Inhibition of vascular adenosine triphosphate-sensitive potassium channels by sympathetic tone during sepsis

Association of serum potassium levels with mortality in critically ill patients with sepsis during hospitalization

BACKGROUND

Electrolyte disturbances are prevalent complications in critically ill patients with sepsis, significantly impacting patient prognosis. However, the specific association between serum potassium levels and mortality risk in this population remains poorly understood. This study aimed to investigate the association between serum potassium levels during hospitalization and the risk of 28-day and 90-day mortality in critically ill patients with sepsis.

METHODS

Data were obtained from the Medical Information Mart for Intensive Care (MIMIC-IV) database, and patients with severe sepsis requiring ICU admission were stratified into quartiles based on their mean serum potassium levels. Outcomes assessed included 28-day and 90-day mortality. A multivariate Cox proportional hazards model was used to investigate the association between serum potassium levels and mortality, with restricted cubic splines to identify potential nonlinear correlations. A dichotomous Cox proportional hazards model was applied to analyze the association further, and Kaplan-Meier analysis assessed the mortality risk across different potassium ranges.

RESULTS

A total of 25,203 patients were included, with 28-day and 90-day mortality rates of 27.84% and 40.48%, respectively. Multivariate analysis showed a significant association between serum potassium levels and mortality. Restricted cubic splines identified an inflection point at 4.4 mmol/L, with potassium levels above this threshold associated with higher mortality (28-day mortality: HR 2.96, 95% CI = 2.43-3.60; 90-day mortality: HR 2.19, 95% CI = 1.81-2.64). Kaplan-Meier analysis confirmed a significantly higher risk of death for patients with serum potassium levels above 4.4 mmol/L compared to those within the 3.5-4.4 mmol/L range (P<0.001).

CONCLUSION

In critically ill patients with sepsis, serum potassium levels exceeding 4.4 mmol/L are associated with an increased risk of death. Maintaining the average serum potassium level within the range of 3.5-4.4 mmol/L appears to be safe and may contribute to better outcomes in this patient population.

Prostanoid EP₂ Receptors Are Up-Regulated in Human Pulmonary Arterial Hypertension: A Key Anti-Proliferative Target for Treprostinil in Smooth Muscle Cells

Prostacyclins are extensively used to treat pulmonary arterial hypertension (PAH), a life-threatening disease involving the progressive thickening of small pulmonary arteries. Although these agents are considered to act therapeutically via the prostanoid IP receptor, treprostinil is the only prostacyclin mimetic that potently binds to the prostanoid EP₂ receptor, the role of which is unknown in PAH. We hypothesised that EP₂ receptors contribute to the anti-proliferative effects of treprostinil in human pulmonary arterial smooth muscle cells (PASMCs), contrasting with selexipag, a non-prostanoid selective IP agonist. Human PASMCs from PAH patients were used to assess prostanoid receptor expression, cell proliferation, and cyclic adenosine monophosphate (cAMP) levels following the addition of agonists, antagonists or EP₂ receptor small interfering RNAs (siRNAs). Immunohistochemical staining was performed in lung sections from control and PAH patients. We demonstrate using selective IP (RO1138452) and EP₂ (PF-04418948) antagonists that the anti-proliferative actions of treprostinil depend largely on EP₂ receptors rather than IP receptors, unlike MRE-269 (selexipag-active metabolite). Likewise, EP₂ receptor knockdown selectively reduced the functional responses to treprostinil but not MRE-269. Furthermore, EP₂ receptor levels were enhanced in human PASMCs and in lung sections from PAH patients compared to controls. Thus, EP₂ receptors represent a novel therapeutic target for treprostinil, highlighting key pharmacological differences between prostacyclin mimetics used in PAH.

Sequential Analysis of a Panel of Biomarkers and Pathologic Findings in a Resuscitated Rat Model of Sepsis and Recovery

Supplemental Digital Content is available in the text.

Objectives:

To characterize the temporal pattern of a panel of blood and urinary biomarkers in an animal model of fecal peritonitis and recovery.

Design:

Prospective observational animal study.

Setting:

University research laboratory.

Subjects:

Male Wistar rats.

Interventions:

A fluid-resuscitated, long-term (3 d) rat model of sepsis (fecal peritonitis) and recovery was used to understand the temporal association of sepsis biomarkers in relation to systemic hemodynamics, inflammation, and renal function. At predefined time points (3, 6, 12, 24, 48, 72 hr), animals (≥ 6 per group) underwent echocardiography, blood and urine sampling, and had kidneys taken for histological analysis. Comparison was made against sham-operated controls and naïve animals.

Measurements and Main Results:

The systemic proinflammatory response was maximal at 6 hours, corresponding with the nadir of stroke volume. Serum creatinine peaked late (24 hr), when clinical recovery was imminent. Histological evidence of tubular injury and cell death was minimal. After a recovery period, all biomarkers returned to levels approaching those observed in sham animals. Apart from urine clusterin and interleukin-18, all other urinary biomarkers were elevated at earlier time points compared with serum creatinine. Urine neutrophil gelatinase-associated lipocalin was the most sensitive marker among those studied, rising from 3 hours. While serum creatinine fell at 12 hours, serum cystatin C increased, suggestive of decreased creatinine production.

Conclusions:

Novel information is reported on the temporal profile of a panel of renal biomarkers in sepsis in the context of systemic and renal inflammation and recovery. Insight into the pathophysiology of acute kidney injury is gleaned from the temporal change markers of renal injury (urine neutrophil gelatinase-associated lipocalin, kidney injury molecule-1, calbindin), followed by a marker of cell cycle arrest (urine insulin-like growth factor-binding protein 7) and, finally, by functional markers of filtration (serum creatinine and cystatin C). These clinically relevant findings should have significant influence on future clinical testing.