LITERATURE MONITOR FOR CRITICAL CARE

BICARBONATES NOT BENEFICIAL IN SEVERE DIABETIC KETOACIDOSIS

Whether bicarbonate therapy is helpful for patients with severe diabetic ketoacidosis remains controversial. However, data from a recent study suggest that this treatment is not beneficial for patients with pH values between 6.90 and 7.10.

Viallon et al retrospectively analyzed records from 39 patients consecutively admitted for severe diabetic ketoacidosis (pH below 7.10). Twenty-four patients received a sodium bicarbonate infusion; the remaining 15 patients did not.

The two groups had similar biochemical and clinical parameters on admission and during the first 24 hours afterward. In addition, the time to normalization of pH and the time to clearance of urine ketone was similar among the two groups. Furthermore, no differences were noted during the first 24 hours in mean serum lactate, chloride, creatinine, or urea concentrations; arterial oxygen tension; or osmolality. Although the decrease in serum potassium levels was similar between the two groups, the bicarbonate group required a significantly greater amount of potassium supplementation.

"Our study does not demonstrate that use of bicarbonate in severe ketoacidosis with pH between 6.90 and 7.10 enables more rapid normalization of biochemical and clinical parameters," Viallon et al concluded. However, further investigation of the efficacy of bicarbonates for patients with pH values less than 6.90 is warranted, they noted.

Viallon A, Zeni F, Lafond P, et al. Does bicarbonate therapy improve the management of severe diabetic ketoacidosis? Crit Care Med. 1999;27:2690-2693.

TREATMENT OF INFECTION: TO WAIT OR NOT TO WAIT?

Waiting for microbiologic data before initiating the treatment of nosocomial infection in febrile surgical patients is not harmful and may, in fact, reduce mortality and length of stay, a prospective study suggests.

Pelletier et al examined 274 patients who suffered a total of 372 episodes of nosocomial infection accompanied by fever. Outcome was evaluated based on whether treatment was initiated within 12 hours of fever onset, between 13 and 24 hours, or after 24 hours. Microbiologic results would be available to guide treatment in those patients treated more than 20 hours after onset of fever, Pelletier et al explained. The patients were divided into subgroups based on severity of illness as determined by APACHE II scores.

Early empiric therapy (within 12 hours) was not associated with decreased mortality or length of stay following initiation of therapy in any subgroup. In fact, among patients with severe illness (APACHE II score above 20), those whose antibiotic treatment began more than 24 hours after fever onset had a lower mortality rate than did those treated no more than 12 hours after fever onset. Patients with mild illness (APACHE II score of 10 or less) had similar mortality rates and lengths of stay regardless of time from fever onset to intervention.

"Directing therapy based on microbiologic data may decrease inappropriate antibiotic use and limit unnecessary cost and exposure to toxic effects," Pelletier et al concluded. However, they warned, the findings need to be confirmed in larger studies.

Pelletier SJ, Crabtree TD, Gleason TG, et al. Waiting for microbiologic data to direct therapy against nosocomial infections in febrile surgical patients: are outcomes worsened? Arch Surg. 1999;134:1300-1307.

PULMONARY EMBOLISM MAY CAUSE FEVER

A low-grade fever is not uncommon in patients with pulmonary embolism (PE) and may be present even in those without pulmonary hemorrhage or infarction, according to findings from a retrospective analysis.

Stein et al compared temperature among 311 patients with angiographically proven PE who were enrolled in the Prospective Investigation of Pulmonary Embolism Diagnosis (PIOPED) study.

In this cohort, 43 patients (14%) presented with fever that could not be attributed to any other cause. Fever was usually low-grade, with only 6% of febrile patients having temperatures of 101ºF or higher.

Fever did not occur more frequently among patients with pulmonary hemorrhage or infarction than in those without. However, patients with fever were more likely to have signs or symptoms of deep venous thrombosis.

"In conclusion, although most patients with PE are afebrile, a low-grade fever may occur, and, rarely, even a high fever may occur," Stein et al reported. Thus, they caution that the presence of fever does not exclude a diagnosis of PE.

Stein PD, Afzal A, Henry JW, Villareal CG. Fever in acute pulmonary embolism. Chest. 2000;117:39-42.

PREDICTORS OF SHOCK AFTER THROMBOLYTIC THERAPY

Age and three other easily measured variables can be used to estimate the risk of cardiogenic shock in patients treated with thrombolytic therapy for acute myocardial infarction (AMI).

Hasdai et al evaluated data on 1,889 patients who developed shock after being randomized to various thrombolytic therapies in the first Global Utilization of Streptokinase and Tissue-Plasminogen Activator for Occluded Coronary Arteries (GUSTO-I) trial.

Older age was the strongest predictor of shock, with a 47% increase in risk for every 10-year increase in age. Systolic blood pressure, heart rate, and Killip class were also strong predictors. Together, these four variables accounted for more than 85% of the information needed to predict shock.

Furthermore, Hasdai et al used these variables to develop a scoring system to predict the risk of shock after thrombolytic therapy. When applied to a different cohort of patients (from the GUSTO-III trial), the scoring system's validated concordance index was quite high--0.796.

Physicians who treat patients with AMI now face "the challenge of promptly identifying [those] at risk and taking measures to avert the occurrence of shock," the researchers concluded.

Hasdai D, Califf RM, Thompson TD, et al. Predictors of cardiogenic shock after thrombolytic therapy for acute myocardial infarction. J Am Coll Cardiol. 2000;35:136-143.

NONINVASIVE VENTILATION FOR TRANSPLANT RECIPIENTS

Antonelli et al randomized 40 patients who had undergone solid organ transplantation and had developed acute respiratory failure to one of two ventilatory strategies: standard treatment (oxygen supplementation delivered by Venturi mask) or NIV administered via face mask. Patients who failed their assigned treatment underwent endotracheal intubation and were mechanically ventilated.

The rate of endotracheal intubation was significantly lower in the NIV group than in the group given standard treatment (20% vs 70%). Patients who received NIV also had a lower frequency of fatal complications (20% vs 50%) and intensive care unit (ICU) mortality (20% vs 50%), compared with patients who received standard treatment. In addition, NIV was associated with a reduced length of stay in the ICU among survivors (5.5 vs 9.0 days with standard treatment). However, overall hospital mortality was similar between the groups.

Furthermore, the NIV group had a lower rate of nosocomial infections and a shorter use of invasive devices. The latter finding is especially important because a longer use of invasive devices was associated with a higher incidence of septic complications in this study.

Antonelli M, Conti G, Bufi M, et al. Noninvasive ventilation for treatment of acute respiratory failure in patients undergoing solid organ transplantation: a randomized trial. JAMA. 2000;283:235-241.

TOPICAL LIDOCAINE MAY EXAGGERATE LARYNGOMALACIA

Application of topical lidocaine to the larynx may cause an increase in laryngeal collapse and stridor among some infants and children undergoing bronchoscopy. This change may exaggerate the severity of laryngeal dysfunction and possibly lead to overly aggressive treatment.

Nielson et al examined 156 infants and children referred for flexible fiberoptic bronchoscopy for a variety of indications--most commonly, wheezing, cough, and stridor. Each subject was sedated with midazolam and nalbuphine, and topical lidocaine was applied to the nasal passage to increase comfort as the bronchoscope was inserted.

The researchers scored the signs of laryngomalacia (ie, the magnitude of collapse of the arytenoids and folding of the epiglottis during inspiration) before and after spraying 1 mL of preservative-free 2% lidocaine solution onto the larynx and vocal cords. Additional doses of lidocaine were applied as necessary to achieve adequate topical anesthesia.

The laryngomalacia score was significantly more likely to increase than decrease after application of topical lidocaine. Subjects less than 100 weeks old were more likely to have laryngomalacia at baseline and to experience an increased laryngomalacia score after application of topical lidocaine than were older children.

To determine if the laryngeal changes were caused by lidocaine's anesthetic properties rather than by other nonspecific effects, 10 additional infants or children with a history and physical findings consistent with laryngomalacia were evaluated at baseline, after a topical dose of normal saline, and after a topical dose of lidocaine. While the laryngomalacia score did not change with the saline spray, it increased after the lidocaine administration.

Recurrent croup, stridor, and wheezing were all positive predictors of laryngomalacia. Nielson et al believe that each child should be considered within the clinical context. "A child who exhibits some signs of malacia after topical anesthesia, but who has no history of stridor or other abnormal breath sounds, probably does not have significant laryngomalacia," they noted.

Nielson DW, Ku PL, Egger M. Topical lidocaine exaggerates laryngomalacia during flexible bronchoscopy. Am J Respir Crit Care Med. 2000;161:147-151.

PREDICTORS OF POOR OUTCOME FOR HIV PATIENTS IN THE ICU

Respiratory failure is the most common cause of death among adults with human immunodeficiency virus (HIV) who are admitted to an intensive care unit (ICU). While long-term survival rates are low in this population, a substantial minority of patients with multiple risk factors for mortality survive, Nickas and Wachter have reported.

These researchers retrospectively reviewed medical charts from 394 adults infected with HIV who were admitted to an ICU between 1992 and 1995. The most common indications for admission were respiratory failure (47%), sepsis (12%), and neurologic disease (11%). The majority of patients survived hospitalization (63%); survival rates at one, two, three, and four years following discharge were 27%, 18%, 13%, and 11%, respectively.

The following factors were independent predictors of hospital mortality: low serum albumin level, high Acute Physiology Score, need for mechanical ventilation, and diagnosis of Pneumocystis carinii pneumonia during ICU admission.

Among patients who survived the initial hospitalization, poor long-term survival was associated with a low CD4+ cell count (below 50 cells/µL), low serum albumin level (below 25 g/L), and need for mechanical ventilation. In fact, only 7% of patients with all three of these factors survived for 2.5 years or more after hospital discharge.

"Given the advances in antiretroviral treatment and their widespread use since 1996-1997, we have even more reason to be optimistic about the long-term survival of patients infected with HIV admitted to an ICU," Nickas and Wachter concluded.

Nickas G, Wachter RM. Outcomes of intensive care for patients with human immunodeficiency virus infection. Arch Intern Med. 2000;160:541-547.

T CELL INVOLVEMENT IN TEN

T cells may play an important role in the development of toxic epidermal necrolysis (TEN), Leyva et al concluded after studying three patients who had a severe reaction upon receiving anticonvulsants. "We propose that an immunologic reaction originating in the skin, triggered by a culprit metabolite, develops a specific mechanism activating immunocompetent CLA+ [cutaneous lymphocyte-associated antigen] T cells, which migrate toward the skin and contribute to the development of TEN," they reported.

Leyva et al took peripheral blood and skin samples from three patients who developed TEN after taking phenytoin or carbamazepine. These samples were used to monitor skin-homing CLA+ T cells and other adhesion molecules, activation markers, and inflammatory interleukins.

In all three patients, the level of CD3+CLA+ T cells in both peripheral blood and skin samples increased progressively as the clinical symptoms worsened. However, these levels returned to normal as the patients' skin condition improved. "CLA expression on the skin T-cell infiltrate remained for a longer period, probably because of a continuous trafficking toward the cutaneous compartment of activated CLA+ T cells and their soluble mediators," the researchers noted.

E-Selectin was detected in cutaneous endothelial cells in parallel with CLA expression on lymphocytes, Leyva et al explained. In addition, peripheral blood mononuclear cells showed an overexpression of tumor necrosis factor alpha, interferon-gamma, and interleukin-2.

Leyva L, Torres MJ, Posadas S, et al. Anticonvulsant-induced toxic epidermal necrolysis: monitoring the immunologic response. J Allergy Clin Immunol. 2000;105:157-165.

PROLONGED ICU STAY CAN IMPROVE FUNCTIONAL STATUS

Most survivors of a prolonged stay in the intensive care unit (ICU) can be expected to return to an independent functional status and adequate quality of life, according to findings from a retrospective review. In this analysis, "all patients, regardless of age, showed significant functional improvement after rehabilitation," Miller et al reported.

The researchers studied medical records from 115 patients age 4 to 89 years who were in the ICU for three weeks or more (mean duration, 36 days).

Overall, 22% of the group died in the hospital. Survivors and nonsurvivors had similar mean days requiring mechanical ventilation and mean ICU length of stay, even though survivors spent significantly more time in the hospital. Interestingly, mean costs were also similar among survivors and nonsurvivors ($193,000 and $218,000, respectively).

Of the remaining 90 patients who survived to discharge, 60% entered a rehabilitation facility, 22% returned home with temporary disability, 8% entered a nursing home, 6% transferred to another area of the hospital. and 4% returned home with permanent disability.

Age was the only predictor of mortality in this study. Elderly patients (age 75 years and older) had a mortality rate of 42%. The researchers noted that "no injury or combination of injuries could predict outcome except for the fact that a significantly higher percentage of patients in the survivor group had severe closed head injuries than were found in the nonsurvivor group."

Next, Miller et al focused on the subgroup of patients who entered an inpatient rehabilitation program. Upon admission to the facility, the patients had a mean functional independence measures (FIM) score of 52, meaning that they were either completely dependent or required moderate assistance. However, by the end of their stay (mean length of stay, 48 days), the patients' mean FIM score improved to 86, indicating the need for minimal contact assistance or supervision only. Furthermore, after three months of follow-up, the mean FIM score increased to 101, signifying modified to complete independence.

This improvement in outcome was also found among elderly patients. Only FIM score at admission was related to improved FIM score after rehabilitation.

Miller RS, Patton M, Graham RM, Hollins D. Outcomes of trauma patients who survive prolonged lengths of stay in the intensive care unit. J Trauma. 2000;48:229-234.

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