Impact of oedema on recovery after major abdominal surgery and potential value of multifrequency bioimpedance measurements

Background: The consequences of generalized oedema following major abdominal surgery are under-recognized, and its causes are poorly understood. Methods: Thirty-eight patients (21 men and 17 women) were observed for the occurrence of oedema after major abdominal surgery. Oedema formation was related to fluid balance, changes in whole-body bioimpedance (Z) measured at four frequencies (5, 50, 100 and 200 kHz), and clinical outcome. Results: The 20 patients who developed oedema were older than those who did not (mean(s.d.) 73(9) versus 63(14) years; P = 0(.)007). Fluid intake over the first 5 days after surgery was similar in both groups, but those with oedema excreted less total fluid (16(.)9(2(.)4) versus 19(.)7(3(.)5) litres; P = 0(.)022). Oedema was associated with a delay in tolerating solid food (P = 0(.)001) and opening bowels (P = 0(.)020), a prolonged hospital stay (median 17 (range 8-59) versus 9 (range 4-27) days; P = 0.001) and more postoperative complications (13 of 20 versus four of 18 patients; P = 0(.)011). The preoperative ratio of whole-body impedance at 200 kHz to that at 5 kHz was higher in those who subsequently developed oedema (0(.)81(0(.)03) versus 0(.)78(0(.)02); P = 0(.)015). Conclusion: The development of oedema after major abdominal surgery is associated with increased morbidity. Age and reduced ability to excrete administered fluid load are significant aetiological factors and bioimpedance analysis can potentially identify patients at risk.