Marcelo Mercado

Fisiopatología de la insuficiencia renal aguda durante la sepsis

Acute renal failure (ARF) is an independent risk factor associated with increased mortality during sepsis. Recent consensus definitions have allowed the standardization of research on the subject. The understanding of the physiopathology of ARF during sepsis is limited by the scarcity of histological studies and the inability to measure renal microcirculatory flows. Historically, ARF during sepsis has been considered to be a consequence of diminished renal blood flow (RBF). Indeed, in early stages of sepsis or in sepsis associated to cardiogenic shock, RBF may decrease. However, recent studies have shown that in resuscitated sepsis, in which cardiac output is characteristically normal or even elevated and there is systemic vasodilatation, RBF is normal or even increased, with no associated histological evidence of significant tubular necrosis. Thus, other factors may participate in the genesis of ARF in sepsis. These include apoptosis, glomerular and medullary microcirculatory disorders, cell changes in response to the pro-inflammatory cascade characteristic of sepsis, oxidative stress, mitochondrial dysfunction and damage induced by mechanical ventilation, among others. Sepsis associated ARF treatment is supportive. In general, renal replacement therapies can be grouped as intermittent or continuous, and as those whose primary objective is the replacement of impaired renal function, versus those whose main objective is to secure hemodynamic stability through the clearing of pro-inflammatory mediators.

Catastrophic respiratory failure from tuberculosis pneumonia: Survival after prolonged extracorporeal membrane oxygenation support

Tuberculosis (TB) is an uncommon cause of severe respiratory failure, even in highly endemic regions. Mortality in cases requiring mechanical ventilation (MV) varies between 60 and 90%. The use of extracorporeal membrane oxygenation (ECMO) is not frequently needed in TB. We report the case of a 24 year old woman diagnosed with bilateral pneumonia that required MV and intensive care, patient was managed with prone ventilation for 48 h, but persisted in refractory hypoxemia. Etiological study was only positive for mycobacterium tuberculosis. As a rescue therapy arterio-venous extracorporeal CO2 removal was started and lased for 4 days, but fails to support the patient due to greater impairment of oxygenation. Veno-venous ECMO was then initiated, thus normalizes gas exchanged and allows lungs to rest. ECMO was maintained for 36 days, with two episodes of serious complication treated successfully. Given the absence of clinical improvement and the lack of nosocomial infection, at 42-day of ICU stay methylprednisolone 250 mg daily for 4 days was started, since secondary organizing pneumonia associated with TB was suspected. Thereafter progressive improvement in pulmonary mechanics and reduction of pulmonary opacities was observed, allowing the final withdrawal of ECMO. Percutaneous tracheostomy was performed and the patient remained connected until her transfer to her base hospital at day 59 of admission to our unit. The tracheostomy was removed prior to hospital discharge, and the patient is today at home. Prolonged ECMO support is a useful and potentially successful tool in catastrophic respiratory failure caused by TB.

Determinantes precoces en el desarrollo de injuria renal aguda durante la sepsis abdominal experimental

Background: Sepsis-induced acute kidney injury (AKI) is an early and frequent organ dysfunction, associated with increased mortality. Aim: To evaluate the impact of macro hemodynamic and microcirculatory changes on renal function and histology during an experimental model of intra-abdominal sepsis. Material and Methods: In 18 anaesthetized pigs, catheters were installed to measure hemodynamic parameters in the carotid, right renal and pulmonary arteries. After baseline assessment and stabilization, animals were randomly divided to receive and intra-abdominal infusion of autologous feces or saline. Animals were observed for 18 hours thereafter. Results: In all septic animals, serum lactate levels increased, but only eight developed AKI (66%). These animals had higher creatinine and interleukin-6 levels, lower inulin and para-aminohippurate clearance (decreased glomerular filtration and renal plasma flow), and a negative lactate uptake. Septic animals with AKI had lower values of mean end arterial pressure, renal blood flow and kidney perfusion pressure, with an associated increase in kidney oxygen extraction. No tubular necrosis was observed in kidney histology. Conclusions: The reduction in renal blood flow and renal perfusion pressure were the main mechanisms associated with AKI, but were not associated with necrosis. Probably other mechanisms, such as microcirculatory vasoconstriction and inflammation also contributes to AKI development.

Controversias en tromboembolismo pulmonar masivo

Massive pulmonary embolism (PE) is associated with high mortality. There is still a broad assortment of severity classifications for patients with PE, which affects the choice of therapies to use. The main clinical criteria for defining a PE as massive is systemic arterial hypotension, which depends on the extent of vascular obstruction and the previous cardiopulmonary status. Right ventricular dysfunction is an important pathogenic element to define the severity of patients and short term clinical prognosis. The recommended treatment is systemic thrombolysis, but in centers with experience and resources, radiological invasive therapies through catheters are useful alternatives that can be used as first choice tools in certain cases.Massive pulmonary embolism (PE) is associated with high mortality. There is still a broad assortment of severity classifications for patients with PE, which affects the choice of therapies to use. The main clinical criteria for defining a PE as massive is systemic arterial hypotension, which depends on the extent of vascular obstruction and the previous cardiopulmonary status. Right ventricular dysfunction is an important pathogenic element to define the severity of patients and short term clinical prognosis. The recommended treatment is systemic thrombolysis, but in centers with experience and resources, radiological invasive therapies through catheters are useful alternatives that can be used as first choice tools in certain cases.

Tromboembolismo pulmonar: estratificación de riesgo y dilemas terapéuticos

Background: The prognosis of pulmonary thromboembolism (PE) is related to the cardiopulmonary reserve of the patient and the magnitude of the embolus that impacts pulmonary circulation. The presence of hemodynamic instability (shock) stratifies a group of patients with high mortality, which should be treated with thrombolysis. Patients without shock but with right ventricular dysfunction can have a dismal evolution and should be managed aggressively. CAT scan, echocardiography and serum markers can be of value to define patients with a higher mortality. The available evidence to define the best diagnostic and therapeutic strategy is scanty, controversial and inconclusive. A good combination of clinical, imaging and biological markers should be defined to identify those patients without shock but with a high rate of complications and mortality, that could benefit from aggressive treatments.

Resultados preliminares y factibilidad del mini lavado bronco-alveolar en pacientes cursando falla respiratoria severa

BACKGROUND To recognize the etiological agent responsible for severe acute respiratory failure (ARF) in patients in mechanical ventilation (MV) is important to determine their treatment and prognosis, and to avoid the excessive use of antibiotics. Mini bronchoalveolar lavage (mini BAL) is a blind, non bronchoscopic procedure, used to obtain samples from the lower respiratory tract from patients on mechanical ventilation (MV). AIM To assess the feasibility, complications and preliminary results of mini BAL among patients with severe ARF on MV. MATERIAL AND METHODS Prospective study in 17 patients with acute lung injury (ALI ) or acute respiratory distress syndrome (ARDS) on MV and with negative conventional microbiological studies. Mini BAL was performed using standardized protocols. Hemodynamic and respiratory parameters where measured before and after the procedure. Samples obtained were sent to quantitative cultures. RESULTS At baseline: APACHE II score of 22 ± 6,7, PaO2/FiO2 ratio was 176.6 ± 48.6 and the oxygenation index was 9.74 ± 3.78. All procedures were performed by an ICU resident. Thirty five percent of the procedures had positive cultures and no complications related to the procedures were reported. The procedure lasted an average of 12 minutes and the instilled and rescued volume were 60 ml and 19.6 ml, respectively. There were no significant differences between hemodynamic and respiratory variables before and after the procedure. CONCLUSIONS Mini BAL is a safe, fast and easy technique for obtaining samples from the inferior airway in patients with ALI or ARDS on MV.