Published on February 29, 2008
Kid Fevers:: Kid Fevers: Lou Romig MD, FAAP, FACEP Miami Children’s Hospital Fever in Kids:: Fever in Kids: Lou Romig MD, FAAP, FACEP Miami Children’s Hospital Slide3: Fever Mythology Hot Topics: Hot Topics What is fever? Facts and fallacies about fever Febrile seizures How and why to treat kids with fever What is fever?: What is fever? Fever is a neurochemical response common to many animals Controlled in the human hypothalamus and mediated by numerous endogenous and exogenous chemicals What is fever?: What is fever? Nerves in the hypothalamus maintain a normal “set point” temperature, usually in a range around 37C (98.6F) Set point varies in a circadian rhythm with lowest at around 4am and highest between 4-8pm What is fever?: What is fever? Endogenous pyrogens can cause: body temp sleepiness appetite Increased immune response Slide9: What about the numbers? What’s “normal”?: What’s “normal”? Most common definitions are based on a study by Wunderlich in 1868 “Normal” 37C (98.6F) “Upper limit of normal” 38C (100.4F) Weaknesses: thermometry used, use of axillary temps What’s “normal”?: What’s “normal”? Mackowiak and Wasserman 1992: 700 oral temps in 148 healthy young adult subjects Individual variation precludes the assignment of any single temperature as the normal. Range 35.6(96.0) – 38.2(100.8) What’s “normal”?: What’s “normal”? There is no substantiation to the belief that the elderly have lower body temps normally A higher normal range of temp in children has not been documented in the research What’s “fever”?: What’s “fever”? Mackowiak and Wasserman: Any oral temp >37.2C (98.9F) in the early morning Any oral temp >37.8C (100F) at any time Thermometry: Thermometry Gold standards are rectal for children and oral for older children and adults Axillary temps are not reliable and may vary as much as 1°C from rectal There is no reliable conversion factor for axillary vs rectal temps Thermometry: Thermometry Tympanic thermometry is not accurate and may be technique-dependent Infrared temporal artery (TA) thermometry is only slightly better than tympanic thermometry TA temps are consistently lower than rectal temps but there is no reliable conversion factor Slide16: How hot is “high”? How hot is “high”?: How hot is “high”? Dubois, 1949 Human upper limit of fever 41 – 42C (105.8-107.6F) Almost never exceeds 42C unless there’s a failure in thermoregulation How hot is “high”?: How hot is “high”? McCarty and Dolan, 1976 40C (104F) may be the upper limit of fever in infants <12 weeks old Remember that young infants can have infections with normal or lowered body temps Slide19: Fever Mythology Slide20: Fever can cause damage… Why the concern?: Why the concern? Seizures and complications Brain damage because of the infection causing the fever (meningitis or encephalitis) Fact or fiction?: Fact or fiction? No human studies published Animal studies suggest that a body temp of >42C (107.6F) in humans may trigger enough adverse effects on a cellular level to cause death Fact or fiction?: Fact or fiction? Animal studies: T> 105 may cause respiratory alkalosis and occasional electrolyte imbalances T > 105.8 may cause cellular swelling and damage in the brain, kidneys and liver Slide24: An infection is more dangerous if it gives a high fever or if the fever doesn’t come down with treatment… Hi temp = “bad” infection?: Hi temp = “bad” infection? No studies have conclusively proven any correlation between height of temperature and outcome of an infection or disease outcome. Hi temp = “bad” infection?: Hi temp = “bad” infection? Several studies suggest that children with temperatures greater than 41°C (105.8°F) have a greater chance of having a serious bacterial illness. Hi temp = “bad” infection?: Hi temp = “bad” infection? Several studies suggest that fever of ≥ 40°C (104 °F) signals increased risk of serious bacterial illness for infants from birth to three months of age. Poor response to tx = bad?: Poor response to tx = bad? Failure of antipyretics to control fever has not been proven to correspond with severity of illness. Improved general appearance after antipyretics may indicate a less severe illness. Cover up if you have chills!: Cover up if you have chills! What’s cookin’ with chills?: What’s cookin’ with chills? Chills are evidence of the hypothalamus causing the body to generate heat to reach the altered set-point. Covering up will only keep in the heat. Don’t give milk to babies with fever!: Don’t give milk to babies with fever! “Doin’ the fever flop”: “Doin’ the fever flop” Characteristics of F.S.: Characteristics of F.S. Incidence of 2-5% in US 6 mo – 3 yrs, median 18-22 mo Boys more often than girls Often occurs with the first fever of an illness Characteristics of F.S.: Characteristics of F.S. 85% of all F.S. last for <15 min and don’t recur within 24 hrs 50% have temp between 39-40C 25% have temp > 40C Characteristics of F.S.: Characteristics of F.S. 1/3 will have recurrence of F.S. The younger the age at 1st F.S., the higher the incidence of recurrence El-Radhi, 1998 Presenting temp <39 for 1st F.S. have 2.5x risk for recurrence within the same illness and 3x risk for recurrence with other illnesses Characteristics of F.S.: Characteristics of F.S. Simple F.S. are generalized tonic-clonic with brief post-ictal period Complex or atypical F.S. can be focal, atonic, or prolonged It’s in the genes: It’s in the genes Multiple studies have shown several genetic loci that code for susceptibility to febrile seizures Fever + Sz Febrile Seizure: Fever + Sz Febrile Seizure Meningitis/Sepsis Seizure disorder Medication/Poison-induced “Febrile seizure” is NOT an EMS diagnosis Febrile Seizures:Fact or Fiction: Febrile Seizures: Fact or Fiction F.S. are caused by the rate of rise of temp: F.S. are caused by the rate of rise of temp Berg, 1993 – failed to prove the rate of rise theory Bottom line – we don’t know what causes F.S.! F.S. cause brain damage: F.S. cause brain damage No studies have demonstrated that febrile seizures without complicating hypoxia cause brain damage One study suggests that recurrent F.S. may result in decreased IQ F.S. can cause “epilepsy”: F.S. can cause “epilepsy” Risk factors for afebrile sz: Complex 1st F.S. Abnormal neuro state before 1st F.S. Afebrile sz history in parents or siblings If >2 risk factors, 10% chance of developing “epilepsy” Treating the fever can prevent F.S.: Treating the fever can prevent F.S. Canfield, 1980; Knudson, 1991; van Stuijvenberg, 1998 Antipyretics are not protective Rectal/oral diazepam at time of fever is protective Daily oral phenobarbital is protective but has undesirable side effects Treating the fever can prevent F.S.: Treating the fever can prevent F.S. There is no evidence that bringing the fever down by any means will stop or prevent a febrile seizure. The Bottom Line for F.S.: The Bottom Line for F.S. They’re more scary than dangerous Most resolve without anticonvulsant treatment Antipyretic treatment does not prevent or treat F.S. Not all seizures with fever are febrile seizures Antipyretics: Antipyretics There is no evidence to support one antipyretic over another when considering effectiveness No delivery route (po/pr) is more effective than another Antipyretics: Antipyretics Several studies have shown that many parents: Don’t even attempt to treat fever before seeking medical evaluation Don’t give correct antipyretic doses Antipyretics: Antipyretics Acetaminophen (APAP) 10-15 mg/kg po/pr q4h There is no difference in effectiveness based on po or pr routes There is no increased effectiveness when pr dose of APAP is increased to 45mg/kg Ibuprofen 10mg/kg po q6-8h APAP vs Ibuprofen: APAP vs Ibuprofen There is no significant benefit to using either antipyretic preferentially There is no benefit in alternating the two meds but there is a significantly increased chance of dosing error and possible overdose Cooling methods: Cooling methods Never use ice, cold water or alcohol Use tepid water or cool compresses over head and pulse points Slide53: Beware of chills if using external cooling Should we even treat fever? : Should we even treat fever? Animal studies suggest that the fever mechanism is a positive adaptive response Triggers host immune responses May stabilize cell membranes (Why) should we treat fever?: (Why) should we treat fever? Reasons to treat fever: Reasons to treat fever Increased metabolic stress and oxygen demand: Patients with poor cardiac reserve Patients with poor pulmonary reserve Lowering the “seizure threshold” Reasons to treat fever: Reasons to treat fever Patient comfort Parent comfort Should EMS providers be treating fever?: Should EMS providers be treating fever? Pro’s: Pro’s Providing an additional service to our customers Comfort measure Con’s: Con’s Treat and release? Documentation of fever Dosing of meds Reinforcement of fears Summary: Summary Fever is not the clearly defined concept many believe it to be. Both the lay public and the medical community need more education about fever. “Fever Phobia” is unfounded. Fever treatment by EMS personnel is controversial.