Volume replacement therapy in critical illness : Focus on acute respiratory failure
The current evidence is derived mostly from observational studies , and more randomised trials are needed to establish a personalised approach to fluid management in acute respiratory failure
Christian Wiedermann MD Department of Public Health , Medical Decision Making and Health Technology Assessment , University of Health Sciences , MedicaI Informatics and Technology , Hall ( Tyrol ), Austria
A positive fluid balance is common among critically ill patients and leads to worse outcomes , particularly in acute lung injury ( ALI ) and acute respiratory distress syndrome ( ARDS ), which is defined by acute onset hypoxaemia with PaO2 / FiO2 < 300 and presence of bilateral opacities in the lungs that cannot be attributed to heart failure or volume overload . 1 Restrictive fluid infusion and active removal of accumulated fluid are being studied as approaches to prevent and treat fluid overload . Restrictive fluid administration , plus early vasopressor use , may reduce fluid balance , and active fluid removal , through diuretics or ultrafiltration , reduces the duration of mechanical ventilation and the intensive care unit ( ICU ) stay .
Respiratory viral infections Up to 50 % of the cases of severe community-acquired respiratory illness are caused by respiratory viral infections ( RVIs ), including those by the influenza virus and the novel coronaviruses ( SARS , MERS , and COVID-19 ). Admission to the ICU of patients with RVIs occurs for hypoxic respiratory failure , ARDS , and sepsis . Antiviral treatment with oseltamivir has proven efficacious when administered early in the course of influenza infection ; however , no proven therapies exist in other RVIs , including disease due to SARS-CoV-2 .
Evidence-based supportive care is currently the mainstay for the management of RVIs . In acute respiratory failure , this supportive care includes non-invasive ventilation versus high-flow nasal cannula , conventional versus high-frequency oscillatory ventilation , prone positioning , administration of neuromuscular blockers , extracorporeal membrane oxygenation ( ECMO ), cardiovascular management , and fluid resuscitation . 2
Fluid resuscitation Hypovolaemia is frequent in sepsis and contributes to worse outcomes , but this condition is difficult to assess and its management is impeded by the low quality of the evidence . 3 , 4 Therefore , the risk of treatment-related harm is real . 3 Recent advances and controversies include triggers and targets for fluid therapy as well as volumes and types of fluid . 4
Colloids vs . crystalloids In a meta-analysis of colloids vs . crystalloids in critically ill , trauma , and surgical patients , 5 colloid administration overall did not lead to increased mortality ( 32 trials , 16,647 patients ; odds ratio ( OR ), 0.99 , 95 % confidence interval ( CI ), 0.92 to 1.06 ), but did increase the risk of developing acute kidney injury ( AKI ) requiring renal replacement therapy
( RRT ; 9 trials , 11,648 patients ; OR , 1.35 , 95 % CI , 1.17 to 1.57 ). Subgroup analyses by type of colloid showed that increased mortality and RRT were associated with use of pentastarch , and increased risk of renal injury and RRT with use of tetrastarch . The subgroup analyses also indicated that the risks of mortality and renal injury attributable to colloids were observed only in critically ill patients with sepsis . 5
Saline in large volumes is associated with hyperchloraemic metabolic acidosis and , in turn , with the development of AKI . 6 In addition , balanced crystalloids are associated with metabolic alkalosis , and substituted anions ( acetate ) have adverse effects . 7 Two pragmatic , multiple-crossover , openlabel randomised controlled trials ( RCTs ), conducted in a single major US medical centre , compared modest volumes of balanced crystalloids vs . saline in non-critically ill ( SALT-ED ) 8 and critically ill ( SMART ) 9 patients . Mortality or need for RRT were not affected ; however , balanced crystalloids reduced occurrence of persistent AKI at day 30 .
Conservative vs . liberal approaches Fluid management strategies for ALI and ARDS include conservative and liberal approaches . In a multicentre , unblinded RCT involving 1001 mechanically ventilated patients with PaO2 / FiO2 < 300 and bilateral infiltrates , the 7-day cumulative fluid balance was lower in the conservative than in liberal strategy group ( −136 versus 6992ml , p < 0.001 ). Survival was not significantly different on day 28 ; however , the conservative strategy was associated with significantly more ventilatorfree days and ICU-free days than was observed in the liberal strategy group ( 14.6 versus 12.1 days , difference 2.5 , 95 % CI 1.1 to 3.9 , and 13.4 vs . 11.2 days , difference 2.2 , 95 % CI 1.1 to 3.3 , respectively ). 10
Adverse effects of fluid imbalance Nearly all critically ill patients receive crystalloids , and additionally they often are administered colloids . The advantages of the former are their low costs , immediate availability , the ability to fill both the intravascular and extravascular fluid spaces , and a non-allergenic potential . Administration of excessive fluid with extravasation can , however , be a problem with crystalloids and promotes the formation of tissue oedema preferentially in the skin , gut , and lung , particularly with large volumes . 11 As exemplified in major abdominal surgery , patients managed in a state of fluid balance fared better than those managed in a state of fluid imbalance . Thus , the recovery time following gastrointestinal surgery was prolonged by two more days when a volume of more than 2l of crystalloids
26 | 2020 | hospitalpharmacyeurope . com