Thrombotic microangiopathy: an atypical cause of acute renal failure in patients with acute pancreatitis.

OBJECTIVE: To report on the development and treatment of thrombotic microangiopathy, an atypical cause of acute renal failure in patients with acute pancreatitis. DESIGN: Case reports. SETTING: A 21-bed medical intensive care unit at an university hospital. PATIENTS: Two men with acute pancreatitis presented with acute renal failure, neurological manifestations, haemolytic anaemia and thrombocytopenia. Both patients required intensive care. MEASUREMENTS: Fragmented red cell count; levels of haptoglobin, amylase and lipase; serological testing for Escherichia Coli O157; computed tomography of the abdomen. MAIN RESULTS: The patients' courses were rapidly favourable after daily plasma exchange. A review of the existing medical literature was also undertaken. CONCLUSION: As thrombotic microangiopathy may be life-threatening without administration of fresh frozen plasma or plasma exchange, physicians should consider this disease as a possible cause of acute renal failure in patients with acute pancreatitis.

Air leaks during mechanical ventilation as a cause of persistent hypercapnia in neuromuscular disorders.

OBJECTIVE: This study investigated whether air leaks from the upper airway during assisted ventilatory support are associated with persistent hypercapnia (PaCO(2) >45 mmHg) in patients with neuromuscular disorders. SETTING: A rehabilitation hospital. PATIENTS: The study was performed in 95 neuromuscular patients; 52 were tracheostomized with a cuffless tracheostomy tube (invasive ventilation), and 43 received noninvasive ventilation. MEASUREMENTS AND RESULTS: The volume of air leaked (VL) and arterial carbon dioxide (PaCO(2)) were routinely measured during mechanical ventilation; PaCO(2) was also measured during spontaneous breathing. VL, expressed as a percentage of tidal volume, was higher in the hypercapnic group (32+/-14%, n=20) than the nonhypercapnic group ( vs. 20+/-14%). PaCO(2) during mechanical ventilation was correlated with both VL and the duration of ventilatory support per day; PaCO(2) during spontaneous breathing was correlated only with the volume of air leaked. In stepwise multiple regression analysis, air leaks contributed to 8% of the variance in PaCO(2) during mechanical ventilation, and daily duration of ventilatory support contributed 5%. In addition, reduction in VL with normalization of PaCO(2) was achieved in five of the noninvasively ventilated patients with persistent hypercapnia by using a chin strap. CONCLUSIONS: Air leaks during wakefulness are an important cause of persistent hypercapnia in both invasively and noninvasively ventilated neuromuscular patients. However, simple practical measures to reduce the volume of air leaks improve the efficacy of ventilation in these patients.

Physiological effects of decannulation in tracheostomized patients.

OBJECTIVE: To evaluate the physiological effects of decannulation on breathing patterns and respiratory mechanics by comparing mouth breathing (MB) to tracheal breathing (TB) in tracheostomized patients. DESIGN AND SETTING: Prospective cross-over study in a critical and neuromuscular care unit. PATIENTS AND METHODS: Nine consecutive neuromuscular tracheostomized patients. Flow, esophageal pressure, gastric pressure, expiratory gas, and arterial blood gases were measured during MB and TB. RESULTS: MB induced an increase in tidal volume (from 330+/-60 ml to 400+/-80 ml) without changing respiratory frequency, inspiratory time, or arterial CO(2) pressure. This ventilation increase was due to a significant increase in physiological dead space (from 156+/-67 to 230+/-82 ml) and was associated with significant increases in work of breathing (from 6.9+/-3.4 to 9.1+/-3.3 J/min), transdiaphragmatic pressure swing (from 10+/-4 to 12.5+/-7 cmH(2)O), diaphragmatic pressure-time product per minute (from 214+/-100 to 271+/-92 cmH(2)O s(-1) min(-1)), and oxygen uptake (from 206+/-30 to 229+/-34 ml/min). Upper airway resistance did not differ from in vitro tracheostomy tube resistance. In addition, total lung-airway resistance, dynamic pulmonary compliance, and intrinsic positive end-expiratory pressure were similar in both conditions. CONCLUSIONS: Decannulation resulted in a dead space increase with no other detectable additional loading. It increased work of breathing by more than 30%. Decannulation deserves special attention in patients with restrictive respiratory disease.

Hyperbaric oxygen therapy for acute domestic carbon monoxide poisoning: two randomized controlled trials.

INTRODUCTION: Although hyperbaric oxygen therapy (HBO) is broadly used for carbon monoxide (CO) poisoning, its efficacy and practical modalities remain controversial. OBJECTIVES: To assess HBO in patients poisoned with CO. DESIGN: Two prospective randomized trial on two parallel groups. SETTING: Critical Care Unit, Raymond Poincaré Hospital, Garches, France. SUBJECTS: Three hundred eighty-five patients with acute domestic CO poisoning. INTERVENTION: Patients with transient loss of consciousness (trial A, n = 179) were randomized to either 6 h of normobaric oxygen therapy (NBO; arm A0, n = 86) or 4 h of NBO plus one HBO session (arm A1, n = 93). Patients with initial coma (trial B, n = 206) were randomized to either 4 h of NBO plus one HBO session (arm B1, n = 101) or 4 h of NBO plus two 2 HBO sessions (arm B2, n = 105). PRIMARY ENDPOINT: Proportion of patients with complete recovery at 1 month. RESULTS: In trial A, there was no evidence for a difference in 1-month complete recovery rates with and without HBO [58% compared to 61%; unadjusted odds ratio, 0.90 (95% CI, 0.47-1.71)]. In trial B, complete recovery rates were significantly lower with two than with one HBO session [47% compared to 68%; unadjusted odds ratio, 0.42 (CI, 0.23-0.79)]. CONCLUSION: In patients with transient loss of consciousness, there was no evidence of superiority of HBO over NBO. In comatose patients, two HBO sessions were associated with worse outcomes than one HBO session.

The use of corticosteroids in severe sepsis and acute respiratory distress syndrome.

During sepsis or acute respiratory distress syndrome, the hypothalamic pituitary adrenal axis is rapidly activated through a systemic pathway, i.e. by circulating pro-inflammatory cytokines and through the vagus nerve. Subsequently, the adrenal glands release cortisol, a hormone which will likely counteract the inflammatory process and restore cardiovascular homeostasis. Both experimental models and studies in humans suggest that inadequate hypothalamic pituitary adrenal axis response to stress accounts, at least partly, for the genesis of shock and organ dysfunction in sepsis and acute respiratory distress syndrome. Relative adrenal insufficiency and peripheral glucocorticoid resistance syndrome are the two main features of the inappropriate hormonal response and provide the grounds for cortisol replacement in these diseases. In practice, a high dose of corticosteroids (i.e. one to four boluses of 30 mg/kg of methylprednisolone, or equivalent) had no effects on survival in severe sepsis or acute respiratory distress syndrome. There are at least seven randomised controlled trials reporting the benefits and risks of low dose corticosteroids (i.e. 200 to 300 mg daily of hydrocortisone or equivalent) given for a prolonged period in severe sepsis or in the late phase of acute respiratory distress syndrome. These trials showed consistently that, in these patients, the use of low dose of corticosteroids alleviated inflammation, restored cardiovascular homeostasis, reduced organ dysfunction, improved survival and was safe. Further studies are ongoing to better identify the target population. In the meantime, cortisol replacement (i.e. 200 to 300 mg daily of hydrocortisone or equivalent) should be considered as standard care for these patients.

Pressure support versus assisted controlled noninvasive ventilation in neuromuscular disease.

INTRODUCTION: Noninvasive ventilation (NIV) is being increasingly used in patients with chronic neuromuscular disorders, but the optimal ventilation mode remains unknown. We compared physiological short-term effects of assist/controlled ventilation (ACV) and two pressure-limited modes (pressure-support ventilation [PSV] and assist pressure-controlled ventilation [ACPV]) in patients with neuromuscular disease who needed NIV. METHODS: Tidal volume was 10 to 12 mL/kg. The ACPV mode used the same respiratory cycle timing as the volume-limited mode. The level of inspiratory support was set to achieve the same tidal volume during the other ventilatory modes. RESULTS: Thirteen patients with neuromuscular disease who met international criteria for NIV were included. The three ventilatory modes increased alveolar ventilation and decreased respiratory effort indices. However, no difference in breathing or respiratory effort was found among the three modes, with the exception that inspiratory peak flow and percentage of triggered cycles were higher during PSV than volume-limited ventilation. Interestingly, no relationship was observed between subjective patient preference and inspiratory effort indices or percentage of triggered cycles. CONCLUSION: In chronic, stable patients with neuromuscular disease, both noninvasive ACV, ACPV, and PSV had similar effects on alveolar ventilation and respiratory muscle unloading, despite some differences in the pattern of breathing and percentage of triggered cycles.

Cardiac and respiratory effects of continuous positive airway pressure and noninvasive ventilation in acute cardiac pulmonary edema.

OBJECTIVE: Continuous positive airway pressure (CPAP) is considered an effective nonpharmacologic method of treating patients with severe acute cardiogenic pulmonary edema. However, we hypothesized that bilevel noninvasive positive-pressure ventilation (NPPV), which combines both inspiratory pressure support and positive expiratory pressure, would unload the respiratory muscles and improve cardiac and hemodynamic function more effectively than CPAP. DESIGN: Randomized crossover study. SETTING: Critical care unit, Raymond Poincaré Hospital. PATIENTS: Six consecutive patients with acute cardiogenic pulmonary edema. INTERVENTIONS: Patients were sequentially treated with 5 cm H2O CPAP, 10 cm H2O CPAP, and NPPV in a random order. MEASUREMENTS AND MAIN RESULTS: Cardiac and hemodynamic function and indexes of respiratory mechanics were measured at each treatment sequence. NPPV reduced the esophageal pressure swing and esophageal pressure-time product compared with baseline (p <.05). There was no reduction in esophageal pressure swing or esophageal pressure-time product with CPAP. NPPV and 10 cm H2O CPAP reduced the mean transmural right and left atrial filling pressures without a change in cardiac index. CONCLUSIONS: This study demonstrates that NPPV was more effective at unloading the respiratory muscles than CPAP in acute cardiogenic pulmonary edema. In addition, NPPV and 10 cm H2O CPAP produced a reduction in right and left ventricular preload, which suggests an improvement in cardiac performance.