Temperature and Homeostasis

1. Temperature and Homeostasis • Normal Temp 36 - 37.5 • Pyrexia Low grade normal to 38, Moderate to high grade 38 - 40 and 40> Hyperpyrexia • Hypothermia < 35 • Temperature should be measured orally or tympanically

2. Heat and Metabolism • Body heat is proportional to metabolic rate • More cellular reactions (higher the metabolic rate) the more ATP produced the more heat is given off • Thyroid hormones increase aerobic cellular respiration, therefore increase heat production • Exercise or stress increase epinephrine and norepinephrine release which increase metabolic rate

3. Heat and Metabolism • Increase in temp = increase in biochemical reactions therefore metabolism may be substantially increased during a fever • Eating raises metabolic rate = thermogenesis, it is greater after eating proteins than carbs or lipids • Age, a child has double the metabolic rate of an older person due to factors related to growth. So temp may be at the higher end of the normal range for kids and vice versa

4. Temperature Monitoring • Receptors in the hypothalamus monitor the temperature of the blood • Receptors in the skin (esp trunk) monitor the external temperature • The Thermoregulatory centre (preoptic area) is in the hypothalamus also and receives input from both these and initiates changes using several negative feedback mechanisms

5. Temperature Changes • Too hot = Heat loss centre in hypothalamus is activated to produce several responses. Some actively cool the body down, others reduce heat production or transfer heat to the surface • Too cold = Heat conservation centre in hypothalamus produces reactions which:- generate heat and others conserve heat

6. Pyrexial • Capillaries dilate • Smooth muscles relax to increase vasodilation • Sweat glands activated • Muscles attached to skin relax to flatten hairs which allows air to circulate over skin • Glands stop secreting epinephrine and thyroxine • Behaviour changes ie finding shade, taking clothes off, stretching out

7. Hypothermia • Smooth muscles contract causing vasoconstriction. Blood heat maintained at core, peripheries may become cyanosed • Muscles in skin contract raising skin hairs to trap layer of insulator air. But not very effective in humans. • Shivering - Skeletal muscles contract and relax rapidly causing heat by friction and increase in metabolism

8. Hypothermia • Glands secrete epinephrine to increase metabolism and thyroxine to increase cellular respiration, therefore heat • Behaviour changes - huddling and curling up, putting on more clothes or finding shelter

9. Hyperthermia - senario related • Pyrogens released by WBC’s can raise body temp by 2-3 degrees. • This helps to kill bacteria and viruses, hence why we become pyretic with infections • Most infectious diseases produce a temp of 37-41 degrees C • Increase in temp also increases the speed Neutrophils move at and how fast they secrete hydrogen peroxide and lyosome (anti-bacterials)

10. Hyperthermia - senario related • Every 1 degree rise in temp = 13% rise in metabolism • Every 0.5 degree increase = extra 10 % loss of water through respiration • UO must be maintained to eliminate waste products of metabolism • Therefore…. Fluid intake must be increased • As metabolism increases so does the need for O2 so if impaired lung function then recovery delayed

11. Opioids • Opioids bind to specific opioid receptors in the central nervous system and in other tissues. • This blocks the transmission of pain messages from the body to the brain

12. Opioid Receptors • μ receptor: (mu) analgesia, sedation, reduced blood pressure, itching, nausea, euphoria, decreased respiration, miosis (constricted pupils) and decreased bowel motility often leading to constipation. • κ receptors: (kappa) analgesia, nausea and dysphoria. • δ receptor: (delta)analgesia and some research suggests that they may also be related to seizures

13. Morphine Morphine is an opioid receptor agonist– its Main effect is binding to and activating the µ Opioid receptors in the central nervous system. Activation of these receptors is associated with analgesia, sedation, euphoria, Physical dependence and respiratory depression. Morphine is also a κ-opioid receptor agonist, with this action associated with spinal analgesia and miosis.

14. Side effects • Nausea and vomiting (particularly in initial stages) • Constipation • Drowsiness • Respiratory depression • Hypotension • Muscle rigidity

15. Dosage • Acute pain, by subcutaneous injection (not suitable for oedematous patients) or by intramuscular injection, 10 mg every 4 hours if necessary (15 mg for heavier well-muscled patients) • Patient controlled analgesia (PCA), consult hospital protocols

16. Non-opioids • Reduces the production of prostoglandins by inhibiting the cyclooxygenase (COX) enzyme • Paracetamol indirectly blocks COX, and that this blockade is ineffective in the presence of peroxides. This might explain why paracetamol is effective in the central nervous system and in endothelial cells but not in platelets and immune cells which have high levels of peroxides.

17. Side effects • The major side effects are rare and include rash and blood disorders. Overdose can cause liver damage and emergency treatment for poisoning is required. • Contraindications hepatic impairment and renal impairement and alcohol dependent patients.

18. Dosage • It is commonly administered in tablet, liquid suspension, suppository or intravenous form. The common adult dose is 500 mg to 1000 mg. The recommended maximum daily dose, for adults, is 4 grams. In recommended doses paracetamol is safe for children and infants as well as for adults. • The effectiveness of paracetamol is often underestimated because of its widespread availability.

19. NSAIDs Drugs with analgesic, antipyretic and anti- inflammatory effects - they reduce pain, fever and inflammation. The term "non-steroidal" is used to distinguish these drugs from steroids, which (amongst a broad range of other effects) have a similar eicosanoid-depressing, Anti-inflammatory action. The most prominent members of this group of drugs are aspirin and ibuprofen.

20. NSAIDs cont… • Most NSAIDs act as non-selective inhibitors of the enzyme cyclooxygenase, inhibiting both the cyclooxygenase-1 (COX-1) and cyclooxygenase-2 (COX-2) isoenzymes. • Cyclooxygenase catalyses the formation of prostaglandins. • Prostaglandins act (among other things) as messenger molecules in the process of inflammation.

21. Uses for NSAIDs • Rheumatoid arthritis • Osteoarthritis • Inflammatory arthropathies (e.g. ankylosin spondylitis, psoriatic arthritis, Reiter‘s syndrome) • Acute gout • Dysmenorrhoea • Metastatic bone pain • Headache and migraine

22. Uses cont….. • Postoperative pain • Mild-to-moderate pain due to inflammation and tissue injury • Pyrexia • Renal colic

23. Side effects • Gastrointestinal disturbances • Renal disturbances These effects are dose-dependent, and in many cases severe enough to pose the risk of ulcer perforation, upper gastrointestinal bleeding, and death, limiting the use of NSAID therapy.

24. References • BMJ (2006) BNF 51 [online]. London: BMJ Publishing Group Ltd and RPS Publishing. Available at: <http://www.bnf.org/bnf/> accessed on 11th July 2006 • Carroll, M. (2000) An evaluation of temperature measurement. Nursing Standard. 14(44) p39-43 • Connell, F. (1997) The causes and treatment of fever: a literature review. Nursing Standard. 12(11) p40-43

25. References cont…. • Henry, J.A. (2004) New guide to medicines & drugs 6th ed. London : Dorling Kindersley • Hewitt, J. and Jordan, S. (2004) Opioids: symptom control. Nursing Standard. 19(6) • Parish, P. (1992) Medicines : a guide for everybody7th ed. London : Penguin • Tortora, G and Grabowski, S. (2003) Principles of Anatomy and Physiology. 10th Ed New Jersey: John Wiley & Sons Inc

26. Referencescont… • Trim, J. (2005) Monitoring Temperature. Nursing Times. 101(20) • Watson, R. (1998) Controlling body temperature in adults. Nursing Standard. 12(20) p49-53