Postoperative intravenous patient-controlled analgesia using hydromorphoneand metamizole (dipyrone). A prospective, randomised study

Most potent opioid analgesics available in Germany have been investigated f or use in postoperative patient-controlled analgesia (PCA). To conclude an older comparative series, it was the aim of the present study to define ana lgesic potency, side effects and patient acceptance of hydromorphone and it s interaction with the non-opioid analgesic metamizole. A total of 120 pati ents recovering from elective abdominal or orthopaedic surgery, performed u nder standardised general anaesthesia, were randomised into 3 double-blind treatment groups to receive intravenous PCA demand doses of hydromorphone 2 83 mug (low dose, LD), 566 mug (high dose, HD) or a combination of hydromor phone 283 mug and metamizole 50 mg (low dose hydromorphone + metamizole, LM ). Demand-independent low-dose background infusions were added to deliver h ydromorphone at 67.9 mug/h in all groups, with additional metamizole at 12 mg/h in group LM. Lockout times were set to 2 min. After an average observa tion time of 24.5 +/-2.6 h (mean, SD) since start of PCA, cumulative PCA hy dromorphone doses in groups LD, HD and LM were 7.8 +/-3.3, 12.1 +/-4.8 and 7.5 +/-2.0 mg, respectively, with the well known large inter-individual var iability in all groups. Although hydromorphone consumption was significantl y higher in group HD, self-reported pain intensities (VAS, retrospective pa in scores) were quite comparable between the groups. Low dose, PCA bolus-li nked metamizole did not significantly reduce hydromorphone consumption nor improve patient acceptance. Side-effects were typical for potent postoperat ive opioids, but never required special treatment; haemodynamic or respirat ory complications were not observed in any patient. It can be concluded by comparison with other PCA opioid investigations performed under the same st udy protocol that hydromorphone is about 3-4 times as potent an analgesic a s morphine under the conditions of intravenous postoperative PCA. Due to a favourable patient acceptance, hydromorphone can be recommended as a suitab le alternative to other opioids for the treatment of postoperative pain.