Closed-Loop Resuscitation of Burn Shock

American Burn Association Clinical Practice Guidelines on Burn Shock Resuscitation

This Clinical Practice Guideline (CPG) addresses the topic of acute fluid resuscitation during the first 48 hours following a burn injury for adults with burns ≥20% of the total body surface area (%TBSA). The listed authors formed an investigation panel and developed clinically relevant PICO (Population, Intervention, Comparator, Outcome) questions. A systematic literature search returned 5978 titles related to this topic and after 3 levels of screening, 24 studies met criteria to address the PICO questions and were critically reviewed. We recommend that clinicians consider the use of human albumin solution, especially in patients with larger burns, to lower resuscitation volumes and improve urine output. We recommend initiating resuscitation based on providing 2 mL/kg/% TBSA burn in order to reduce resuscitation fluid volumes. We recommend selective monitoring of intra-abdominal and intraocular pressure during burn shock resuscitation. We make a weak recommendation for clinicians to consider the use of computer decision support software to guide fluid titration and lower resuscitation fluid volumes. We do not recommend the use of transpulmonary thermodilution-derived variables to guide burn shock resuscitation. We are unable to make any recommendations on the use of high-dose vitamin C (ascorbic acid), fresh frozen plasma (FFP), early continuous renal replacement therapy, or vasopressors as adjuncts during acute burn shock resuscitation. Mortality is an important outcome in burn shock resuscitation, but it was not formally included as a PICO outcome because the available scientific literature is missing studies of sufficient population size and quality to allow us to confidently make recommendations related to the outcome of survival at this time.

MAN VERSUS MACHINE: PROVIDER DIRECTED VERSUS PRECISION AUTOMATED CRITICAL CARE MANAGEMENT IN A PORCINE MODEL OF DISTRIBUTIVE SHOCK

ABSTRACT

Background: Critical care management of shock is a labor-intensive process. Precision Automated Critical Care Management (PACC-MAN) is an automated closed-loop system incorporating physiologic and hemodynamic inputs to deliver interventions while avoiding excessive fluid or vasopressor administration. To understand PACC-MAN efficacy, we compared PACC-MAN to provider-directed management (PDM). We hypothesized that PACC-MAN would achieve equivalent resuscitation outcomes to PDM while maintaining normotension with lower fluid and vasopressor requirements. Methods : Twelve swine underwent 30% controlled hemorrhage over 30 min, followed by 45 min of aortic occlusion to generate a vasoplegic shock state, transfusion to euvolemia, and randomization to PACC-MAN or PDM for 4.25 h. Primary outcomes were total crystalloid volume, vasopressor administration, total time spent at hypotension (mean arterial blood pressure <60 mm Hg), and total number of interventions. Results : Weight-based fluid volumes were similar between PACC-MAN and PDM; median and IQR are reported (73.1 mL/kg [59.0-78.7] vs. 87.1 mL/kg [79.4-91.8], P = 0.07). There was no statistical difference in cumulative norepinephrine (PACC-MAN: 33.4 μg/kg [27.1-44.6] vs. PDM: 7.5 [3.3-24.2] μg/kg, P = 0.09). The median percentage of time spent at hypotension was equivalent (PACC-MAN: 6.2% [3.6-7.4] and PDM: 3.1% [1.3-6.6], P = 0.23). Urine outputs were similar between PACC-MAN and PDM (14.0 mL/kg vs. 21.5 mL/kg, P = 0.13). Conclusion : Automated resuscitation achieves equivalent resuscitation outcomes to direct human intervention in this shock model. This study provides the first translational experience with the PACC-MAN system versus PDM.

Performance of closed-loop systems for intravenous drug administration: a systematic review and meta-analysis of randomised controlled trials

Closed-loop drug delivery systems are autonomous computers able to administer medication in response to changes in physiological parameters (controlled variables). While limited evidence suggested that closed-loop systems can perform better than manual drug administration in certain settings, this technology remains a research tool with an uncertain risk/benefit profile. Our aim was comparing the performance of closed-loop systems with manual intravenous drug administration in adults. We searched MEDLINE, CENTRAL, and Embase from inception until November 2022, without restriction to language. We assessed for inclusion randomised controlled trials comparing closed-loop and manual administration of intravenous drugs in adults, intraoperatively or in the Intensive Care Unit. We identified 32 studies on closed-loop administration of propofol, noradrenaline, phenylephrine, insulin, neuromuscular blockers, and vasodilators. Most studies were at moderate or high risk of bias. The results showed that closed-loop systems reduced the duration of blood pressure outside prespecified targets during noradrenaline (MD 14.9%, 95% CI 9.6-20.2%, I2 = 66.6%) and vasodilators administration (MD 7.4%, 95% CI 5.2-9.7%, I2 = 62.3%). Closed-loop systems also decreased the duration of recovery after propofol (MD 1.3 min, 95% CI 0.4-2.1 min, I2 = 58.6%) and neuromuscular blockers (MD 9.0 min, 95% CI 7.9-10.0 min, I2 = 0%). The certainty of the evidence was low or very low for most outcomes. Automatic technology may be used to improve the hemodynamic profile during noradrenaline and vasodilators administration and reduce the duration of postanaesthetic recovery.Registration: This systematic review was registered with PROSPERO (CRD42022336950) on the 7th of June 2022.

Regional Burn Review: Neither Parkland Nor Brooke Formulas Reach 85% Accuracy Mark for Burn Resuscitation

Prolonged resuscitation can result in burn wound conversion and other complications. Our team switched from using Parkland formula (PF) to the modified Brooke formula (BF) in January 2020. Secondary to difficult resuscitations using BF, we sought to review our data to identify factors associated with resuscitation requiring greater than predicted resuscitation with either formula, defined as 25% or more of predicted, hereafter referred to as over-resuscitation. Patients admitted to the burn unit between January 1, 2019 and August 29, 2021 for a burn injury with a percentage of total body surface area (%TBSA) ≥15% were included. Subjects <18 years, or weighing <30 kg, and those who died or had care withdrawn within 24 hours of admission were excluded. Demographics, injury information, and resuscitation information were collected. Univariate and multivariate analyses were performed to identify factors associated with over-resuscitation by either formula. P < .05 was considered significant. Sixty-four patients were included; 27 were resuscitated using BF and 37 using PF. No significant differences were observed in demographics and burn injury between the groups. Patients required a median of 3.59 ml/kg/%TBSA for BF and 3.99 ml/kg/%TBSA for PF to reach maintenance (P = .32). Over-resuscitation was more likely to occur when using BF compared to PF (59.3% vs 32.4%, P = .043). Over-resuscitation was associated with longer time to reach maintenance (OR = 1.179 [1.042-1.333], P = .009) and arrival via ground transportation (OR = 10.523 [1.171-94.597], P = .036). Future studies are warranted to identify populations in which BF under-performs and sequelae associated with prolonged resuscitation.

Precision Automated Critical Care Management: Closed-loop critical care for the treatment of distributive shock in a swine model of ischemia-reperfusion

BACKGROUND

Goal-directed blood pressure management in the intensive care unit can improve trauma outcomes but is labor-intensive. Automated critical care systems can deliver scaled interventions to avoid excessive fluid or vasopressor administration. We compared a first-generation automated drug and fluid delivery platform, Precision Automated Critical Care Management (PACC-MAN), to a more refined algorithm, incorporating additional physiologic inputs and therapeutics. We hypothesized that the enhanced algorithm would achieve equivalent resuscitation endpoints with less crystalloid utilization in the setting of distributive shock.

METHODS

Twelve swine underwent 30% hemorrhage and 30 minutes of aortic occlusion to induce an ischemia-reperfusion injury and distributive shock state. Next, animals were transfused to euvolemia and randomized into a standardized critical care (SCC) of PACC-MAN or an enhanced version (SCC+) for 4.25 hours. SCC+ incorporated lactate and urine output to assess global response to resuscitation and added vasopressin as an adjunct to norepinephrine at certain thresholds. Primary and secondary outcomes were decreased crystalloid administration and time at goal blood pressure, respectively.

RESULTS

Weight-based fluid bolus volume was lower in SCC+ compared with SCC (26.9 mL/kg vs. 67.5 mL/kg, p = 0.02). Cumulative norepinephrine dose required was not significantly different (SCC+: 26.9 μg/kg vs. SCC: 13.76 μg/kg, p = 0.24). Three of 6 animals (50%) in SCC+ triggered vasopressin as an adjunct. Percent time spent between 60 mm Hg and 70 mm Hg, terminal creatinine and lactate, and weight-adjusted cumulative urine output were equivalent.

CONCLUSION

Refinement of the PACC-MAN algorithm decreased crystalloid administration without sacrificing time in normotension, reducing urine output, increasing vasopressor support, or elevating biomarkers of organ damage. Iterative improvements in automated critical care systems to achieve target hemodynamics in a distributive-shock model are feasible.

A Comprehensive Analysis and Review of Artificial Intelligence in Anaesthesia

In the field of anaesthesia, artificial intelligence (AI) has become a game-changing technology. Applications of AI include keeping records, monitoring patients, calculating and administering drugs, and carrying out mechanical procedures. This article explores the current uses, challenges, and prospective applications of AI in anaesthesia practices. This review discusses AI-supported systems like anaesthesia information management systems (AIMS), mechanical robots for carrying out procedures, and pharmacological models for drug delivery. AIMS has helped in automated record-keeping, predicting bad events, and monitoring the vital signs of the patient. Their application has a vital role in improving the efficacy of anaesthesia management and patient safety. The application of AI in anaesthesia comes with its own unique difficulties. Noteworthy obstacles include issues with data quantity and quality, technical limitations, and moral and legal dilemmas. The key to overcoming these barriers is to set guidelines for the ethical use of AI in healthcare, improve the reliability and comprehension of AI systems, and certify the health data precision and security. AI has very bright potential. Exciting future directions include developments in AI and machine learning thus development of new applications, and the possible enhancement in training and education. Potential research areas include the application of AI to chronic disease management, pain management, and the reinforcement of anaesthesiologists' education. AI could be used to design authentic lifelike training simulations and individualized student feedback systems, hence transforming anaesthesia education and training methodology. For this review, we conducted a PubMed, Google Scholar, and Cochrane Database search in 2022-2023 and retrieved articles on AI and its uses in anaesthesia. Recommendations for future research and development include strengthening the safety and reliability of health data, building a better understanding of AI systems, and looking into new areas of use. The power of AI can be used to innovate anaesthesia practices by concentrating on these areas.

Hardware-in-Loop Comparison of Physiological Closed-Loop Controllers for the Autonomous Management of Hypotension

Trauma and hemorrhage are leading causes of death and disability worldwide in both civilian and military contexts. The delivery of life-saving goal-directed fluid resuscitation can be difficult to provide in resource-constrained settings, such as in forward military positions or mass-casualty scenarios. Automated solutions for fluid resuscitation could bridge resource gaps in these austere settings. While multiple physiological closed-loop controllers for the management of hypotension have been proposed, to date there is no consensus on controller design. Here, we compare the performance of four controller types—decision table, single-input fuzzy logic, dual-input fuzzy logic, and proportional–integral–derivative using a previously developed hardware-in-loop test platform where a range of hemorrhage scenarios can be programmed. Controllers were compared using traditional controller performance metrics, but conclusions were difficult to draw due to inconsistencies across the metrics. Instead, we propose three aggregate metrics that reflect the target intensity, stability, and resource efficiency of a controller, with the goal of selecting controllers for further development. These aggregate metrics identify a dual-input, fuzzy-logic-based controller as the preferred combination of intensity, stability, and resource efficiency within this use case. Based on these results, the aggressively tuned dual-input fuzzy logic controller should be considered a priority for further development.

Evaluation of a Proportional-Integral-Derivative Controller for Hemorrhage Resuscitation Using a Hardware-in-Loop Test Platform

Hemorrhage is a leading cause of preventable death in trauma, which can often be avoided with proper fluid resuscitation. Fluid administration can be cognitive-demanding for medical personnel as the rates and volumes must be personalized to the trauma due to variations in injury severity and overall fluid responsiveness. Thus, automated fluid administration systems are ideal to simplify hemorrhagic shock resuscitation if properly designed for a wide range of hemorrhage scenarios. Here, we highlight the development of a proportional-integral-derivative (PID) controller using a hardware-in-loop test platform. The controller relies only on an input data stream of arterial pressure and a target pressure; the PID controller then outputs infusion rates to stabilize the subject. To evaluate PID controller performance with more than 10 controller metrics, the hardware-in-loop platform allowed for 11 different trauma-relevant hemorrhage scenarios for the controller to resuscitate against. Overall, the two controller configurations performed uniquely for the scenarios, with one reaching the target quicker but often overshooting, while the other rarely overshot the target but failed to reach the target during severe hemorrhage. In conclusion, PID controllers have the potential to simplify hemorrhage resuscitation if properly designed and evaluated, which can be accomplished with the test platform shown here.

Closed-Loop Control for Fluid Resuscitation: Recent Advances and Future Challenges

Fluid therapy is extensively used to treat traumatized patients as well as patients during surgery. The fluid therapy process is complex due to interpatient variability in response to therapy as well as other complicating factors such as comorbidities and general anesthesia. These complexities can result in under- or over-resuscitation. Given the complexity of the fluid management process as well as the increased capabilities in hemodynamic monitoring, closed-loop fluid management can reduce the workload of the overworked clinician while ensuring specific constraints on hemodynamic endpoints are met with higher accuracy. The goal of this paper is to provide an overview of closed-loop control systems for fluid management and highlight several key steps in transitioning such a technology from bench to the bedside.

Automated Blood Pressure Control

Arterial pressure management is a crucial task in the operating room and intensive care unit. In high-risk surgical and in critically ill patients, sustained hypotension is managed with continuous infusion of vasopressor agents, which most commonly have direct α agonist activity like phenylephrine or norepinephrine. The current standard of care to guide vasopressor infusion is manual titration to an arterial pressure target range. This approach may be improved by using automated systems that titrate vasopressor infusions to maintain a target pressure. In this article, we review the evidence behind blood pressure management in the operating room and intensive care unit and discuss current and potential future applications of automated blood pressure control.

Closed-loop hemodynamic management

As the operating room and intensive care settings become increasingly complex, the required vigilance practitioners must dedicate to a wide array of clinical systems has increased concordantly. The resulting shortage of available attention to these various clinical tasks creates a vacuum for the introduction of systems that can administer well-established goal-directed therapies without significant provider feedback. Recently, there has been an explosion of academic exploration into creating such automated systems, with a strong specific focus on hemodynamic control. Within this field, the largest focus has been on goal-directed fluid therapy as systems automating vasopressor administration have only recently become viable options. Our goal in this review article is to summarize the validity of the relevant goal-directed hemodynamic systems and explore the expanding role of automation within these systems.

A pilot study evaluating adaptive closed-loop fluid resuscitation during states of absolute and relative hypovolemia in dogs

OBJECTIVE

To evaluate and determine the performance of a partially automated as well as a fully automated closed-loop fluid resuscitation system during states of absolute and relative hypovolemia.

DESIGN

Prospective experimental trial.

SETTING

Research laboratory.

ANIMALS

Five adult Beagle dogs.

METHODS

Isoflurane anesthetized mechanically ventilated dogs were subjected to absolute hypovolemia (controlled: 2 trials; uncontrolled: 3 trials), relative hypovolemia (2 trials), and the combination of relative and absolute controlled hypovolemia (2 trials). Controlled and uncontrolled hypovolemia were produced by withdrawing blood from the carotid or femoral artery. Relative hypovolemia was produced by increasing the isoflurane concentration (1 trial) or by infusion of intravenous sodium nitroprusside (1 trial). Relative hypovolemia combined with controlled absolute hypovolemia was produced by increasing the isoflurane concentration (1 trial) and infusion of IV sodium nitroprusside (1 trial). Hemodynamic parameters including stroke volume variation (SVV) were continuously monitored and recorded in all dogs. A proprietary closed-loop fluid administration system based on fluid distribution and compartmental dynamical systems administered a continuous infusion of lactated Ringers solution in order to restore and maintain SVV to a predetermined target value.

MEASUREMENTS AND MAIN RESULTS

A total of 9 experiments were performed on 5 dogs. Hemodynamic parameters deteriorated and SVV increased during controlled or uncontrolled hypovolemia, relative hypovolemia, and during relative hypovolemia combined with controlled hypovolemia. Stroke volume variation was restored to baseline values during closed-loop fluid infusion.

CONCLUSIONS

Closed-loop fluid administration based on IV fluid distribution and compartmental dynamical systems can be used to provide goal directed fluid therapy during absolute or relative hypovolemia in mechanically ventilated isoflurane anesthetized dogs.

Control-oriented physiological modeling of hemodynamic responses to blood volume perturbation

This paper presents a physiological model to reproduce hemodynamic responses to blood volume perturbation. The model consists of three sub-models: a control-theoretic model relating blood volume response to blood volume perturbation; a simple physics-based model relating blood volume to stroke volume and cardiac output; and a phenomenological model relating cardiac output to blood pressure. A unique characteristic of this model is its balance for simplicity and physiological transparency. Initial validity of the model was examined using experimental data collected from 11 animals. The model may serve as a viable basis for the design and evaluation of closed-loop fluid resuscitation controllers.

Burn Shock and Resuscitation: Proceedings of a Symposium Conducted at the Meeting of the American Burn Association, Chicago, IL, 21 April 2015

The Special Interest Groups of the American Burn Association provide a forum for interested members of the multidisciplinary burn team to congregate and discuss matters of mutual interest. At the 47th Annual Meeting of the American Burn Association in Chicago, IL, the Fluid Resuscitation Special Interest Group sponsored a special symposium on burn resuscitation. The purpose of the symposium was to review the history, current status, and future direction of fluid resuscitation of patients with burn shock. The reader will note several themes running through the following presentations. One is the perennial question of the proper role for albumin or other fluid-sparing strategies. Another is the unique characteristics of the pediatric burn patient. A third is the need for multicenter trials of burn resuscitation, while recognizing the obstacles to conducting randomized controlled trials in this setting.

Inaccuracy of Urine Output Measurements due to Urinary Retention in Catheterized Patients in the Burn ICU

Electronic urinary output monitors, intended to provide urine output information to guide fluid therapy during burn resuscitation, can be inaccurate because of airlocks causing urine retention in the drainage tube and bladder. In this study, the authors explore the effects of airlock formation on urine output measured using an electronic urinary output monitor connected to either a standard commercial drainage tubing system or a drainage tubing system with an automated airlock clearing mechanism. In a multicenter study in the burn intensive care unit, urine output was compared between 10 control patients with a standard commercial drainage tubing system and 10 test patients with a novel automated airlock clearing drainage tubing system. The comparison was focused on identifying the number and magnitude of surges in urinary output because of airlocks and associated periods of false oliguria. In the control group, 5 of 10 (50%) patients had drainage line flow impediments from 8 airlocks. In addition, control patients experienced six associated periods of false oliguria. Airlock surge volumes ranged from 50 to 329 ml, and false oliguria duration ranged from 39.4 to 185.2 minutes. In the test group, 0 of 10 (0%) patients had drainage line impediments from airlocks (P < .01), and hence, there were no periods of false oliguria. Airlocks and associated periods of false oliguria occur with standard commercial drainage tubing and are eliminated using an automated airlock clearing drainage tube. Electronic urinary output monitoring with self-clearing drainage has the potential to improve tracking of real-time urine output and decrease caregiver workload.

Burn State of the Science: Fluid Resuscitation

Recognition of fluid creep has driven a large amount of the scientific investigation in the area of acute fluid resuscitation for burn patients. The role of colloids in ameliorating fluid creep is controversial, despite the fact that a fluid-sparing effect of colloids has been recognized for some time. All but one of the available prospective studies using colloids are more than a decade old, and a modern randomized controlled trial (RCT) comparing crystalloids to colloids is long overdue. While urinary output continues to be the main endpoint for fluid titration, there has been a moderate amount of interest in the use of transpulmonary thermodilution to guide fluid resuscitation. The available studies have found that transpulmonary thermodilution has had an inconsistent effect on limiting fluid resuscitation volumes and improving clinical outcomes. Computerized Decision Support Systems show great promise in optimizing fluid titration and reducing fluid resuscitation volumes, and an RCT comparing Computerized Decision Support Systems with conventional titration approaches will be the important next step. Use of high-dose vitamin C (ascorbic acid) has become a popular approach to limit fluid resuscitation volumes and edema formation, but it has been investigated in only two clinical studies: one a pseudo-randomized prospective study and the other a retrospective study. Improvements in clinical outcome have not been convincingly demonstrated, and concerns persist surrounding the possibility of induction of an osmotic diuresis, leading to intravascular volume depletion. An RCT is urgently required to evaluate high-dose vitamin C as an adjunct to crystalloid resuscitation compared with the use of crystalloids alone.

In-human subject-specific evaluation of a control-theoretic plasma volume regulation model

The goal of this study was to conduct a subject-specific evaluation of a control-theoretic plasma volume regulation model in humans. We employed a set of clinical data collected from nine human subjects receiving fluid bolus with and without co-administration of an inotrope agent, including fluid infusion rate, plasma volume, and urine output. Once fitted to the data associated with each subject, the model accurately reproduced the fractional plasma volume change responses in all subjects: the error between actual versus model-reproduced fractional plasma volume change responses was only 1.4 ± 1.6% and 1.2 ± 0.3% of the average fractional plasma volume change responses in the absence and presence of inotrope co-administration. In addition, the model parameters determined by the subject-specific fitting assumed physiologically plausible values: (i) initial plasma volume was estimated to be 36 ± 11 mL/kg and 37 ± 10 mL/kg in the absence and presence of inotrope infusion, respectively, which was comparable to its actual counterpart of 37 ± 4 mL/kg and 43 ± 6 mL/kg; (ii) volume distribution ratio, specifying the ratio with which the inputted fluid is distributed in the intra- and extra-vascular spaces, was estimated to be 3.5 ± 2.4 and 1.9 ± 0.5 in the absence and presence of inotrope infusion, respectively, which accorded with the experimental observation that inotrope could enhance plasma volume expansion in response to fluid infusion. We concluded that the model was equipped with the ability to reproduce plasma volume response to fluid infusion in humans with physiologically plausible model parameters, and its validity may persist even under co-administration of inotropic agents.

Pediatric burn resuscitation: past, present, and future

Burn injury is a leading cause of unintentional death and injury in children, with the majority being minor (less than 10%). However, a significant number of children sustain burns greater than 15% total body surface area (TBSA), leading to the initiation of the systemic inflammatory response syndrome. These patients require IV fluid resuscitation to prevent burn shock and death. Prompt resuscitation is critical in pediatric patients due to their small circulating blood volumes. Delays in resuscitation can result in increased complications and increased mortality. The basic principles of resuscitation are the same in adults and children, with several key differences. The unique physiologic needs of children must be adequately addressed during resuscitation to optimize outcomes. In this review, we will discuss the history of fluid resuscitation, current resuscitation practices, and future directions of resuscitation for the pediatric burn population.

Resuscitation using less fluid has no negative impact on hydration status in children with moderate sized scalds: a prospective single-centre UK study

BACKGROUND

After a burn, optimal fluid resuscitation is critical for positive patient outcome. Although national guidelines advocate using resuscitation fluids of 4mL per kg body weight and percent body surface area (%BSA) for paediatric burns of >10% BSA, evidence in adults suggest that such volumes lead to over-resuscitation and related complications. Our aim was to investigate whether children managed with biosynthetic dressings (Biobrane™) and reduced fluid volumes remain well hydrated, as determined by clinical and laboratory parameters.

METHODS

At a single UK Burn Centre, children with scalds of 10-19%BSA managed with Biobrane were given 80% maintenance fluids and no formal burn resuscitation (permissive hypovolaemia [PH] group). Urine output (UO), serum sodium, urea, and creatinine were used as 24h markers of hydration and concentrations compared to those in a patient cohort treated within the same centre when traditional resuscitation was used (TR group).

RESULTS

Serum sodium concentrations and UO in the PH group were similar to those in the TR group (median sodium: PH=136, TR=136, P=1.00; median UO: PH=1.5, TR=1.8, P=0.25). Urea concentrations were lower and creatinine concentrations higher in the TR group compared to the PH group (median urea: PH=3.2, TR=2.3, P=0.04; median creatinine: PH=21, TR=30, P<0.001). A higher proportion of TR patients than PH patients fell outside the reference ranges for urea (61% vs. 23%; P=0.04) and creatinine (44% vs. 8%; P=0.03).

CONCLUSION

Based on markers of hydration, children with moderate-sized scalds managed with Biobrane can be safely managed with less fluid.

Protocolized Resuscitation of Burn Patients

Fluid resuscitation of burn patients is commonly initiated using modified Brooke or Parkland formula. The fluid infusion rate is titrated up or down hourly to maintain adequate urine output and other endpoints. Over-resuscitation leads to morbid complications. Adherence to paper-based protocols, flow sheets, and clinical practice guidelines is associated with decreased fluid resuscitation volumes and complications. Computerized tools assist providers. Although completely autonomous closed-loop control of resuscitation has been demonstrated in animal models of burn shock, the major advantages of open-loop and decision-support systems are identifying trends, enhancing situational awareness, and encouraging burn team communication.

Modeling Fluid Resuscitation by Formulating Infusion Rate and Urine Output in Severe Thermal Burn Adult Patients: A Retrospective Cohort Study

Acute burn injuries are among the most devastating forms of trauma and lead to significant morbidity and mortality. Appropriate fluid resuscitation after severe burn, specifically during the first 48 hours following injury, is considered as the single most important therapeutic intervention in burn treatment. Although many formulas have been developed to estimate the required fluid amount in severe burn patients, many lines of evidence showed that patients still receive far more fluid than formulas recommend. Overresuscitation, which is known as “fluid creep,” has emerged as one of the most important problems during the initial period of burn care. If fluid titration can be personalized and automated during the resuscitation phase, more efficient burn care and outcome will be anticipated. In the present study, a dynamic urine output based infusion rate prediction model was developed and validated during the initial 48 hours in severe thermal burn adult patients. The experimental results demonstrated that the developed dynamic fluid resuscitation model might significantly reduce the total fluid volume by accurately predicting hourly urine output and has the potential to aid fluid administration in severe burn patients.

Principles of pharmacologic hemodynamic management and closed-loop systems

Every day, physicians in critical-care settings are challenged with the hemodynamic management of patients with severe cardiovascular derangements. There is a potential role for closed-loop (automated) systems to assist clinicians in managing these patients and growing interest in the possible applications. In this review, we discuss the basic principles of critical-care hemodynamic management and the closed-loop systems that have been developed to help in this setting.

Innovative designs for the smart ICU: Part 3: Advanced ICU informatics

This third and final installment of this series on innovative designs for the smart ICU addresses the steps involved in conceptualizing, actualizing, using, and maintaining the advanced ICU informatics infrastructure and systems. The smart ICU comprehensively and electronically integrates the patient in the ICU with all aspects of care, displays data in a variety of formats, converts data to actionable information, uses data proactively to enhance patient safety, and monitors the ICU environment to facilitate patient care and ICU management. The keys to success in this complex informatics design process include an understanding of advanced informatics concepts, sophisticated planning, installation of a robust infrastructure capable of both connectivity and interoperability, and implementation of middleware solutions that provide value. Although new technologies commonly appear compelling, they are also complicated and challenging to incorporate within existing or evolving hospital informatics systems. Therefore, careful analysis, deliberate testing, and a phased approach to the implementation of innovative technologies are necessary to achieve the multilevel solutions of the smart ICU.

Impact of reduced resuscitation fluid on outcomes of children with 10-20% body surface area scalds

'Permissive hypovolaemia' fluid regimes in adult burn care are suggested to improve outcomes. Effects in paediatric burn care are less well understood. In a retrospective audit, outcomes of children from the South West Children's Burn Centre (SWCBC) less than 16 years of age with scalds of 10-20% burn surface area (BSA) managed with a reduced volume fluid resuscitation regime (post-2007) were compared to (a) an historical local protocol (pre-2007) and (b) current regimes in burn services across England and Wales (E&W). Outcomes included length of stay per percent burn surface area (LOS/%BSA), skin graft requirement and re-admission rates. 92 SWCBC patients and 475 patients treated in 15 other E&W burn services were included. Median LOS/%BSA for patients managed with the reduced fluid regime was 0.27 days: significantly less than pre-2007 and other E&W burn services (0.54 days, 0.50 days, p<0.001). Skin grafting to achieve healing reduced post-2007 compared to pre-2007 and remains comparable with other E&W services. Re-admission rates were comparable between all groups. A reduced fluid regime has significantly shortened LOS/%BSA without compromising burn depth as measured by skin grafting to achieve healing. A prospective trial comparing permissive hypovolaemia to current regimes for moderate paediatric scald injuries would help clarify.

Optimal management of the critically ill: anaesthesia, monitoring, data capture, and point-of-care technological practices in ovine models of critical care

Animal models of critical illness are vital in biomedical research. They provide possibilities for the investigation of pathophysiological processes that may not otherwise be possible in humans. In order to be clinically applicable, the model should simulate the critical care situation realistically, including anaesthesia, monitoring, sampling, utilising appropriate personnel skill mix, and therapeutic interventions. There are limited data documenting the constitution of ideal technologically advanced large animal critical care practices and all the processes of the animal model. In this paper, we describe the procedure of animal preparation, anaesthesia induction and maintenance, physiologic monitoring, data capture, point-of-care technology, and animal aftercare that has been successfully used to study several novel ovine models of critical illness. The relevant investigations are on respiratory failure due to smoke inhalation, transfusion related acute lung injury, endotoxin-induced proteogenomic alterations, haemorrhagic shock, septic shock, brain death, cerebral microcirculation, and artificial heart studies. We have demonstrated the functionality of monitoring practices during anaesthesia required to provide a platform for undertaking systematic investigations in complex ovine models of critical illness.

Closed-loop fluid resuscitation: robustness against weight and cardiac contractility variations

BACKGROUND

Surgical patients present with a wide variety of body sizes and blood volumes, have large differences in baseline volume status, and may exhibit significant differences in cardiac function. Any closed-loop fluid administration system must be robust against these differences. In the current study, we tested the stability and robustness of the closed-loop fluid administration system against the confounders of body size, starting volume status, and cardiac contractility using control engineering methodology.

METHODS

Using an independently developed previously published hemodynamic simulation model that includes blood volumes and cardiac contractility, we ran a Monte-Carlo simulation series with variation in starting blood volume and body weight (phase 1, weight 35-100 kg), and starting blood volume and cardiac contractility (phase 2, contractility from 1500 [severe heart failure] to 6000 [hyperdynamic]). The performance of the controller in resuscitating to the target set point was evaluated in terms of milliliters of blood volume error from optimal, with <250 mL of error defined as "successful."

RESULTS

One thousand simulations were run for each of the 2 phases of the study. The phase 1 mean blood volume error ± SD from optimal was 25 ± 59 mL. The phase 2 mean blood volume error from optimal was -60 ± 89 mL. The lower 95% Clopper-Pearson binomial confidence interval for resuscitation to within 250 mL of optimal blood volume for phase 1 and 2 was 99.6% and 97.1%, respectively.

CONCLUSION

The results indicate that the controller is highly effective in targeting optimal blood and stroke volumes, regardless of weight, contractility or starting blood volume.

Optimized fluid management improves outcomes of pediatric burn patients

BACKGROUND

One of the major determinants for survival of severely burned patients is appropriate fluid resuscitation. At present, fluid resuscitation is calculated based on body weight or body surface area, burn size, and urinary output. However, recent evidence suggests that fluid calculation is inadequate and that over- and under-resuscitations are associated with increased morbidity and mortality. We hypothesize that optimizing fluid administration during the critical initial phase using a transcardiopulmonary thermodilution monitoring device (pulse contour cardiac output [PiCCO]; Pulsion Medical Systems, Munich, Germany) would have beneficial effects on the outcome of burned patients.

METHODS

A cohort of 76 severely burned pediatric patients with burns over 30% of the total body surface area who received adjusted fluid resuscitation using the PiCCO system were compared with 76 conventionally monitored patients (C). Clinical hemodynamic measurements, organ function (DENVER2 score), and biomarkers were recorded prospectively for the first 20d after burn injury.

RESULTS

Both cohorts were similar in demographic and injury characteristics. Patients in the PiCCO group received significantly less fluids (P<0.05) with similar urinary output, resulting in a significantly lower positive fluid balance (P<0.05). The central venous pressure in the PiCCO group was maintained in a more controlled range (P<0.05), associated with a significantly lower heart rate and significantly lower incidence of cardiac and renal failure (P<0.05).

CONCLUSIONS

Fluid resuscitation guided by transcardiopulmonary thermodilution during hospitalization represents an effective adjunct and is associated with beneficial effects on postburn morbidity.

Review article: closed-loop systems in anesthesia: is there a potential for closed-loop fluid management and hemodynamic optimization?

Closed-loop (automated) controllers are encountered in all aspects of modern life in applications ranging from air-conditioning to spaceflight. Although these systems are virtually ubiquitous, they are infrequently used in anesthesiology because of the complexity of physiologic systems and the difficulty in obtaining reliable and valid feedback data from the patient. Despite these challenges, closed-loop systems are being increasingly studied and improved for medical use. Two recent developments have made fluid administration a candidate for closed-loop control. First, the further description and development of dynamic predictors of fluid responsiveness provides a strong parameter for use as a control variable to guide fluid administration. Second, rapid advances in noninvasive monitoring of cardiac output and other hemodynamic variables make goal-directed therapy applicable for a wide range of patients in a variety of clinical care settings. In this article, we review the history of closed-loop controllers in clinical care, discuss the current understanding and limitations of the dynamic predictors of fluid responsiveness, and examine how these variables might be incorporated into a closed-loop fluid administration system.

Resuscitation after severe burn injury using high-dose ascorbic acid: a retrospective review

Resuscitation of burn victims with high-dose ascorbic acid (vitamin C [VC]) was reported in Japan in the year 2000. Benefits of VC include reduction in fluid requirements, resulting in less tissue edema and body weight gain. In turn, these patients suffer less respiratory impairment and reduced requirement for mechanical ventilation. Despite these results, few burn centers resuscitate patients with VC in fear that it may increase the risk of renal failure. A retrospective review of 40 patients with greater than 20% TBSA between 2007 and 2009 was performed. Patients were divided into two groups: one received only lactated Ringer's (LR) solution and another received LR solution plus 66 mg/kg/hr VC. Both groups were resuscitated with the Parkland formula to maintain stable hemodynamics and adequate urine output (>0.5 ml/kg/hr). Patients with >10-hour delay in transfer to the burn center were excluded. Data collected included age, gender, weight, %TBSA, fluid administered in the first 24 hours, urine output in the first 24 hours, and Acute Physiology and Chronic Health Evaluation II score. PaO2 in millimeters mercury:%FIO2 ratio and positive end-expiratory pressure were measured at 12-hour intervals, and hematocrit was measured at 6-hour intervals. Comorbidities, mortality, pneumonia, fasciotomies, and renal failure were also noted. After 7 patients were excluded, 17 patients were included in the VC group and 16 in the LR group. VC and LR were matched for age (42 ± 16 years vs 50 ± 20 years, P = .2), burn size (45 ± 21%TBSA vs 39 ± 15%TBSA, P = .45), Acute Physiology and Chronic Health Evaluation II (17 ± 7 vs 18 ± 8, P = .8), and gender. Fluid requirements in the first 24 hours were 5.3 ± 1 ml/kg/%TBSA for VC and 7.1 ± 1 ml/kg/%TBSA for LR (P < .05). Urine output was 1.5 ± 0.4 ml/kg/hr for VC and 1 ± 0.5 ml/kg/hr for LR (P < .05). Vasopressors were needed in four VC patients and nine LR patients (P = .07). VC patients required vasopressors to maintain mean arterial pressure for a mean of 6 hours, but LR needed vasopressors for 11 hours (P = .2). No significant differences in PaO2 in millimeters mercury:%FIO2 ratio, positive end-expiratory pressure, frequency of pneumonia, renal failure, or inhalation injury were found. VC group had four mortalities, and LR group had three mortalities (P = 1). VC is associated with a decrease in fluid requirements and an increase in urine output during resuscitation after thermal injury. Although this study did not find a difference in outcomes with VC administration, it demonstrates that VC can be safely used without an increased risk of renal failure. The effects of VC should be further studied in a large-scale, prospective, randomized trial.

Burn resuscitation: the results of the ISBI/ABA survey

INTRODUCTION

There are valid concerns that burn shock resuscitation is inadequate; a tendency to over-resuscitate the patient seems to exist which may increase complications such as compartment syndrome. The purpose of this study was to survey members of the ISBI and ABA to determine current practices of burn resuscitation.

METHODS

A survey asking for practices of burn shock resuscitation was provided to all participants of a recent ABA meeting. Around the same time, the survey was sent to all members of the ISBI through the internet. The results of the 101 respondents (ABA--59, ISBI--42, approximately a 15% response rate) are described.

RESULTS

Surveys were returned from all the continents except Africa. Respondents included directors (48%), staff physicians (19%), nurses (23%) and others. Most programs admitted adults (87%) and children (75%) with a mean of 289 admissions per year. The cut off to initiate resuscitation was 15% TBSA and most preferred peripheral IVs (70%) and central lines (47.5%). The Parkland formula was preferred (69.3%) while others were used: Brooke--6.9%, Galveston--8.9%, Warden--5.9%, and colloid 11.9%. Lactated Ringer's (LR) was the preferred solution (91.9%), followed by normal saline--5%, hypertonic saline--4%, albumin--20.8%, FFP--13.9%, and LR/NaHCO(3)--12.9%. Approximately half (49.5%) added colloid before 24h. Urine output is the major indicator of success (94.9%) while 22.7% use other monitors. Most (88.8%) feel their protocols work well, with 69.8% feel that it provides the right amount of fluid (24%--too much, 7%--too little). Despite this feeling, they still feel that they give more fluid than the formula in 55.1%, less than formula in 12.4% and the right amount in 32.6%. Approximately 1/3 use an oral resuscitation formula and 81.8% feel that an oral formula works for burns<15% TBSA.

CONCLUSION

Large variations exist in resuscitation protocols but the Parkland formula using LR is still the dominant method. Most feel that their resuscitation protocol works well.

Fluid resuscitation for major burn patients with the TMMU protocol

BACKGROUND

Fluid resuscitation is one of the critical treatments for the major burn patient in the early phases after injury. We evaluated the practice of fluid resuscitation for severely burned patients with the Third Military Medical University (TMMU) protocol, which is most widely used in many regions of China.

METHODS

Patients with major burns (>30% total body surface area (TBSA)) presenting to Southwest Hospital, Third Military Medical University, between January 2005 and October 2007, were included in this study. Fluid resuscitation was initiated by the TMMU protocol.

RESULTS

A total of 71 patients were (46 adults and 25 children) included in this study. All patients survived the first 48 h after injury smoothly and none developed abdominal compartment syndrome or other recognised complications associated with fluid resuscitation. The average quantity of fluid infused was 3.3-61.33% more than that calculated based on the TMMU protocol in both adult and paediatric groups. The average urine output during the first 24h after injury was about 1.2 ml per kg body weight per hour in the two groups, but reached 1.2 ml and 1.7 ml during the second 24h in adult and pediatric groups, respectively.

CONCLUSION

This study indicates that the TMMU protocol for fluid resuscitation is a feasible option for burn patients. Individualised resuscitation - guided by the physiological response to fluid administration - is still important as in other protocols.

Modern trends in fluid therapy for burns

The majority of burn centres use the crystalloid-based Parkland formula to guide fluid therapy, but patients actually receive far more fluid than the formula predicts. Resuscitation with large volumes of crystalloid has numerous adverse consequences, including worsening of burn oedema, conversion of superficial into deep burns, and compartment syndromes. Resuscitation fluids influence the inflammatory response to burns in different ways and it may be possible, therefore to affect this response using the appropriate fluid, at the appropriate time. Starches are effective volume expanders and early use of newer formulations may limit resuscitation requirements and burn oedema by reducing inflammation and capillary leak. Advanced endpoint monitoring may guide clinicians in when to 'turn off' aggressive fluid therapy and therefore avoid the problems of over-resuscitation.

Maintaining the continuum of en route care

BACKGROUND

As life-sustaining and life-preserving surgical capability is moved far forward, it creates the opportunity to salvage casualties who may have otherwise died of their wounds. The remarkable capabilities and effectiveness of the small, austere surgical resuscitation teams (mobile forward surgical team, flying ambulance surgical trauma, forward resuscitative surgery system teams) has been amply demonstrated during the recent conflicts of Operation Iraqi Freedom and Operation Enduring Freedom.

DISCUSSION

The life-saving capability of far-forward surgery creates the need for a new and unique capability, which is the cornerstone of the en route care continuum, namely, the ability to move stabilized, but not necessarily stable, patients. The current system of en route care serves as a primary and indispensable portion of the continuum of critical care.

SUMMARY

The scope of this article describes the origins, composition, equipment sets, medical considerations, and future directions of the en route care support process and the U.S. Air Force Critical Care Aeromedical Transport Teams.

Burn resuscitation

Current guidelines outlining the resuscitation of severely burned patients, in the United States, were developed over 30 years ago. Unfortunately, clinical burn resuscitation has not advanced significantly since that time despite ongoing research efforts. Many formulas exist and have been developed with the intention of providing appropriate, more precise fluid resuscitation with decreased morbidity as compared to the current standards, such as the Parkland and modified Brooke formulas. The aim of this review was to outline the evolution of burn resuscitation, while closely analyzing current worldwide guidelines, adjuncts to resuscitation, as well as addressing future goals.

Closed-loop strategies for patient care systems

Military operations, mass casualty events, and remote work sites present unique challenges to providers of immediate medical care, who may lack the necessary skills for optimal clinical management. Moreover, the number of patients in these scenarios may overwhelm available health care resources. Recent applications of closed-loop control (CLC) techniques to critical care medicine may offer possible solutions for such environments. Here, feedback of a monitored variable or group of variables is used to control the state or output of a dynamic system. Some potential advantages of CLC in patient management include limiting task saturation when there is simultaneous demand for cognitive and active clinical intervention, improving quality of care through optimization of the titration of medications, conserving limited consumable supplies, preventing secondary insults in traumatic brain injury, shortening the duration of mechanical ventilation, and achieving appropriate goal-directed resuscitation. The uses of CLC systems in critical care medicine have been increasingly explored across a wide range of therapeutic modalities. This review will provide an overview of control system theory as applied to critical care medicine that must be considered in the design of autonomous CLC systems, and introduce a number of clinical applications under development in the context of deployment of such applications to austere environments.

Closed-loop control of fluid therapy for treatment of hypovolemia

Closed-loop algorithms and resuscitation systems are being developed to control IV infusion rate during early resuscitation of hypovolemia. Although several different physiologic variables have been suggested as an endpoint to guide fluid therapy, blood pressure remains the most used variable for the initial assessment of hemorrhagic shock and the treatment response to volume loading. Closed-loop algorithms use a controller function to alter infusion rate inversely to blood pressure. Studies in hemorrhaged conscious sheep suggest that: (1) a small reduction in target blood pressure can result in a significant reduction in volume requirement; (2) nonlinear algorithms may reduce the risk of increased internal bleeding during resuscitation; (3) algorithm control functions based on proportional-integral, fuzzy logic, or nonlinear decision tables were found to restore and maintain blood pressure equally well. Proportional-integral and fuzzy logic algorithms reduced mean fluid volume requirements compared with the nonlinear decision table; and (4) several algorithms have been constructed to the specific mechanism of injury and the volume expansion properties of different fluids. Closed-loop systems are undergoing translation from animal to patient studies. Future smart resuscitation systems will benefit from new noninvasive technologies for monitoring blood pressure and the development of computer controlled high flow intravenous pumps.

[How the drug allergy risk in the intensive care software is considered? About a comparative study]

The aim of this study was to evaluate the way the drug allergy risk was considered in five intensive care software available for the French market. It is an observational study conducted by a survey with the five firms asked during the 26th International Symposium on Intensive Care and Emergency Medicine in Brussels (March 2006). The drug allergic risk is documented to various degrees among the software selections. However, no software proposes an alternative or blocking of the prescription in case of allergy to a drug.

Advances in burn care

PURPOSE OF REVIEW

This article reviews and critiques new developments in the critical care of burn patients.

RECENT FINDINGS

The practice of restrictive transfusion is slowly gaining traction. Abdominal compartment syndrome is associated with resuscitation volumes of 300 ml/kg per 24 h, and percutaneous decompression may be a treatment option. Adrenal insufficiency is common, but whom and when to treat are unclear. Imaging or noninvasive monitoring may confirm renal perfusion before urine output, and the concept of permissive hypovolemia should be explored. There is progress in the laboratory in smoke inhalation and myocardial depression, but no human translation. Antibiotic pharmacokinetics in large burns are unpredictable, and so aminoglycosides (measurable concentrations) are not obsolete. Selective digestive decontamination remains controversial. Nutritional predictions by formula are inaccurate. Oxandrolone is safe and effective in promoting anabolism in large burns. Deep venous thrombosis prophylaxis remains guided only by expert opinion. Females fare worse than male patients after burns.

SUMMARY

The application of the scientific method to burn care is improving slowly. Randomized controlled trials are becoming more common. There is a need for translation of excellent animal work to the human arena.

The phenomenon of "fluid creep" in acute burn resuscitation

Several reports have documented that modern burn patients receive far more resuscitation fluid than predicted by the Parkland formula-a phenomenon termed "fluid creep." This article reviews the incidence, consequences, and possible etiologies of fluid creep in modern practice and uses this information to propose some therapeutic strategies to reduce or eliminate excessive fluid resuscitation in burn care. A literature review was performed of historical references that form the foundation of modern fluid resuscitation, as well as reports of fluid creep and its consequences. The original Parkland formula required a 24-hour volume of 4 ml/kg/%TBSA lactated Ringer's solution followed by an infusion of 0.3-0.5 ml/kg/ %TBSA plasma. Modern iterations of this formula have omitted the colloid bolus. Numerous exceptions to the formula have been noted, most consistently patients with inhalation injuries. In contrast, recent reports document greatly increased fluid requirements in unselected patients, which seems to consist largely of progressive edema formation in unburned areas, increasing after the first 8 hours post-burn. This has been linked to occurrence of the abdominal compartment syndrome and other serious complications. Strategies to reduce fluid creep include the avoidance of early overresuscitation, use of colloid as a routine component of resuscitation or for "rescue," and adherence to protocols for fluid resuscitation. Fluid creep is a significant problem in modern burn care. Review of original investigations of burn shock, coupled with modern reports of fluid creep, suggests several mechanisms by which this problem can be controlled. Prospective trials of these therapies are needed to confirm their effectiveness.