**8. Conclusion**

The effects of red blood cell transfusions also seem to be quite variable. One of the other commonly used therapy is transfusions of red blood cells (RBC), which is used in critically ill patients to restore oxygen-carrying capacity. But, transfusion decisions are based on serum haemoglobin levels, and it is difficult to notice because normal microvascular haematocrit is much lower than systemic values. Although the beneficial effect of RBC transfusions over microcirculatory parameters in septic patients is still not clear, RBC transfusions are effective in improving tissue oxygen transport by promoting RBC delivery to the

60 Hyperbaric Oxygen Treatment in Research and Clinical Practice - Mechanisms of Action in Focus

Fluid resuscitation in combination with vasoactive and inotropic support is effective in improving the microcirculation. Recruitment of the microcirculation can be achieved with combination therapies. An anti-inflammatory agent or specific iNOS inhibitor can reduce pathological shunting and improve blood flow to recruit weak microcirculatory units. The effects can be seen in the early phase of sepsis, within 24 h of diagnosis, but if cardiac output

The use of steroids in sepsis may provide a clinical benefit in modulating the systemic inflammatory response. It can preserve the endothelial glycocalyx and attenuate rolling of leucocytes to the endothelium, may improve endothelial function and thereby ameliorate the

Statins, which are cholesterol-lowering agents also have pleiotropic effects and have an antiinflammatory and anti-oxidant activity during sepsis. They increase levels of eNOS, with the down-regulation of iNOS, so this regulation of NOS increases NO levels, restoring the auto-

Vasodilator substances may have a role to restore the microcirculation and decrease the effect of excessive vasoconstriction which causes decreased vascular density and stopped-flow capillaries. In a research, it was reported that nitroglycerin administration rapidly improved the

In haemorrhagic shock, reducing the blood flow to the microvascular units may prevent hypoxia. This downregulation of cellular metabolism is called conformance or hibernation. However, increase in lactate level during the acute phase of haemorrhagic shock indicates the limits of this adaptative metabolic downregulation. The critical factor in microvascular regulation to meet oxygen supply is the local regulation of arteriolar tone. Many mechanisms contribute to the local regulation of arteriolar tone, which includes response to myogenic response, shear-dependent response, and tissue metabolic response. During haemorrhagic shock, the decrease in DO2 reduces the generation of adenosine 5′ triphosphate (ATP) and adenosine 5′ diphosphate (ADP) which results in the accumulation of ADP and its degrada-

shock, the therapeutic precedence is to stop the bleeding and to prevent the increase of bleeding. Fluid resuscitation may promote coagulopathy by diluting coagulation factors [55, 56].

Reduced microvascular perfusion is a characteristic feature of sepsis and implicated in organ dysfunction with multiple organ failure. Hyperbaric oxygen (HBO) has potentially beneficial effects for the microcirculation improvement in sepsis . It was shown that HBOT improves

is a strong vasodilator, which accumulates when there is an increase in cel-

during tissue hypoperfusion. In haemorrhagic

is increased, no improvement will be made after 48 h [51].

microcirculation [50].

distributive defect [52].

regulatory functions [53].

microcirculation [54].

tion products. CO2

lular metabolism or reduced clearance of CO2

In conclusion, microcirculation plays a critical role in the physiological process such as oxygen supply to vital organs, nutritional exchange and modulation of inflammation. The most important function of the microcirculation is the regulation of flow within the different organs. Microcirculatory changes include various mechanisms such as redistribution of blood flow from the skin and the splanchnic area to brain or heart, or with endothelial activation and injury which results with the loss of the glycocalyx around endothelium. The assessment of the microcirculation enables us for the early detection of possible deterioration and potential organ dysfunctions. Microcirculatory blood flow can be detected at the bedside by different techniques which are simple and gives quantitative data. Fluid resuscitation and vasoactive agents are one of the main therapies for the hemodynamic resuscitation that aims to restore the circulating volume, and increasing the cardiac output and arterial blood pressure and play a critical role with the goal of improving tissue perfusion. HBOT inhibits replicating, spreading of anaerobic and some other bacteria and is a clinical treatment adjunct to traditional surgery and antibiotic therapy for the deadly serious necrotizing infection. Also, HBOT applied in acute ischemic stroke, femoral head necrosis and carbon monoxide intoxication aim to increase oxygen supply to the ischemic tissue and to reduce the extent of irreversible tissue damage.
