Critical care medicine
-
Critical care medicine · Feb 2003
Comparative StudyPerformance of the partial CO2 rebreathing technique under different hemodynamic and ventilation/perfusion matching conditions.
The partial CO2 rebreathing technique has been demonstrated to accurately measure the effective pulmonary capillary blood flow (PCBF) in different clinical situations. Usually, PCBF is calculated from changes in CO2 elimination (VCO2) and end-tidal partial pressure of CO2 (PetCO2 ), which can be obtained noninvasively. In this study, we investigated the performance of the partial CO2 rebreathing technique under different conditions of ventilation/perfusion matching and hemodynamic states. In addition, we investigated whether the determination of arterial blood gases combined with mathematical modeling of gas exchange can improve the performance of this method. ⋯ Although PCBF is systematically underestimated during hyperdynamic cardiac output states and high alveolar deadspaces, the performance of the partial CO2 rebreathing technique can be improved by means of arterial blood gas sampling and an algorithm that takes in account the effects of nonequilibration of PetCO2 during rebreathing and the variation of Pc'CO2 to PetCO2 differences from the nonrebreathing to the rebreathing period. Such an algorithm may prove useful under moderately increased alveolar deadspace and normal to hypodynamic cardiac output states.
-
Critical care medicine · Feb 2003
Noninvasive mechanical ventilation in clinical practice: a 2-year experience in a medical intensive care unit.
To evaluate the feasibility and outcome results of noninvasive mechanical ventilation (NIV) in daily clinical practice outside any prospective protocol-driven trial. ⋯ This study confirms the results of controlled trials and demonstrates the feasibility and efficacy of NIV applied in daily clinical practice. These results suggest that NIV should be considered as a first-line ventilatory treatment in various etiologies of acute respiratory failure and as a promising weaning technique and postextubation ventilatory support. However, NIV should certainly be performed by a motivated and sufficiently trained care team.
-
Critical care medicine · Feb 2003
Time course of hemoglobin concentrations in nonbleeding intensive care unit patients.
To evaluate the time course of hemoglobin concentrations in nonbleeding intensive care unit patients. ⋯ Hemoglobin concentrations typically decline by >0.5 g/dL/day during the first days of intensive care unit stay in nonbleeding patients. Beyond the third day, hemoglobin concentrations can remain relatively constant in nonseptic patients but continue to decrease in septic patients, as well as patients with high sepsis-related organ failure assessment or Acute Physiology and Chronic Health Evaluation II scores. These observations may help in the interpretation of hemoglobin concentrations in critically ill patients.
-
Critical care medicine · Feb 2003
Hyponatremia after hip arthroplasty may be related to a translocational rather than to a dilutional mechanism.
Postoperative hyponatremia is a frequent metabolic disturbance that may cause life-threatening complications. It results from both a positive electrolyte-free water (EFW) balance and an antidiuretic hormone release. During surgery, intracellular solutes may leak out of cells because of an increased membrane permeability leading to increased osmolality, cellular water shift, and redistribution hyponatremia, a concept coined the sick cell syndrome. Because of release of osmotically active solutes, plasma or urinary osmolar gap should increase. Therefore, we tested the hypothesis that postoperative hyponatremia may be related to a translocational mechanism evidenced by a postoperative increase of the osmolar gap rather than to a positive EFW balance. ⋯ Hyponatremia after hip arthroplasty may not be related to a positive EFW balance. The postoperative increase of the OG(p) and the greater postoperative OG(u) in patients developing postoperative hyponatremia suggest the release of osmotically active solutes leading to cellular water shift from intracellular to extracellular spaces. These data may support the clinical relevance of the sick cell syndrome in the postoperative context.
-
Critical care medicine · Feb 2003
Induced hyperthermia exacerbates neurologic neuronal histologic damage after asphyxial cardiac arrest in rats.
Temperature is an important modulator of the evolution of ischemic brain injury--with hypothermia lessening and hyperthermia exacerbating damage. We recently reported that children resuscitated from predominantly asphyxial arrest often develop an initial spontaneous hypothermia followed by delayed hyperthermia. The initial hypothermia observed in these children was frequently treated with warming lights which, despite careful monitoring, often resulted in overshoot hyperthermia. We have previously reported in a rat model of asphyxial cardiac arrest that active warming, to prevent spontaneous hypothermia, worsens brain injury. ⋯ Induced hyperthermia when administered at 24 hrs, but not 48 hrs, worsens ischemic brain injury in rats resuscitated from asphyxial cardiac arrest. This may have implications for postresuscitative management of children and adults resuscitated from cardiac arrest. The common clinical practice of actively warming patients with spontaneous hypothermia might result in iatrogenic injury if warming results in hyperthermic overshoot. Avoidance of hyperthermia induced by active warming at critical time periods after cardiac arrest may be important.