Perioperative fluid therapy impairs lymphatic pump function in male rats

Abstract

Because of its life-saving benefits, perioperative IV fluid therapy remains a cornerstone of medical treatment. However, it also induces sustained edemagenic stress. The resulting persistent interstitial edema-excessive fluid accumulation in the interstitium-significantly delays recovery and worsens patient outcomes. Therefore, to gain a detailed understanding of the lymphatic functional consequences of perioperative fluid therapy, this study aimed to test the hypothesis that perioperative IV fluid therapy compromises lymphatic pump function within 3 days after major surgery. Following a midline laparotomy, animals received IV fluid therapy over 48 h during recovery (FLTP). Three days post-surgery, mesenteric lymphatic vessels from FLTP and sham surgery (CTRL) animals were isolated, and lymphatic pump function was assessed in vitro. The transmural pressure-pump flow and circumferential length-wall tension relationships of FLTP vessels were altered-contraction frequency and normalized pump flow and active and passive wall tensions were significantly lower than CTRL. In vessels from another group of animals with surgically produced mesenteric venous hypertension to induce sustained edemagenic stress, only the pressure-pump flow relationship was altered similarly to FLTP. These results demonstrate the detrimental effects of perioperative fluid therapy on lymphatic pumping, which is essential for restoring interstitial fluid pressure and resolving edema and inflammation.

Keywords: enhanced recovery after surgery; goal‐directed fluid therapy; gut edema; intestinal dysfunction; resuscitation.

FIGURE 1

End‐diastolic (a), end‐systolic (b), and passive diameters (c) measured in mesenteric lymphatic vessels in CTRL (sham surgery, n = 7, filled‐black), FLTP (surgery plus fluid therapy, n = 7, open), and SMVH (surgery plus superior mesenteric venous hypertension, n = 8, filled‐gray) groups. Notably, some FLTP (n = 4) and SMVH (n = 2) vessels did not exhibit spontaneous contractions at 1 cmH₂O transmural pressure, resulting in undefined systolic diameters for these vessels. The diameters in CTRL, FLTP, and SMVH vessels were compared using a two‐way ANOVA with transmural pressure as a repeated measure, employing Geisser–Greenhouse correction for unequal variability of differences. ANOVA showed no significant differences in end‐diastolic (p = 0.7971), end‐systolic (p = 0.5843), or passive diameters (p = 0.4318) among groups. “n” indicates the number of vessels. p < 0.05, a significant difference.

FIGURE 2

Pumping indexes of mesenteric lymphatic vessels in CTRL (sham surgery, n = 7, filled‐black), FLTP (surgery plus fluid therapy, n = 7, open), and SMVH (surgery plus superior mesenteric venous hypertension, n = 8, filled‐gray) groups. Contraction frequency (a), normalized stroke volume (b), normalized pump flow (c), and diastolic tone (d) are shown. Notably, some FLTP (n = 4) and SMVH (n = 2) vessels did not exhibit spontaneous contractions at 1 cmH₂O transmural pressure, evident by zero contraction frequency, normalized stroke volume, and normalized pump flow. To compare the pumping indexes of CTRL, FLTP, and SMVH vessels, a two‐way ANOVA was performed with transmural pressure as a repeated measure and Geisser–Greenhouse correction for unequal variability of differences, followed by Tukey's test for pairwise comparisons, as appropriate. ANOVA revealed significant effects of treatment on contraction frequency (p = 0.0002) and normalized pump flow (p = 0.0019), but not on normalized stroke volume (p = 0.8965) or diastolic tone (p = 0.0589). “n” indicates the number of vessels. p < 0.05, a significant difference.

FIGURE 3

Circumferential length‐wall tension relationships of mesenteric lymphatic vessels in CTRL (sham surgery, n = 5, □), FLTP (surgery plus fluid therapy, n = 6, ∆), and SMVH (surgery plus superior mesenteric venous hypertension, n = 6, ○) groups. Total wall tensions after stretch (a) were subtracted from total wall tensions after stimulation (b) to determine agonist‐stimulated developed tensions (c). Total wall tensions after stretch and after stimulation and agonist‐stimulated developed tensions at L = L_max of CTRL, FLTP, and SMVH vessels were compared using one‐way ANOVA followed by Tukey's post hoc test. At L = L_max, one‐way ANOVA detected significant differences in total wall tension after stretch (p = 0.0168) and after stimulation (p = 0.0202), but not in agonist‐stimulated developed tension (p = 0.2874). Total wall tensions after stretch and after stimulation did not differ significantly between CTRL and FLTP (p = 0.0593, p = 0.0517, respectively) or between CTRL and SMVH (p = 0.8980, p = 0.9801, respectively).' n' ndicates the number of vessels. p < 0.05, a significant difference.

FIGURE 4

Circumferential length‐wall tension relationships of mesenteric lymphatic vessels in CTRL (sham surgery, □), FLTP (surgery plus fluid therapy, ∆), and SMVH (surgery plus superior mesenteric venous hypertension, ○) groups. Active tensions after stretch (a) and after stimulation (b) were determined by subtracting passive tensions (c) from total wall tensions after stretch and after stimulation (CTRL, n = 5; FLTP, n = 6; SMVH, n = 6). Data from a vessel in the FLTP group exhibiting an abrupt change in passive tension at higher stretch levels was excluded from the passive length‐tension analysis (CTRL, n = 5; FLTP, n = 5; SMVH, n = 6). Active tensions after stretch and after stimulation at L = L_max, as well as the constants α and β of CTRL, FLTP, and SMVH vessels, were compared by one‐way ANOVA followed by Tukey's test for pairwise comparisons. One‐way ANOVA detected treatment effects on active tensions after stretch (p = 0.0098) and after stimulation (p = 0.0184) at L = L_max, and constants α (p = 0.0116) and β (p = 0.0040). Active tensions after stretch (p = 0.9840) and after stimulation (p = 0.9998) did not differ significantly between CTRL and SMVH groups. The constants α and β of FLTP vessels (α, 1.02e‐4 ± 9.01e‐5; β, 5.62 ± 1.31) differed significantly from those of CTRL (α, 1.37e‐6 ± 1.19e‐6, p = 0.0196; β, 9.79 ± 0.85, p = 0.0077) and SMVH vessels (α, 7.38e‐6 ± 1.42e‐5, p = 0.0217; β, 9.58 ± 2.55, p = 0.0080). However, the two constants were not significantly different between CTRL and SMVH vessels (α, p = 0.9792; β, p = 0.9813). ‘n’ indicates the number of vessels. p < 0.05, a significant difference.

FIGURE 5

Percent change in animal weights during the 3‐day recovery period across the CTRL (sham surgery, n = 20, □), FLTP (surgery plus fluid therapy, n = 16, ∆), and SMVH (surgery plus superior mesenteric venous hypertension, n = 20, ○) groups. Percent weight changes, analyzed using one‐way ANOVA, did not differ significantly among the three groups (p = 0.8781). “n” indicates the number of animals. p < 0.05, a significant difference.

FIGURE 6

Intestinal morphology in animals from CTRL (sham surgery, n = 8, □), FLTP (surgery plus fluid therapy, n = 5, ∆), and SMVH (surgery plus superior mesenteric venous hypertension, n = 6, ○) groups. Formalin‐fixed, paraffin‐embedded jejunal sections stained with hematoxylin and eosin (a) were imaged at 200× magnification. Mucosal morphology was evaluated using the Chiu scoring system (b) (Chiu et al., 1970). Scores were compared across groups using one‐way ANOVA, and no significant differences were observed (p = 0.8947). “n” indicates the number of animals. p < 0.05, a significant difference. Scale bar: 200 μm.