Critical care : the official journal of the Critical Care Forum
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New technology using partial carbon dioxide rebreathing has been developed to measure cardiac output. Because rebreathing increases respiratory effort, we investigated whether a newly developed system with 35 s rebreathing causes a lesser increase in respiratory effort under partial ventilatory support than does the conventional system with 50 s rebreathing. We also investigated whether the shorter rebreathing period affects the accuracy of cardiac output measurement. ⋯ When patients breathe spontaneously the partial carbon dioxide rebreathing technique increases minute ventilation and arterial carbon dioxide tension, but the effect is less with a shorter rebreathing period. The 35 s rebreathing period yielded cardiac output measurements similar in accuracy to those with 50 s rebreathing.
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Review
Bench-to-bedside review: adjuncts to mechanical ventilation in patients with acute lung injury.
Mechanical ventilation is indispensable for the survival of patients with acute lung injury and acute respiratory distress syndrome. However, excessive tidal volumes and inadequate lung recruitment may contribute to mortality by causing ventilator-induced lung injury. ⋯ To enhance CO2 elimination when tidal volume is reduced, the following are possible: first, ventilator respiratory frequency can be increased without necessarily generating intrinsic positive end-expiratory pressure; second, instrumental dead space can be reduced by replacing the heat and moisture exchanger with a conventional humidifier; and third, expiratory washout can be used for replacing the CO2-laden gas present at end expiration in the instrumental dead space by a fresh gas (this method is still experimental). For optimizing lung recruitment and preventing lung derecruitment there are the following possibilities: first, recruitment manoeuvres may be performed in the most hypoxaemic patients before implementing the preset positive end-expiratory pressure or after episodes of accidental lung derecruitment; second, the patient can be turned to the prone position; third, closed-circuit endotracheal suctioning is to be preferred to open endotracheal suctioning.
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Acute metabolic acidosis of non-renal origin is usually a result of either lactic or ketoacidosis, both of which are associated with a high anion gap. There is increasing recognition, however, of a group of acidotic patients who have a large anion gap that is not explained by either keto- or lactic acidosis nor, in most cases, is inappropriate fluid resuscitation or ingestion of exogenous agents the cause. ⋯ The levels of certain low molecular weight anions usually associated with intermediary metabolism were found to be significantly elevated in the plasma ultrafiltrate obtained from patients with metabolic acidosis. Our results suggest that these hitherto unmeasured anions may significantly contribute to the generation of the anion gap in patients with lactic acidosis and acidosis of unknown aetiology and may be underestimated in diabetic ketoacidosis. These anions are not significantly elevated in patients with normal anion gap acidosis.
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Respiratory variation in arterial pulse pressure is a reliable predictor of fluid responsiveness in mechanically ventilated patients with circulatory failure. The main limitation of this method is that it requires an invasive arterial catheter. Both arterial and pulse oximetry plethysmographic waveforms depend on stroke volume. We conducted a prospective study to evaluate the relationship between respiratory variation in arterial pulse pressure and respiratory variation in pulse oximetry plethysmographic (POP) waveform amplitude. ⋯ Respiratory variation in arterial pulse pressure above 13% can be accurately predicted by a respiratory variation in POP waveform amplitude above 15%. This index has potential applications in patients who are not instrumented with an intra-arterial catheter.
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Case Reports
Case report: severe heat stroke with multiple organ dysfunction - a novel intravascular treatment approach.
We report the case of a patient who developed a severe post-exertional heat stroke with consecutive multiple organ dysfunction resistant to conventional antipyretic treatment, necessitating the use of a novel endovascular device to combat hyperthermia and maintain normothermia. ⋯ In this case of severe heat stroke, presenting with multiple organ dysfunction and elevation of cytokines and chemokines, which was resistant to conventional cooling therapies, endovascular cooling may have contributed significantly to the reduction of body temperature and, possibly, avoided a fatal result.