Category Archives: Intensive care medicine

Microcirculatory changes

Since shock is a syndrome caused by inadequate tissue perfusion, the final common pathway for the pathophysiological changes is the microcirculation. In the early stages of septic shock there is vasodilatation, maldistribution of flow, arteriovenous shunting and increased capillary permeability with interstitial oedema. Although these microvascular abnormalities may largely account for the reduced oxygen ext

Acute disturbances of haemodynamic function (shock)

Shock is difficult to define. The term is used to describe acute circulatory failure with inadequate or inappropriately distributed tissue perfusion resulting in generalized cellular hypoxia. Causes The causes are shown. Very often shock can result from a combination of these factors. PATHOPHYSIOLOGY Sympatho-adrenal response to shock Hypotension stimulates the baroreceptors, and to a lesser extent the chemor

Mixed venous P02 (P902)

This is the partial pressure of oxygen in pulmonary arterial blood that has been thoroughly mixed during its passage through the heart. If Pa02 remains constant, the PV<>2 will fall if more oxygen has to be extracted from each unit volume of blood arriving at the tissues. A fall in PV<>2 therefore indicates that either oxygen delivery has fallen or that tissue oxygen requirements have increased w

Oxyhaemogiobin dissociation curve

The saturation of haemoglobin with oxygen is determined by the partial pressure of oxygen (P02) in the blood, the relationship between the two being described by the oxyhaemoglobin dissociation curve. The sigmoid shape of this curve is important clinically for a number of reasons: • Falls in Pa02 may be tolerated provided that the percentage saturation remains above 90%. • Increasing the Pa02 to above nor

Oxygen delivery

Oxygen delivery (oxygen flux) is defined as the total amount of oxygen delivered to the tissues per unit time. It is dependent on the volume of blood flowing through the microcirculation per minute (i.e. the total cardiac output – Q,) and the amount of oxygen contained in that blood (i.e. the arterial oxygen content- C.02). Oxygen is transported in combination with haemoglobin or dissolved in plasma. T

Intensive care medicine

Introduction Intensive care medicine (or ‘critical care medicine’) is concerned predominantly with the management of patients with acute life-threatening conditions (‘the critically ill’) in a specialized unit. It also encompasses the resuscitation and transport of those who become acutely ill, or are injured, either elsewhere in the hospital or in the community. Ai; well as emergency