Critical Care Bulletin: June 2022

 

The obesity paradox for survivors of critically ill patients

 

by Dawei Zhou, Chao Wang, Qing Lin and Tong Li 

 

Critical Care volume 26, Article number: 198 (2022) Published: 03 July 2022

 

The obesity paradox has been observed in short-term outcomes from critical illness. However, little is known regarding the impact of obesity on long-term outcomes for survivors of critically ill patients. We aimed to evaluate the influence of obesity on long-term mortality outcomes after discharge alive from ICU. The adult patients who were discharged alive from the last ICU admission were extracted. After exclusion, a total of 7619 adult patients discharged alive from ICU were included, with 4-year mortality of 32%. The median body mass index (BMI) was 27.2 (IQR 24–31.4) kg/m2, and 2490 (31.5%) patients were classified as obese or morbidly obese. The morbidly obese patients had the highest ICU and hospital length of stay. However, higher BMI was associated with lower hazard ratio for 4-year mortality. The results showed the obesity paradox may be also suitable for survivors of critically ill patients.

 

Pulse oximetry, racial bias and statistical bias

 

by Martin J. Tobin and Amal Jubran 

 

Annals of Intensive Care volume 12, Article number: 2 (2022) Published: 04 January 2022

 

On November 21, 2021, the British Health Minister, Sajid Javid, published an article in the Sunday Times pointing out that pulse oximeters tend to be inaccurate in patients with dark skin pigmentation [1]. The Minister remarked that “technologies are created and developed by people, and so bias, however inadvertent, can be an issue here too.” The article attracted immediate and widespread attention, being covered by newspapers and television channels around the world. Mr. Javid expanded on his concerns during interviews with Andrew Maar on the BBC and Trevor Phillips on Sky News.

A few years after the introduction of pulse oximetry in the 1980s, we noticed that oximeters were less reliable in Black patients. In a 1990 article focusing on oxygenation in mechanically ventilated patients, we reported that pulse oximetry was almost 2½ times less accurate in Black patients [2].

Given that pulse oximetry operates by shining a light through the skin at two wavelengths—660 nm (red) and 940 nm (infrared)—and measuring the difference in light absorbance at the two wavelengths to estimate arterial oxygen saturation [3], we surmised that inaccuracy in Black patients is related to skin pigmentation. Supporting evidence is the increase in the difference in light absorbance between red and infrared wavelengths with use of black nail varnish, causing pulse oximeters to register falsely low saturations [4].

Estimates of oxygen saturation by pulse oximetry differ from true oxygen saturation in an arterial blood sample (the reference standard). The magnitude of the difference between non-invasive estimates and reference-standard measurements (in a group of patients) is quantified as mean and standard deviation, which statisticians dub “bias and precision.” In White patients, the mean and standard deviation of the difference between non-invasive estimates of oxygen saturation and the reference standard are each around 2%, whereas they both exceed 3% in Black patients [2]. In our study, a pulse oximeter target of 92% ensured a safe arterial oxygen tension (PaO2) greater than 60 mmHg in 91.7% of White patients, but in only 50% of our Black patients [2].

In the first rigorous description of happy hypoxia in COVID-19, a situation where patients experience life-threateningly low oxygen saturations without provoking dyspnoea, we discussed several contributors to the phenomenon including the greater unreliability of pulse oximetry in Black patients [5]. Managing patients with unreliable measurements of oxygenation is hazardous, partly because dangerously low saturations are missed, but also because low saturations are exaggerated and lead to unnecessary intubation [6]. A major contributor to patient mortality in COVID-19 is inappropriate intubation [7], and it is possible that unreliable measurements of the oxygen saturations have contributed to increased mortality reported in Black patients [8].

In our 1990 article, we deduced that pulse oximetry was less reliable in Black patients because calibration data were drawn largely from White subjects [2]. The algorithms employed within software of pulse oximeters are trade secrets and not open to scrutiny [3]. We recommended that manufacturers collect data in Black patients to develop better calibration algorithms. In the 31 years since we made this recommendation, we are not aware of any manufacturer attempting to incorporate adjusted algorithms into pulse oximeters. The inaccuracy of pulse oximetry in Black patients is one further example of how medical information generated in (and for) White people contributes to inferior clinical outcome in patients of colour [9].

Hopefully, the attention generated by Mr. Javid’s highlighting of a significant problem with pulse oximetry will rouse manufacturers into action. Mr. Javid is working with his US counterpart, Xavier Becerra, to introduce new international medical standards. In the meantime, it would help if authors reverted to the more mundane (and precise) terminology of mean and standard deviation and refrained from use of the dodgy terms “bias and precision”, which gives rise to the notion that inanimate objects are capable of racial prejudice.

 

 

Racial Disparities in ICU Outcomes: A Systematic Review*

 

by McGowan, Samuel K.; Sarigiannis, Kalli A.; Fox, Samuel C.; Gottlieb, Michael A.; Chen, Elaine 

 

Critical Care Medicine: January 2022 - Volume 50 - Issue 1 - p 1-20

 

Objectives: 

Racial disparities in the United States healthcare system are well described across a variety of clinical settings. The ICU is a clinical environment with a higher acuity and mortality rate, potentially compounding the impact of disparities on patients. We sought to systematically analyze the literature to assess the prevalence of racial disparities in the ICU.

Data Sources: 

We conducted a comprehensive search of PubMed/MEDLINE, Scopus, CINAHL, and the Cochrane Library.

Study Selection: 

We identified articles that evaluated racial differences on outcomes among ICU patients in the United States. Two authors independently screened and selected articles for inclusion.

Data Extraction: 

We dual-extracted study characteristics and outcomes that assessed for disparities in care (e.g., in-hospital mortality, ICU length of stay). Studies were assessed for bias using the Newcastle-Ottawa Scale.

Data Synthesis: 

Of 1,325 articles screened, 25 articles were included (n = 751,796 patients). Studies demonstrated race-based differences in outcomes, including higher mortality rates for Black patients when compared with White patients. However, when controlling for confounding variables, such as severity of illness and hospital type, mortality differences based on race were no longer observed. Additionally, results revealed that Black patients experienced greater financial impacts during an ICU admission, were less likely to receive early tracheostomy, and were less likely to receive timely antibiotics than White patients. Many studies also observed differences in patients’ end-of-life care, including lower rates on the quality of dying, less advanced care planning, and higher intensity of interventions at the end of life for Black patients.

Conclusions: 

This systematic review found significant differences in the care and outcomes among ICU patients of different races. Mortality differences were largely explained by accompanying demographic and patient factors, highlighting the effect of structural inequalities on racial differences in mortality in the ICU. This systematic review provides evidence that structural inequalities in care persist in the ICU, which contribute to racial disparities in care. Future research should evaluate interventions to address inequality in the ICU.

The Effect of Vitamin C on Clinical Outcome in Critically Ill Patients: A Systematic Review With Meta-Analysis of Randomized Controlled Trials*

The Effect of Vitamin C on Clinical Outcome in Critically Ill Patients: A Systematic Review With Meta-Analysis of Randomized Controlled Trials*

Critical Care Medicine: June 2019 - Volume 47 - Issue 6 - p 774–783

Objectives: The effects of vitamin C administration on clinical outcome in critically ill patients remain controversial.

Data Sources: Online databases were searched up to October 1, 2018.

Study Selection: We included randomized controlled trials on the use of vitamin C (any regimen) in adult critically ill patients versus placebo or no therapy.

Data Extraction: Risk ratio for dichotomous outcome and standardized mean difference for continuous outcome with 95% CI were calculated using random-effects model meta-analysis.

Data Synthesis: Forty-four randomized studies, 16 performed in ICU setting (2,857 patients) and 28 in cardiac surgery (3,598 patients), published between 1995 and 2018, were included in the analysis. In ICU patients, vitamin C administration was not associated with a difference in mortality (risk ratio, 0.90; 95% CI, 0.74–1.10; p = 0.31), acute kidney injury, ICU or hospital length of stay compared with control. In cardiac surgery, vitamin C was associated to a reduction in postoperative atrial fibrillation (risk ratio, 0.64; 95% CI, 0.52–0.78; p < 0.0001), ICU stay (standardized mean difference, –0.28 d; 95% CI, –0.43 to –0.13 d; p = 0.0003), and hospital stay (standardized mean difference, –0.30 d; 95% CI, –0.49 to –0.10 d; p = 0.002). Furthermore, no differences in postoperative mortality, acute kidney injury, stroke, and ventricular arrhythmia were found.

Conclusions: In a mixed population of ICU patients, vitamin C administration is associated with no significant effect on survival, length of ICU or hospital stay. In cardiac surgery, beneficial effects on postoperative atrial fibrillation, ICU or hospital length of stay remain unclear. However, the quality and quantity of evidence is still insufficient to draw firm conclusions, not supporting neither discouraging the systematic administration of vitamin C in these populations. Vitamin C remains an attractive intervention for future investigations aimed to improve clinical outcome.

Short-Term Adverse Outcomes Associated With Hypoglycemia in Critically Ill Children

Short-Term Adverse Outcomes Associated With Hypoglycemia in Critically Ill Children

by Faustino, Edward Vincent S et al: Critical Care Medicine: May 2019 - Volume 47 - Issue 5 - p 706–714

Objectives: Previous studies report worse short-term outcomes with hypoglycemia in critically ill children. These studies relied on intermittent blood glucose measurements, which may have introduced detection bias. We analyzed data from the Heart And Lung Failure-Pediatric INsulin Titration trial to determine the association of hypoglycemia with adverse short-term outcomes in critically ill children.

Design: Nested case-control study.

Setting: Thirty-five PICUs. A computerized algorithm that guided the timing of blood glucose measurements and titration of insulin infusion, continuous glucose monitors, and standardized glucose infusion rates were used to minimize hypoglycemia.

Patients: Nondiabetic children with cardiovascular and/or respiratory failure and hyperglycemia. Cases were children with any hypoglycemia (blood glucose < 60 mg/dL), whereas controls were children without hypoglycemia. Each case was matched with up to four unique controls according to age group, study day, and severity of illness.

Interventions: None.

Measurements and Main Results: A total of 112 (16.0%) of 698 children who received the Heart And Lung Failure-Pediatric INsulin Titration protocol developed hypoglycemia, including 25 (3.6%) who developed severe hypoglycemia (blood glucose < 40 mg/dL). Of these, 110 cases were matched to 427 controls. Hypoglycemia was associated with fewer ICU-free days (median, 15.3 vs 20.2 d; p = 0.04) and fewer hospital-free days (0 vs 7 d; p = 0.01) through day 28. Ventilator-free days through day 28 and mortality at 28 and 90 days did not differ between groups. More children with insulin-induced versus noninsulin-induced hypoglycemia had zero ICU-free days (35.8% vs 20.9%; p = 0.008). Outcomes did not differ between children with severe versus nonsevere hypoglycemia or those with recurrent versus isolated hypoglycemia.

Conclusions: When a computerized algorithm, continuous glucose monitors and standardized glucose infusion rates were used to manage hyperglycemia in critically ill children with cardiovascular and/or respiratory failure, severe hypoglycemia (blood glucose < 40 mg/dL) was uncommon, but any hypoglycemia (blood glucose < 60 mg/dL) remained common and was associated with worse short-term outcomes.

Association Between Hospital Case Volume of Sepsis, Adherence to Evidence-Based Processes of Care and Patient Outcomes

Association Between Hospital Case Volume of Sepsis, Adherence to Evidence-Based Processes of Care and Patient Outcomes

Fawzy, A, Walkey, AJ
Critical Care Medicine: June 2017 - Volume 45 - Issue 6 - p 980–988

Objectives: We sought to explore potential mechanisms underlying hospital sepsis case volume-mortality associations by investigating implementation of evidence-based processes of care. Design: Retrospective cohort study. We determined associations of sepsis case volume with three evidence-based processes of care (lactate measurement during first hospital day, norepinephrine as first vasopressor, and avoidance of starch-based colloids) and assessed their role in mediation of case volume-mortality associations. Setting: Enhanced administrative data (Premier, Charlotte, NC) from 534 U.S. hospitals. Subjects: A total of 287,914 adult patients with sepsis present at admission between July 2010 and December 2012 of whom 58,045 received a vasopressor for septic shock during the first 2 days of hospitalization. Interventions: None. 
Measurements and Main Results: Among patients with sepsis, 1.9% received starch, and among patients with septic shock, 68.3% had lactate measured and 64% received norepinephrine as initial vasopressor. Patients at hospitals with the highest case volume were more likely to have lactate measured (adjusted odds ratio quartile 4 vs quartile 1, 2.8; 95% CI, 2.1–3.7) and receive norepinephrine as initial vasopressor (adjusted odds ratio quartile 4 vs quartile 1, 2.1; 95% CI, 1.6–2.7). Case volume was not associated with avoidance of starch products (adjusted odds ratio quartile 4 vs quartile 1, 0.73; 95% CI, 0.45–1.2). Adherence to evidence-based care was associated with lower hospital mortality (adjusted odds ratio, 0.81; 95% CI, 0.70–0.94) but did not strongly mediate case volume-mortality associations (point estimate change ≤ 2%). 
Conclusions: In a large cohort of U.S. patients with sepsis, select evidence-based processes of care were more likely implemented at high-volume hospitals but did not strongly mediate case volume-mortality associations. Considering processes and case volume when regionalizing sepsis care may maximize patient outcomes.