Hypothermia, immune suppression and SDD: can we have our cake and eat it?

In vitro studies and clinical observations suggest that both accidental and controlled/therapeutic hypothermia have a strong immunosuppressive effect, and that hypothermia increases the risk of infections, especially wound infections and pneumonia. In the previous issue of Critical Care, Kamps and colleagues report that when hypothermia was used for prolonged periods in patients with severe traumatic brain injury in conjunction with selective decontamination of the digestive tract, the risks of infection were the same or lower in patients treated with therapeutic cooling. The risk of infection is widely regarded as the most important danger of therapeutic cooling. The findings of Kamps and colleagues need to be verified in prospective trials and in higher-resistance environments, but raise the possibility of cooling for prolonged periods with greatly reduced risk. We may be able to have our cake and eat it

Severe electrolyte disorders following cardiac surgery: a prospective controlled observational study

INTRODUCTION: Electrolyte disorders are an important cause of ventricular and supraventricular arrhythmias as well as various other complications in the intensive care unit. Patients undergoing cardiac surgery are at risk for development of tachyarrhythmias, especially in the period during and immediately after surgical intervention. Preventing electrolyte disorders is thus an important goal of therapy in such patients. However, although levels of potassium are usually measured regularly in these patients, other electrolytes such as magnesium, phosphate and calcium are measured far less frequently. We hypothesized that patients undergoing cardiac surgical procedures might be at risk for electrolyte depletion, and we therefore conducted the present study to assess electrolyte levels in such patients. METHODS: Levels of magnesium, phosphate, potassium, calcium and sodium were measured in 500 consecutive patients undergoing various cardiac surgical procedures who required extracorporeal circulation (group 1). A total of 250 patients admitted to the intensive care unit following other major surgical procedures served as control individuals (group 2). Urine electrolyte excretion was measured in a subgroup of 50 patients in both groups. RESULTS: All cardiac patients received 1 l cardioplegia solution containing 16 mmol potassium and 16 mmol magnesium. In addition, intravenous potassium supplementation was greater in cardiac surgery patients (mean ± standard error: 10.2 ± 4.8 mmol/hour in cardiac surgery patients versus 1.3 ± 1.0 in control individuals; P < 0.01), and most (76% versus 2%; P < 0.01) received one or more doses of magnesium (on average 2.1 g) for clinical reasons, mostly intraoperative arrhythmia. Despite these differences in supplementation, electrolyte levels decreased significantly in cardiac surgery patients, most of whom (88% of cardiac surgery patients versus 20% of control individuals; P < 0.001) met criteria for clinical deficiency in one or more electrolytes. Electrolyte levels were as follows (mmol/l [mean ± standard error]; cardiac patients versus control individuals): phosphate 0.43 ± 0.22 versus 0.92 ± 0.32 (P < 0.001); magnesium 0.62 ± 0.24 versus 0.95 ± 0.27 (P < 0.001); calcium 1.96 ± 0.41 versus 2.12 ± 0.33 (P < 0.001); and potassium 3.6 ± 0.70 versus 3.9 ± 0.63 (P < 0.01). Magnesium levels in patients who had not received supplementation were 0.47 ± 0.16 mmol/l in group 1 and 0.95 ± 0.26 mmol/l in group 2 (P < 0.001). Urinary excretion of potassium, magnesium and phosphate was high in group 1 (data not shown), but this alone could not completely account for the observed electrolyte depletion. CONCLUSION: Patients undergoing cardiac surgery with extracorporeal circulation are at high risk for electrolyte depletion, despite supplementation of some electrolytes, such as potassium. The probable mechanism is a combination of increased urinary excretion and intracellular shift induced by a combination of extracorporeal circulation and decreased body temperature during surgery (hypothermia induced diuresis). Our findings may partly explain the high risk of tachyarrhythmia in patients who have undergone cardiac surgery. Prophylactic supplementation of potassium, magnesium and phosphate should be seriously considered in all patients undergoing cardiac surgical procedures, both during surgery and in the immediate postoperative period. Levels of these electrolytes should be monitored frequently in such patients

Acute lung injury, overhydration or both?

Acute lung injury or acute respiratory distress syndrome (ALI/ARDS) in the course of sepsis is thought to result from increased pulmonary capillary permeability and resultant edema. However, when the edema is assessed at the bedside by measuring the extravascular thermal volume by transpulmonary dilution, some ALI/ARDS patients with sepsis may have normal extravascular lung water (EVLW). Conversely, a raised EVLW may be present even when criteria for ALI/ARDS are not met, according to GS Martin and colleagues in this issue of Critical Care. This commentary puts the findings into a broader perspective and focuses on the difficulty, at the bedside, in recognizing and separating various types of pulmonary edema. Some of these forms of edema, classically differentiated on the basis of increased permeability and cardiogenic/hydrostatic factors, may overlap, whereas the criteria for ALI/ARDS may be loose, poorly reproducible, relatively insensitive and nonspecific, and highly therapy-dependent. Overhydration is particularly difficult to recognize. Additional diagnostics may be required to improve the delineation of pulmonary edema so as to redirect or redefine treatment and improve patient morbidity and, perhaps, mortality. Monitoring EVLW by single transpulmonary thermal dilution, for instance, might have a future role in this process

Novel applications of therapeutic hypothermia: report of three cases

Therapeutic hypothermia can provide neuroprotection in various situations where global or focal neurological injury has occurred. Hypothermia has been shown to be effective in a large number of animal experiments. In clinical trials, hypothermia has been used in patients with postanoxic injury following cardiopulmonary resuscitation, in traumatic brain injury with high intracranial pressure, in the perioperative setting during various surgical procedures and for various other indications. There is thus evidence that hypothermia can be effective in various situations of neurological injury, although a number of questions remain unanswered. We describe three patients with unusual causes of neurological injury, whose clinical situation was in fundamental aspects analogous to conditions where hypothermia has been shown to be effective

Hospital-acquired sinusitis is a common cause of fever of unknown origin in orotracheally intubated critically ill patients

INTRODUCTION: Sinusitis is a well recognised but insufficiently understood complication of critical illness. It has been linked to nasotracheal intubation, but its occurrence after orotracheal intubation is less clear. We studied the incidence of sinusitis in patients with fever of unknown origin (FUO) in our intensive care unit with the aim of establishing a protocol that would be applicable in everyday clinical practice. METHODS: Sinus X-rays (SXRs) were performed in all patients with fever for which an initial screening (physical examination, microbiological cultures and chest X-ray) revealed no obvious cause. All patients were followed with a predefined protocol, including antral drainage in all patients with abnormal or equivocal results on their SXR. RESULTS: Initial screening revealed probable causes of fever in 153 of 351 patients (43.6%). SXRs were taken in the other 198 patients (56.4%); 129 had obvious or equivocal abnormalities. Sinus drainage revealed purulent material and positive cultures (predominantly Pseudomonas and Klebsiella species) in 84 patients. Final diagnosis for the cause of fever in all 351 patients based on X-ray results, microbiological cultures, and clinical response to sinus drainage indicated sinusitis as the sole cause of fever in 57 (16.2%) and as contributing factor in 48 (13.8%) patients with FUO. This will underestimate the actual incidence because SXR and drainage were not performed in all patients. CONCLUSION: Physicians treating critically ill patients should be aware of the high risk of sinusitis and take appropriate preventive measures, including the removal of nasogastric tubes in patients requiring long-term mechanical ventilation. Routine investigation of FUO should include computed tomography scan, SXR or sinus ultrasonography, and drainage should be performed if any abnormalities are found