Myocardial dysfunction in meningococcal septic shock

Type IV pilus retraction enables sustained bacteremia and plays a key role in the outcome of meningococcal sepsis in a humanized mouse model

Neisseria meningitidis (the meningococcus) remains a major cause of bacterial meningitis and fatal sepsis. This commensal bacterium of the human nasopharynx can cause invasive diseases when it leaves its niche and reaches the bloodstream. Blood-borne meningococci have the ability to adhere to human endothelial cells and rapidly colonize microvessels. This crucial step enables dissemination into tissues and promotes deregulated inflammation and coagulation, leading to extensive necrotic purpura in the most severe cases. Adhesion to blood vessels relies on type IV pili (TFP). These long filamentous structures are highly dynamic as they can rapidly elongate and retract by the antagonistic action of two ATPases, PilF and PilT. However, the consequences of TFP dynamics on the pathophysiology and the outcome of meningococcal sepsis in vivo have been poorly studied. Here, we show that human graft microvessels are replicative niches for meningococci, that seed the bloodstream and promote sustained bacteremia and lethality in a humanized mouse model. Intriguingly, although pilus-retraction deficient N. meningitidis strain (ΔpilT) efficiently colonizes human graft tissue, this mutant did not promote sustained bacteremia nor induce mouse lethality. This effect was not due to a decreased inflammatory response, nor defects in bacterial clearance by the innate immune system. Rather, TFP-retraction was necessary to promote the release of TFP-dependent contacts between bacteria and, in turn, the detachment from colonized microvessels. The resulting sustained bacteremia was directly correlated with lethality. Altogether, these results demonstrate that pilus retraction plays a key role in the occurrence and outcome of meningococcal sepsis by supporting sustained bacteremia. These findings open new perspectives on the role of circulating bacteria in the pathological alterations leading to lethal sepsis.

Meningococcal purpura fulminans and severe myocarditis with clinical meningitis but no meningeal inflammation: a case report

Background

During fulminant meningococcal septicaemia, meningococci are often observed in the cerebrospinal fluid (CSF) although the patients have frequently no meningeal symptoms. Meningococcal meningitis, by contrast, usually features clinical meningeal signs and biochemical markers of inflammation with elevated white blood cell count (pleiocytosis) in the CSF. Cases of typical symptomatic meningitis without these biochemical features are uncommon in adults.

Case presentation

A 21-year-old male presented with meningococcal purpura fulminans and disseminated intravascular coagulation (DIC) associated with multiple organ dysfunction syndrome requiring hospitalization in the Intensive Care Unit. Despite typical meningeal clinical signs, lumbar puncture showed no pleiocytosis, normal glycorachia and normal proteinorachia, whereas the lactate concentration in the CSF was high (5.8 mmol/L). CSF culture showed a high inoculum of serogroup C meningococci. On day 2, after initial improvement, a recurrence of hypotension led to the diagnosis of acute meningococcal myocarditis, which evolved favourably within a week. During the hospitalization, distal ischemic and necrotic lesions were observed, predominantly on the fingertips, which were treated with local and systemic vasodilators.

Conclusions

We report a rare case of adult meningococcal disease characterized by an intermediate form of meningitis between purulent meningitis and meningeal inoculation from fulminant meningococcal septicaemia, without classical signs of biological inflammation. It highlights the diagnostic value of CSF lactate, which may warrant administration of a meningeal dosing regimen of beta-lactam antibiotics. This case also demonstrates the potential severity of meningococcal myocarditis; we discuss its pathophysiology, which is distinct from other sepsis-related cardiomyopathies. Finally, the observed effects of vasodilators on the meningococcal skin ischemia in this case encourages future studies to assess their efficacy in DIC-associated necrosis.

Experimental Evidence of Bacterial Colonization of Human Coronary Microvasculature and Myocardial Tissue during Meningococcemia

Meningococcal septic shock is associated with profound vasoplegia, early and severe myocardial dysfunction, and extended skin necrosis responsible for a specific clinical entity designated purpura fulminans (PF). PF represents 90% of fatal meningococcal infections. One characteristic of meningococcal PF is the myocardial dysfunction that occurs in the early phase of sepsis. Furthermore, hemodynamic studies have shown that the prognosis of meningococcal sepsis is directly related to the degree of impairment of cardiac contractility during the initial phase of the disease. To gain insight into a potential interaction of Neisseria meningitidis with the myocardial microvasculature, we modified a previously described humanized mouse model by grafting human myocardial tissue to SCID mice. We then infected the grafted mice with N. meningitides Using the humanized SCID mouse model, we demonstrated that N. meningitidis targets the human myocardial tissue vasculature, leading to the formation of blood thrombi, infectious vasculitis, and vascular leakage. These results suggest a novel mechanism of myocardial injury in the course of severe N. meningitidis sepsis that is likely to participate in primary myocardial dysfunction.

Multimodal monitoring for hemodynamic categorization and management of pediatric septic shock: a pilot observational study*

OBJECTIVES

To evaluate the cardiovascular aberrations using multimodal monitoring in fluid refractory pediatric septic shock and describe the clinical characteristics of septic myocardial dysfunction.

DESIGN

Prospective observational study of patients with unresolved septic shock after infusion of 40 mL/kg fluid in the first hour.

SETTING

Two tertiary care referral Indian PICUs.

PATIENTS

Patients aged 1 month to 16 years who had fluid refractory septic shock.

INTERVENTIONS

Changes in therapy were based on findings of clinical assessment, bedside echocardiography, and invasive blood pressure monitoring within 6 hours of recognition of septic shock.

MEASUREMENTS AND MAIN RESULTS

Over a 4-year period, 48 patients remained in septic shock despite at least 40 mL/kg fluid infusion. On clinical examination, 21 patients had cold shock and 27 had warm shock. Forty-one patients (85.5%) had vasodilatory shock on invasive blood pressure; these included 14 patients who initially presented with cold shock. The commonest echocardiography findings were impaired left ± right ventricular function in 19 patients (39.6%) and hypovolemia in 16 patients (33%). Three patients who had normal myocardial function on day 1 developed secondary septic myocardial dysfunction on day 3. Echocardio graphy, along with invasive arterial pressure monitoring, allowed fluid, inotropy, and pressors to be titrated more precisely in 87.5% of patients. Shock resolved in 46 of 48 patients (96%) and 44 patients (91.6%) survived to discharge.

CONCLUSION

Bedside echocardiography provided crucial information leading to the recognition of septic myocardial dysfunction and uncorrected hypovolemia that was not apparent on clinical assessment. With invasive blood pressure monitoring, echocardiography affords a simple noninvasive tool to determine the cause of low cardiac output and the physiological basis for adjustment of therapy in patients who remain in shock despite 40 mL/kg fluid.

Myocardial involvement during ischemia-induced acute liver failure in the pig

OBJECTIVE

The objective of this experimental study was to investigate a possible myocardial involvement in acute liver failure.

MATERIALS AND METHODS

A porcine model of acute liver failure induced by hepatic devascularization was used. Twenty animals were allocated to the Acute Liver Failure (ALF) or Control Group (CG). Serum cardiac troponin I (cTnI), MB isoenzyme of creatine kinase (CK-MB), and also hemodynamic variables were measured and compared before surgery (T1), at 4 hr (T2), and at 7 hr (T3) after the end of surgery.

RESULTS

Data from 10 pigs in the ALF and 7 in the CG were analyzed. In the ALF group, cTnI increased from 0.3 ± 0.055 to 0.35 ± 0.696 and 0.39 ± 0.06 ng/ml at T1, T2, and T3 time points, respectively (p < .001). In the CG, cTnI was not significantly changed from 0.29 ± 0.07, to 0.31 ± 0.01, and 0.31 ± 0.11 ng/ml at T1, T2, and T3 time points, respectively (p = .895). A statistically significant difference was found in cTnI between the groups at T3 (z = -2.93, p = .002). CK-MB increased significantly in both groups: in ALF group, CK-MB changed from 3.43 ± 0.53 to 4.33 ± 0.73 and 7.14 ± 1.12 ng/ml at T1, T2, and T3 time points, respectively (p < .001). In the CG, CK-MB changed from 3.6 ± 0.597 to 4.6 ± 1.07 and 6.2 ± 1.17 ng/ml at T1, T2, and T3 time points, respectively, (p = .001). Mean arterial pressure (MAP) was significantly reduced in the ALF group.

CONCLUSIONS

In a porcine model of acute liver failure, a significant increase of cTnI serum levels was found, indicating that a subclinical myocardial damage may occur as a result of heart involvement in the multiple organ dysfunction.

Norepinephrine supplemented with dobutamine or epinephrine for the cardiovascular support of patients with septic shock

Background and Aims:

Sepsis management remains a great challenge for intensive care medicine. The aim of this study was to evaluate the effect of adding dobutamine versus epinephrine to norepinephrine in treating septic shock patients refractory to fluid therapy.

Materials and Methods:

Sixty adult patients with the diagnosis of septic shock were included in this study. Norepinephrine infusion was started at a dose of 0.05 μg/kg/min, and increased gradually up to 0.1 μg/kg/min. Upon reaching this dose, patients with mean arterial pressure <70 mmHg were further divided randomly into two equal groups. In group I: the patients continued on norepinephrine and dobutamine was added at a starting dose of 3 μg/kg/min and increased in increments of 2 μg/kg/min up to 20 μg/kg/min. In group II: the patients continued on norepinephrine and epinephrine was added in a starting dose of 0.05 μg/kg/ min and increased in increments of 0.03 μg/kg/min up to 0.3 μg/kg/min.

Results:

Group II patients developed significantly better cardiovascular parameters, lower arterial pH and higher serum lactate and urine output; however, the 28-day mortality and major adverse effects were comparable in both groups.

Conclusions:

The addition of epinephrine to norepinephrine has positive effects on the cardiovascular parameters but negative results on the serum lactate concentration and systemic pH compared with the addition of dobutamine to norepinephrine.

Advanced hemodynamic monitoring in critically ill children

Circulatory shock is an important cause of pediatric morbidity and mortality and requires early recognition and prompt institution of adequate treatment protocols. Unfortunately, the hemodynamic status of the critically ill child is poorly reflected by physical examination, heart rate, blood pressure, or laboratory blood tests. Advanced hemodynamic monitoring consists, among others, of measuring cardiac output, predicting fluid responsiveness, calculating systemic oxygen delivery in relation to oxygen demand, and quantifying (pulmonary) edema. We discuss here the potential value of these hemodynamic monitoring technologies in relation to pediatric physiology.

Hemodynamics in preterm infants with late-onset sepsis

OBJECTIVE

To describe the hemodynamic changes with time in preterm infants with clinical sepsis.

STUDY DESIGN

Blood pressure, right ventricular output (RVO), left ventricular output (LVO), and superior vena cava (SVC) flow of infants who had a suspected infection and showed signs of cardiovascular compromise were measured every 12 hours or until there was considered clinical improvement.

RESULTS

Twenty infants with a median gestational age of 27 weeks (range, 25-32 weeks) and weight of 995 g (range, 650-1980 g) were examined. Five patients died. The mean (SD) RVO, LVO, and SVC flow at the first measurement were 555 (133), 441 (164), and 104 (39) mL/kg/min, respectively. The calculated systemic vascular resistance (SVR) was 0.08 (0.04) mm Hg/mL/kg/min. There was no significant change in flow in the 15 surviving infants. Blood pressure and SVR increased from the first to the last measurement (mean difference: blood pressure, 8 mm Hg; 95% CI 3 to -13; systemic vascular resistance, 0.02 mm Hg/mL/kg/min; 95% CI, 0.01 to -0.04). Flows decreased and SVR increased in the 5 non-surviving infants (mean difference: RVO, -318 mL/kg/min; 95% CI, -463 to -174; LVO, -292 mL/kg/min; 95% CI, -473 to -111; SVC flow, -46 mL/kg/min; 95% CI, -77 to -16).

CONCLUSION

Preterm neonates with sepsis have relatively high left and right cardiac outputs and low SVRs. A decrease in RVO or LVO >50% compared with the initial measurement is associated with mortality.

Carbon monoxide in sepsis

Despite modern practices in critical care medicine, sepsis or systemic inflammatory response syndrome remains a leading cause of morbidity and mortality in the intensive care unit. Thus, the need to identify new therapeutic tools for the treatment of sepsis is urgent. In this context, carbon monoxide has become a promising therapeutic molecule that can potentially prevent uncontrolled inflammation in sepsis. In humans, carbon monoxide arises endogenously from the degradation of heme by heme oxygenase enzymes. Both endogenously synthesized and exogenously applied carbon monoxide can exert antiinflammatory and antiapoptotic effects in cells and tissues. Based on these properties, carbon monoxide, when applied at low concentration, conferred protection in a variety of cellular and rodent models of sepsis, and furthermore reduced morbidity and mortality in vivo. Therefore, application of carbon monoxide may have a major impact on the future of sepsis treatment. This review summarizes evidence for salutary effects of carbon monoxide in sepsis of various organs, including lung, heart, kidney, liver, and intestine, and discusses the potential translation of the data into human clinical trials.

The effect of adrenomedullin on the L-type calcium current in myocytes from septic shock rats: signaling pathway

Adrenomedullin (ADM) is upregulated in cardiac tissue under various pathophysiological conditions, particularly in septic shock. The intracellular mechanisms involved in the effect of ADM on adult rat ventricular myocytes are still to be elucidated. Ventricular myocytes were isolated from adult rats 4 h after an intraperitoneal injection of lipopolysaccharide (LPS, 10 mg/kg). Membrane potential and L-type calcium current ( ICa,L) were determined using whole cell patch-clamp methods. APD in LPS group was significantly shorter than control values (time to 50% repolarization: LPS, 169 ± 2 ms; control, 257 ± 2 ms, P < 0.05; time to 90% repolarization: LPS, 220 ± 2 ms; control, 305 ± 2 ms, P < 0.05). ICa,Ldensity was significantly reduced in myocytes from the LPS group (−3.2 ± 0.8 pA/pF) compared with that of control myocytes (−6.7 ± 0.3 pA/pF, P < 0.05). The ADM antagonist ADM-(22-52) reversed the shortened APD and abolished the reduction of ICa,Lin shock myocytes. In myocytes from control rats, incubating with ADM for 1 h induced a marked decrease in peak ICa,Ldensity. This effect was reversed by ADM-(22-52). The Giprotein inhibitor, pertussis toxin (PTX), the protein kinase A (PKA) inhibitor, KT-5720, and the specific cyclooxygenase 2 (COX-2) inhibitor, nimesulide, reversed the LPS-induced reduction in peak ICa,L. The results suggest a COX-2-involved PKA-dependent switch from Gscoupled to PTX-sensitive Gicoupling by ADM in adult rat ventricular myocytes. The present study delineates the intracellular pathways involved in ADM-mediated effects on ICa,Lin adult rat ventricular myocytes and also suggests a role of ADM in sepsis.