SYSTEMIC EFFECTS OF NITROUS OXIDE WHEN USED WITH HALOTHANE AND OXYGEN ANAESTHESIA AT NORMAL BODY TEMPERATURE

Observations made during thirty-five routine operations, using0.5–2.0 per cent halothane in a 70–80 per cent mixtureof nitrous oxide with oxygen, indicate that addition of nitrousoxide to halothane and oxygen may be associated with decreasein blood pressure, heart rate, tidal volume and muscle tone,and increase in respiratory rate; reversal of these changesmay be obtained by withdrawal of nitrous oxide. In three offive observations the rise in respiratory rate was inadequateto compensate for the fall in tidal volume, and minute volumefell by 16–37 per cent. In patients with chronic respiratorydisease, a fall in minute volume of this order might resultin serious arterial oxygen desaturation, particularly when oxygenconstitutes 25 per cent or less of the inspired gas. When halothane,which also depresses ventilation, is used together with highconcentrations of nitrous oxide, this might result in seriousrespiratory depression. Present address: Institute of Orthopaedics, Stanmore, Middlessex.     

IMAGE BASED RENAL STONE TRACKING TO IMPROVE EFFICACY IN EXTRACORPOREAL LITHOTRIPSY

Purpose

We describe a method to reduce the number of shocks necessary to fragment renal stones during extracorporeal shock wave lithotripsy by automatically taking into account stone movements.

Materials and Methods

Echotrack computer software was developed and implemented on a lithotriptor. One software module uses image processing to detect instantaneous stone location based on ultrasound images generated by the lithotriptor. A second module uses the detected location to control the shock wave generator position, and automatically adjusts it to improve coincidence between the focal volume and stone. The reliability of the tracking algorithm was clinically tested in 65 patients with renal stones. These in vivo tests were qualitative and the goal was to assess software ability to track stones during actual treatments. A quantitative evaluation of the reduction in shocks necessary for fragmentation was performed in vitro. Artificial stones were moved according to computer generated trajectories. Each trajectory was applied once with and once without automatic adjustment of the generator position.

Results

The in vivo tests demonstrated software ability to track stones as far as they were visible in the images. During in vitro tests automatic adjustments of the generator position reduced the number of shocks necessary to fragment stones completely by a factor of 1.64.

Conclusions

Image based renal stone tracking software that automatically adjusts the shock wave generator position according to the displacement of renal stones is useful during extracorporeal shock wave lithotripsy. Treatment time was significantly shorter with this software.     

Bupivacaine causes cytotoxicity in mouse C2C12 myoblast cells： involvement of ERK and Akt signaling pathways

Aim:

The adverse effects of local anesthetics (LAs) on wound healing at surgical sites have been suggested, and may be related to their cytotoxicity. This study was aimed to compare the cellular toxicity of bupivacaine and lidocaine (two well-known LAs), and to explore the molecular mechanism(s).

Methods:

Toxicity of bupivacaine and lidocaine was assessed in cultured mouse C2C12 myoblasts by cell viability and apoptosis assays. Effects of LAs on extracellular signal-regulated kinase (ERK) and protein kinase B (Akt) activation, which are essential for cell proliferation and survival, were evaluated by immunoblotting.

Results:

Both LAs, especially bupivacaine, prevented cell growth and caused cell death in a dose-dependent manner. The half maximal inhibitory concentrations (IC₅₀) for bupivacaine and lidocaine were 0.49±0.04 and 3.37±0.53 mmol/L, respectively. When applied at the same dilutions of commercially available preparations, the apoptotic effect induced by bupivacaine was more severe than that of lidocaine in C2C12 cells. Furthermore, bupivacaine significantly diminished the ERK activation, which may underlie its anti-proliferative actions. Both LAs suppressed Akt activation, which correlated with their effects on apoptosis.

Conclusion:

Our study demonstrated that, when used at the same dilutions from clinically relevant concentrations, bupivacaine is more cytotoxic than lidocaine in vitro. Anti-proliferation and cell death with concomitant apoptosis mediated by bupivacaine may offer an explanation for its adverse effects in vivo (eg slowing wound healing at the surgical sites). A less toxic, long-acting anesthetic may be needed.