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This study compares the neuromuscular blocking effect of succinylcholine (0.8 mg • kg−1) and atracurium (0.6 mg • kg−1) on the diaphragm (D) and the adductor pollicis (AP) in 20 patients anesthetized with nitrous oxide, oxygen, and fentanyl. The diaphragm was monitored by measuring transdiaphragmatic pressure following bilateral phrenic nerve stimulation. After succinylcholine, the time from injection of succinylcholine to maximum depression of the single twitch response (onset time) was of 50 ± 11 s (±SD) for D compared to 80 ± 24 s for AP (P < 0.001). After succinylcholine, recovery from paralysis was earlier for D than AP. Single twitch height (TH) returned to 25% of its control value (T25) after 5 ± 2 min for D compared to 7 ± 3 min for AP (P < 0.001). Complete recovery of TH (T100) was achieved after 9 ± 4 min for D and 11 ± 5 min for AP (P < 0.01). Recovery index (T25–75) was of 2 ± 1 min for both muscles. After atracurium, the onset time for D was of 137 ± 31 s compared to 181 ± 45 s for AP (P < 0.001). The T25 was achieved after 38 ± 7 min for D compared to 63 ± 13 min for AP (P < 0.001). The TH of D returned to T100 after 60 ± 12 min compared to 87 ± 17 min for AP (P < 0.01). The train-of-four ratio returned to 1 after 64 ± 15 min for D compared to 99 ± 21 min for AP (P < 0.001). After an intubating dose of succinylcholine (0.8 mg • kg−1) or atracurium (0.6 mg • kg−1), D was always completely paralyzed, when the TH of AP was abolished and the TH of D had completely recovered when the TH of the AP had returned to 100%.

The oxygen delivery (DO2) and consumption (VO2) relationship in brain-dead organ donors is unknown. Therefore, in a prospective study, we determined the DO2/VO2 relationship in 21 consecutive brain-dead patients. Patients were allocated to one of two groups, according to plasma lactate concentration: normal (group NL, n = 11) or high (> 2.5 mmol litre-1) (group HL, n = 10). VO2 was measured independently, using indirect calorimetry, under control conditions, during low DO2 challenge with PEEP administration, and high DO2 challenge with inflation of medical antishock trousers and volume expansion or blood transfusion, as required. Under control conditions, there were no significant differences between groups NL and HL in haemodynamic or oxygenation variables, both groups having a low VO2 (mean 114 (SD 21) ml min-1 m-2). In group HL there was a different DO2/VO2 relationship pattern, with a dependent VO2 only. The mean slope of the DO2/VO2 relationship was significantly higher in group HL than in group NL (0.12 (0.09) vs 0.04 (0.07), P < 0.05). We conclude that brain death was associated with a low VO2, and patients in group HL exhibited DO2/VO2 dependency which was not observed in patients in group NL.

Indirect measurements of respiratory muscle action based on pressure and chest wall motion are easier than are assessments based on implanted electromyogram electrodes and sonomicrometers that measure electric activity and muscle length, respectively, directly. Interpretation requires numerous assumptions and detailed analysis of phase relations among the variables. In patients after thoracic surgery, however, these measurements strongly point to a shift in the distribution of motor output toward muscles other than the diaphragm.

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