Dependence of oxygen consumption on cardiac output in sepsis

We studied the relationship between oxygen consumption (Vo2) and cardiac output in 17 hemodynamically stable, septic and eight nonseptic ICU patients. Each received 300 ml of fresh-frozen plasma or 25% albumin with up to 500 ml of crystalloids, in addition to regular maintenance fluids; this treatment increased pulmonary wedge pressure (WP) by 3 to 4 mm Hg. Measurements were performed before and after approximately 5 h of volume loading. Because cardiac index (CI) decreased as WP increased in four septic and three nonseptic patients, we grouped the data according to the state of flow instead of the recording time sequence. From low to high flows, mean CI increased in septic patients and nonseptic patients. Oxygen delivery (Do2) increased in septic and nonseptic patients. Vo2 remained unchanged in nonseptic patients, while it increased in septic patients. Accordingly, arteriovenous oxygen difference narrowed in nonseptic patients from 4.46 +/- 1.62 to 3.59 +/- 1.21 ml/dl (p less than .05) but did not change in septic patients. In the septic group, the difference in CI between high and low flows was significantly (p less than .05) greater in survivors than in nonsurvivors. We conclude that the septic state is accompanied by a peripheral oxygen deficit, which can be partially reversed by maintaining an above-normal CI and Do2.     

Hemodynamics and oxygen transport in patients with surgical sepsis during hemofiltration

Effects of hemofiltration (HF) on central hemodynamics and oxygen transport are studied in 35 patients with surgical sepsis and multiple organ failure. HF is paralleled by development of hypovolemia and decrease of myocardial contractility, determining a decrease in cardiac output and oxygen transport. As a result, oxygen utilization by tissues decreases and hypoxia progresses. The only compensatory mechanism of oxygen supply in such patients is maintenance of cardiac output, which should be borne in mind when carrying out HF.     

Effect of blood transfusion on oxygen consumption in pediatric septic shock

Treatment plans for pediatric septic shock advocate increasing oxygen consumption (VO2). Recent studies in septic shock indicate that improving oxygen delivery (DO2) by increasing blood flow will increase VO2. We prospectively examined the effect on VO2 of improving DO2 by increasing oxygen content (CO2) with blood transfusion in eight hemodynamically stable septic shock patients. Transfusion consisted of 8 to 10 ml/kg of packed RBC over 1 to 2 h. Hemodynamic and oxygen transport measurements were obtained before and after blood transfusion. Transfusion significantly (p less than .05) increased Hgb and Hct from 10.2 +/- 0.8 g/dl and 30 +/- 2% to 13.2 +/- 1.4 g/dl and 39 +/- 4%, respectively (mean +/- SD). DO2 significantly (p less than .05) increased after transfusion (599 +/- 65 to 818 +/- 189 ml/min.m2), but VO2 did not change (166 +/- 68 to 176 +/- 74 ml/min.m2; NS). In pediatric septic shock patients, increasing CO2 by blood transfusion may not increase VO2.     

Blood transfusion

Patients in hospitals receive 10,000 transfusions every day due to blood disorders, trauma and disease. Nurses play a significant role in the safe administration of blood and its products. This guide describes the nursing care of the patient before, during and after a blood transfusion.     

Blood transfusion

This Clinical Update considers issues relating to transfusion of blood components--erythrocytes, platelets and plasma products--obtained from human donors.     

Blood transfusion

Blood transfusion is a potentially dangerous treatment in which adverse reactions are rare but can be fatal. This article introduces recently published national guidelines for the care of recipients of a blood transfusion (BCSH 1999) and focuses in particular on the responsibilities of nurses and midwives.     

Red blood cell transfusion does not increase oxygen consumption in critically ill septic patients

Background  

Red blood cell (RBC) transfusion is commonly used to increase oxygen transport in patients with sepsis. However it does not consistently increase oxygen uptake at either the whole-body level, as calculated by the Fick method, or within individual organs, as assessed by gastric intra-mucosal pH.     

Oxygen consumption in sepsis and septic shock

This review article examines the pathophysiology of septic shock, with special attention to the concept of supply-dependent consumption and the implications this concept has for therapy. Patients with septic shock require higher levels of oxygen delivery (DO2) to maintain aerobic metabolism. When DO2 is inadequate, peripheral tissues switch to anaerobic metabolism and oxygen consumption decreases. The lactic acidosis that occurs is a reasonable clinical marker of supply dependency and inadequate tissue perfusion. Maximizing DO2 is an important part of the hemodynamic resuscitation of patients with septic shock. To achieve this goal, intravascular volume must be restored and the myocardial depression associated with sepsis must be treated to optimize cardiac output. The normalization of arterial lactate concentration is a reasonable goal of resuscitative efforts.     

Blood transfusion in liver transplantation

Liver transplantation is a relatively new procedure in which unusually large quantities of blood are used. Blood use in 68 adult and 49 pediatric liver transplants was reviewed. The median (range) intraoperative red cell use for adults and children was 28.5 (3-251) and 11 (2-55), respectively. Blood use closely correlated with the patient's primary diagnosis. Adult patients with primary biliary cirrhosis and carcinoma used about one-half as much blood as those with a diagnosis of sclerosing cholangitis, hepatitis, or cirrhosis. Patients in the former diagnostic groups also had better survival rates. Total red cell use for the patient's entire hospitalization was about twice that used during surgery. Fresh-frozen plasma use paralleled red cell transfusions, but platelet use was modest. These data can serve as a baseline in helping other hospital transfusion services prepare for the advent of liver transplantation in their institutions.     

Blood transfusion and cross matching

To avoid hemolytic transfusion reactions different methods of cross match techniques are described and the relation between the recipient's and the donor's blood quantities are discussed in this regard.     

Microcirculation and red cell transfusion in patients with sepsis

Early identification of sepsis followed by diagnostic blood cultures and prompt administration of appropriate intravenous antibiotics covering all likely pathogen remains the corner stone in the initial management of sepsis. Source control, obtained by harvesting microbiological cultures and removal or drainage of the infected foci, is mandatory. However, optimization of hemodynamically unstable patients including volume support supplemented with vasopressor, inotropic and transfusion of red blood cells (RBCs) in case of persistent hypoperfusion have the potential to reduce morbidity and mortality. Given the imbalance between the ability of the cardiovascular system to deliver enough oxygen to meet the oxygen demand, transfusion of RBCs should theoretically provide the ideal solution to the challenge. However, both changes in the septic patients’ RBCs induced by endogenous factors as well as the storage lesion affecting transfused RBCs have negative effects on the microcirculation. RBC morphology, distribution of fatty acids on the membrane surface, RBC deformability needed for capillary circulation and the nitrogen oxide (NO) signaling systems are involved. Although these deteriorating effects develop during storage, transfusion of fresh RBCs has not proven to be beneficial, possibly due to limitations of the studies performed. Until better evidence exists, transfusion guidelines recommend a restrictive strategy of RBC transfusion i.e. transfuse when hemoglobin (Hb) <7 g/dL in septic patients.