Original article
Fever and standard monitoring parameters of ICU patients: A descriptive study

https://doi.org/10.1016/j.iccn.2007.04.001Get rights and content

Summary

Objective

To investigate the effect of fever episodes and fever characteristics on heart rate, arterial blood pressure and arterial oxygen saturation of intensive care unit (ICU) patients.

Methods

This was a prospective study conducted in the medical–surgical ICU of General University Hospital of Patras, Greece. All patients who were consecutively admitted from October 2005 to February 2006 and manifested fever during ICU stay were enrolled. A tympanic membrane or an axillary thermometer was used for the measurement of patient temperature. Standard monitoring parameters were recorded by nursing personnel at 1-h intervals.

Results

Seventy-five ICU patients manifested fever during the study period. Increase of core temperature during fever episodes was followed by a significant increase in heart rate (p < 0.001) and decreases in arterial blood pressure (p < 0.001) and arterial oxygen saturation (p = 0.002). Alterations of heart rate and arterial blood pressure were significantly affected by magnitude of fever, while alteration of arterial oxygen saturation was affected by etiology of fever.

Conclusions

The present findings confirmed the effect of fever episodes on standard monitoring parameters of ICU patients. However, alterations of these parameters, although statistically significant, were not clinically important and cannot guide antipyretic treatment.

Introduction

Fever is defined as the elevation of body core temperature attributed to the upregulation of thermostatic set point, controlled by hypothalamus (Mackowiak, 1998). Core temperature is normally maintained within narrow limits (36.5–37.5 °C) by the activation of thermoeffector mechanisms, mainly vasoconstriction and shivering. The alteration of the normal set point comes as a response to circulating mediators called cytokines (Ryan and Levy, 2003). During fever, core temperature follows a dynamic course of three distinct phases (Holtzclaw, 1992). During the chill phase, body heat content progressively increases and temperature rises within the new range. The plateau phase follows, in which thermoregulation is maintained at a higher temperature level. The defervescence phase is characterized by the reset of hypothalamus to euthermic levels and heat dissipation. Fever is a component of the acute phase response, which further includes endocrine, metabolic and autonomic alterations and provides adaptive advantages to the host, by aiming at the inhibition of bacterial growth (Mackowiak, 1998).

Section snippets

Review of literature

Standard monitoring of ICU patients includes the observation of electrocardiogram, heart rate, arterial blood pressure and oxygen saturation of arterial blood. The first three of these are proper indicators of cardiovascular function which allow the detection of hemodynamic instability. Pulse oximetry is a non-invasive method of assessing oxygenation and detecting respiratory complications (mainly hypoxemia). The diagnostic value of standard monitoring parameters is high when these are

Objective

The aim of the present study was to investigate the effect of fever episodes on heart rate, arterial blood pressure and arterial oxygen saturation in critically ill patients. The effect of fever characteristics, such as magnitude and etiology, was further evaluated.

Study population

The present study was conducted in the ICU of the General University Hospital of Patras, Patras, Greece, a 14-bed ICU, which admits medical and surgical adult patients. A prospective, descriptive approach was used. All patients who were consecutively admitted in the ICU from 1 October 2005 to 28 February 2006, stayed in the ICU for at least 12 h and manifested fever were included in the study. Fever was defined as an increase of core temperature ≥38.3 °C, in accordance with the consensus

Results

Normally distributed continuous variables are presented as mean ± standard deviation, while non-normally distributed variables are presented as median (interquartile range). Seventy-five febrile patients were included in the study. There were 59 (78.7%) male and 38 (50.3%) medical patients (including trauma patients). Regarding medical patients, the most common causes of admission were trauma (including traumatic brain injury, 44.7%), respiratory dysfunction (31.6%) and severe infection (15.8%).

Discussion

Due to the methodology used in this study, peak temperatures of fever episodes taken into consideration were obviously lower than true peak temperatures. To explain this, first, it is possible that hourly measurements were not sufficient for capturing true peak temperatures of patients. Second, the higher the magnitude of fever, the more time is usually needed for the temperature to reach this level. Thus, there is an increased possibility of performing, in the meantime, a medical-nursing

Conclusions

This study has provided information regarding the effects of fever episodes on standard hemodynamic and respiratory monitoring parameters of ICU patients. Results have demonstrated that core temperature elevation was followed by statistically significant alterations of these parameters, namely an increase of heart rate and decreases of arterial blood pressure and arterial oxygen saturation. Heart rate and arterial blood pressure were also affected by magnitude of fever, while arterial oxygen

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