Effects of thiopental on bispectral index and heart rate variability.

BACKGROUND AND OBJECTIVE: Thiopental has been reported to reduce sympathetic tone, however, it is not clear whether change in heart rate variability is associated with depth of anaesthesia. The purpose of the present study was to evaluate changes in heart rate variability at different depths of hypnosis during induction of anaesthesia with thiopental. METHODS: We studied 17 ASA I patients scheduled for minor surgery. The depth of hypnosis was monitored by the BIS. Spectral analysis of heart rate variability using a maximum entropy method resulted in a characteristic power spectrum with two main regions, a high frequency and a low frequency. Haemodynamics, entropy, low frequency, high frequency and low frequency/high frequency were monitored in an awake state and after the induction of anaesthesia. RESULTS: Heart rate increased in a BIS-dependent manner, whereas blood pressure showed no significant changes during the study period. High frequency, entropy and low frequency decreased with a reduction in the BIS value. Low frequency/high frequency showed no significant change during the study period. CONCLUSIONS: Induction of anaesthesia with thiopental increased heart rate and decreased high frequency, entropy and low frequency in a BIS-dependent manner, indicating that thiopental reduces cardiac parasympathetic tone depending on the depth of hypnosis.

[Cardiovascular responses during laryngeal mask airway insertion in normotensive, hypertensive and chronic renal failure patients].

The hemodynamic response to the insertion of the laryngeal mask airway (LM) following induction with propofol 2 mg.kg-1 was assessed and compared in normotensive (Normal), hypertensive (HT) and chronic renal failure (CRF) patients (n = 23 in each group). Before induction, in HT and CRF groups blood pressure and rate pressure products (RPP) were higher than in Normal group (P < 0.05). Although blood pressure and RPP were decreased in every patient by induction with propofol, no patients needed vasopressor drugs. The decreases of blood pressure and RPP were larger in HT and CRF groups than in Normal group (P < 0.05). There were no differences between groups in heart rate and rate of successful LM insertion. We concluded that LM insertion with propofol 2 mg.kg-1 was an effective induction method preventing the adverse circulatory responses in normotensive, hypertensive and chronic renal failure patients.

[Changes in circulation and end-tidal sevoflurane concentration during infusion of sevoflurane into vaporizer].

We observed the changes in circulation and endtidal sevoflurane concentration during the infusion of the anesthetic into a vaporizer, and investigated some techniques to prevent these changes during general anesthesia. The patients were randomly divided into three groups: conventional, high concentration (conc.) and low flow groups. Inspiratory concentration of sevoflurane was kept at 1.0% and the duration of the pause in sevoflurane supply was 90 sec. The high conc. group was exposed to 2.0% sevoflurane for 60 sec. just before and after the pause, and the low flow group had a low fresh gas flow (0.5 l.min-1) during the pause. An increase in blood pressure and a tendency towards tachycardia were observed in the conventional group, and the circulation was kept constant best in the low flow group. The lowest concentrations of sevoflurane during the pause were 0.46, 0.46 and 0.93% in the conventional, high conc., and low flow groups, respectively, and exposure to high concentration of the anesthetic could not prevent the decrease. These results indicate that low flow anesthesia is a useful technique to prevent undesirable changes in circulation and anesthetic concentration.

[An analysis of the status of surgical transfusion in Sapporo Medical University Hospital].

To evaluate the present status of blood transfusion during operation in our hospital, we retrospectively analyzed the amount of preoperative preparation & intraoperative use of homologous blood and the circumstances of autologous blood transfusions. The amount of prepared blood was 4,505 units of which 1,187 units were transfused; the mean cross matched-to-transfused (C/T) ratio was 3.8. A trial of maximum surgical blood order schedule (MSBOS, C/T = 1.5) revealed that we could save over 70% of the homologous blood presently prepared. Preoperative blood donation (PBD) and intraoperative autologous blood transfusion (IAT) were performed in 74 cases (47.4%) and 55 cases (35.3%), respectively, of all 156 blood-transfused cases, and the operations were performed without homologous blood transfusion in 88.0% of PBD cases and 67.3% of IAT cases respectively. We are sure that the introduction of MSBOS will lead to a more efficient use of autologous blood, and that we should use homologous blood transfusion techniques so far as is possible to avoid autologous blood transfusion.

Scanning electron microscopy of the glomerular filtration membrane in the rat kidney.

The rat kidney was perfused with saline and glutaraldehyde, treated with Murakami's tannin-osmium impregnation method, ethanol-freeze cracked and dried by the critical point method. Gold-palladium evaporated specimens were observed in a field-emission scanning electron microscope. The glomerular filtration membrane, fractured in different planes was observed with the following results: 1. Adjacent pedicles originate from different podocytes. No interpedicular bridges of apparent cytoplasmic nature could be found. 2. The basement membrane, in grazing fractures shows a horizontally layered architecture. 3. The attenuated endothelial sheet (lamina fenestrata) is divided into compartments, which we suggest should be called "areolae fenestratae", by cytoplasmic crests radiating from the nucleated portion of the endothelial cell. A crest also occurs along the cell margin, which contacts a similar crest at the margin of the adjacent cell. 4. The pores in the areolae fenestratae are variable in size (30-150 nm diameter). A knob-like projection from the apparently naked basement membrane is found in a portion of the pores. 5. Numerous microvilli may occur on the endothelium. Some of them anastomose and fuse with one another to form a net whose meshes appear identical with the endothelial pores. Domes and shelves formed of a fenestrated cytoplasmic sheet also occur above the ordinary level of the endothelial lining. A hypothesis implicating microvilli in the partial renewal of the endothelial sheet is proposed.