Sensitization to continued nociceptive stimulation is supposed to be involved in the development of chronic pain at several levels of the CNS, but experimental studies investigating the perceptual dynamics of sensitization in humans are rare, and the diagnostic validity of experimental pain models is not known. The present study used a tonic heat paradigm to assess early sensitization (15-100 s) to experimental pain in 30 chronic pain patients (15 musculoskeletal/back pain, 15 headache) and 23 healthy controls. Change in pain sensation during prolonged stimulation was measured by a dual sensitization method which combines subjective ratings and behavioural responses in an indirect psychophysical protocol protected against response bias. Phasic and tonic pain thresholds were measured for control purposes. The degree of sensitization was linearly related to stimulus temperature, and groups differed significantly in this 'sensitization gradient': chronic pain patients sensitized earlier and stronger than healthy subjects, musculoskeletal pain patients showed the strongest effect. Pain thresholds were lowered in headache patients only. Discriminant analysis demonstrated good sensitivity and specificity of individual sensitization measures for distinguishing pain syndromes, particularly in combination with pain thresholds. The results are in accordance with current models of spinal plasticity contributing to pathological pain states. They argue for the diagnostic value of psychophysical measures of sensitization.

It should be remembered that almost any drug given during labour may have negative effects on the child. On the other hand withholding a drug that is otherwise indicated may carry as many risks as giving an overdose or failure to treat at the appropriate time. In addition drug therapy may affect the child indirectly, for example by reducing placental function. During general anaesthesia, the interval between induction and cutting the umbilical cord determines the degree of drug load for the child. The interval should ideally be between 3-15 minutes. In addition the effect of drugs on the fetus depends on many additional factors such as gestational age, plasma binding of the drug and amount of fat.

The variations in plasma erythropoietin (EPO) concentration during preoperative deposit of autologous blood were studied in 12 patients (8 men, 4 women). Four donations were scheduled at weekly intervals. A predonation hemoglobin concentration of 11 g per dL (110 g/L) was required. Hemoglobin concentration decreased from 14.3 ± 1.1 g per dL (143 ± 11 g/L) (mean ± SD) before the first donation to 11.7 ± 0.7 g per dL (117 ± 7 g/L) on Day 22 (p<0.0001). Reticulocyte counts increased from a median of 31,800 (range, 4900-95,000) per \xL (median, 32 x 10 9 /L [range, 5-95 x 10 9 /L]) to 93,800 (16,800-194,900) per \iL (median, 94 x 10 9 /L [range, 17-195 x 10 9 /L]) on Day 28 (p<0.01). Plasma EPO concentration was 17.8 ± 5.1 mU per mL prior to the first donation and displayed a small and transient peak after each donation. A sustained elevation followed each peak. Although plasma EPO concentration differed significantly from the baseline value after the first donation, only the peak concentrations after the second (35.5 ± 15.5 mU/mL), third (38.0 ± 14.5 mU/ mL), and fourth (36.1 ±11.0 mU/mL) donations exceeded the normal range. The moderate, biphasic increase in plasma EPO concentration and the moderate increase in erythropoiesis suggest two strategies in autologous blood donation that should be investigated with respect to efficiency and safety: 1) more aggressive donation schemes, which reduce donation intervals and/or the minimum hemoglobin concentration and 2) the administration of recombinant human EPO. TRANSFUSION 1991;31:650-654. Abbreviations: EPO = erythropoietin.THE IMMUNOLOGIC AND INFECTIOUS risks of transfusion 1,2 can be minimized by the use of autologous blood. Preoperative autologous blood donation considerably reduces homologous transfusion requirements in surgery. 3 " 8 Frozen storage of red cells allows the preoperative deposit of a large number of blood units, but it is costly and time-consuming. On the other hand, liquid storage is limited to 5 weeks for whole blood and 7 weeks for packed red cells. 9,10 The efficiency of preoperative deposit in the liquid state thus depends on the rate of recovery from blood loss, that is, on the degree of stimulation of erythropoiesis.Erythropoietin (EPO) is the primary humoral regulator of erythropoiesis. 11 Increasing the availability of EPO may therefore enhance the efficiency of preoperative donation programs. This increased availability of EPO may be achieved by allowing the modulation of donation schemes (shorter donation intervals, lower minimum

In 23 patients with advanced stages of acute respiratory failure, the value of various parameters for estimating the efficiency of ventilation with PEEP were analysed. PEEP increments of 1 cm of water corresponded to an increase of PaO2 of 2 mmHg. The cardiac output decreased from 8.3 +/- 0.3 l/min mean value at ZEEP to 7.3 +/- 0.3 L/min at a PEEP of +15 cm H2O. Corresponding to this, the oxygen transport showed a decrease from 1042 +/- 62 ml/min to 894 +/- 115 ml/min. The total compliance of 34 ml/cm H2O at ZEEP is already significantly reduced (a sign of the severe respiratory failure) and falls still further at a PEEP of 15 cm H2O to 22 ml/cm H2O. No notable recruitment of non ventilated alveolar spaces can be expected, in spite of the slight increase in the arterial oxygen tension. Taking the "best PEEP" (PEEP with maximum oxygen transport) as a reference point, arterial and mixed venous oxygen tension increase, the cardiac output decreases above this point and the total respiratory compliance shows no obvious changes. In the advanced stage of severe respiratory failure one cannot use the mixed venous oxygen tension or the compliance to find the best PEEP. The danger of barotrauma by PEEP ventilation in cases of significantly reduced compliance has to be considered in the choice of the ventilation pattern. The arterial oxygen tension may lead to a wrong estimation of the total efficiency of PEEP.

Homologous transfusion is associated with infectious and immunological risks. Preoperative autologous deposit reduces homologous transfusion requirements considerably. Usually donations are carried out at weekly intervals. In this study we investigated the effect of shorter donation intervals on erythropoiesis and perioperative transfusion requirements. METHODS. A total of 40 consecutive patients scheduled for hip arthroplasty and taking part in an autologous donation programme were randomly assigned to two groups: group I gave blood on days 0, 3, 7 (and 14), group II at weekly intervals. The aim was deposit of three blood units of 450 ml. A patient was deferred if hemoglobin concentration prior to donation fell below 11 g/dl, and in this case 100 mg Fe 2+ three times daily was prescribed. Blood was stored with CP-DA-1 anticoagulant. Surgery was performed between day 28 and 35. A perioperative hemoglobin concentration lower than 9 g/dl was considered a transfusion trigger. RESULTS. Group I was made up of 21 patients (10 women, 11 men, aged 39-69 years) who gave blood at short intervals, and group II of 19 patients (10 women, 9 men, aged 37-77 years) who gave blood at weekly intervals. General data, calculated blood volume and erythrocyte mass prior to donation were comparable. Each patient donated three units. Four patients had to be deferred once, one in group I, three in group II. The hemoglobin concentration in group I decreased from 13.9 +/- 1.2 g/dl (mean +/- SD) to 13.3 +/- 1.0 g/dl prior the operation, in group II from 13.5 +/- 1.3 g/dl to 12.5 +/- 1.1 g/dl. Preoperatively the hemoglobin concentrations differed significantly (P < 0.05), as did calculated erythrocyte mass (1633 versus 1474 ml, P < 0.05). Reticulocytes increased from 46 x 10(3)/microliters (median) to a maximum of 94 x 10(3)/microliters on day 7 in group I, and from 44 x 10(3)/microliters to 108 x 10(3)/microliters in group II on day 14. Serum ferritin decreased from 122 micrograms/l (median) to 82 micrograms/l in group I, and from 140 micrograms/l to 77 micrograms/l in group II. These parameters did not differ statistically between the two groups. Intra- and postoperative blood loss amounted to 2175 ml (median) in group I versus 1430 ml in group II (P < 0.05). The perioperative hemoglobin concentration was similar in the two groups. Homologous transfusion requirements were similar in the two groups (1 unit in group I, vs 3 units in one patient and 1 unit in two patients in group II). CONCLUSIONS. Short donation intervals resulted in a higher preoperative erythrocyte mass after similar preoperative deposit, and significantly higher blood loss was tolerated with similar homologous transfusion volume.