INTRAVENOUS ANALGESIA FOR EXTRACORPOREAL SHOCK-WAVE LITHOTRIPSY - SUFENTANIL VERSUS ALFENTANIL

Extracorporeal shock-wave lithotripsy (ESWL) is the method of choice f or the treatment of solitary stones in the kidney or ureter. Early lit hotripters required prolonged immobility of the patient and caused con siderable pain, necessitating general or epidural anaesthesia during t he procedure. Modern lithotripters are quicker, but still require anal gesia. Intravenous opioids are currently the drugs in favour. The opio ids most commonly used are fentanyl and its shorter-acting analogue, a lfentanil. The latter has a more rapid onset and, because of its reduc ed lipid solubility, is less cumulative. Sufentanil is a new opioids t hat is also of the phenylpiperidone group and has been recently licens ed and introduced in Germany. Its pharmacokinetic and pharmacodynamic properties suggest an intermediate duration of action, high analgesic potency, and cardiovascular stability with diminished respiratory depr ession. In this prospective double-blind study, the effects of alfenta nil and sufentanil on cardiovascular and respiratory parameters, the q uality of analgesia, degree of sedation and the number and type of sid e-effects were compared. Patients and Methods. After giving informed c onsent and with the approval of the hospital ethics committee, 62 pati ents (ASA I or II) were investigated. They were randomly allocated to two groups, either receiving sufentanil (n=32) or alfentanil (n=30) du ring ESWL. No premedication was given. Excluded were patients with pai n prior to treatment, patients treated with a spasmolytic or analgesic drug and those who had undergone ESWL within the last 6 months. The l oading dose was given as a 5-min infusion to each group. The heart rat e, systolic and diastolic blood pressure, percutaneous oxygen saturati on (SpO(2)), and the transcutaneous capillary carbon dioxide tension ( PtcCO2) were recorded prior to the procedure (i.e. before administrati on of opioid), after 1000 and after 2000 shock waves and then 1 and 2 h after the end of lithotripsy. After 1000 and 2000 shock waves, and 1 an 2 h after the treatment, the patients were asked to express their degree of tiredness and pain on a visual analogue scale (VAS). The occ urrence of side-effects such as nausea, vomiting, pruritus or other un pleasant sensations were noted by an anaesthesia nurse. Simultaneously , the anaesthetist recorded his/her impression of the patient's tiredn ess and degree of pain, both by using the VAS. He was not allowed to q uestion the patient, nor was he aware of the patient's own scores. At the end of the observation period both the patient and the anaesthetis t related their overall satisfaction with the anaesthetic procedure, a gain by using the VAS. Data were analysed with the Mann-Whitney-U for comparisons between groups and with the Wilcoxon test within each grou p. The side-effects were analysed with the Chi-square test. Results. T he systolic and diastolic blood pressure remained stable in both group s during and after treatment. The mean heart rate was different betwee n the two groups at the beginning, acid after the end of the treatment it dropped in both groups, but no significant difference was seen bet ween groups. The PtcCO2 rose from an initial mean of 36.8 mm Hg to a m aximum of 44.6 mm Hg after 1000 shock waves in the sufentanil group, a nd from 37.8 mm Hg to 46.0 mm Hg after 2000 shock waves in the alfenta nil group. The differences were significant within groups until 1 h af ter the end of the treatment, but there was no significant difference between groups. The oxygen saturation SpO(2) dropped slightly in both groups. The differences were not significant between groups. In the al fentanil group, one patient had a maximum carbon dioxide tension of 83 mm Hg after 2000 shock waves, whereas in the sufentanil treated group the oxygen saturation fell to 72% in one case. Sufentanil-treated pat ients felt more tired than those who received alfentanil. While the di fference in patient's judgement was significant from 2000 shock waves until the end of the observation period, the anaesthetists' assessment showed only a slight trend towards more tiredness after sufentanil. B oth opioids provided good analgesia, as judged by both the anaesthesis t and the patient, with no differences between groups. The overall sat isfaction with the treatment was less with sufentanil than with alfent anil as judged by both the anaesthetist (6.52 vs 7.64) and the patient (7.77 vs 8.86). The adverse effects observed were significantly more frequent in the sufentanil group (24 vs 11). This was mainly due to a higher incidence of itching and nausea. Other side-effects, such as ex trapyramidal motor disorders, chest wall and muscular rigidity or dist urbed swallowing, were only seen in patients who received sufentanil. Both drugs caused vomiting, motor restlessness and anxiety with the sa me frequency. Discussion. Each of the drugs used in this study provide d good or excellent pain relief for ESWL with good haemodynamic stabil ity. The increase in carbon dioxide tension and the drop in oxygen sat uration in some cases suggest that the routine use of a transcutaneous carbon dioxide analyser and a pulse oximeter to monitor extreme hyper carbia or hypoxaemia is necessary. We did not find less respiratory de pression in sufentanil-treated patients, although the maximum measured PtcCO2 was not as high as in the alfentanil group. However, this stud y clearly showed that sufentanil had more of a sedative effect, as per ceived by the patient. With the dosage regimens used in this study, th ere was a higher incidence of side-effects in the sufentanil group wit hout any advantage over alfentanil. It is our opinion that these side- effects lead to both anaesthetists and patients rating alfentanil as b etter than sufentanil. Perhaps a reduction in the sufentanil maintenan ce dose would decrease the incidence of side-effects without adversely affecting analgesia. Further studies with a reduced doses of sufentan il are required to answer this question.