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1bulbar blocks could lead to some passage of local anaesthetic across the optic chiasma and cause a contralateral block and blindness [I 1,121. This did not occur in our series. Theoretically, the use of a larger volume for retrobulbar block could lead to an increase in ocular tension and make the eye rather hard, but this effect is mitigated by the action of the local anaesthetic on the extra-ocular musculature [13]. In our study there was no increase in eye tension as assessed by the surgeon.In conclusion, local anaesthesia has a significant role in cataract surgery, particularly in the elderly and the chronically ill. This small study has established that good operating conditions can be achieved by a single retrobulbar block using a slightly higher volume of local anaesthetic solution than previously described. This method is satisfactory for both the surgeon and the patient.
Changes in the expiratory dimensions of the rib cage and abdomen on induction of anaesthesia with eltanolone, propofol and thiopentone were measured in 76 patients using respiratory inductance bands. Calibration of the respiratory inductance plethysmograph was by simultaneous flow measurement with a pneumotachograph. Movement of the vertebral column was restrained with a rigid mattress to allow volume change to be estimated more accurately from rib cage and abdominal dimensions. Rib cage volumes decreased by a median of 125 ml, while the median change in the abdominal compartment was 0. These findings suggest that a reduction in rib cage volume may contribute to the decrease in functional residual capacity after induction of anaesthesia, but that changes in the diaphragmatic-abdominal compartment are not important.
We recorded the ventilatory effects of eltanolone 0.75 mg kg-1, propofol 2.5 mg kg-1 and thiopentone 4 mg kg-1 at induction of anaesthesia in 76 unpremedicated patients, aged 18-65 yr. Measurements were made using a pneumotachograph incorporated between a close-fitting face mask and a T-piece delivering 35% oxygen. Eltanolone caused significantly less apnoea than propofol (incidence 57% vs 100%) and less reduction in ventilation than propofol (median maximum decrease 4.8 vs 7.8 litre min-1), but the differences between eltanolone and thiopentone were smaller and generally not significant. Ventilatory frequency was maintained well in the eltanolone group.
Using a specific RIA, we have investigated in patients and volunteers whether fasting, diminished hepatic clearance, hemoconcentration, or within-day biological variation might be responsible for the transient increases in plasma glutathione S-transferase (GST) concentration observed after anesthesia. GST concentration was measured in 44 healthy volunteers after an overnight fast and at 3, 6, and 24 h after the fasting sample. The concentration was significantly lower at 3 and 6 h after than in the fasting sample (P = 0.0019 and P = 0.015, respectively). The change in GST concentration caused by fasting was examined in 30 subjects by comparing pre- and postfasting values. Fasting had no significant effect on GST concentration overall (P = 0.4721), but two individuals showed a marked increase in GST concentration after fasting overnight. In a separate study of 10 patients, plasma amylase activity and plasma concentrations of GST and albumin were measured immediately before and 3 h after induction of halothane anesthesia. Although GST concentration was increased at 3 h in each of the 10 patients, plasma amylase activity and plasma albumin concentration were significantly decreased in all patients (P = 0.002). Apparently, increases in GST concentration after anesthesia do not result from incidental factors.
We agree with the authors that the correlation between spread of contrast and sensory blockade is poor. We did not use the radiographic findings in our case to demonstrate the exact segment-to-segment relationship of the contrast and local anaesthetic, but to demonstrate the mechanical block at L, and cephalad spread of dye. The radiographs were taken immediately after injection of contrast (to limit reabsorption), with the patient in the lateral position, thus obviating the lumbosacral curve. We did not feel larger volumes of contrast would clarify matters further. Indeed, large volumes of low concentration dye can result in the contrast not being visible on X-rays [ 11.
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