Predicting Fluid Responsiveness

Dr. Trivedi

Monnet X, Dres M, Ferré A, Le Teuff G, Jozwiak M, Bleibtreu A, Le Deley MC, Chemla D, Richard C, Teboul JL. Prediction of fluid responsiveness by a continuous non-invasive assessment of arterial pressure in critically ill patients: comparison with four other dynamic indices. Br J Anaesth. 2012 Sep;109(3):330-8. Epub 2012 Jun 26.

            A debate within the realm of anesthesia continues over the best hemodynamic monitoring tool. Traditional static measures such as central venous pressure and pulmonary artery occlusion pressures are now being replaced by dynamic indices. Monnet and colleagues sought to compare non invasive arterial pulse pressure variation (PPV) to invasive PPV, respiratory variation of pulse contour-derived stroke volume, and changes in cardiac index induced by passive leg raising (PLR) and end-expiratory occlusion (EEO) tests. The PPV, the respiratory variation of arterial pulse pressures induced by mechanical ventilation, estimates stroke volume with relatively good accuracy. PLR acts as a “self volume challenge” and the effects of PLR on the cardiac output can predict fluid responsiveness. The EEO is a newer tool which involves  occluding the respiratory circuit for a few seconds at end-expiration interrupting the venous return that occurs at each mechanical inspiration resulting increase in cardiac preload.  Patient populations which may have the greatest benefit from new dynamic indices, the critically ill with hemodynamic failure, were chosen as the focus for this study. 47 critically ill patients were chosen. Baseline non-invasive and invasive PPVs, stroke volume variation, and changes in cardiac index induced by PLR and EEO were recorded. The patient was then administered 500 ml of saline and the response recorded. CNAP could not record arterial pressures in 8 patients which the authors attribute to severe vasoconstriction from vasopressors and/or micro thrombi. Fluid increased cardiac index by ≥15% in 17 'responders' out of the remaining 39 patients. A limitation is that in patients with low tidal volumes the changes in intrathoracic pressure might be so low that changes in cardiac preload could be too low to challenge the preload-dependent stroke volume. The PLR may be useful in this case since it would allow testing for fluid responsiveness even in ventilated patients with low tidal volumes and lung compliance. The authors found that combing multiple dynamic indices did not prove to have higher accuracy in terms of fluid responsiveness and that non-invasive assessment of PPV appears to be of great utility in this patient population. 

Estimating fluid status in the post surgical ICU can be challenging as patients indices are increasingly challenged by failing organs and influenced by measures such as dialysis. In addition to the influence of ventilation, the PPV can also be invalidated by developed arrhythmias which are frequent in this population. In addition to the use of PPV and other static and dynamic measures, I found the use of transthoracic ultrasound to be of great utility in a situation of uncertainty. A quick look at the heart by the anesthesiologist at bedside can reveal valuable information about the overall function/contractility of the heart as well as fluid status as the heart may appear overfilled/ volume overloaded or under filled/ “kissing.”

Hypotensive Resuscitation and Mortality

Dr. Dong

Hypotensive Resuscitation during Active Hemorrhage: Impact on In-Hospital Mortality

Dutton MD, Mackenzie MD, Scalea MD

J Trauma 2005

This article focuses on the latest strategies to improve the outcomes of patients suffering from acute hemorrhagic shock as a result of trauma. It aims to support findings from a study done in the early 1990’s from Houston which proposed the idea of holding intravenous crystalloids and allowing permissive hypotension until the active source of bleeding is located and resolved. However the authors at the University of Maryland Shock Trauma Center noted multiple shortcomings from the previous study and embarked on a mission to re-create the aforementioned trend. 110 patients were reenrolled over 20 months, in which 55 were placed in a group with an average SBP being 114mmHg and the other 100mmHg. Variables such as injury severity score, and duration of hemorrhage were similar between the groups. In the end however, both groups demonstrated similar outcomes in which survivability was 92.7% in each group with 4 deaths each. The article mentions that the possible reasons for the lack of differentiation could have been improvements in the overall diagnostic and theurapeutic technology, short duration of the study, major difference in the mechanism of trauma and the imprecision of manual SBP readings. 

Nighttime intensivist staffing and mortality

Dr. Chang

Wallace DJ, Angus DC et al. Nighttime intensivist staffing and mortality among critically ill patients. NEJM 366; 2093: 2012.

Summary: 

There has been an increasingly hot debate regarding the degree to which nighttime intensivists are associated with improvements in the quality of ICU care. Proponents suggest nighttime intensivists provide earlier establishment of treatment plans, more timely resuscitation of unstable patients, and more consistent decision-making all hours of the day. Opponents feel intensivists at night contribute to a high cost of hospitals' investments and that most judgment is based on lack of concrete evidence. Two prior studies showed: benefit of nighttime staffing involved in ICU care with low-intensity daytime staffing (Lancet, 2000); and no reduction for in-hospital mortality after adding night intensivists to already high-intensity staffing.

In brief, the study in this article was conducted over 2009-2010 and designed surveys were sent out to clinical coordinators at sites that utilize the APACHE scoring system. The primary outcome variable was in-hospital mortality (excluded patient discharged to hospice care). Multiple statistical analyses were performed, which included multivariate models to assess a relationship between nighttime intensivist staffing and in-hospital mortality. Adjustments were made for daytime intensivist staffing, illness severity, and case mix. Results were based on 65,752 (66% of total ICU admission) admitted to 49 ICUs in 25 hospitals:

- LOW-intensity daytime staffing: nighttime staffing associated with reduction in risk-adjusted in-hospital mortality (P=0.04)

- HIGH-intensity daytime staffing: no benefit with respect to risk-adjusted in-hospital mortality (P=0.78)

The discussion suggests that nighttime intensivists are more accessible to nursing staff and other providers, which ultimately aims to reduce medical errors. This is especially applicable in the setting of sepsis where studies have shown that rapid assessment improves outcomes. Limitations discussed included: lack of a random sample, definition of ‘nighttime’ broad in that it did not measure individualized clinical behavior, and that it did not evaluate increasing role of ICU telemedicine. In concluded that a general endorsement of 24-hour intensivist coverage is premature.

Recombinant Human Activated Protein C in Sepsis

Bahar Mjos, DO

 

Evaluating the use of recombinant human activated protein C in adult severe sepsis: Results of the Surviving Sepsis Campaign*

Casserly, Brian MD; Gerlach, Herwig MD, PhD; Phillips, Gary S. MAS; Marshall, John C. MD; Lemeshow, Stanley PhD; Levy, Mitchell M. MD

After the PROWESS-SHOCK trial and Cochrane review in 2012, it appeared that the controversy related to efficacy of activated protein C and its role in sever sepsis had been resolved. However, this month in the journal of Critical Care Medicine, revisited this topic.

It has been shown that after adjusting for multiple confounders, patients who received rhAPC had statistically significantly lower in-hospital mortality. “Propensity score matching was used to validate the risk adjusted multivariate regression model, and the results were similar. Patients with thrombocytopenia and coagulopathy also were found to have lower, and statistically significant, adjusted risks of hospital mortality”.

As of October 2011 Xigris (activated protein C) has been withdrawn from the market.

“While further discussions about rhAPC might be considered moot, it is worth noting that previous rigorously conducted clinical trials occasionally have yielded discordant results compared to observational, “real-life” investigations. The recent moratorium on the use of rhAPC appears to represent yet another failure of immunomodulatory agents to impact outcomes for critically ill patients with sepsis; however, the infrequent use of rhAPC, in selected populations, was found to be associated with a significant improvement in adjusted hospital mortality in this study.”

Early vs Late TPN in ICU Patients, Dr. Mjos

Bahar Mjos, DO
PGY-4 Resident at RCRMC who will do a Critical Care Fellowship at John's Hopkins University on graduation

Early versus Late Parenteral Nutrition in Critically Ill Adults

Prior data on early vs. late feeding in critically ill patients have been difficult to interpret. *A metaanalysis of 15 studies examining early enteral nutrition (containing 753 subjects) suggested that early enteral nutrition was associated with a significantly lower incidence of infections (RR 0.45; p =.00006) and a reduced hospital stay (mean 2.2 days; p =.004), however there were no significant differences in mortality* or noninfectious complications. The results of this meta-analysis must be interpreted with some caution because of the *significant heterogeneity between studies.*

More recently, seven Belgian ICUs performed *The Early Parenteral Nutrition Completing Enteral Nutrition in Adult Critically Ill Patients (EPaNIC) Study *, a prospective, randomized, controlled, parallel-group, multicenter investigator-initiated trial (partially funded by Baxter) in which 4640 nutritionally at-risk patients were randomized to early (within 48 hours) vs. late (at least 8 days) initiation of parenteral nutrition (2007 to 2010). While the early nutrition group clearly received more nutrition (both in terms of total energy and percentage of target), *the late group was discharged from the ICU one day earlier (p = 0.04), had a lower

incidence of hypoglycemia (p = 0.001), fewer infections (22.8% vs. 26.2%, p = 0.008), and a reduction in total healthcare costs of ~ $1600 (€1,110)*. Mortality was the same. Importantly, mean units of insulin and average glucose in the early and late groups were 58U/107 mg/dL and 31U/102 mg/dL, respectively.

Microcirculation and Sepsis Treatment, Dr. Perz

Katie Perz, D.O.

Article:

Early Increases in Microcirculatory Perfusion During Protocol-Directed Resuscitation are Associated with Reduced Multi-Organ Failure at 24 hours in Patients with Sepsis

Trzeciak, S., McCoy, J., Dellinger, P., Arnold, R., Rizzuto, M, Abate, N., Shapiro, N., Parrillo, J., Hollenberg, S.,

Summary:

Sepsis is a common and lethal disease.  Development of acute multi-organ failure is one of the primary determinants of sepsis mortality.  Early evidence of multi-organ failure and early changes in organ function, specifically changes over the first 24 hours of severe sepsis presentation, are especially prognostic.  The objective of this article was to investigate whether changes in microcirculatory blood flow during the first 24 hours of sepsis are associated with changes in organ failure.  The study used direct visualization of the sublingual microcirculation with sidestream dark field (SDF) videomicroscopy to detect direct and indirect assessments of tissue perfusion.  Using this initial SDF, early goal directed therapy was initiated, and results were measured using a sequential organ failure assessment score. This score took respiration (PaO2/FiO2), coagulation (platelet levels), liver tests (bilirubin levels), cardiovascular status (hypotension or pressor use), and renal status (Creatinine levels) to evaluate the effectiveness of early goal directed therapy following microcirculation visualization with SDF videomicroscopy.

The article concluded that early increases in microcirculatory blood flow during protocol-directed resuscitation were associated with reduced organ failure at 24 hours in patients with sepsis.  The data supported the hypothesis that goal directed fluid therapy targeting the microcirculation distinct from the macrocirculation could potentially improve organ failure in sepsis.

Will Aspirin prevent acute lung injury in critically ill patients? Dr. Kang

Vimmi Kang, DO

Article Review

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

Source: Anesthesia. 20012 FEB 11

            This article looked to examine if aspirin would protect against transfusion related acute lung injury in critically ill patients. This article stemmed from the recent models that showed aspirin to be beneficial in improving outcomes in transfusion related injury in animals. This study was conducted as a post analysis of a case-control study. It looked at Transfusion-related acute lung injury cases compared with the control. Study consisted of 218 patients of which 66 used aspirin. Results showed that use of aspirin did not change the risk of transfusion related acute lung injury after transfusion of platelets or plasma.

In conclusion, aspirin did not decrease or protect against transfusion-related acute lung injury in critically ill patients.