The arterial blood pressure associated with terminal cardiovascular collapse in critically ill patients: a retrospective cohort study

Permissive Hypotension in a Patient with Severe Hypernatremia: A Case Report

Introduction

Severe hypernatremia is a critical situation, and when coupled with intravascular depletion and hypotension can create a treatment dilemma.

Case Report

We present the case of a medically complex patient who had gradually worsening alteration of mental status and mean arterial pressures in the 50s on presentation to the emergency department.

Conclusion

Final diagnoses included severe hypernatremia and hypovolemic shock secondary to poor oral intake. We used judicious fluid repletion with gradual improvement in sodium levels and permissive hypotension to avoid rapid osmotic shifts. Balancing reperfusion and the risk for osmotic effects of aggressive fluid resuscitation can be a challenging situation for the multidisciplinary team.

Recovery and Survival of Patients After Out-of-Hospital Cardiac Arrest: A Literature Review Showcasing the Big Picture of Intensive Care Unit-Related Factors

As an important public health issue, out-of-hospital cardiac arrest (OHCA) requires several stages of high quality medical care, both on-field and after hospital admission. Post-cardiac arrest shock can lead to severe neurological injury, resulting in poor recovery outcome and increased risk of death. These characteristics make this condition one of the most important issues to deal with in post-OHCA patients hospitalized in intensive care units (ICUs). Also, the majority of initial post-resuscitation survivors have underlying coronary diseases making revascularization procedure another crucial step in early management of these patients. Besides keeping myocardial blood flow at a satisfactory level, other tissues must not be neglected as well, and maintaining mean arterial pressure within optimal range is also preferable. All these procedures can be simplified to a certain level along with using targeted temperature management methods in order to decrease metabolic demands in ICU-hospitalized post-OHCA patients. Additionally, withdrawal of life-sustaining therapy as a controversial ethical topic is under constant re-evaluation due to its possible influence on overall mortality rates in patients initially surviving OHCA. Focusing on all of these important points in process of managing ICU patients is an imperative towards better survival and complete recovery rates.

In Vivo Laser-Induced Vasoactive Microenvironmental Setting via a Stimuli-Responsive Microstructured Depot

A stimuli-responsive polymeric three-dimensional microstructured film (PTMF) is a 3D structure with an array of sealed chambers on its external surface. In this work, we demonstrate the use of PTMF as a laser-triggered stimulus-response system for local in vivo targeted blood vessels stimulation by vasoactive substances. The native vascular networks of the mouse mesentery were used as model tissues. Epinephrine and KCl were used as vasoactive agents that were sealed into individual chambers upon precipitation in the amount of pictograms. We demonstrated the method for non-damaged one-by-one chamber activation using a focused 532 nm laser light passed through biological tissues. To avoid laser-induced photothermal damage to biological tissues, the PTMF was functionalized with Nile Red dye, which effectively absorbs laser light. Chemically stimulated blood vessel fluctuations were analyzed using digital image processing methods. Hemodynamics changes were measured and visualized using the particle image velocimetry approach.

Management of Hemorrhagic Shock: Physiology Approach, Timing and Strategies

Hemorrhagic shock (HS) management is based on a timely, rapid, definitive source control of bleeding/s and on blood loss replacement. Stopping the hemorrhage from progressing from any named and visible vessel is the main stem fundamental praxis of efficacy and effectiveness and an essential, obligatory, life-saving step. Blood loss replacement serves the purpose of preventing ischemia/reperfusion toxemia and optimizing tissue oxygenation and microcirculation dynamics. The "physiological classification of HS" dictates the timely management and suits the 'titrated hypotensive resuscitation' tactics and the 'damage control surgery' strategy. In any hypotensive but not yet critical shock, the body's response to a fluid load test determines the cut-off point between compensation and progression between the time for adopting conservative treatment and preparing for surgery or rushing to the theater for rapid bleeding source control. Up to 20% of the total blood volume is given to refill the unstressed venous return volume. In any critical level of shock where, ab initio, the patient manifests signs indicating critical physiology and impending cardiac arrest or cardiovascular accident, the balance between the life-saving reflexes stretched to the maximum and the insufficient distal perfusion (blood, oxygen, and substrates) remains in a liable and delicate equilibrium, susceptible to any minimal change or interfering variable. In a cardiac arrest by exsanguination, the core of the physiological issue remains the rapid restoration of a sufficient venous return, allowing the heart to pump it back into systemic circulation either by open massage via sternotomy or anterolateral thoracotomy or spontaneously after aorta clamping in the chest or in the abdomen at the epigastrium under extracorporeal resuscitation and induced hypothermia. This is the only way to prevent ischemic damage to the brain and the heart. This is accomplishable rapidly and efficiently only by a direct approach, which is a crush laparotomy if the bleeding is coming from an abdominal +/- lower limb site or rapid sternotomy/anterolateral thoracotomy if the bleeding is coming from a chest +/- upper limbs site. Without first stopping the bleeding and refilling the heart, any further exercise is doomed to failure. Direct source control via laparotomy/thoracotomy, with the concomitant or soon following venous refilling, are the two essential, initial life-saving steps.

Outcomes of Pediatric Patients with Sepsis Managed on Extracorporeal Membrane Oxygenation: An Analysis of the Extracorporeal Life Support Organization Registry

Extracorporeal membrane oxygenation (ECMO) support is increasingly used for refractory septic shock. There is a lack of data on the outcomes of children requiring ECMO support for refractory septic shock. Our study objective was to describe the variables associated with survival, risk factors for mortality, and outcomes of children requiring ECMO support for refractory shock. This was retrospective registry study of 340 international centers contributing data to the ELSO Registry, analyzing children <18 years who received ECMO with septic shock, severe sepsis, sepsis, systemic inflammatory response syndrome, toxic shock syndrome, shock associated with infection, and septicemia from any organism from 1990 to 2015. Outcomes were analyzed by categorizing the data into survivors and nonsurvivors. Logistic regression models were used to describe the association of dependent variable and multiple independent variables. A total of 1,928 patients were identified who met the inclusion criteria. In total, 744 (38.5%) of the cohort survived. Survivors in this cohort tend to have a longer duration of ECMO (230 vs. 201 hours, p = 0.005) and shorter time from intubation to ECMO cannulation (87 vs. 116 hours, p = 0.0033) when compared to nonsurvivors. Survivors were also noted to have higher pH, higher serum bicarbonate, higher saturations, and higher systolic, diastolic, and mean arterial pressures compared to nonsurvivors. These results suggest that early initiation of ECMO therapy for refractory sepsis is associated with better patient outcomes. ECMO is unlikely to recover patients once circulatory and metabolic collapse has developed.

Development and Internal Validation of a New Prognostic Model Powered to Predict 28-Day All-Cause Mortality in ICU COVID-19 Patients-The COVID-SOFA Score

Background: The sequential organ failure assessment (SOFA) score has poor discriminative ability for death in severely or critically ill patients with Coronavirus disease 2019 (COVID-19) requiring intensive care unit (ICU) admission. Our aim was to create a new score powered to predict 28-day mortality. Methods: Retrospective, observational, bicentric cohort study including 425 patients with COVID-19 pneumonia, acute respiratory failure and SOFA score ≥ 2 requiring ICU admission for ≥72 h. Factors with independent predictive value for 28-day mortality were identified after stepwise Cox proportional hazards (PH) regression. Based on the regression coefficients, an equation was computed representing the COVID-SOFA score. Discriminative ability was tested using receiver operating characteristic (ROC) analysis, concordance statistics and precision-recall curves. This score was internally validated. Results: Median (Q1−Q3) age for the whole sample was 64 [55−72], with 290 (68.2%) of patients being male. The 28-day mortality was 54.58%. After stepwise Cox PH regression, age, neutrophil-to-lymphocyte ratio (NLR) and SOFA score remained in the final model. The following equation was computed: COVID-SOFA score = 10 × [0.037 × Age + 0.347 × ln(NLR) + 0.16 × SOFA]. Harrell’s C-index for the COVID-SOFA score was higher than the SOFA score alone for 28-day mortality (0.697 [95% CI; 0.662−0.731] versus 0.639 [95% CI: 0.605−0.672]). Subsequently, the prediction error rate was improved up to 16.06%. Area under the ROC (AUROC) was significantly higher for the COVID-SOFA score compared with the SOFA score for 28-day mortality: 0.796 [95% CI: 0.755−0.833] versus 0.699 [95% CI: 0.653−0.742, p < 0.001]. Better predictive value was observed with repeated measurement at 48 h after ICU admission. Conclusions: The COVID-SOFA score is better than the SOFA score alone for 28-day mortality prediction. Improvement in predictive value seen with measurements at 48 h after ICU admission suggests that the COVID-SOFA score can be used in a repetitive manner. External validation is required to support these results.

A Review of Push-Dose Vasopressors in the Peri-operative and Critical Care Setting

During hospitalization, the risk of hypotension and associated sequelae remain important considerations for patient outcomes. The use of push-dose vasopressors (PDP) outside of the operating room has increased in recent years to combat the negative effects of hypotension. This narrative review evaluates the utility of PDP in its traditional perioperative setting as well as in areas of increasing use such as the emergency department and intensive care unit. Articles evaluating PDP highlight successful increases in blood pressure with all agents but differ in rates of adverse events and most lack direct comparison of PDP agents in regard to safety and efficacy. Agents utilized as PDP, including epinephrine, phenylephrine, norepinephrine, vasopressin, and ephedrine vary in mechanism of action, onset of action, and duration of action. These variations in pharmacology along with published literature may lead to differences in the preferred PDP for various clinical scenarios. Many adverse events associated with PDP have been due to dosing errors highlighting the importance of education surrounding the use of these agents. Additional research is necessary to further elucidate the risks and benefits of PDP in clinical practice, and to determine which PDP is truly preferred. Careful consideration should be given when determining the appropriateness of this administration method of vasopressors in various clinical scenarios.

Regional perfusion monitoring in shock

PURPOSE OF REVIEW

Despite restoration of adequate systemic blood flow in patients with shock, single organs may remain hypoperfused. In this review, we summarize the results of a literature research on methods to monitor single organ perfusion in shock. We focused on methods to measure heart, brain, kidney, and/or visceral organ perfusion. Furthermore, only methods that can be used in real-time and at the bedside were included.

RECENT FINDINGS

We identified studies on physical examination techniques, electrocardiography, echocardiography, contrast-enhanced ultrasound, near-infrared spectroscopy, and Doppler sonography to assess single organ perfusion.

SUMMARY

Physical examination techniques have a reasonable negative predictive value to exclude single organ hypoperfusion but are nonspecific to detect it. Technical methods to indirectly measure myocardial perfusion include ECG and echocardiography. Contrast-enhanced ultrasound can quantify myocardial perfusion but has so far only been used to detect regional myocardial hypoperfusion. Near-infrared spectroscopy and transcranial Doppler sonography can be used to assess cerebral perfusion and determine autoregulation thresholds of the brain. Both Doppler and contrast-enhanced ultrasound techniques are novel methods to evaluate renal and visceral organ perfusion. A key limitation of most techniques is the inability to determine adequacy of organ blood flow to meet the organs' metabolic demands.

[Diagnosing acute organ ischemia : A practical guide for the emergency and intensive care physician]

Ischemia refers to a reduction or interruption of the blood flow to one or more organs. Early recognition of shock, a global ischemic state of the body, is of key importance in emergency and intensive care medicine. The physical examination and point-of-care laboratory diagnostics (i.e. lactate, base deficit, central/mixed venous oxygen saturation, venous-arterial carbon dioxide partial tension) are the methods of choice to diagnose shock in clinical practice. Importantly, a state of shock can also be present in patients with normo- or hypertensive arterial blood pressures. In shock, hypoperfusion of vital and visceral organs occurs. In the second part of this article, physical examination techniques, laboratory and diagnostic methods to detect shock-related hypoperfusion of the brain, heart, kidney and gastrointestinal tract are reviewed.

From a pressure-guided to a perfusion-centered resuscitation strategy in septic shock: Critical literature review and illustrative case

PURPOSE

To support a paradigm shift in the management of septic shock from pressure-guided to perfusion-centered, expected to improve outcome while reducing adverse effects from vasopressor therapy and aggressive fluid resuscitation.

MATERIAL AND METHODS

Critical review of the literature cited in support of vasopressor use to achieve a predefined mean arterial pressure (MAP) of 65 mmHg and review of pertinent clinical trials and studies enabling deeper understanding of the hemodynamic pathophysiology supportive of a perfusion-centered approach, accompanied by an illustrative case.

RESULTS

Review of the literature cited by the Surviving Sepsis Campaign revealed lack of controlled clinical trials supporting outcome benefits from vasopressors. Additional literature review revealed adverse effects associated with vasopressors and worsened outcome in some studies. Vasopressors increase MAP primarily by peripheral vasoconstriction and in occasions by a modest increase in cardiac output when using norepinephrine. Thus, achieving the recommended MAP of 65 mmHg using vasopressors should not be presumed indicative that organ perfusion has been restored. It may instead create a false sense of hemodynamic stability hampering shock resolution.

CONCLUSIONS

We propose focusing the hemodynamic management of septic shock on reversing organ hypoperfusion instead of attaining a predefined MAP target as the key strategy for improving outcome.

ECMO with vasopressor use during early endotoxic shock: Can it improve circulatory support and regional microcirculatory blood flow?

Introduction

While extracorporeal membrane oxygenation (ECMO) is effective in preventing further hypoxemia and maintains blood flow in endotoxin-induced shock, ECMO alone does not reverse the hypotension. In this study, we tested whether concurrent vasopressor use with ECMO would provide increased circulatory support and blood flow, and characterized regional blood flow distribution to vital organs.

Methods

Endotoxic shock was induced in piglets to achieve a 30% decrease in mean arterial pressure (MAP). Measurements of untreated pigs were compared to pigs treated with ECMO alone or ECMO and vasopressors.

Results

ECMO provided cardiac support during vasodilatory endotoxic shock and improved oxygen delivery, but vasopressor therapy was required to return MAP to normotensive levels. Increased blood pressure with vasopressors did not alter oxygen consumption or extraction compared to ECMO alone. Regional microcirculatory blood flow (RBF) to the brain, kidney, and liver were maintained or increased during ECMO with and without vasopressors.

Conclusion

ECMO support and concurrent vasopressor use improve regional blood flow and oxygen delivery even in the absence of full blood pressure restoration. Vasopressor-induced selective distribution of blood flow to vital organs is retained when vasopressors are administered with ECMO.

Human Errors and Adverse Hemodynamic Events Related to "Push Dose Pressors" in the Emergency Department

BACKGROUND

Though the use of small bolus doses of vasopressors, termed "push dose pressors," has become common in emergency medicine, data examining this practice are scant. Push dose pressors frequently involve bedside dilution, which may result in errors and adverse events. The objective of this study was to assess for instances of human error and adverse hemodynamic events during push dose pressor use in the emergency department.

METHODS

This was a structured chart and video review of all patients age ≥ 16 years undergoing resuscitation and receiving push dose pressors from a single center from January 2010 to November 2017. Push dose pressors were defined as intended intravenous boluses of phenylephrine (any dose) or epinephrine (≤ 100 mcg).

RESULTS

A total of 249 patients were analyzed. Median age was 60 years (range, 16-97), 58% were male, 49% survived to discharge. Median initial epinephrine dose was 20 mcg (n = 139, IQR 10-100, range 1-100); median phenylephrine dose was 100 mcg (n = 110, IQR 100-100, range 25-10,000). Adverse hemodynamic events occurred in 98 patients (39%); 30 in the phenylephrine group (27%; 95% CI, 19-36%), and 68 in the epinephrine group (50%; 95% CI, 41-58%). Human errors were observed in 47 patients (19%), including 7 patients (3%) experiencing dosing errors (all overdoses; range, 2.5- to 100-fold) and 43 patients (17%) with a documentation error. Only one dosing error occurred when a pharmacist was present.

CONCLUSIONS

Human errors and adverse hemodynamic events were common with the use of push dose pressors in the emergency department. Adverse hemodynamic events were more common than in previous studies. Future research should determine if push dose pressors improve outcomes and if so, how to safely implement them into practice.

Targeting low-normal or high-normal mean arterial pressure after cardiac arrest and resuscitation: a randomised pilot trial

PURPOSE

We aimed to determine the feasibility of targeting low-normal or high-normal mean arterial pressure (MAP) after out-of-hospital cardiac arrest (OHCA) and its effect on markers of neurological injury.

METHODS

In the Carbon dioxide, Oxygen and Mean arterial pressure After Cardiac Arrest and REsuscitation (COMACARE) trial, we used a 23 factorial design to randomly assign patients after OHCA and resuscitation to low-normal or high-normal levels of arterial carbon dioxide tension, to normoxia or moderate hyperoxia, and to low-normal or high-normal MAP. In this paper we report the results of the low-normal (65-75 mmHg) vs. high-normal (80-100 mmHg) MAP comparison. The primary outcome was the serum concentration of neuron-specific enolase (NSE) at 48 h after cardiac arrest. The feasibility outcome was the difference in MAP between the groups. Secondary outcomes included S100B protein and cardiac troponin (TnT) concentrations, electroencephalography (EEG) findings, cerebral oxygenation and neurological outcome at 6 months after cardiac arrest.

RESULTS

We recruited 123 patients and included 120 in the final analysis. We found a clear separation in MAP between the groups (p < 0.001). The median (interquartile range) NSE concentration at 48 h was 20.6 µg/L (15.2-34.9 µg/L) in the low-normal MAP group and 22.0 µg/L (13.6-30.9 µg/L) in the high-normal MAP group, p = 0.522. We found no differences in the secondary outcomes.

CONCLUSIONS

Targeting a specific range of MAP was feasible during post-resuscitation intensive care. However, the blood pressure level did not affect the NSE concentration at 48 h after cardiac arrest, nor any secondary outcomes.

Field Expedient Vasopressors During Aeromedical Evacuation: A Case Series from the Puerto Rico Disaster Response

IntroductionEmergency physicians are using bolus-dose vasopressors to temporize hypotensive patients until more definitive blood pressure support can be established. Despite a paucity of clinical outcome data, emergency department applications are expanding into the prehospital setting. This series presents two cases of field expedient vasopressor use by emergency medicine providers for preflight stabilization during aeromedical evacuation to a hospital ship as part of the United States Navy disaster response in Puerto Rico. A critical approach and review of the literature are discussed.Case ReportTwo critically ill patients were managed in an austere environment as a result of the devastation from Hurricane Maria (Yabucoa, Puerto Rico; 2017). They both exhibited signs of respiratory distress, hemodynamic instability, and distributive shock requiring definitive airway management and hemodynamic support prior to aeromedical evacuation.DiscussionThe novel use of field expedient vasopressors prior to induction for rapid sequence intubation was successfully and safely employed in both cases. Both patients had multiple risk factors for peri-induction cardiac arrest given their presenting hemodynamics. Despite their illness severity, both patients were induced, transported, and ultimately admitted to the intensive care unit (ICU) in stable condition following administration of the field expedient vasopressors.Conclusion:Field expedient vasopressors were safely and effectively employed in an austere field environment during a disaster response. This case series contributes to the growing body of literature of safe bolus-dose vasopressor use by emergency physicians to temporize hypotensive patients in resource-constrained situations. HardwickJM, MurnanSD, Morrison-PonceDP, DevlinJJ. Field expedient vasopressors during aeromedical evacuation: a case series from the Puerto Rico disaster response. Prehosp Disaster Med. 2018;33(6):668-672.

Association between Blood Glucose and cardiac Rhythms during pre-hospital care of Trauma Patients - a retrospective Analysis

Background

Deranged glucose metabolism is frequently observed in trauma patients after moderate to severe traumatic injury, but little data is available about pre-hospital blood glucose and its association with various cardiac rhythms and cardiac arrest following trauma.

Methods

We retrospectively investigated adult trauma patients treated by a nationwide helicopter emergency medical service (34 bases) between 2005 and 2013. All patients with recorded initial cardiac rhythms and blood glucose levels were enrolled. Blood glucose concentrations were categorised; descriptive and regression analyses were performed.

Results

In total, 18,879 patients were included, of whom 185 (1.0%) patients died on scene. Patients with tachycardia (≥100/min, 7.0 ± 2.4 mmol/L p < 0.0001), pulseless ventricular tachycardia (9.8 ± 1.8, mmol/L, p = 0.008) and those with ventricular fibrillation (9.0 ± 3.2 mmol/L, p < 0.0001) had significantly higher blood glucose concentrations than did patients with normal sinus rhythm between 61 and 99/min (6.7 ± 2.1 mmol/L). In patients with low (≤2.8 mmol/L, 7/79; 8.9%, p < 0.0001) and high (> 10.0 mmol/L, 70/1271; 5.5%, p < 0.0001) blood glucose concentrations cardiac arrest was more common than in normoglycaemic patients (166/9433, 1.8%). ROSC was more frequently achieved in hyperglycaemic (> 10 mmol/L; 47/69; 68.1%) than in hypoglycaemic (≤4.2 mmol/L; 13/31; 41.9%) trauma patients (p = 0.01).

Conclusions

In adult trauma patients, pre-hospital higher blood glucose levels were related to tachycardic and shockable rhythms. Cardiac arrest was more frequently observed in hypoglycaemic and hyperglycaemic pre-hospital trauma patients. The rate of ROSC rose significantly with rising blood glucose concentration. Blood glucose measurements in addition to common vital parameters (GCS, heart rate, blood pressure, breathing frequency) may help identify patients at risk for cardiopulmonary arrest and dysrhythmias.

Evaluation and Management of Aortic Stenosis for the Emergency Clinician: An Evidence-Based Review of the Literature

INTRODUCTION

Aortic stenosis is a common condition among older adults that can be associated with dangerous outcomes, due to both the disease itself and its influence on other conditions.

OBJECTIVE

This review provides an evidence-based summary of the current emergency department (ED) evaluation and management of aortic stenosis.

DISCUSSION

Aortic stenosis refers to significant narrowing of the aortic valve and can be caused by calcific disease, congenital causes, or rheumatic valvular disease. Symptoms of advanced disease include angina, dyspnea, and syncope. Patients with these symptoms have a much higher mortality rate than asymptomatic patients. Initial evaluation should include an electrocardiogram, complete blood count, basic metabolic profile, coagulation studies, troponin, brain natriuretic peptide, type and screen, and a chest radiograph. Transthoracic echocardiogram is the test of choice, but point-of-care ultrasound has been found to have good accuracy when a formal echocardiogram is not feasible. Initial management should begin with restoring preload and ensuring a normal heart rate, as both bradycardia and tachycardia can lead to clinical decompensation. For patients with high blood pressure and heart failure symptoms, nitrate agents may be reasonable, but hypotension should be avoided. Dobutamine can increase inotropy. For hypotensive patients, vasopressors should be used at the lowest effective dose. The treatment of choice is valve replacement, but extracorporeal membrane oxygenation and percutaneous balloon dilatation of the aortic valve have been described as temporizing measures.

CONCLUSION

Aortic stenosis is an important condition that can lead to dangerous outcomes and requires prompt recognition and disease-specific management in the ED.

Systolic Blood Pressure Threshold for HEMS-Witnessed Arrests

OBJECTIVE

Defining vital sign thresholds has focused on mortality, which may be delayed for hours, days, or weeks after injury. This limits the immediate clinical significance in guiding therapy to avoid arrest. The aim of this study was to identify a systolic blood pressure (SBP) threshold indicating imminent cardiopulmonary arrest.

METHODS

This was a retrospective, observational study analyzing physiological data from air medical patients suffering witnessed arrest. We limited the analysis to a subgroup of adult (> 14 years) patients with hypoperfusion-related arrest. Prearrest SBP values were plotted over time, with arrest defined as "time zero." Multiple linear regression was used to define a best fit curve to identify an inflection point beyond which arrest was imminent.

RESULTS

A total of 53 eligible patients were identified; 33 (62%) were trauma victims. A fifth-degree equation showed appropriate goodness of fit (r = -.66, P < .0001). An inflection point was identified at an SBP of 78 mm Hg, with arrest occurring approximately 3 minutes later.

CONCLUSION

An inflection point below SBP 80 mm Hg was identified, suggesting a predictable physiological pattern for perfusion-related deterioration. This may help guide therapy to reverse deterioration and prevent arrest.

The Compensatory Reserve For Early and Accurate Prediction Of Hemodynamic Compromise: A Review of the Underlying Physiology

Shock is deadly and unpredictable if it is not recognized and treated in early stages of hemorrhage. Unfortunately, measurements of standard vital signs that are displayed on current medical monitors fail to provide accurate or early indicators of shock because of physiological mechanisms that effectively compensate for blood loss. As a result of new insights provided by the latest research on the physiology of shock using human experimental models of controlled hemorrhage, it is now recognized that measurement of the body's reserve to compensate for reduced circulating blood volume is the single most important indicator for early and accurate assessment of shock. We have called this function the "compensatory reserve," which can be accurately assessed by real-time measurements of changes in the features of the arterial waveform. In this paper, the physiology underlying the development and evaluation of a new noninvasive technology that allows for real-time measurement of the compensatory reserve will be reviewed, with its clinical implications for earlier and more accurate prediction of shock.

Fuzzy risk stratification and risk assessment model for clinical monitoring in the ICU

BACKGROUND

The decisions that clinicians make in intensive care units (ICUs) based on monitored parameters reflecting physiological deterioration are of major medical and biomedical engineering interest. These parameters have been investigated and assessed for their usefulness in risk assessment.

METHODS

Totally, 127 ICU adult patients were studied. They were selected from a MIMIC II Waveform Database Matched Subset and had continuous monitoring of heart rate, invasive blood pressure, and oxygen saturation. The monitored data were dimension reduced using deep learning autoencoders and then used to train a support vector machine model (SVM). A combination of methods including fuzzy c-means clustering (FCM), and a random forest (RF) was used to determine the risk levels.

RESULTS

When classifying patients into stable or deteriorating groups the main performance parameter was the receiver operating characteristics (ROC). The area under the ROC (AUROC) was 93.2 (95% CI (92.9-93.4)) with sensitivity and specificity values of 0.80 and 0.89, respectively. The suggested fuzzy risk levels using the combined method of the FCM clustering and RF achieved an accuracy of 1 (0.9999, 1), with both sensitivity and specificity values equal to 1.

CONCLUSIONS

The potential for using models in risk assessment to estimate a patient's physiological status, stable or deteriorating, within 4 h has been demonstrated. The study was based on retrospective analysis and further studies are needed to evaluate the impact on clinical outcomes using this model.

Time delays associated with vasoactive medication preparation and delivery in simulated patients at risk of cardiac arrest

PURPOSE

To compare, quantify, and describe the time-delays associated with four common methods of adrenaline administration in the simulated setting of impending cardiac arrest.

METHODS

Using sham medication and a high-fidelity simulator, experienced Nurses prepared, then delivered, adrenaline by: i) bolus, ii) lower-concentration infusion iii) higher-concentration infusion, and iv) higher-concentration infusion plus carrier-line. We recorded medication preparation and delivery time, plus administration errors and self-reported competence.

RESULTS

Median total delay was i) 120s for bolus (95% CI 112-128s); ii) 179s for lower concentration infusion (95% CI 172-186s); iii) 296s for higher concentration infusion (95% CI 285-307s); and iv) 411s for higher concentration infusion plus carrier line (95% CI 399-423s). Time to prepare/deliver a bolus was less than any infusion (p<0.001). Time to prepare/deliver a lower-concentration infusion was less than either higher-concentration infusion (p<0.001). No substantial equipment failures or medication errors were observed. Participants reported high-competence. The majority of delay was from drug preparation not delivery.

CONCLUSIONS

We highlight potentially dangerous delays with administration of life-saving medications by all four methods. We should prioritize boluses, and focus on improving drug preparation times and human performance, more than drug delivery and equipment.

Bolus dose of epinephrine for refractory post-arrest hypotension

Post-cardiac arrest hypotension is associated with worse outcomes. However, a significant proportion of patients may not be responsive to intravenous (IV) fluids, and vasopressor infusions require significant time to initiate. This case series describes the successful use of a bolus dose of epinephrine to rapidly treat IV fluid refractory hypotension among three patients in the post-arrest period. A bolus dose of epinephrine may be considered as a treatment for post-arrest hypotension that does not respond to IV fluids, but further studies should be performed prior to routine use.

Integrated Compensatory Responses in a Human Model of Hemorrhage

Hemorrhage is the leading cause of trauma-related deaths, partly because early diagnosis of the severity of blood loss is difficult. Assessment of hemorrhaging patients is difficult because current clinical tools provide measures of vital signs that remain stable during the early stages of bleeding due to compensatory mechanisms. Consequently, there is a need to understand and measure the total integration of mechanisms that compensate for reduced circulating blood volume and how they change during ongoing progressive hemorrhage. The body's reserve to compensate for reduced circulating blood volume is called the 'compensatory reserve'. The compensatory reserve can be accurately evaluated with real-time measurements of changes in the features of the arterial waveform measured with the use of a high-powered computer. Lower Body Negative Pressure (LBNP) has been shown to simulate many of the physiological responses in humans associated with hemorrhage, and is used to study the compensatory response to hemorrhage. The purpose of this study is to demonstrate how compensatory reserve is assessed during progressive reductions in central blood volume with LBNP as a simulation of hemorrhage.

Pharmacologic agents for acute hemodynamic instability: recent advances in the management of perioperative shock- a systematic review

Despite the growing body of evidence evaluating the efficacy of vasoactive agents in the management of hemodynamic instability and circulatory shock, it appears no agent is superior. This is becoming increasingly accepted as current guidelines are moving away from detailed algorithms for the management of shock, and instead succinctly state that vasoactive agents should be individualized and guided by invasive hemodynamic monitoring. This extends to the perioperative period, where vasoactive agent selection and use may still be left to the discretion of the treating physician with a goal-directed approach, consisting of close hemodynamic monitoring and administration of the lowest effective dose to achieve the hemodynamic goals. Successful therapy depends on the ability to rapidly diagnose the etiology of circulatory shock and thoroughly understand its pathophysiology as well as the pharmacology of vasoactive agents. This review focuses on the physiology and resuscitation goals in perioperative shock, as well as the pharmacology and recent advances in vasoactive agent use in its management.