Comparison of differences in cohort (forwards) and case control (backwards) methodological approaches for validation of the Hypotension Prediction Index

BACKGROUND

The Hypotension Prediction Index (the index) software is a machine learning algorithm that detects physiological changes that may lead to hypotension. The original validation used a case control (backwards) analysis that has been suggested to be biased. We therefore conducted a cohort (forwards) analysis and compared this to the original validation technique.

METHODS

We conducted a retrospective analysis of data from previously reported studies. All data were analysed identically with 2 different methodologies and receiver operating characteristic curves (ROC) constructed. Both backwards and forwards analyses were performed to examine differences in area under the ROC for HPI and other haemodynamic variables to predict a MAP < 65mmHg for at least 1 minute 5, 10 and 15 minutes in advance.

RESULTS

Two thousand and twenty-two patients were included in the analysis, yielding 4,152,124 measurements taken at 20 second intervals. The area-under-the-curve for the index predicting hypotension analysed by backward and forward methodologies respectively was 0.957 (95% CI, 0.947-0.964) vs 0.923 (95% CI, 0.912-0.933) 5 minutes in advance, 0.933 (95% CI, 0.924-0.942) vs 0.923 (95% CI, 0.911-0.933) 10 minutes in advance , and 0.929 (95% CI, 0.918-0.938) vs. 0.926 (95% CI, 0.914-0.937) 15 minutes in advance. No other variable had an area-under-the-curve > 0.7 except for MAP. Area-under-the-curve using forward analysis for MAP predicting hypotension 5, 10, and 15 minutes in advance was 0.932 (95% CI, 0.920-0.940), 0.929 (95% CI, 0.918-0.938), and 0.932 (95% CI, 0.921-0.940). The R 2 for the variation in the index due to MAP was 0.77.

CONCLUSION

Using an updated methodology, we found the utility of the HPI index to predict future hypotensive events is high, with an area under the receiver-operating-characteristics curve similar to that of the original validation method.

Identification of new drugs to counteract anti-spike IgG-induced hyperinflammation in severe COVID-19

Previously, we and others have shown that SARS-CoV-2 spike-specific IgG antibodies play a major role in disease severity in COVID-19 by triggering macrophage hyperactivation, disrupting endothelial barrier integrity, and inducing thrombus formation. This hyperinflammation is dependent on high levels of anti-spike IgG with aberrant Fc tail glycosylation, leading to Fcγ receptor hyperactivation. For development of immune-regulatory therapeutics, drug specificity is crucial to counteract excessive inflammation whereas simultaneously minimizing the inhibition of antiviral immunity. We here developed an in vitro activation assay to screen for small molecule drugs that specifically counteract antibody-induced pathology. We identified that anti-spike-induced inflammation is specifically blocked by small molecule inhibitors against SYK and PI3K. We identified SYK inhibitor entospletinib as the most promising candidate drug, which also counteracted anti-spike-induced endothelial dysfunction and thrombus formation. Moreover, entospletinib blocked inflammation by different SARS-CoV-2 variants of concern. Combined, these data identify entospletinib as a promising treatment for severe COVID-19.

Ethics in transfusion medicine: Are the intricate layers of ethics all universal? A global view

Ethical principles have been considered, and in several respects regulated, along the entire blood procurement chain from donor motivation to transfusion to the patient. Consent of donors and voluntary non-remunerated donation are fields which have been addressed by codes of ethics and legislation. Caring for donor health is an area of further development of ethical standards. In part, blood products have also become a market, where commercial principles may synergize, but also creating issues in equality and maintaining human dignity that challenge societal solutions. At the bedside, the main global challenge remains to procure enough blood products for each patient in medical need. Allocation of rare blood, ethical evaluation of transfusion triggers, attitudes towards refusing blood transfusion and provision of blood products to remote settings are areas which should receive consideration.

Association of intraoperative hypotension with postoperative morbidity and mortality: systematic review and meta-analysis

Background

Intraoperative hypotension, with varying definitions in literature, may be associated with postoperative complications. The aim of this meta-analysis was to assess the association of intraoperative hypotension with postoperative morbidity and mortality.

Methods

MEDLINE, Embase and Cochrane databases were searched for studies published between January 1990 and August 2018. The primary endpoints were postoperative overall morbidity and mortality. Secondary endpoints were postoperative cardiac outcomes, acute kidney injury, stroke, delirium, surgical outcomes and combined outcomes. Subgroup analyses, sensitivity analyses and a meta-regression were performed to test the robustness of the results and to explore heterogeneity.

Results

The search identified 2931 studies, of which 29 were included in the meta-analysis, consisting of 130 862 patients. Intraoperative hypotension was associated with an increased risk of morbidity (odds ratio (OR) 2.08, 95 per cent confidence interval 1.56 to 2.77) and mortality (OR 1.94, 1.32 to 2.84). In the secondary analyses, intraoperative hypotension was associated with cardiac complications (OR 2.44, 1.52 to 3.93) and acute kidney injury (OR 2.69, 1.31 to 5.55). Overall heterogeneity was high, with an I² value of 88 per cent. When hypotension severity, outcome severity and study population variables were added to the meta-regression, heterogeneity was reduced to 50 per cent.

Conclusion

Intraoperative hypotension during non-cardiac surgery is associated with postoperative cardiac and renal morbidity, and mortality. A universally accepted standard definition of hypotension would facilitate further research into this topic.

The use of a machine-learning algorithm that predicts hypotension during surgery in combination with personalized treatment guidance: study protocol for a randomized clinical trial

BACKGROUND

Intraoperative hypotension is associated with increased morbidity and mortality. Current treatment is mostly reactive. The Hypotension Prediction Index (HPI) algorithm is able to predict hypotension minutes before the blood pressure actually decreases. Internal and external validation of this algorithm has shown good sensitivity and specificity. We hypothesize that the use of this algorithm in combination with a personalized treatment protocol will reduce the time weighted average (TWA) in hypotension during surgery spent in hypotension intraoperatively.

METHODS/DESIGN

We aim to include 100 adult patients undergoing non-cardiac surgery with an anticipated duration of more than 2 h, necessitating the use of an arterial line, and an intraoperatively targeted mean arterial pressure (MAP) of > 65 mmHg. This study is divided into two parts; in phase A baseline TWA data from 40 patients will be collected prospectively. A device (HemoSphere) with HPI software will be connected but fully covered. Phase B is designed as a single-center, randomized controlled trial were 60 patients will be randomized with computer-generated blocks of four, six or eight, with an allocation ratio of 1:1. In the intervention arm the HemoSphere with HPI will be used to guide treatment; in the control arm the HemoSphere with HPI software will be connected but fully covered. The primary outcome is the TWA in hypotension during surgery.

DISCUSSION

The aim of this trial is to explore whether the use of a machine-learning algorithm intraoperatively can result in less hypotension. To test this, the treating anesthesiologist will need to change treatment behavior from reactive to proactive.

TRIAL REGISTRATION

This trial has been registered with the NIH, U.S. National Library of Medicine at ClinicalTrials.gov, ID: NCT03376347 . The trial was submitted on 4 November 2017 and accepted for registration on 18 December 2017.

Reducing errors in the administration of medication with infusion pumps in the intensive care department: A lean approach

Background:

Medication errors occur frequently and may potentially harm patients. Administering medication with infusion pumps carries specific risks, which lead to incidents that affect patient safety.

Objective:

Since previous attempts to reduce medication errors with infusion pumps failed in our intensive care unit, we chose the Lean approach to accomplish a 50% reduction of administration errors in 6 months. Besides improving quality of care and patient safety, we wanted to determine the effectiveness of Lean in healthcare.

Methods:

We conducted a before-and-after observational study. After baseline measurement, a value stream map (a detailed process description, used in Lean) was made to identify important underlying causes of medication errors. These causes were discussed with intensive care unit staff during frequent stand-up sessions, resulting in small improvement cycles and bottom-up defined improvement measures. Pre-intervention and post-intervention measurements were performed to determine the impact of the improvement measures. Infusion pump syringes and related administration errors were measured during unannounced sequential audits.

Results:

Including the baseline measurement, 1748 syringes were examined. The percentage of errors concerning the administration of medication by infusion pumps decreased from 17.7% (95% confidence interval, 13.7–22.4; 55 errors in 310 syringes) to 2.3% (95% confidence interval, 1–4.6; 7 errors in 307 syringes) in 18 months (p < 0.0001).

Conclusion and Relevance:

The Lean approach proved to be helpful in reducing errors in the administration of medication with infusion pumps in a high complex intensive care environment.

The practice of diagnosing and reporting transfusion-associated circulatory overload: a national survey among physicians and haemovigilance officers

OBJECTIVES

This study aims at identifying factors that disciplines consider when diagnosing and reporting transfusion-associated circulatory overload ('TACO').

BACKGROUND

TACO is a clinical diagnosis based mainly on subjective factors. Therefore, TACO could be an underreported complication of blood transfusion.

METHODS

A survey was conducted among critical care physicians, anaesthesiologists, haematologists, transfusion medicine physicians and haemovigilance officers using case vignettes and a questionnaire. Factors that may affect diagnosing TACO were investigated using conjoint analysis. A positive B-coefficient indicates a positive preference for diagnosing TACO. Participants rated factors influencing reporting TACO on a 0- to 100-point scale.

RESULTS

One hundred and seven surveys were returned (62%). Vignettes showed preferences in favour of diagnosing TACO with the onset of symptoms within 2 h [β 0·4(-0·1-1·0)], positive fluid balance [β 0·9(0·4-1·5)] and history of renal failure [β 0·6(0·1-1·2)]. Compared with transfusion of a single unit of red blood cells (RBC), respondents showed a preference for diagnosing TACO following a single unit of solvent/detergent (S/D) plasma or pooled platelet concentrate (PPC) [β 0·3(-0·2-0·7) resp. 0·5(-0·1-1·2)]. Multiple transfusion (6 RBC + 4 S/D plasma) was a strong preference for diagnosing TACO compared to 1 RBC and 1 S/D plasma [β 0·3(-0·8-1·3)]. Respondents did not fully take into account new hypertension and tachycardia when reporting TACO [median 70 (IQR 50-80) resp. 60 (IQR 50-80)]. No differences were observed between disciplines involved.

CONCLUSION

When diagnosing and reporting TACO, physicians and haemovigilance officers do consider known risk factors for TACO. Reporting could be improved by increasing the awareness of haemodynamic variables in future education programmes.

Activated protein C attenuates pulmonary coagulopathy in patients with acute respiratory distress syndrome

OBJECTIVE

Acute respiratory distress syndrome (ARDS) frequently complicates critical illness. We hypothesized that an infusion of recombinant human activated protein C (rh-APC), a natural anticoagulant, would attenuate pulmonary coagulopathy and injury.

METHODS

In this sub study of a multicenter open-label randomized controlled trial of patients with ARDS, we compared an intravenous (i.v.) infusion of rh-APC (24 mcg kg(-1)  h(-1) for 96 h) with placebo. Patients with sepsis or septic shock were excluded.

RESULTS

In 27 patients serial non-directed bronchoalveolar lavage fluid (NBLF) samples were obtained: 16 patients were treated with rh-APC and 11 patients with placebo. The rh-APC infusion was associated with higher APC levels in plasma during the infusion period of 4 days (P = 0.001), as well as higher APC levels in NBLF up to day 5 after the start of the infusion (P = 0.028). An infusion of rh-APC was associated with lower levels of thrombin-antithrombin complexes (P = 0.009) and soluble tissue factor (P = 0.011) in NBLF, compared with treatment with placebo. An infusion of rh-APC affected fibrinolysis, as plasminogen activator activity levels in NBLF were higher in the patients treated with rh-APC (P = 0.01), presumably as a result of lower NBLF levels of plasminogen activator inhibitor 1, (P = 0.01). The rh-APC infusion decreased the lung injury score (P = 0.005) and simplified the acute physiology score (P = 0.013) on day 5, when compared with baseline. The rh-APC infusion was not associated with bleeding complications.

CONCLUSION

An infusion of rh-APC in patients with ARDS attenuates pulmonary coagulopathy and injury.

The effect of aspirin in transfusion-related acute lung injury in critically ill patients

Aspirin has been found to improve outcomes in an animal model of transfusion-related acute lung injury. We examined the association of aspirin use before admission to the intensive care unit and the development of transfusion-related acute lung injury in critically ill patients. We performed a post-hoc analysis of a nested case-control study that had been undertaken in a tertiary referral hospital. Transfusion-related acute lung injury cases were matched with controls (transfused patients not developing lung injury). Of these 218 patients, 66 used aspirin (30%). Use of aspirin did not alter the risk of transfusion-related acute lung injury after transfusion of platelets (OR 1.06, CI 0.59-1.91, p = 0.85), plasma (OR 1.06, 95% CI 0.59-1.92, p = 0.84), or red blood cells (OR 1.09, 95% CI 0.61-1.94, p = 0.77). Adjustment for confounding variables using propensity scoring also did not affect the risk of acquiring transfusion-related acute lung injury (p = 0.66). In conclusion, aspirin did not protect against transfusion-related lung injury in this cohort of critically ill patients.

Lack of evidence of CD40 ligand involvement in transfusion-related acute lung injury

Activated platelets have been implicated in playing a major role in transfusion-related acute lung injury (TRALI), as platelets can trigger neutrophils, resulting in vascular damage. We hypothesized that binding of platelet CD40 ligand (CD40L) to endothelial CD40 is essential in the onset of TRALI. Mice were challenged with monoclonal major histocompatibility complex (MHC)-1 antibody which induced TRALI, evidenced by pulmonary oedema, accompanied by significantly elevated bronchoalveolar fluid (BALF) levels of total protein and elevated plasma levels of keratinocyte-derived chemokine (KC) and macrophage inflammatory protein-2 (MIP-2) compared to infusion of isotype antibody (all Ps < 0·05). Treatment with ciglitazone, which inhibits platelet CD40L expression, had no effect on pulmonary and systemic inflammation compared to controls. In addition, treatment with anti-CD40L antibody, which antagonizes all CD40-CD40L interactions, also did not abrogate the TRALI reaction. Furthermore, levels of soluble CD40L were measured in a cohort of cardiac surgery patients, who were followed prospectively for the onset of TRALI after transfusion. Plasma levels of sCD40L at baseline and at time of developing TRALI did not differ between TRALI patients and controls (transfused cardiac surgery patients not developing acute lung injury) (275 ± 192 versus 258 ± 346 and 93 ± 82 versus 93 ± 123 pg/ml, respectively, not significant). In conclusion, these results do not support the idea that the CD40-CD40L interaction is involved in mediating TRALI.

The relation between aged blood products and onset of transfusion-related acute lung injury. A review of pre-clinical data

Transfusion-related acute lung injury (TRALI) is the leading cause of transfusion related morbidity and mortality. TRALI is suggested to be a "two hit" event. The "first hit" is the underlying condition of the patient which results in sequestration and priming of neutrophils in the pulmonary compartment. The "second hit" is the transfusion of either human leukocyte antibodies or aged blood products which results in activation of the primed neutrophils and finally in pulmonary edema. The present review focuses on pre-clinical studies investigating the role of blood products containing aged cells (red blood cells, RBCs, and platelet concentrates, PLTs) and the onset of TRALI. Several mechanisms are under scrutiny. The first suggested mechanism is that soluble mediators accumulating during storage of RBCs and PLTs may play a role, including bio-active lipids or soluble CD40L. These soluble factors were found to cause lung injury in the presence of a "first hit". Another proposed mechanism involves the aged erythrocyte itself. During storage, the erythrocyte undergoes numerous changes in its biochemical and structural condition and acquires pro-inflammatory properties, sometimes collectively referred to as the "red cell storage lesion". Although it could be speculated that all of these factors may be involved in the onset of TRALI, only one pre-clinical study shows an association between the aged erythrocyte and the onset of TRALI. The suggested mechanism is a decrease in the chemokine scavenging function of the erythrocyte by reduction of the Duffy antigen expression resulting in an increase in lung injury. Further research is needed to elucidate possible mechanisms of onset of TRALI by aged blood products.

Transfusion-related acute lung injury: a change of perspective

Two decades ago, transfusion-related acute lung injury (TRALI) was considered a rare complication of transfusion medicine. Nowadays, TRALI has emerged as the leading cause of transfusion-related mortality, presumably as a consequence of reaching international agreement on defining TRALI with subsequent increased recognition and reporting of TRALI cases. Specific patient populations such as critically ill patients have an increased risk of developing TRALI, which may be explained by the two-event hypothesis. The first event is the underlying condition of the patient resulting in priming of neutrophils. The second event is the transfusion of a blood product, after which either antibodies or bioactive lipids activate the primed neutrophils, resulting in pulmonary oedema. As opposed to the traditional view that TRALI has a good prognosis, TRALI may have a significant impact on morbidity and outcome, at least in specific patient groups. The association of transfusion with adverse outcome calls for blood product and donor management strategies aimed at decreasing the risk of acquiring TRALI. Excluding female donors from plasma donation seems to have reduced, but not prevented the occurrence of TRALI . Additional research is needed to determine whether the use of fresh blood products may be an additional measure to reduce TRALI. Studies are also needed to identify at-risk patients. In these studies, we advocate the use of the consensus definition to improve comparability of risk factors and outcome of TRALI across patient populations.