pulmonary immune effects of different ventilatory settings in patients undergoing thoracic surgery

Abstract: Mechanical ventilation using tidal volume [Vt] around 10 ml/kg and zero positive end-expiratory pressure [ZEEP] is still commonly used in anesthesia. Experimental data suggest that mechanical ventilation with high Vt and ZEEP induces not only cytokine release but also translocation of cytokines from the lungs to the systemic circulation. In addition, inflammatory responses to mechanical stress caused by mechanical ventilation may aggravated by inflammatory co-stimulation. One-lung ventilation is an established procedure during thoracic surgery. Commonly, Vt used during two-lung ventilation [TLV] are recommended during OLV to maintain arterial oxygenation and carbon dioxide elimination. Previous experimental and clinical studies on TLV showed a progressive alteration of pulmonary immune function during anesthesia and surgery. Accordingly, in surgical patients undergoing OLV with high and low Vt, a time-dependent increase of proinflammatory variables may be found. In this prospective, randomized, clinical study, we therefore examined whether a standard ventilation setting [V[T] = 10 mL/kg] may result in a time-dependent alteration of pulmonary immune function in patients undergoing open thoracic surgery and OLV. Furthermore, we tested whether ventilation with different Vt and positive end expiratory pressure [PEEP] modifies pulmonary immune function, hemodynamics, and gas exchange during OLV

Methods: Forty five patients undergoing open thoracic surgery were randomized to receive mechanical ventilation with either [1] Vt = 10 ml/kg on ZEEP, [2] Vt = 6 ml/kg on ZEEP, or [3] Vt = 6 ml/kg on PEEP of 10 cm H2O. Because interleukin-6 and macrophage inflammatory protein-2 are more sensitive markers of ventilation-induced cytokine release, serum and bronchoalveolar lavage samples were examined for these mediators. Cells, protein, tumor necrosis factor [TNF]-[alpha], interleukin [IL]-8, soluble intercellular adhesion molecule [sICAM]-1, IL-10, and elastase were determined in the bronchoalveolar lavage. Data were analyzed by parametric or nonparametric tests, as indicated. In all patients, an increase of proinflammatory variables was found. Concentrations were significantly smaller after OLV with Vt = 6 mL/kg on PEEP of 10 cm H2O

Conclusion: Mechanical ventilation can induce a cytokine response that may be attenuated by a strategy to minimize overdistention and recruitment/derecruitment of the lung. Whether these physiological improvements are associated with improvements in clinical end points should be determined in future studies

Influence of hydroxyethyl starch 130/0.4 versus ringer lactate on renal function during acute normovolemic haemodilution in combination with controlled hypotension

The risks associated with banked homologous blood products are well known. Several techniques for management of surgical patients without homologous blood transfusion are available. Controlled hypotension and acute normovolemic haemodilution [ANH] have been proven effective in decreasing operative blood loss and the need for transfusion of allogenic blood. The combined reduction of oxygen carrying capacity and perfusion pressure during combination of ANH and controlled hypotension raises the concerns of hypoperfusion and ischaemic injury to the kidney. Forty patients undergoing major abdominal surgery were allocated to receive controlled hypotension induced by Na nitroprusside [mean arterial pressure 50 mm Hg] and acute normovolemic haemodilution [post ANH haematocrite 29%]. ANH was established by withdrawing venous blood into standard blood bags and replacing it by HES 130/0.4 [Group I] or RL [group II]. The shed blood was reinfused at the end of surgery. Subclinical alteration in renal integrity detected by sensitive markers of tubular damage has been reported in the absence of overt change in creatinine serum concentration and creatinine clearance in both groups. These markers have returned to normal values after 24 hours. Sensitive markers of kidney dysfunction have increased in both groups indicating moderate alterations in renal integrity during combination of ANH and controlled hypotension. Both volume replacement regimens did not differ with regard to kidney integrity

Enteral nutrition in critically ill patients

Critical illness, stress, and surgery place increased demands on the body's nutritional requirements. These conditions promote a catabolic state and negative nitrogen balance. Nutritional problems are common in critically ill patients. Nutritional supplementation affords the opportunity of slowing down or stopping the catabolic process, restoring nitrogen balance, and preventing malnutrition. Enteral nutrition preserve the integrity of the gastrointestinal mucosa and enhance immune function. Early enteral nutrition administration to critically ill patients can decrease the number of infectious complications, length of stay and mortality. However, early enteral nutrition in the critically ill is often limited by gastroparesis, which impairs gastric emptying, thereby promoting gastroesophageal reflux and aspiration pneumonia. However, Early enteral nutrition is the treatment of choice with an A level of recommendation for some authors. A total of two hundred critically ill adult patients were enrolled in the study. Daily 18-hrs enteral nutrition via a 14F gastric tube was initiated either immediately after stabilization in group I, or later than 48hrs after admition in group II. Residual gastric volume was measured every 6hrs, and enteral nutrition was discontinued if exceed 300ml or vomiting occurred. Nutritional outcome measures included the percentage of the goal rate achieved during the study period, volume ratio, and gastrointestinal complications rate. Clinical outcomes included the incidence of ventilator associated pneumonia, multiple organ failure score, the duration of mechanical ventilation, and the length of ICU stay. Overall, the evidence suggests that early enteral feeding is beneficial to critically ill patients. In our study early intervention was associated with shorter duration of mechanical ventilation and ICU stay. Patients in the early feeding group had less sever form of MOF, and decreased infectious complications and mortality. The early institution of nutritional support and the use of enteral nutrition optimize nutritional status of the patient and reduce complications associated with bowel rest resulting in improved clinical outcomes in critically ill patients