1 and 3, at 1 and 2 h after surgery. The delay between intra-articular injection and further postoperative analgesic administration was significantly longer (P < 0.05) in group 2 (533 +/- 488 min) compared to groups 1 and 3 (70 +/- 30 min and 132 +/- 90 min, respectively). The difference was not significant between group 4 (300 +/- 419 min) and the other groups. We conclude that a low dose of intra-articular clonidine produces analgesia unrelated to vascular uptake of the drug. This study further supports a peripheral analgesic effect of clonidine.

When alkalinized lidocaine instead of air is used to fill the endotracheal tube (ETT) cuff, coughing, and bucking are decreased during extubation when ventilation is controlled with N2O. However, sodium bicarbonate (NaHCO3) used to transform lidocaine hydrochloride (L-HCl) to lidocaine base induces a pH increase that could be irritating for mucosa in the case of cuff rupture. Therefore, we determined, in a randomized controlled study with controlled patient ventilation without N2O, whether the smallest concentrations of NaHCO3 (1.4% versus 8.4%) reduced diffusion (in vitro evaluation) and other secondary clinical benefits. After pH determination of different solutions (2 mL of 2% L-HCl and 2 to 6 mL of 8.4%, or 1.4% NaHCO3), an in vitro lidocaine diffusion through the ETT cuffs was evaluated (2 mL of 2% L-HCl and 3 mL of 8.4% or 1.4% NaHCO3). Then, adult patients scheduled for total thyroidectomy surgery were consecutively enrolled (n = 20 for each group). The ETT cuff was filled with air (group air) or with alkalinized lidocaine (2 mL of 2% L-HCl) using 8.4% (group large dose) or 1.4% (group small dose) of NaHCO3. After tracheal extubation, sore throat was evaluated by visual analog scale as the main end-point of the study. Hoarseness, bucking, dysphonia, dysphagia, cough, restlessness, and postoperative nausea and vomiting were also evaluated. There was a slight tendency toward a slower release when a small concentration of NaHCO3 was used (i.e., 1.4%). Compared with group air, the alkalinized-lidocaine groups had a significant reduction in sore throat during the 24-h postoperative period (P < 0.0001). The difference was not significant between the two alkalinized lidocaine groups. This increase in ETT tolerance was confirmed by the analysis of secondary end-points. No laryngospasm, rupture of ETT cuff, or depression of the swallowing reflex were recorded. A decrease in sore throat during the postoperative period was recorded when the cuff was inflated with a small dose of alkalinized lidocaine (i.e., 40 mg of L-HCl and 1.4% of NaHCO3) rather than with air when ventilation was controlled without N2O.