Effects of arterial load variations on dynamic arterial elastance: an experimental study.

BACKGROUND.: Dynamic arterial elastance (Ea dyn ), the relationship between pulse pressure variation (PPV) and stroke volume variation (SVV), has been suggested as a functional assessment of arterial load. The aim of this study was to evaluate the impact of arterial load changes during acute pharmacological changes, fluid administration, and haemorrhage on Ea dyn . METHODS.: Eighteen anaesthetized, mechanically ventilated New Zealand rabbits were studied. Arterial load changes were induced by phenylephrine ( n =9) or nitroprusside ( n =9). Thereafter, animals received a fluid bolus (10 ml kg -1 ), followed by stepwise bleeding (blood loss: 15 ml kg -1 ). The influence of arterial load and cardiac variables on PPV, SVV, and Ea dyn was analysed using a linear mixed-effects model analysis. RESULTS.: After phenylephrine infusion, mean ( sd ) Ea dyn decreased from 0.89 (0.14) to 0.49 (0.12), P <0.001; whereas after administration of nitroprusside, Ea dyn increased from 0.80 (0.23) to 1.28 (0.21), P <0.0001. Overall, the fluid bolus decreased Ea dyn [from 0.89 (0.44) to 0.73 (0.35); P <0.01], and haemorrhage increased it [from 0.78 (0.23) to 0.95 (0.26), P =0.03]. Both PPV and SVV were associated with similar arterial factors (effective arterial elastance, arterial compliance, and resistance) and heart rate. Furthermore, PPV was also related to the acceleration and peak velocity of aortic blood flow. Both arterial and cardiac factors contributed to the evolution of Ea dyn throughout the experiment. CONCLUSIONS.: Acute modifications of arterial load induced significant changes on Ea dyn ; vasodilatation increased Ea dyn , whereas vasoconstriction decreased it. The Ea dyn was associated with both arterial load and cardiac factors, suggesting that Ea dyn should be more properly considered as a ventriculo-arterial coupling index.

Preemptive hemodynamic intervention restricting the administration of fluids attenuates lung edema progression in oleic acid-induced lung injury.

OBJECTIVE: A study is made of the influence of preemptive hemodynamic intervention restricting fluid administration upon the development of oleic acid-induced lung injury. DESIGN: A randomized in vivo study in rabbits was carried out. SETTING: University research laboratory. SUBJECTS: Sixteen anesthetized, mechanically ventilated rabbits. VARIABLES: Hemodynamic measurements obtained by transesophageal Doppler signal. Respiratory mechanics computed by a least square fitting method. Lung edema assessed by the ratio of wet weight to dry weight of the right lung. Histological examination of the left lung. INTERVENTIONS: Animals were randomly assigned to either the early protective lung strategy (EPLS) (n=8) or the early protective hemodynamic strategy (EPHS) (n=8). In both groups, lung injury was induced by the intravenous infusion of oleic acid (OA) (0.133mlkg-1h-1 for 2h). At the same time, the EPLS group received 15mlkg-1h-1 of Ringer lactate solution, while the EPHS group received 30mlkg-1h-1. Measurements were obtained at baseline and 1 and 2h after starting OA infusion. RESULTS: After 2h, the cardiac index decreased in the EPLS group (p<0.05), whereas in the EPHS group it remained unchanged. Lung compliance decreased significantly only in the EPHS group (p<0.05). Lung edema was greater in the EPHS group (p<0.05). Histological damage proved similar in both groups (p=0.4). CONCLUSIONS: In this experimental model of early lung injury, lung edema progression was attenuated by preemptively restricting the administration of fluids.

Postoperative arterial hypotension: the unnoticed enemy.

Postoperative hypotension is a frequently underestimated health problem associated with high morbidity and mortality and increased use of health care resources. It also poses significant clinical, technological, and human challenges for healthcare. As it is a modifiable and avoidable risk factor, this document aims to increase its visibility, defining its clinical impact and the technological challenges involved in optimizing its management, taking clinical-technological, humanistic, and economic aspects into account.

Fluid challenges in operating room: A planned sub study of the Fluid Day observational study.

BACKGROUND: Intraoperative fluid administration is a ubiquitous intervention in surgical patients. But inadequate fluid administration may lead to poor postoperative outcomes. Fluid challenges (FCs), in or outside the so-called goal-directed fluid therapy, allows testing the cardiovascular system and the need for further fluid administration. Our primary aim was to evaluate how anesthesiologists conduct FCs in the operating room in terms of type, volume, variables used to trigger a FC and to compare the proportion of patients receiving further fluid administration based on the response to the FC. METHODS: This was a planned substudy of an observational study conducted in 131 centres in Spain in patients undergoing surgery. RESULTS: A total of 396 patients were enrolled and analysed in the study. The median [interquartile range] amount of fluid given during a FC was 250ml (200-400). The main indication for FC was a decrease in systolic arterial pressure in 246 cases (62.2%). The second was a decrease in mean arterial pressure (54.4%). Cardiac output was used in 30 patients (7.58%), while stroke volume variation in 29 of 385 cases (7.32%). The response to the initial FC did not have an impact when prescribing further fluid administration. CONCLUSIONS: The current indication and evaluation of FC in surgical patients is highly variable. Prediction of fluid responsiveness is not routinely used, and inappropriate variables are frequently evaluated for assessing the hemodynamic response to FC, which may result in deleterious effects.

A critical review of the perioperative fluid therapy and hemodynamic monitoring recommendations of the Enhanced Recovery of the Adult Pathway (RICA): A position statement of the fluid therapy and hemodynamic monitoring Subcommittee of the Hemostasis, Transfusion Medicine and Fluid Therapy Section (SHTF) of the Spanish Society of Anesthesiology and Critical Care (SEDAR).

In an effort to standardize perioperative management and improve postoperative outcomes of adult patients undergoing surgery, the Ministry of Health, through the Spanish Multimodal Rehabilitation Group (GERM), and the Aragonese Institute of Health Sciences, in collaboration with multiple Spanish scientific societies and based on the available evidence, published in 2021 the Spanish Intensified Adult Recovery (RICA) guideline. This document includes 12 perioperative measures related to fluid therapy and hemodynamic monitoring. Fluid administration and hemodynamic monitoring are not straightforward but are directly related to postoperative patient outcomes. The Fluid Therapy and Hemodynamic Monitoring Subcommittee of the Hemostasis, Transfusion Medicine and Fluid Therapy Section (SHTF) of the Spanish Society of Anesthesiology and Critical Care (SEDAR) has reviewed these recommendations and concluded that they should be revised as they do not follow an adequate methodology.

Research priorities in perioperative fluid therapy and hemodynamic monitoring: A Delphi Consensus Survey from the Fluid Therapy and Hemodynamic Monitoring Subcommittee of the Hemostasis, Transfusion Medicine and Fluid Therapy Section (SHTF) of the Spanish Society of Anesthesiology and Critical Care (SEDAR).

BACKGROUND: Research in fluid therapy and perioperative hemodynamic monitoring is difficult and expensive. The objectives of this study were to summarize these topics and to prioritize these topics in order of research importance. METHODS: Electronic structured Delphi questionnaire over three rounds among 30 experts in fluid therapy and hemodynamic monitoring identified through the Fluid Therapy and Hemodynamic Monitoring Subcommittee of the Hemostasis, Transfusion Medicine and Fluid Therapy Section of the Spanish Society of Anesthesiology and Critical Care. RESULTS: 77 topics were identified and ranked in order of prioritization. Topics were categorized into themes of crystalloids, colloids, hemodynamic monitoring and others. 31 topics were ranked as essential research priority. To determine whether intraoperative hemodynamic optimization algorithms based on the invasive or noninvasive Hypotension Prediction Index versus other management strategies could decrease the incidence of postoperative complications. As well as whether the use of renal stress biomarkers together with a goal-directed fluid therapy protocol could reduce hospital stay and the incidence of acute kidney injury in adult patients undergoing non-cardiac surgery, reached the highest consensus. CONCLUSIONS: The Fluid Therapy and Hemodynamic Monitoring Subcommittee of the Hemostasis, Transfusion Medicine and Fluid Therapy Section of the Spanish Society of Anesthesiology and Critical Care will use these results to carry out the research.

[Evidence on the utility of hemodynamic monitorization in the critical patient]. / Evidencia de la utilidad de la monitorización hemodinámica en el paciente crítico.

Hemodynamic monitoring is a tool of great value for the assessment of critically ill patients. It can not only detect and determine the source of hemodynamic instability, but also guide the choice of appropriate treatment and further evaluate its effectiveness. However, monitoring per se is not a therapeutic tool and its use in the absence of a well-defined objective, need not affect patient outcome. To improve outcome, hemodynamic monitoring necessarily must be coupled to a treatment protocol that has effectively been shown to improve outcome. Accordingly, the usefulness of monitoring systems should be evaluated not only on the basis of the accuracy and reliability of their measurements, but also on the ability to positively affect patient outcome. In this regard, many of the arguments against the use of hemodynamic monitoring are a consequence of non-protocolized use and of application not directed towards specific hemodynamic objectives of proven benefit for the patient.

[Incidence, characteristics and outcome of barotrauma during open lung ventilation]. / Incidencia, características y evolución del barotrauma durante la ventilación mecánica con apertura pulmonar.

OBJECTIVE: To describe the incidence and main clinical characteristics of barotrauma during open lung ventilation (OLV). DESIGN: A retrospective, observational, descriptive study was made of 100 patients with acute respiratory failure and bilateral pulmonary infiltrates. INTERVENTIONS: 1) A lung recruitment maneuver (LRM) with fixed ventilation pressure and progressive positive end-expiratory pressure (PEEP) elevations was carried out, followed by stepwise decreases until establishing open-lung PEEP at the value associated to maximum respiratory compliance; 2) assisted/controlled pressure ventilation to achieve a tidal volume of 6-8 ml/kg; and 3) chest X-rays after LRM and daily for as long as respiratory failure persisted. RESULTS: Nine patients, 7 with pneumonia and 2 with chest trauma, developed barotrauma (2 subcutaneous emphysemas and 7 cases of pneumothorax), representing an overall incidence of 9% and 16% in patients with primary lung injury. In 7 patients barotrauma was only a radiological finding; in the other 2 patients, it manifested as bilateral and tension pneumothorax, inducing pulmonary hypoventilation without hemodynamic impairment. Only in these two cases was the ventilatory strategy modified. There were no differences in the airway pressures or volumes between patients with and without barotrauma. Mortality was similar in both groups. CONCLUSIONS: Barotrauma was an exclusive complication of patients with primary lung injury, and the incidence in this group was high. In most cases, there were only radiological findings without clinical significance that did not require the suspension of OLV. Barotrauma was neither related to high pressures and volumes nor associated with increased mortality.

[Respiratory and hemodynamic changes during lung recruitment maneuvering through progressive increases and decreases in PEEP level]. / Cambios respiratorios y hemodinámicos durante una maniobra de reclutamiento pulmonar mediante incrementos y decrementos progresivos de PEEP.

OBJECTIVE: To evaluate the respiratory and hemodynamic changes during lung recruitment maneuvering (LRM) through stepwise increases and decreases in PEEP level. DESIGN AND SETTING: A retrospective study in a 17-bed ICU was carried out. PATIENTS: Twenty-one patients with acute respiratory failure and bilateral pulmonary infiltration. INTERVENTION: LRM was carried out, consisting of stepwise increases in PEEP (4 cmH(2)O every 3 minutes), with fixed ventilation pressure, until reaching a maximal value of 36 cmH(2)O PEEP (ascending branch), followed by progressive decreases in PEEP (2 cmH(2)O every 3 minutes) until establishing the open-lung PEEP at the value associated to maximum respiratory compliance (Crs) (descending branch). Continuous hemodynamic monitoring was performed using an esophageal echodoppler probe. RESULTS: Crs gradually decreased in the ascending branch of the LRM, and progressively increased surpassing the initial value after establish the open-lung PEEP in the descending branch, reducing the ventilation pressure and increasing the SpO(2)/FiO(2) ratio. Hemodynamic changes primarily consisted of a fall in cardiac output and left ventricular preload, together with an increased heart rate and cardiac contractility. At comparable levels of PEEP and mean airway pressure, these changes were more pronounced during the descending branch of the LRM. CONCLUSIONS: 1) LRM increased Crs, improving oxygenation and decreasing ventilation pressure; 2) the main hemodynamic consequence was the drop in cardiac output and left ventricular preload; and 3) the unequal hemodynamic derangement in both branches, at the same level of PEEP and mean airway pressure, showed that, along with intrathoracic pressure, other factor such as Crs and hypercapnia may have influenced the hemodynamic consequences of this type of LRM.

The value of hypotensive prediction index and dP/dtmax to predict and treat hypotension in a patient with a dilated cardiomyopathy. / Valor del índice de predicción de la hipotensión y el dP/dtmax para predecir y tratar la hipotensión en un paciente con miocardiopatía dilatada.

The Hypotension Prediction Index (HPi) is a new parameter, recently developed to predict the risk of a patient developing a hypotensive event, defined as a fall in mean arterial pressure below 65 mmHg. The calculated HPi value is displayed on a monitor as a number ranging from 1 to 100; where the first warning for the appearance of such event occurs when HPi values exceed 85. A secondary screen shows the stroke volume variation value; the dP/dt max; and the dynamic arterial elastance. We described a patient with a mild to moderately dilated cardiomyopathy that presented several episodes of hypotension after induction of anaesthesia and how by using HPi technology, these were successfully solved. We recommend the use of a HPi value >85 as a warning of intervention, and to use the secondary screen to determine the cause and the treatment. We consider that HPi technology may be a valid alternative for the anaesthetic management of patients with a dilated cardiomyopathy.