Regulation of the Peripheral Vasculature and Tissue Oxygention in Health and Disease

Extracellular Water to Total Body Water Ratio in Septic Shock Patients Receiving Protocol-Driven Resuscitation Bundle Therapy

(1) Bio-electrical impedance analysis (BIA) is a rapid, simple, and noninvasive tool for evaluating the metabolic status and for assessing volume status in critically ill patients. Little is known, however, the prognostic value of body composition analysis in septic shock patients. This study assessed the association between parameters by body composition analysis and mortality in patients with septic shock in the emergency department (ED). (2) Data were prospectively collected on adult patients with septic shock who underwent protocol-driven resuscitation bundle therapy between December 2019 and January 2021. The primary outcome was 30-day mortality. (3) The study included 261 patients, the average ratio of extracellular water (ECW) to total body water (TBW) was significantly higher in non-survivors than in survivors (0.414 vs. 0.401, p < 0.001). Multivariate analysis showed that ECW/TBW ≥ 0.41 (odds ratio (OR), 4.62; 95% confidence interval (CI), 2.31–9.26, p < 0.001), altered mental status (OR, 2.88; 95% CI, 1.28–6.46, p = 0.010), and lactate level (OR, 1.24; 95% CI, 1.12–1.37, p < 0.001) were significantly associated with 30-day mortality in patients with septic shock. (4) ECW/TBW ≥ 0.41 may be associated with 30-day mortality in patients with septic shock receiving protocol-driven resuscitation bundle therapy in the ED.

Teicoplanin use in adult patients with haematological malignancy: Exploring relationships between dose, trough concentrations, efficacy and nephrotoxicity

In 2010, our hospital introduced a higher target teicoplanin trough concentration of ≥20 mg/L by Day 3 for haematological malignancy patients. This study aimed to explore whether target trough concentrations were achieved, to identify factors associated with trough concentrations attained, and to assess clinical efficacy with teicoplanin treatments and nephrotoxicity. This was a retrospective, single-centre, cohort study of 172 teicoplanin treatments in 104 adults with haematological malignancy. Mixed-effects regression was used to evaluate factors affecting trough concentrations, and logistic regression was used to assess the relationship between trough concentrations and treatment outcomes. Nephrotoxicity was assessed using the RIFLE criteria. Considerable variability in trough concentrations was observed, with trough concentrations ≥20 mg/L rarely achieved early in therapy. A mixed-effects regression model explaining 52% of the variation in trough concentrations was developed. Dose and day of therapy were positively associated with trough concentration, whilst estimated renal function and, interestingly, acute myeloid leukaemia diagnosis were negatively associated (P<0.05). Results suggested a positive relationship between trough concentration and the likelihood of a favourable outcome for coagulase-negative staphylococcal central line-associated bloodstream infections. Elucidation of a specific target concentration requires further investigation. Teicoplanin was well tolerated renally. Findings suggest a risk of underexposure if conventional teicoplanin doses are used in haematological malignancy patients. Given the variability in trough concentrations observed, the identified factors affecting trough concentrations attained and the suggested link with clinical outcome, individualised initial dosing followed by therapeutic drug monitoring is recommended to ensure early adequate exposure in this vulnerable patient group.

Pharmacokinetic and pharmacodynamic considerations when treating patients with sepsis and septic shock

Sepsis and septic shock are accompanied by profound changes in the organism that may alter both the pharmacokinetics and the pharmacodynamics of drugs. This review elaborates on the mechanisms by which sepsis-induced pathophysiological changes may influence pharmacological processes. Drug absorption following intramuscular, subcutaneous, transdermal and oral administration may be reduced due to a decreased perfusion of muscles, skin and splanchnic organs. Compromised tissue perfusion may also affect drug distribution, resulting in a decrease of distribution volume. On the other hand, the increase in capillary permeability and interstitial oedema during sepsis and septic shock may enhance drug distribution. Changes in plasma protein binding, body water, tissue mass and pH may also affect drug distribution. For basic drugs that are bound to the acute phase reactant alpha(1)-acid glycoprotein, the increase in plasma concentration of this protein will result in a decreased distribution volume. The opposite may be observed for drugs that are extensively bound to albumin, as the latter protein decreases during septic conditions. For many drugs, the liver is the main organ for metabolism. The determinants of hepatic clearance of drugs are liver blood flow, drug binding in plasma and the activity of the metabolic enzymes; each of these may be influenced by sepsis and septic shock. For high extraction drugs, clearance is mainly flow-dependent, and sepsis-induced liver hypoperfusion may result in a decreased clearance. For low extraction drugs, clearance is determined by the degree of plasma binding and the activity of the metabolic enzymes. Oxidative metabolism via the cytochrome P450 enzyme system is an important clearance mechanism for many drugs, and has been shown to be markedly affected in septic conditions, resulting in decreased drug clearance. The kidneys are an important excretion pathway for many drugs. Renal failure, which often accompanies sepsis and septic shock, will result in accumulation of both parent drug and its metabolites. Changes in drug effect during septic conditions may theoretically result from changes in pharmacodynamics due to changes in the affinity of the receptor for the drug or alterations in the intrinsic activity at the receptor. The lack of valid pharmacological studies in patients with sepsis and septic shock makes drug administration in these patients a difficult challenge. The patient's underlying pathophysiological condition may guide individual dosage selection, which may be guided by measuring plasma concentration or drug effect.

Effect of dobutamine on the arterial ketone body ratio and portal blood flow velocity in cirrhosis

We studied the relationship between the portal blood flow velocity and the arterial ketone body ratio in patients with chronic liver disease receiving a dobutamine infusion. We used an ultrasonic Doppler duplex system to evaluate the portal blood flow velocity. Dobutamine was given intravenously at 5 micrograms/kg/min for 20 min. Dobutamine infusion induced smaller changes in the portal blood flow velocity and ketone body ratio in liver cirrhosis than in chronic hepatitis. The existence of shunts and the poor increase of the cardiac index in response to dobutamine explained the limited improvement of portal blood flow velocity in cirrhosis patients. The ketone body ratio was improved by dobutamine in cirrhosis patients whose portal blood flow velocity was increased by more than 10%, while this ratio decreased when the increase of it was less than 10%. There was no change in portal oxygen extraction in the cirrhosis group, and portal oxygen uptake only increased when the portal blood flow velocity rose by more than 10%. Dobutamine should only be used to treat liver failure if the portal blood flow velocity is increased by more than 10% or the arterial ketone body ratio is improved by a test infusion.

High permeability pulmonary oedema: pathophysiology and mechanisms of injury

Many critically ill patients are at risk for developing HPPE. Since 60% of patients develop HPPE within 24 hours of the pulmonary insult with 11% developing respiratory failure within 72 hours, it is imperative that the critical care nurse understand the pathophysiological responses (Bernard & Bradley, 1986). While the pathophysiological responses are specific, injury to the alveolar-capillary membrane, the mechanisms of injury are diffuse. Knowing the mechanisms can alert health care providers to those patients who are at risk for developing HPPE and more quickly mobilize interventions to alleviate or lessen its occurrence.

Effects of normobaric hyperoxia on hemodynamics and O2 utilization in conscious dogs

Normobaric hyperoxia decreased resting whole-body O2 consumption in conscious dogs by equal (Fick) contributions from decreases in cardiac output and in the arterial-venous difference in O2 content. The decrease in O2 consumption was fully developed by 20 min, was maintained for at least 1 h, and was both reversible and reproducible. Hyperoxia also decreased heart rate, right and left ventricular work rates (and therefore, presumably myocardial O2 consumption), and pulmonary vascular resistance; and increased systemic vascular resistance and right atrial pressure. Paradoxically, hyperoxia did not change O2 delivery. This latter observation together with the decrease in O2 consumption produced a unique vertical orientation to the O2 consumption-delivery relationship induced by hyperoxia. It is concluded that hyperoxia may decrease metabolic rate and substantially alter hemodynamics, which may have important implications for understanding the metabolic regulation of oxygen utilization and for the medical and nonmedical uses of oxygen.

Lactic acidosis

An understanding of the pathophysiology of lactic acidosis is crucial in facilitating the optimal care of critically ill patients. The relevant biochemistry of lactic acidosis is reviewed, and the more controversial aspects relating to the genesis of the acidosis are highlighted. The current system of classification of lactic acidosis divides etiologies on the basis of the presence or absence of clinical signs of tissue hypoperfusion. Several types of lactic acidosis in which clinical evidence of tissue hypoperfusion is lacking demonstrate hemodynamic evidence of occult hypoperfusion. The diagnostic and therapeutic implications of this observation are discussed. Current diagnostic criteria for lactic acidosis include a pH less than 7.35 and blood lactate concentration greater than 5 to 6 mM/L. An important issue relates to the implications of lactate values that are greater than normal but below this diagnostic range. The use of the oxygen flux test may be valuable in the diagnosis of occult tissue hypoperfusion in patients with low-grade elevations in lactate levels. The current therapy for lactic acidosis involves addressing the primary cause and supportive management. The use of bicarbonate in the therapy for lactic acidosis is controversial due to potential adverse effects on cardiac function. The specifics of this controversy are outlined, and newer therapeutic alternatives are reviewed. The use of blood lactate concentration as a prognostic index may be more useful in patients with shock than without shock.

Abnormal tissue oxygenation in patients with cirrhosis and liver failure

Systemic haemodynamic and hepatic venous pressures, arterial and mixed venous gases and arterial lactate concentration were measured in 35 patients with histologically proven alcoholic cirrhosis who had been classified into three groups (A, B and C). Eight alcoholic patients without cirrhosis on liver biopsy were also studied. Compared with group A patients, group C patients had significantly higher hepatic venous pressure gradient, cardiac index, O2 transport and arterial lactate concentration and significantly lower systemic vascular resistance, arteriovenous O2 content difference and O2 uptake. In group B patients, corresponding values fell between those of groups A and C. Group A patients, unlike group C patients, were not significantly different from patients without cirrhosis with respect to cardiac index, systemic vascular resistance, O2 uptake and arterial lactate concentration. Our results suggest that in patients with cirrhosis, liver failure-associated hyperdynamic circulation may be accompanied by an abnormal tissue oxygenation.