The impact of post operative oedema on clinical recovery and its potential causes

Abstract

The postoperative period is characterized by massive shifts of fluid between body compartments and accumulation of fluid in the extracellular space, which may manifest clinically as central and or peripheral oedema. The incidence of oedema in patients undergoing routine major abdominal surgery (MAS) is unknown and there are no objective means of quantifying or monitoring its presence. Furthermore, the aetiological factors responsible for post-surgical oedema formation in patients with no overt signs of cardiovascular disturbance are poorly understood and the relationship between the development of oedema and clinical outcomes such as the recovery of gastrointestinal function, postoperative complications and duration of hospital stay is unclear.
Observational studies were therefore conducted on patients undergoing MAS. The presence of oedema was related to changes whole-body impedance (Z), obtained at four frequencies (5, 50, 100 and 200 kilohertz (kHz)) using bioelectrical impedance analysis (BIA) and to clinical outcomes. The fluid intake and output and changes in plasma concentration of albumin, total protein, C-reactive protein (CRP) and reduced glutathione in whole blood (GSH) were compared before and after surgery in patients who subsequently developed oedema (OD group) and patients who consistently remained free of oedema (NOD group) Oedema occurred in 40 per cent of the patients observed prospectively and was significantly related to age (odds ratio 1.087 (95 per cent confidence interval (c.i), 1.016 -1.163; P =0.016). The preoperative ratio of Z at 200 kHz to 5 kHz (Z200/Z5) was higher in patients who subsequently developed oedema than those who did not (0.809 v 0.799; P = 0.015), suggesting that it may be possible to identify patients who are prone to abnormal fluid shifts preoperatively. The change in (Z) was greater in the oedematous than non-oedematous groups (at all frequencies (P < 0.001)), and more so at lower frequencies (5kHz) than higher frequencies (100 kHz) (P < 0.001). The impedance quotient (ht2/Z) in the whole group changed in a similar direction at each frequency but to a greater extent in the OD compared to NOD groups. The total volumes of administered fluids in both groups of patients were similar but the average urine output per kg body weight was significantly lower in the OD compared to NOD patients (29.4(2.3) versus 40.5(3.7) mls/kg, P = 0.023). There were no significant differences before and after surgery in the concentrations of albumin, total proteins and GSH in both patient groups. Preoperative CRP concentration in the OD and NOD patients were similar but the mean (s.d) CRP concentration over duration of observation in the OD compared to the NOD patients was significantly greater (148 (54.1) versus 89.6 (43.8) mg/L, P = 0.006). Oedema was associated with a significant delay in the recovery of gut function (median (range) (6(3-17) versus 5(1-13) days, P = 0.020) and prolonged hospital stay (17(8-59) versus 9(4-27) days, P = 0.001) and increased incidence of postoperative complications (65 versus 22%, P = 0.011).
This study shows that the incidence of early postoperative oedema is high and preoperative identification and monitoring of surgical patients vulnerable to abnormal fluid shifts may be possible with non-invasive techniques. Age, impaired ability to excrete administered fluid load and an exaggerated inflammatory response to surgical trauma rather than hypoalbuminaemia and hypoproteinaemia were significant factors for oedema formation. Postoperative oedema was associated with a significant increase in postoperative morbidity.

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