Melatonin prevents secondary intra-abdominal hypertension in rats possibly through inhibition of the p38 MAPK pathway

Exogenous administration of melatonin has been demonstrated to down-regulate inflammatory responses and attenuate organ damage in various models. However, the salutary effect of melatonin against secondary intra-abdominal hypertension (IAH) remains unclear. This study sought to test the influence of melatonin on secondary IAH in a pathophysiological rat model and the underlying mechanisms involved. Before resuscitation, male rats underwent a combination of induced portal hypertension, applying an abdominal restraint device, and hemorrhaging to mean arterial pressure (MAP) of 40mmHg for 2h. After blood reinfusion, the rats were treated with lactated Ringer solution (LR) (30mL/h), melatonin (50mg/kg) +LR, and SB-203580 (10μmol/kg)+LR. LR was continuously infused for 6h. MAP, the inferior vena cava pressure and urine output were monitored. Histopathological examination, immunofluorescence of tight junction proteins, and transmission electron microscopy were administered. Intestinal permeability, myeloperoxidase activity, malondialdehyde, glutathione peroxidase, and levels of TNF-a, IL-2, and IL-6, were assessed. The expression of extracellular signal-regulated kinase, p38, c-Jun NH2-terminal kinase, translocation of nuclear factor kappa B subunit, signal transducers and activators of transcription and tight junction proteins were detected by Western blot. We found that melatonin inhibited the inflammatory responses, decreased expression of p38 MAPK, attenuated intestinal injury, and prevented secondary IAH. Moreover, administration of SB203580 abolished the increase in p38 MAPK and also attenuated intestinal injury. These data indicate that melatonin exerts a protective effect in intestine in secondary IAH primarily by attenuating the inflammatory responses which are in part attributable to p38 MAPK inhibition.

Intra-abdominal pressure correlates with extracellular water content

Background

Secondary increase in intra-abdominal pressure (IAP) may result from extra-abdominal pathology, such as massive fluid resuscitation, capillary leak or sepsis. All these conditions increase the extravascular water content. The aim of this study was to analyze the relationship between IAP and body water volume.

Material and Methods

Adult patients treated for sepsis or septic shock with acute kidney injury (AKI) and patients undergoing elective pharyngolaryngeal or orthopedic surgery were enrolled. IAP was measured in the urinary bladder. Total body water (TBW), extracellular water content (ECW) and volume excess (VE) were measured by whole body bioimpedance. Among critically ill patients, all parameters were analyzed over three consecutive days, and parameters were evaluated perioperatively in surgical patients.

Results

One hundred twenty patients were studied. Taken together, the correlations between IAP and VE, TBW, and ECW were measured at 408 time points. In all participants, IAP strongly correlated with ECW and VE. In critically ill patients, IAP correlated with ECW and VE. In surgical patients, IAP correlated with ECW and TBW. IAP strongly correlated with ECW and VE in the mixed population. IAP also correlated with VE in critically ill patients. ROC curve analysis showed that ECW and VE might be discriminative parameters of risk for increased IAP.

Conclusion

IAP strongly correlates with ECW.

[Effect of mechanical ventilation guided by transpulmonary pressure on hemodynamics and oxygen metabolism of porcine model of intra-abdominal hypertension]

OBJECTIVE

To assess the effect of mechanical ventilation (MV) guided by transpulmonary pressure (Ptp) on hemodynamics and oxygen metabolism of porcine model of intra-abdominal hypertension (IAH).

METHODS

All 6 pigs were anesthetized and received MV. Volume-assist control was set: tidal volume (V(T)) was 10 ml/kg, respiratory rate (RR) was 16 bpm, inhaled oxygen concentration (FiO(2)) was 0.40 and positive end-expiratory pressure (PEEP) was set at 5 cm H(2)O (1 cm H(2)O=0.098 kPa). Following baseline observations, high intra-abdominal pressure (IAP) with intraperitoneal nitrogen inflation was induced in all 6 pigs. The IAP was increased to 25 mm Hg (1 mm Hg=0.133 kPa). Two hours later, PEEP was adjusted to such a level that Ptp during end-expiratory occlusion remained at a level above 0 cm H(2)O for 2 hours by measuring esophageal pressure, and with the rest parameters of breathing machine remaining constant. During the experimental period, hemodynamic parameters including heart rate (HR), mean arterial pressure (MAP), cardiac output index (CI), central venous pressure (CVP), pulmonary arterial wedge pressure (PAWP), and respiratory mechanics index of peak airway pressure (Ppeak), plateau pressure (Pplat), esophageal pressure (Pes) and static compliance (Cst) were continuously recorded with the aid of Swan-Ganz catheter and electrocardiogram. Oxygen partial pressure of arterial blood (PaO(2) ) and carbon dioxide partial pressure of arterial blood (PaCO(2)) were measured by blood-gas analysis. Systemic oxygen delivery (DO(2) )and systemic oxygen consumption(VO(2) )were calculated according to blood-gas analysis of arterial and central venous blood.

RESULTS

No porcine model showed barotrauma and death. Compared with baseline, at 1 hour and 2 hours after induction of IAH in the animals, HR(bpm) increased significantly (134.3±5.8, 127.3±3.3 vs. 117.7±1.5). MAP(mm Hg), CVP (mm Hg) and PAWP (mm Hg) became higher (MAP:120.7±3.8, 117.3±4.8 vs. 100.4±6.6; CVP: 7.3±0.3, 7.6±0.9 vs. 5.6±0.2; PAWP: 14.0±0.6, 14.0±1.0 vs. 12.3±0.3), CI (L×min(-1)×kg(-1)) was lowered (0.150±0.019, 0.137±0.014 vs. 0.179±0.021), Ppeak(cm H(2)O), Pplat (cm H(2)O), Pes (cm H(2)O) were increased significantly (Ppeak: 46.3±2.3, 47.0±3.2 vs. 11.0±1.6; Pplat: 25.7±1.3, 26.0±1.6 vs. 9.0±0.6; Pes: 13.7±0.3, 14.3±0.3 vs. 2.3±0.3), Cst (ml/cm H(2)O), PaO(2) (mm Hg) and DO(2) (ml×min(-1)×kg(-1)) showed significant lowering (Cst: 8.3±0.3, 9.0±0.6 vs. 23.0±1.6; PaO(2) : 142.0±13.2, 140.0±16.0 vs. 166.3±11.3; DO(2) : 19.40±2.90, 19.88 ±4.14 vs. 25.07±6.30, all P<0.05).However, compared to routine ventilation, at 1 hour and 2 hours after PEEP had been adjusted according to measurements of esophageal pressure, PaO(2) , DO(2) and Cst increased significantly (PaO(2) : 161.6±11.9, 164.0±13.6; DO(2) : 21.90±6.21, 21.16±2.78; Cst: 12.0±1.6, 12.7±2.9). CI became lower (0.121±0.013, 0.120±0.012)and Pplat was higher(31.3±3.4, 31.7±3.2, all P<0.05). The lactate (mmol/L) was also decreased significantly (1.60±0.12 vs. 2.70±0.44, 1.67±0.07 vs. 2.27±0.13, both P<0.05). PaCO(2), HR, MAP, CVP and PAWP showed no significant differences compared to IAH pigs ventilated with lower PEEP (all P>0.05).

CONCLUSION

There were remarkable effects on oxygen metabolism and Cst and less influence on hemodynamics in response to MV guided by Ptp. The results of this study are in favor of setting Ptp according to measurements of esophageal pressure in pigs with IAH.

[Effect of decompression in different time on hemodynamics and oxygen metabolism of porcine model with severe acute pancreatitis combined intra-abdominal hypertension]

OBJECTIVE

To assess the effect of decompression in different time on systemic hemodynamics and oxygen metabolism in a 24 h lasting porcine model of severe acute pancreatitis (SAP) incorporating intra-abdominal hypertension (IAH).

METHODS

Following baseline registrations, SAP was induced in all 18 animals. A N(2) pneumoperitoneum was used to increase the intra-abdominal pressure (IAP) to 25 mmHg (1 mmHg = 0.133 kPa) in 12 of 18 SAP animals. After 6 hours, decompression was applied in 6 of these 12 pigs and the other 6 animals received decompression at 9 h since the induction of IAH. The investigation period was 24 h. Heart rate (HR), cardiac output (CO), central venous pressure (CVP), mean arterial pressure (MAP) and pulmonary arterial wedge pressure (PAWP) were continuously recorded with the aid of Swan-Ganz catheter and electrocardiography monitor; Oxygen partial pressure of artery (PaO(2)), carbon dioxide partial pressure of artery (PaCO(2)) and central venous oxygen saturation (ScvO(2)) were measured by blood-gas analysis. Besides that, systemic oxygen delivery (DO(2)) and systemic oxygen consumption (VO(2)) were calculated according to blood-gas analysis in arterial and central venous blood.

RESULTS

After decompression, HR, CO, MAP, CVP, PAWP, PaO(2) and DO(2) showed no significant differences in the 6 h group when compared to SAP pigs. In the 9 h group, however, CO decreased significantly and HR, CVP, PAWP increased significantly after decompression than SAP only animals (all P < 0.05). PaO(2), ScvO(2) and DO(2) showed lower after 3 h of decompression compared with another two groups. VO(2) increased higher in IAH groups during 6 h of experiment than SAP pigs (all P < 0.05). Then VO(2) showed a trend to fall and no differences in three groups.

CONCLUSIONS

There are remarkable and relatively irreversible effects on global hemodynamics and oxygen metabolism in response to the decompression in different time after sustained IAH with the underlying condition of SAP. The results of this study are in favor of a decompression in patients of SAP with IAH in early time.

[Open abdomen management treatment of liver injury in rats with abdominal compartment syndrome and sepsis]

OBJECTIVE

To evaluate the open and closed management treatment of liver injury in rats with sepsis and abdominal compartment syndrome (ACS).

METHODS

The sepsis and ACS rats (n = 72) were randomized divided into two groups. One group used closed management (n = 36), the other accepted the open abdomen management (n = 36). The rats were killed at 1, 6 h, 1, 3, 5, 7 d after operation. Blood was collected for liver function tests. Liver sections assessed pathologically and the expressions of Toll-like receptor 4 (TLR4), tumor necrosis factor (TNF)-α, interleukin (IL)-6, signal transducers actuators of transcription (STAT3) and suppressor of cytokine signaling 3 (SOCS3) of rat livers were examined by RT-PCR.

RESULTS

The early stage after operation, TNF-α and IL-6 concentrations, STAT3 expressions in rat liver were higher in open abdomen rats than the closed management ones (P < 0.05). TLR4 and SOCS3 expressions were lower in open abdomen rats than the closed management ones (P < 0.05). Aspartate aminotransferase, alanine aminotransferase levels also was lower in open abdomen ones (P < 0.05).

CONCLUSIONS

The randomized study demonstrates that open abdomen management could improve liver regeneration in the early stage after operation. Also open abdomen could reduce inflammatory response by reducing TLR4 expressions.