Body Temperature

Fever Clinical Pathophysiology September 7, 2005 Fred Arthur Zar, MD, FACP Professor of Clinical Medicine University of Illinois at Chicago fazar@uic.edu Body Temperature • “Core Temperature” – Aortic blood temperature – Esophageal temperature – Tympanic membrane temperature • Clinical Approximates – Sublingual (oral) temperature = 0.7o F < core – Axillary temperature = 1.8o F < core – Rectal temperature = 0.9o F > core • Afferent Sensing Normal Thermoregulation – Cold receptors –> A delta fibers – Warm receptors –> C fibers – Integrated in spinal cord and CNS –> hypothalamus – 20% each contribution from: skin, deep chest and abdomen, spinal cord, CNS, hypothalamus – Skin input predominates behavioral responses – Cold and warm response thresholds only 0.4º apart • Central Integration • Efferent Responses – Behavioral (clothing, adjusting environment) – Response to heat: sweat, cutaneous dilation – Response to cold: digital vasoconstriction (–agonism) Nonshivering thermogenesis ( –agonism) Shivering Sessler DI: NEJM 336:1730–7, 1997. Endogenous Pyrogens Interleukin–1 (alpha*, beta) Interleukin–6 Interleukin–11 Tumor necrosis factor (alpha) Interferon (alpha, beta, gamma) • Prostaglandin–E2 • Platelet activating factor • Ciliary neurotropic factor (CNTF) • Oncostatin M • Cardiotropin–1 *first cloned by Auron PE: Proc Natl Acad Sci USA 81:7907–11, 1984. • • • • • Pyrogenic Cytokine Producing Cells • Monocytes, tissue • • • • • • • • • macrophages Keratinocytes Gingival epithelium Corneal epithelium Renal mesangial cells Brain astrocytes Vascular endothelium Vascular smooth muscle NK cells Fibroblasts Fever and Host Defense Enhancement • Neutrophil function – Enhanced migration – Enhanced superoxide production • Mononuclear function – Enhanced interferon production • Enhanced interferon tumor and viral activity – T–cell proliferation The Structure of the Febrile State • Endocrine/Metabolic CRH –> ACTH –> GC GH Aldosterone Insulin (if available) Glucagon Acute phase reactants • Autonomic • Behavioral Cutaneous vasoconstriction PR BP Sweating Seek warmth (chill) Shivering (rigor) Anorexia Somnolence Malaise TSH ADH Cytokines Inducing Acute Phase Reactants • Interleukin–1 • Interleukin–6 • Interleukin–11 • Tumor Necrosis Factor • Oncostatin–M • Ciliary Neurotrophic Factor • Cardiotropin–1 • Leukemic Inhibitory Factor Dinarello CA: Sem Onc 24:288–98, 1997. Acute Phase Proteins (The concentration changes +/– 25%) • Increased in Sepsis • Decreased in Sepsis – Ceruloplasmin, ferritin, hemopexin, haptoglobin – 1–protease inhibitor, 1–antichymotrypsin, pancreatic secretory trypsin inhibitor, inter––trypsin inhibitors – C3, C4, C9, C1 inhibitor, C4b–binding protein, C4b–binding lectin, factor B – Fibrinogen, plasminogen, TPA, urokinase, protein S, vitronectin, plasminogen activator inhibitor–1 – CRP, serum amyloid A, 1-acid glycoprotein, 2 macroglobulin, phospholipase A2, fibronectin, manose binding protein, lipopolysaccharide–binding protein, IL–1 receptor antagonist, GCSF – Albumin, transthyretin, transferrin, 2-HS glycopreotein, FP, TBG, insulin–like growth factor, Factor XII Mackowiak PA: Arch IM 158:1870–81, 1998. Gabay C: NEJM 340:448-54, 1999 Afebrile Infections in the Elderly • Incidence – Bacteremia 5–31% – Endocarditis 7–21% – Pneumonia 20–56% – Meningitis 41% – Technical “pseudo-euthermia” – Chronic antipyretic drug ingestion – Behavioral changes – Physiologic changes • • • • • Decreased BMR Late, less efficient shivering Autonomic neuropathy Decreased temperature perception Decreased production of endogenous pyrogens • Poorly taken oral/axillary temps • Mechanisms Intrinsic Antipyretics • • • • • • • • • Somatostatin Melanocyte–stimulating factor Vasopressin CRH–>ACTH–>GC Thyroliberin GIP Neuropeptide Y Bombesin IL–1ra, soluble TNF receptor Antipyretic Drugs • Cyclo–oxygenase (COX) Inhibitors – Acetaminophen • Poor peripheral activity – 0.02% as active as indomethacin • In CNS oxidized by p450 to potent inhibitor of PGE2 synthesis – 10% as active as indomethacin • Corticosteroids • Phenothiazines – Acetylsalacyclic acid (ASA) – Other NSAIDs – Inhibit phospholipase A2 –> PGE2 synthesis – Block mRNA transcription of pyrogenic cytokines – Block peripheral vasoconstriction “Two critical assumptions are made when prescribing antipyretic therapy. One is that fever is, at least in part, noxious, and the oth is that suppression of fever will reduce, if not eliminate, the noxious effects of fever. At present, neither assumption has been validated experimentally”. Mackowiak, P: CID 31(Supple 5): S185–9, 2000. The Downside of Antipyresis • The febrile state is beneficial to the host • Fever is rarely harmful • Fever is a useful parameter to follow response to Rx • Intermittent defervescence is uncomfortable • Animal studies – decreased survival if febrile response to infection is ablated1–5 • Human studies 1 5 – slower healing of varicella6 and longer duration of ARRD 130:857-62, 1984. JID 155:991-7, 1987. J Vet Pharm Ther 1:69-76, 1978. Fed Proc 36:511, 1977. malaria7 infection if antipyretics are given 2 3 4 Brain Res Bull 5:69-73,1980. 6Doran TF: J Ped 114:1045-8, 1989. 7Brandts CH: Lancet 350:705–9, 1997. Adverse Effects of Fever • Central Nervous System oC oF 41 42 41.6–42.0 max)* Consequences 105.8 Delerium, seizures 107.6 Coma, CNS damage 106.9–7.6 Death (critical thermal Ox phos uncouples • Other Consequences – BMR 15% per 1oC – PR 15 bpm per 1oC – Muscle proteolysis for acute phase reactant synthesis – Bone resorption –> hypercalcuria *Bynum GD: Am J Phys 235:R228–36, 1978. Fever vs. Hyperthermia • Fever – Hypothalamic set–point increased by cytokines – Peripheral mechanisms generate and conserve heat – Response to antipyretics • Hyperthermia – Hypothalamic set–point is normal – Peripheral mechanisms fail to match set– point Marathon Hyperthermia Finish Line, Chicago Marathon October 22, 2000 Non–Infectious Etiologies of “Fever” • CNS lesions – Stroke, trauma, encephalitis – High cord transection – Autonomic neuropathy • Miscellaneous – Severe CHF – Malignant hyperthermia – Neuroleptic malignant syndrome – Vasculitides – Malignancies – Inflammatory bowel disease • Endocrine diseases • Skin Diseases – Pheochromocytoma – Thyrotoxicosis – Addison’s disease – Ichthyosis – Absent sweat glands Causes of True Hyperthermia • Increased Heat Production – – – – – – – – – – Exertional hyperthermia Exertional heat stroke Malignant hyperthermia Neuroleptic malignant syndrome Lethal catatonia Thyrotoxicosis Pheochromocytoma Delerium tremens Status epilepticus Tetanus • Drugs – – – – – – – – ß–blockers Sympathomimetics Anti-cholinergics Salicylate toxicity Classic heat stroke Occlusive dressings Dehydration Autonomic dysfunction • Decreased Heat Loss Clinically Benign Fevers • • • • • • Diurnal variation Meals Ovulation Smoking Chewing gum/tobacco Exercise Weinstein L: RID 7:692, 1985. Low Grade and High Grade Fevers Temperature < 102o Acute cholecystitis Acute MI Simple phlebitis Pulmonary emboli Acute pancreatitis Viral hepatitis (A–E) Wound infection vulnificus Gastrointestinal bleed Cystitis Atelectasis Hematoma Temperature > 102o Cholangitis Pericarditis Pyophlebitis Septic pulmonary emboli Abscess/infected pseudocyst Leptospirosis/drug fever SubQ abscess/Strep., V. Bowel infarction Pyelonephritis Pneumonia Infected hematoma The Isolated Fever Spike • Manipulation of colonized surface – Wound debridement/irrigation – Flushing of drainage devices – Endoscopies – Foley in or out – Lines in or out • Blood/blood product • transfusions Contaminated infusates Temperatures > • • • • • • • Central fever Drug fever Heat stroke Malignant hyperthermia Neuroleptic malignant syndrome Malaria Smallpox o 106 Central Fever • Reason • Plateau fever curve • Poor response to • • antipyretics Relative bradycardia No sweating Mechanisms of Drug Fever • Hypersensitivity Reactions – Drug as hapten, tissue binding, cell mediated • Idiosyncratic Mechanisms • Altered Thermoregulatory Mechanisms • Cytolysis – Jarisch–Herxheimer reaction – Cancer chemotherapy – G6PD induced hemolysis – Endotoxin in drug/vaccine – Amphotericin B, bleomycin – Malignant hyperthermia, neuroleptic malignant syndrome – Thyroxine, sympathomimetics, anticholinergics, MAOI • Administration Related Fever Tumors Commonly Causing Fever • Lymphomas • • • • • • • • • • • – Hodgkin’s disease (IL–1, IL–6, TNF) – Non-Hodgkin’s lymphoma (IL–1) Leukemias – AML, ALL, CML, HCL (IL–1) – CLL (IL–1, IL–6) – Adult T–cell leukemia (IL–1) Multiple myeloma (IL–1, IL–6) Renal cell carcinoma (IL–6) Hepatoma, hepatoblastoma (IL–1) Atrial myxoma (IL–6) Melanoma (IL–1) Ovarian CA (IL–1) Transitional cell CA (IL–1) Osteogenic SA (IL–1) Malignant histiocytosis Metastatic tumors to liver Dinarello CA: Sem Onc 24:288–98, 1997.