Powerful 3-µm lasers acousto-optically Q-switched with KYW and KGW crystals.

We report, to the best of our knowledge, the first use of KY(WO4)2 and KG(WO4) acousto-optical Q-switches in 3-µm powerful lasers. Q-switches of two different designs (normal incidence with antireflection coatings, and Brewster-angle cut crystals) operate in lasers based on Er:YAG, Cr:Yb:Ho:YSGG, and Cr:Er:YSGG laser crystals. Gain and lifetime of laser crystals significantly influence the regime of Q-switched generation. Er:YAG and Cr:Yb:Ho:YSGG lasers deliver pulses with 10.8 mJ and 17.5 mJ energy, respectively. Pulses with energy of 29.6 mJ and duration of 75 ns in the TEM00 mode are obtained in a Cr:Er:YSGG laser. The energy is scaled up to 85.7 mJ in the two-stage master oscillator power amplifier system. Powerful laser systems of this kind are in the region of interest for pumping other mid-IR laser media (e.g., Fe:ZnSe and Fe:CdSe), OPOs, CO2 lasers, and amplifiers. Preliminary experiments on microstructuring of transparent materials by the laser-induced backside wet etching method demonstrate the potential of such lasers to build the foundation for dye-free tissue and cell engineering concepts.

[Calculated and measured blood propofol concentrations during target-control infusion by means of a Diprifusor system during operations under extracorporeal circulation].

The study was undertaken to compare measured versus calculated propofol concentrations (C(m) and C(c), respectively), by using Diprifusor technology in cardiac surgery with cardiopulmonary bypass (CPB). The study included 10 NYHA II-III patients (aged 27-45 years) undergoing mitral valve replacement. Propofol (Diprivan PFS 50 ml, AstraZeneca) was target-control infused (TCI) by the Diprifusor system (Graseby 3500). C(c) was titrated to maintain the BIS value close to 40. Propofol in doses of 2.1 +/- 0.05 mg/kg was required for induction. Anesthesia before, during, and after CPB required propofol in doses of 5.4 +/- 0.3, 3.9 +/- 0.2, and 3.1 +/- 0.2 mg/kg/h, respectively. The doses of fentanyl were 4.4 +/- 0.1 microg/kg for induction of anesthesia and 4.5 +/- 0.4, 2.4 +/- 0.2, and 0.2 +/- 0.1 mg/kg/h for its maintenance before, during, and after CPB, respectively. The patients received rocuronium in the standard doses for neuromuscular relation. C(m) was determined by high-performance liquid chromatography with ultraviolet detection (Agilent 1100, column C18, Altima). Blood propofol concentrations were measured at: 1) intubation; 2) skin incision; 3) sternotomy; 4) aortic cannulation; 5) 30 min of CPB; 6) 60 min of CPB; 7) the end of CPB; 8) 30 min following CPB; 9) skin closure; 10) awakening. Data were expressed as mean +/- SEM. The values were compared by linear regression. Student's t-test was used with p < 0.05. C(m) was 2 times higher than C(c) at all stages. A close correlation was found between C(m) and C(c): r = 0.83, p = 0.038. It is concluded that Marsh's PK/PD model predicts the trend in blood propofol concentrations during uncomplicated operations on the open heart satisfactorily, but C(c) was constantly 2 times less than C(m).

[Maintenance of the hypnotic component of general anesthesia with feed-back regulation]. / Podderzhanie gipnoticheskogo komponenta obshchei anestezii s reguliatsiei po printsipu obratnoi sviazi.

The purpose of the study was to design and investigate the closed-loop propofol system (CLPS) with a mean arterial pressure (MAP) controller in open-heart surgery. CLPS consists of a 386 PC, a blood pressure sensor and an infusion pump. The C language computer program sets the propofol infusion rate based on an empirical algorithm including proportional component to maintain the measured MAP more closely to the target MAP (85% of patient standard MAP). The propofol concentrations were calculated by the pharmacokinetic/pharmacodynamic model differential equations solving every 30s. CLPS was used in 214 NYHA II-IV patients, aged 16-74, undergoing various open-heart procedures. The mean target MAP was 75.2 +/- 4.5 mm Hg. The measured and target MAP difference did not exceed 22% perioperatively. The bispectral index varied from 42.7 +/- 1.2 (tracheal intubation) to 41.8 +/- 0.1 (skin suture) with a variation of the propofol site effect concentration ranging from 2.9 +/- 0.09 to 1.8 +/- 0.1 microg/ml. It was a closed negative correlation (r = 0.84; p < 0.01) between the propofol site effect and the MAP during the initial period of anesthesia. There were not any significant changes in the blood cortisole level during the procedures. The recovery time was 1.4 +/- 1.5 min after propofol infusion; 95.5% of patients were extubated in the operating room.

[Intraoperative monitoring of a neuromuscular conduction blockade]. / Intraoperatsionnyi monitoring blokady nervno-myshechnoi provodimosti.

Preliminary results of intraoperative monitoring of the degree of neuromuscular blockade using a portable device based on the technique of evoked electromyography are presented. The device has an analogue outlet for the connection with a computer. The technique used is simple and reliable and makes it possible to work out a computerized system for automatic graded supply of current myorelaxants on a feedback principle. Such a system does not only ensure an adequate level of myorelaxation with a minimum expenditure of expensive drugs, but also gives a new approach to the study of neuromuscular conduction during anesthesiological supply in various surgical interventions.