Risk factors and outcomes for prolonged versus brief fever: a prospective cohort study

Current State of Knowledge on the Definition, Pathophysiology, Etiology, Outcomes, and Management of Fever in the Intensive Care Unit

Fever-an elevated body temperature-is a prominent feature of a wide range of disease conditions and is a common finding in intensive care, affecting up to 70% of patients in the intensive care unit (ICU). The causes of fever in the ICU are multifactorial, and it can be due to a number of infective and noninfective etiologies. The production of fever represents a complex physiological, adaptive host response that is beneficial for host defense and survival but can be maladaptive and harmful if left unabated. Despite any cause, fever is associated with a wide range of cellular, local, and systemic effects, including multiorgan dysfunction, systemic inflammation, poor neurological recovery, and an increased risk of mortality. This narrative review presents the current state-of-the-art knowledge on the definition, pathophysiology, etiology, and outcomes of fever in the ICU and highlights evidence-based findings regarding the management of fever in the intensive care setting.

Associations Between Core Temperature Disorders and Outcomes of Pediatric Intensive Care Unit Patients

BACKGROUND

The few studies of associations between fever and outcomes in pediatric intensive care unit (PICU) patients have conflicting findings. Associations between hypothermia and patient outcomes have not been studied.

OBJECTIVE

To investigate the incidence and characteristics of fever and hypothermia and their associations with adverse outcomes among PICU patients.

METHODS

Patients consecutively admitted to 2 PICUs in a 2-year period were prospectively studied. Core temperature was mainly measured by rectal or axillary thermometry. Fever and hypothermia were defined as core temperatures of greater than 38.0 °C and less than 36.0 °C, respectively. Prolonged mechanical ventilation, prolonged PICU stay, and PICU mortality were the adverse patient outcomes studied. Associations between patient outcomes and core temperature disorders were evaluated with univariate comparisons and multivariate analyses.

RESULTS

Of 545 patients enrolled, fever occurred in 299 (54.9%) and hypothermia occurred in 161 (29.5%). Both temperature disorders were independently associated with prolonged mechanical ventilation and prolonged PICU stay (P < .001) but not with PICU mortality. Late onset of fever (P < .001) and hypothermia (P = .009) were independently associated with prolonged mechanical ventilation, fever magnitude and duration (both P < .001) were independently associated with prolonged PICU stay, and fever magnitude (P < .001) and infectious cause of hypothermia (P= .01) were independently associated with higher PICU mortality.

CONCLUSIONS

These findings provide evidence that the manifestation and characteristics of fever and hypothermia are independent predictors of adverse outcomes in PICU patients.

Aetiologies and Risk Factors of Prolonged Fever Admission in Samtse Hospital, Bhutan, 2020

Febrile illness is a common cause of hospital admission in developing countries, including Bhutan. Prolonged fever admission can add considerable strain on healthcare service delivery. Therefore, identifying the underlying cause of prolonged hospital stays can improve the quality of patient care by providing appropriate empirical treatment. Thus, the study’s aims were to evaluate the aetiologies and factors of prolonged fever admission in Samtse Hospital, Bhutan. Fever admission data from 1 January to 31 December 2020 were retrieved from the Samtse Hospital database. Prolonged hospital stay was defined as those with >5 days of hospital admission. Univariable and multivariable logistic regression was used to identify risk factors for a prolonged hospital stay. Of 290 records, 135 (46.6%) were children (≤12 years), 167 (57.6%) were males, and 237 (81.7%) patients were from rural areas. The common aetiologies for fever admissions were respiratory tract infection (85, 29.3%) and acute undifferentiated febrile illness (48, 16.6%). The prolonged stay was reported in 87 (30.0%) patients. Patients from rural areas (adjusted odds ratio [AOR] = 4.02, 95% CI = 1.58−10.24) and those with respiratory tract infections (AOR = 5.30, 95% CI = 1.11−25.39) and urinary tract infections and kidney disease (AOR = 8.16, 95% CI = 1.33−49.96) had higher odds of prolonged hospital stay. This epidemiological knowledge on prolonged hospital stay can be used by the physician for the management of fever admission in Samtse Hospital.

Fever and Fever of Unknown Origin: Review, Recent Advances, and Lingering Dogma

Fever has preoccupied physicians since the earliest days of clinical medicine. It has been the subject of scrutiny in recent decades. Historical convention has mostly determined that 37.0°C (98.6°F) should be regarded as normal body temperature, and more modern evidence suggests that fever is a complex physiological response involving the innate immune system and should not be characterized merely as a temperature above this threshold. Fever of unknown origin (FUO) was first defined in 1961 by Petersdorf and Beeson and continues to be a clinical challenge for physicians. Although clinicians may have some understanding of the history of clinical thermometry, how average body temperatures were established, thermoregulation, and pathophysiology of fever, new concepts are emerging. While FUO subgroups and etiologic classifications have remained unchanged since 1991 revisions, the spectrum of diseases, clinical approach to diagnosis, and management are changing. This review considers how newer data should influence both definitions and lingering dogmatic principles. Despite recent advances and newer imaging techniques such as 18-fluorodeoxyglucose-positron emission tomography, clinical judgment remains an essential component of care.

Effects of the Incidence Density of Fever (IDF) on Patients Resuscitated From In-Hospital Cardiac Arrest: A Mediation Analysis

Objective: The aim of this research was to study the factors contributing to the survival rate of in-hospital cardiac arrest (IHCA) and to determine whether the incidence density of fever (IDF) acts as a mediator.

Methods: Data from patients with IHCA who survived more than 48 h were collected from 2011 to 2017. IDF was defined as the fever duration divided by the hospitalization duration, prolonged fever was defined as fever lasting for more than 5 days, and early fever was defined as an initial onset within the first 2 days of IHCA. Possible clinical variables associated with IDF were examined by linear regression, and possible clinical variables associated with survival rate were examined by univariate and multivariate analyses. IDF was investigated as a mediator of the indirect effects of the risk factors on survival.

Results: In our retrospective study, the median IDF was 0, with an interquartile range from 0 to 0.42. Prolonged fever was noted in 16% (97/605) of the total, and early fever was noted in 17.2% (104/605) of the total. Linear regression results showed that positive chest X-ray, central venous catheter and Glasgow Coma Score (GCS) ≤ 8 were related to IDF. The IDF (OR: 0.36, 95% CI, 0.13–0.97, P = 0.04), prolonged fever (adjusted OR = 0.13, 95% CI, 0.06–0.29, P < 0.001), positive chest X-ray (OR: 0.67, 95% CI, 0.46–0.98, P = 0.04), central venous catheter placement (OR: 0.54, 95% CI, 0.34–0.89, P = 0.01), and endotracheal intubation (OR: 0.47, 95% CI, 0.33–0.69, P < 0.001) were also related to the negative outcome of hospital discharge after adjustment. Additionally, positive chest X-ray had a 19% effect on survival outcome through IDF as a mediator, and the indirect effect of central venous catheter mediated by IDF accounted for 10% of the total.

Conclusions: A higher IDF, prolonged fever, a positive chest X-ray, the use of a central venous catheter and endotracheal intubation reduced the survival rate of these patients, and the detrimental impacts of a positive chest X-ray and the use of a central venous catheter on survival outcomes were partially mediated by IDF.

Fever Is Associated with Reduced, Hypothermia with Increased Mortality in Septic Patients: A Meta-Analysis of Clinical Trials

Background

Sepsis is usually accompanied by changes of body temperature (T_b), but whether fever and hypothermia predict mortality equally or differently is not fully clarified. We aimed to find an association between T_b and mortality in septic patients with meta-analysis of clinical trials.

Methods

We searched the PubMed, EMBASE, and Cochrane Controlled Trials Registry databases (from inception to February 2016). Human studies reporting T_b and mortality of patients with sepsis were included in the analyses. Average T_b with SEM and mortality rate of septic patient groups were extracted by two authors independently.

Results

Forty-two studies reported T_b and mortality ratios in septic patients (n = 10,834). Pearson correlation analysis revealed weak negative linear correlation (R² = 0.2794) between T_b and mortality. With forest plot analysis, we found a 22.2% (CI, 19.2–25.5) mortality rate in septic patients with fever (T_b > 38.0°C), which was higher, 31.2% (CI, 25.7–37.3), in normothermic patients, and it was the highest, 47.3% (CI, 38.9–55.7), in hypothermic patients (T_b < 36.0°C). Meta-regression analysis showed strong negative linear correlation between T_b and mortality rate (regression coefficient: -0.4318; P < 0.001). Mean T_b of the patients was higher in the lowest mortality quartile than in the highest: 38.1°C (CI, 37.9–38.4) vs 37.1°C (CI, 36.7–37.4).

Conclusions

Deep T_b shows negative correlation with the clinical outcome in sepsis. Fever predicts lower, while hypothermia higher mortality rates compared with normal T_b. Septic patients with the lowest (< 25%) chance of mortality have higher T_b than those with the highest chance (> 75%).

The Association of Fever with Total Mechanical Ventilation Time in Critically Ill Patients

This research aims to investigate the impact of fever on total mechanical ventilation time (TVT) in critically ill patients. Subgroup analysis was conducted using a previous prospective, multicenter observational study. We included mechanically ventilated patients for more than 24 hours from 10 Korean and 15 Japanese intensive care units (ICU), and recorded maximal body temperature under the support of mechanical ventilation (MAX(MV)). To assess the independent association of MAX(MV) with TVT, we used propensity-matched analysis in a total of 769 survived patients with medical or surgical admission, separately. Together with multiple linear regression analysis to evaluate the association between the severity of fever and TVT, the effect of MAX(MV) on ventilator-free days was also observed by quantile regression analysis in all subjects including non-survivors. After propensity score matching, a MAX(MV) ≥ 37.5°C was significantly associated with longer mean TVT by 5.4 days in medical admission, and by 1.2 days in surgical admission, compared to those with MAX(MV) of 36.5°C to 37.4°C. In multivariate linear regression analysis, patients with three categories of fever (MAX(MV) of 37.5°C to 38.4°C, 38.5°C to 39.4°C, and ≥ 39.5°C) sustained a significantly longer duration of TVT than those with normal range of MAX(MV) in both categories of ICU admission. A significant association between MAX(MV) and mechanical ventilator-free days was also observed in all enrolled subjects. Fever may be a detrimental factor to prolong TVT in mechanically ventilated patients. These findings suggest that fever in mechanically ventilated patients might be associated with worse mechanical ventilation outcome.

Clinical factors and incidence of prolonged fever in neurosurgical patients

AIMS AND OBJECTIVES

To describe the incidence of prolonged fever in patients admitted to the neurosurgery department, and the corresponding risk indicators.

BACKGROUND

Prolonged fever was defined as a temperature higher than 38·3°C lasting more than five days. Prolonged fever is a common phenomenon and could lead to worsened outcomes in specific patient groups, especially for those with brain injury. However, the studies on prolonged fever in neurosurgical patients are limited and insufficient.

DESIGN

A retrospective observational study.

METHODS

Retrospective data were collected from 1 January 2014 to 31 December 2014, at the neurosurgical department of a large teaching hospital. We performed univariate and multivariate analyses to identify independent indicators for prolonged fever vs. short-term fever.

RESULTS

Among 2845 patients, prolonged fever occurred in 466 (16%). The older patients were associated with longer duration of mechanical ventilation and hospital stay. It predominantly occurred in patients with subarachnoid haemorrhage (SAH) and traumatic brain injury. Patients receiving antibiotic treatment tended to manifest prolonged fever more frequently. Multivariate analysis revealed that the use of antibiotics, central venous catheter and prolonged mechanical ventilation were independent risk predictors for prolonged fever. Patients diagnosed with brain tumour seemed to be not associated with prolonged fever.

CONCLUSIONS

Prolonged fever is the common complication in neurosurgical patients. The risks of prolonged fever in patients are attributed to antibiotic therapy, use of central venous catheter and prolonged mechanical ventilation. Indicators of prolonged fever are helpful for better identification of high-risk patients and fever control.

RELEVANCE TO CLINICAL PRACTICE

A better reveal on the epidemiology and predictable factors of prolonged fever in neurosurgical patients will provide a better understanding on those patients who are most at risk, and therefore contribute to fever control and better outcome.

[Is control fever mandatory in severe infections?]

Temperature control during severe sepsis is currently used in intensive care and involves 66% and 70% of severe sepsis and septic shock, respectively. Nevertheless, the conclusive evidence of the benefit of such a strategy is still lacking.We might wonder, with regards to experimental works and recent noninterventional studies, about the risk of a control strategy on an ongoing infectious process, the patient's outcome, and the safety of the means implemented to obtain temperature control. On the other hand, it is also demonstrated that fever increases oxygen consumption, which may lead in some clinical situations to tissular ischemia and that fever may be associated with a deleterious focal inflammatory process. Methods to control the temperature include external and/or internal cooling and/or antipyretic medications such as paracetamol and nonsteroidal antiinflammatory drugs. In septic patients, external cooling and paracetamol are the mains means used to control temperature. Despite the uncertainties about the benefit to control or not the temperature, it could be stated that extreme temperature (hypo- or hyperthermia) should be avoided and that the benefit/risk of temperature control must be individually weighted.

Respective impact of lowering body temperature and heart rate on mortality in septic shock: mediation analysis of a randomized trial

PURPOSE

We previously showed that external cooling decreases day 14 mortality in febrile septic shock. Because cooling may participate in heart rate control, we studied the respective impact of heart rate and temperature lowering on mortality.

METHODS

Post hoc analysis of the Sepsiscool randomized controlled trial database (NCT00527007). Cooling was applied to maintain normothermia (36.5-37 °C) during 48 h. We assessed the time spent below different thresholds of temperature and heart rate on day 14 mortality. The best threshold was selected by AUC-ROC and tested as a potential mediator of mortality reduction. Mediation analysis was adjusted for severity and treatments influencing temperature and heart rate evolution. Sensitivity analysis was done using only patients with appropriate antimicrobial therapy.

RESULTS

A total of 197/200 patients with adequate heart rate and temperature monitoring were analyzed. The best threshold differentiating survivors and nonsurvivors was 38.4 °C for temperature and 95 b/min for heart rate. During the 48 h of intervention, cooling significantly increased the time spent with a temperature below 38.4 °C, p = 0.001, and with a heart rate below 95 b/min, p < 0.01. The longer was the time spent with a temperature below 38.4 °C, the lower was the mortality [adjOR 0.17 (0.06-0.49), p = 0.001]. The time spent with a heart rate below 95 b/min was similar in survivors and nonsurvivors [adjOR 0.68 (0.27-1.72), p = 0.42]. Mediation analysis showed that the time spent with a temperature below 38.4 °C was a significant mediator of mortality.

CONCLUSION

The time spent with a temperature below 38.4 °C was independently associated with patient's outcome and explained 73% of the effect of the randomization on the day 14 mortality. Heart rate lowering was not a mediator of mortality.

Early temperature and mortality in critically ill patients with acute neurological diseases: trauma and stroke differ from infection

BACKGROUND

Fever suppression may be beneficial for patients with traumatic brain injury (TBI) and stroke, but for patients with meningitis or encephalitis [central nervous system (CNS) infection], the febrile response may be advantageous.

OBJECTIVE

To evaluate the relationship between peak temperature in the first 24 h of intensive care unit (ICU) admission and all-cause hospital mortality for acute neurological diseases.

DESIGN, SETTING AND PARTICIPANTS

Retrospective cohort design from 2005 to 2013, including 934,159 admissions to 148 ICUs in Australia and New Zealand (ANZ) and 908,775 admissions to 236 ICUs in the UK.

RESULTS

There were 53,942 (5.8 %) patients in ANZ and 56,696 (6.2 %) patients in the UK with a diagnosis of TBI, stroke or CNS infection. For both the ANZ (P = 0.02) and UK (P < 0.0001) cohorts there was a significant interaction between early peak temperature and CNS infection, indicating that the nature of the relationship between in-hospital mortality and peak temperature differed between TBI/stroke and CNS infection. For patients with CNS infection, elevated peak temperature was not associated with an increased risk of death, relative to the risk at 37-37.4 °C (normothermia). For patients with stroke and TBI, peak temperature below 37 °C and above 39 °C was associated with an increased risk of death, compared to normothermia.

CONCLUSIONS

The relationship between peak temperature in the first 24 h after ICU admission and in-hospital mortality differs for TBI/stroke compared to CNS infection. For CNS infection, increased temperature is not associated with increased risk of death.

[Therapeutic hypothermia for severe traumatic brain injury]

Therapeutic hypothermia (TH) is considered a standard of care in the post-resuscitation phase of cardiac arrest. In experimental models of traumatic brain injury (TBI), TH was found to have neuroprotective properties. However, TH failed to demonstrate beneficial effects on neurological outcome in patients with TBI. The absence of benefits of TH uniformly applied in TBI patients should not question the use of TH as a second-tier therapy to treat elevated intracranial pressure. The management of all the practical aspects of TH is a key factor to avoid side effects and to optimize the potential benefit of TH in the treatment of intracranial hypertension. Induction of TH can be achieved with external surface cooling or with intra-vascular devices. The therapeutic target should be set at a 35°C using brain temperature as reference, and should be maintained at least during 48 hours and ideally over the entire period of elevated intracranial pressure. The control of the rewarming phase is crucial to avoid temperature overshooting and should not exceed 1°C/day. Besides its use in the management of intracranial hypertension, therapeutic cooling is also essential to treat hyperthermia in brain-injured patients. In this review, we will discuss the benefit-risk balance and practical aspects of therapeutic temperature management in TBI patients.

The continuing question of how fever duration is associated with patient outcome

Although fever magnitude and etiology have been associated with outcomes of critically ill patients, possible associations between fever duration and mortality remain inconclusive. Since long-lasting fever is generally attributed to severe pathologic conditions, it is expected to be an indicator of adverse outcome. It also seems plausible that persistent fever in specific patient groups, mainly those with cerebral damage or limited cardiorespiratory reserve, could lead to worsened outcomes. Existing studies on these associations have been considerably limited because of methodological flaws, which may account for controversial findings that have been reported. Well-designed, large-sample studies using diverse measures of fever duration need to be conducted.