Heart & lung : the journal of critical care
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A major responsibility of the critical care practitioner is to assure adequate ventilation of the critically ill patient. The traditionally used methods for evaluating ventilation, such as physical examination and measurement of vital signs, are indirect. The most commonly used direct method, measurement of arterial carbon dioxide tension, is invasive and intermittent. ⋯ We review relevant respiratory physiology as a basis for understanding the value of capnography. The technology on which capnography is based is described with emphasis on methods of gas sampling, limitations of capnography, and features available on currently marketed instruments. Representative capnograms are presented and the data interpreted to enable the practitioner to determine when capnography is an appropriate monitor for the critically ill adult.
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Comparative Study
Comparison of thermodilution and transthoracic electrical bioimpedance cardiac outputs.
Current methods of measuring cardiac output require the invasive insertion of a thermodilution catheter with its concomitant risks and complications. We examined the noninvasive method of transthoracic electrical bioimpedance (TEB) in comparison with thermodilution cardiac outputs in a sample of 44 critically ill patients with poor left ventricular function (left ventricular ejection fraction less than 30%) and with either ischemic or idiopathic dilated cardiomyopathy. Dyspnea, mitral regurgitation, tricuspid regurgitation, and difference between real and ideal weight had the most marked effects on the correlation between the two methods, with lesser influence by left ventricular ejection fraction, height, weight, hemoglobin, hematocrit, and aortic regurgitation. TEB and thermodilution cardiac outputs were correlated, at r = 0.51 (p less than 0.00009), but the low reliability and low percentage of TEB readings within 0.5 L/min of thermodilution cardiac outputs (31%) renders TEB inadequate for clinical measurement of cardiac outputs in this patient population.
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Cardiopulmonary resuscitation (CPR) is a technique that saves lives and is a measure that critical care practitioners use without hesitation. Potential complications from CPR, however, include injury. The reported incidence of such injuries ranges from 21% to more than 65%. ⋯ Limiting these injuries is important. Discovering them in successfully resuscitated victims, however, is critical to long-term recovery and rehabilitation. As future techniques for CPR evolve, further research needs to focus on those techniques that limit the potential for injury.
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The immediate transfusion of uncrossmatched type O blood in the initial resuscitation of the trauma victim remains controversial. To examine difficulties in crossmatching blood for later transfusions after use of uncrossmatched type O blood, we undertook a prospective 23-month study at a level I trauma center. One hundred thirty-five severely injured patients received uncrossmatched type O blood during the study period. ⋯ There were no major transfusion reactions. Six patients had blood antigen-antibodies present on admission, and such antibodies developed in three patients during hospitalization. We conclude that uncrossmatched type O blood may be used safely in the exsanguinating patient, but blood antigen-antibodies, which may complicate later crossmatching, can develop after its use.
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An unintended fall in body temperature is commonly associated with surgery. One promising strategy to help conserve body heat is use of covers made of aluminum-coated plastic. We compared the effect of three combinations of the covers (head cover, body covers, both) and a control condition on tympanic temperature in 60 adults having major abdominal surgery under general anesthesia. ⋯ After controlling for background variables affecting body temperature, adjusted PACU entry temperature was higher in the two groups with aluminized body covers. Regression analysis showed that use of the body covers accounted for 7% of the temperature variance at PACU entry and predicted a 0.9 degree F (0.5 degree C) higher temperature at that time. These findings indicate that aluminized body covers help to reduce heat loss in patients having major abdominal surgery.