Mechanisms of fever in pulmonary atelectasis

Early Postoperative Fever and Atelectasis in Patients Undergoing Upper Abdominal Surgery

BACKGROUND

Atelectasis is a common complication after upper abdominal surgery and considered as a cause of early postoperative fever (EPF) within 48 hours after surgery. However, the pathophysiologic mechanism of how atelectasis causes fever remains unclear.

STUDY DESIGN

Data for adult patients who underwent elective major upper abdominal surgery under general anesthesia at Seoul National University Hospital between January and December of 2021 were retrospectively analyzed. The primary outcome was the association between fever and atelectasis within 2 days after surgery.

RESULTS

Of 1,624 patients, 810 patients (49.9%) developed EPF. The incidence of atelectasis was similar between the fever group and the no-fever group (51.6% vs 53.9%, p = 0.348). Multivariate analysis showed no significant association between atelectasis and EPF. Culture tests (21.7% vs 8.8%, p < 0.001) and prolonged use of antibiotics (25.9% vs 13.9%, p < 0.001) were more frequent in the fever group compared to the no-fever group. However, the frequency of bacterial growth on culture tests and postoperative pulmonary complications within 7 days were similar between the two groups.

CONCLUSIONS

EPF after major upper abdominal surgery was not associated with radiologically detected atelectasis. EPF also was not associated with the increased risk of postoperative pulmonary complications, bacterial growth on culture studies, or prolonged length of hospital stay.

Atelectasis as a cause of postoperative fever: where is the clinical evidence?

BACKGROUND

Atelectasis is considered to be the most common cause of early postoperative fever (EPF) but the existing evidence is contradictory. We sought to determine if atelectasis is associated with EPF by analyzing the relevant published evidence.

METHODS

We performed a systematic search in PubMed and Scopus databases to identify studies examining the association between atelectasis and EPF.

RESULTS

A total of eight studies, including 998 cardiac, abdominal, and maxillofacial surgery patients, were eligible for analysis. Only two studies specifically examined our question, and six additional articles reported sufficient data to be included. Only one study reported a significant association between postoperative atelectasis and fever, whereas the remaining studies indicated no such association. The performance of EPF as a diagnostic test for atelectasis was also assessed, and EPF performed poorly (pooled diagnostic OR, 1.40; 95% CI, 0.92-2.12). The significant heterogeneity among the studies precluded a formal metaanalysis.

CONCLUSION

The available evidence regarding the association of atelectasis and fever is scarce. We found no clinical evidence supporting the concept that atelectasis is associated with EPF. More so, there is no clear evidence that atelectasis causes fever at all. Large studies are needed to precisely evaluate the contribution of atelectasis in EPF.

Fever in the ICU

Fever is a common problem in ICU patients. The presence of fever frequently results in the performance of diagnostic tests and procedures that significantly increase medical costs and expose the patient to unnecessary invasive diagnostic procedures and the inappropriate use of antibiotics. ICU patients frequently have multiple infectious and noninfectious causes of fever, necessitating a systematic and comprehensive diagnostic approach. Pneumonia, sinusitis, and blood stream infection are the most common infectious causes of fever. The urinary tract is unimportant in most ICU patients as a primary source of infection. Fever is a basic evolutionary response to infection, is an important host defense mechanism and, in the majority of patients, does not require treatment in itself. This article reviews the common infectious and noninfectious causes of fever in ICU patients and outlines a rational approach to the management of this problem.

Lack of association between atelectasis and fever

Postoperative fever occurs in many patients. If no infection is found, atelectasis, if present, may be blamed. This study of 100 postoperative cardiac surgery patients followed up from day of surgery through the second postoperative day with daily portable chest radiographs and continuous bladder thermometry was designed to look for an association between atelectasis and fever. The daily incidence of atelectasis increased from 43 to 69 to 79%. However, the incidence of fever, defined as temperature > or = 38.0 degrees C fell from 37 to 21 to 17%. When defined as temperature > or = 38.5 degrees C, the daily incidence of fever fell daily from 14 to 3 to 1%. Using chi 2 analysis, no association could be found between fever and amount of atelectasis. This contradicts common textbook dogma but agrees with previous human study and animal experiments.

Stacked inspiratory spirometry reduces pulmonary shunt in patients after coronary artery bypass

Atelectasis is a major factor in postoperative morbidity for patients undergoing cardiopulmonary surgery. We evaluated the effectiveness of stacked inspiratory spirometry (STIS) in 17 patients status postcoronary artery bypass graft in a nonrandomized fashion. We measured pulmonary shunt as an endpoint, and compared the magnitudes before and after the STIS maneuver. Our results showed an 8.66 percent reduction in pulmonary shunt (p < 0.05). The reduction in shunt was modest; however, repetitive maneuvers might result in greater improvement.

Can bacteremia be predicted in surgical intensive care unit patients?

OBJECTIVES

To determine which clinical features are associated with bacteremia in a SICU. To determine if infections are identified prior to bacteremia via culturing of other body fluids. To determine if antibiotic regimens are changed after the results of the blood culture were obtained.

DESIGN

A retrospective, unit-based, case control study.

SETTING

A 10 bed SICU in a 552-bed, tertiary care and Level I Trauma center.

PATIENTS

All SICU patients with one or more positive blood cultures over a 2 year period (n = 24) were matched by diagnosis, procedure, and age to SICU patients with negative blood cultures (n = 48).

MEASUREMENTS AND RESULTS

Bacteremic and control patients had similar APACHE II scores though death was more likely in bacteremic patients (p < 0.05) and they had higher hospital charges (p < 0.02). There was no difference in any of the clinical variables studied (minimum and maximum temperature, maximum white blood cell count, minimum mean arterial blood pressure) between the bacteremic and control groups on the days leading up to and the day of the positive blood culture. Coincident infections of lung, bladder, wound, and central venous catheters were identified in 42% of bacteremic patients. The identification of organisms found in the blood had a direct impact on the antibiotic regimen of 54% of the bacteremic patients.

CONCLUSIONS

A better screen for obtaining blood cultures in this SICU was not identified. If antibiotics are begun empirically before the results of blood cultures are known, the results of other body fluid cultures can be used to guide therapy initially. However, the data obtained from positive blood cultures was often helpful in changing empirical therapy. Therefore, blood cultures remain important diagnostic tools.

Pulmonary aspiration. The three syndromes

Pulmonary aspiration of oropharyngeal secretions, inert fluids and/or particulate material, or gastric contents produces three distinct clinical syndromes. Optimum management, although largely supportive, requires that the clinician understand the clinical presentation and course of each syndrome. Prevention is the primary goal. Early recognition of high-risk patients coupled with prompt institution of simple preventive measures can reduce the incidence and severity of these syndromes.

Physiology and complications of bed rest

Prolonged bed rest causes major cardiovascular, respiratory, musculoskeletal, and neuropsychological changes. Complications often result from these effects of bed rest, especially when aging has already decreased the reserves in these systems. These problems can be limited by judicious prescription of modified bed rest.

Preoperative identification and evaluation of the patient with lung disease

Preoperative pulmonary function evaluation begins with the bedside, clinical identification of the presence of significant lung disease. Once a patient is so identified, preoperative pulmonary-function studies are indicated. The optimal screening studies for most patients are spirometry and arterial blood gas analysis. Patients who are identified as having marginal function by screening techniques should be studied further by more specialized studies, including radioisotopic evaluation of regional lung function. If a patient is identified as an operative candidate, but one who has increased risk of postoperative morbidity, prophylactic measures should be instituted to reduce postoperative complications. The essence of such measures is increased care preoperatively, intraoperatively, and postoperatively. The use of preoperative evaluation of pulmonary function presents a different magnitude of problem in defining the risk of morbidity in contrast to that of mortality. Available data provide a firm basis for the identification of the patient at increased risk of morbidity. After 23 years and dozens of spirometric studies involving thousands of patients, it is apparent that there is no spirometric number, percentage, or category that will absolutely separate the operable from the inoperable patient. There are estimates of risk--guidelines, to be sure--but no absolutes. The patient whose lung function would have been considered to prohibit lung resection in the 1950s has been successfully operated on in the 1980s. In dealing with the risk of mortality, the physician should always bear in mind that, although statistics apply to groups, they often do not apply to individual patients.