La cláusula de conciencia

Fever affects human thermoregulatory systems, and thus thermal care needs may be different for infants because of their immature thermoregulation, different circadian rhythms, response to fever and body surface to volume ratios. Beliefs regarding the harm and benefit caused by fever, among both health professionals and among different cultural groups, have been discussed in the previous chapter.

This section explores the evidence regarding benefits or harm from fever.

3.3.13.1 Fever phobia

In 2007 the National Institute for Health and Clinical Excellence (NICE) assessed evidence for the costs and benefits of anti-pyretics. They recommended that all infants 0-3 months with a temperature of more than 38˚C should receive urgent medical attention. Given that normal body temperature is considered to be

80 37˚C (Blatteis 2002), a reading of 38˚C could easily be a result of instrument error and not a true indication of fever. One of the perceived risks of fever is seizures.

Mukherjee and Mukherjee (2002) point out that not all young children are at risk of fever-induced seizures. They note that the young children most at risk are those with a family member with a history of infant febrile convulsions, those who have been in a neonatal nursery for more than 30 days, those with developmental delays, or those who are placed in day care. They also claim that there is a significant genetic component which determines susceptibility, and argue that not all infants will experience fits or seizures with high fever. In addition there are also risks involved with the use of anti-pyretic drugs such as paracetamol and aspirin. There is some evidence that use of paracetamol after first vaccinations for haemophilus influenza, diphtheria, tetanus, and pertussis weakens the immune response to these vaccinations by causing a significantly weaker antibody response (Mackowiak 1994).

3.3.13.2 Benefits of fever to the infant

Some of the arguments against the administration of anti-pyretics focus on the benefits of fever, and suggest that fever is an adaptation of vertebrates and some invertebrates that has contributed to defence against pathogens for millions of years (Kluger 1986; Soszynski 2003). Several authors have considered the adaptive value of fever and observed how fever has been associated with decreased

incidence of mortality and morbidity (Blatteis 2002; Hasday 2000; Herman 1997;

Kluger 1986; Kluger and colleagues 1996; Romanovsky and Szekely 1998;

Soszynski 2003). Romanovsky and Szekely (1998) looked at the benefits of fever versus hypothermia, and suggested that fever may be beneficial if the body has sufficient energy resources, but noted that hypothermia is an alternative strategy to conserve energy and protect vital organs.

The most common explanation for the benefit of fever is that the increased body temperature itself may kill the pathogen. The association between increased body temperatures and healing was noted hundreds of years ago, with malaria being given as a remedy for syphilis (Blackwell 2007 pers. comm. 26.10). The value of temperature to kill certain pathogens have been established for optimum

81 temperature in vitro,¹⁵but such values are hard to find in real body conditions because the chemical and thermal environment in the body is never constant. It is useful to know that tuberculosis, rhinovirus, and influenza thrive just below the normal body temperature of 37˚C (Blatteis 2002)., lending support to the cultural belief that “getting cold gives you a cold”. However, because of the different optimum temperatures preferred by different pathogens, Blatteis (2002) has suggested that keeping warm cannot kill off all pathogens, and in some cases increased temperature might provide optimum conditions for other pathogens. The implications of different temperatures at various sites in the body when they are invaded by pathogens must also be considered. For example, the nasal passages are cooler than the core body temperature. This temperature difference helps explain why respiratory pathogens thrive at a lower temperature than the core body temperature, and also explains why tuberculosis invades the internal organs

because of its preference for a higher optimum temperature ( Blackwell 2007, pers comm. 26.10).

The most significant explanation for why fever, or keeping the body warm, might be advantageous in fighting off pathogens is that increased body temperature makes the immune system more active and efficient (Blatteis 2002; Kluger 1986;

Mackowiak 1994; Padopoulos and colleagues 1999; Rodriguez and colleagues 2006). Qing and colleagues (2006) explain in greater detail why the immune system might be stimulated at higher body temperatures. They found evidence that lymphocytes were transported more efficiently at higher temperatures due to a thermally sensitive alert system depending on the thermal stress experienced. Van den Brink (2002) also found, when considering the old adage “feed a cold, starve a

15Optimum temperatures for pathogens are as follows (Blatteis:2002:6) – Bacterial: 31-32˚C Leprosy; 33-35˚C Syphillis; 36-37˚C Tuberculosis; 38-39˚C Meningitis and typhoid. Fungal:

25˚C Mycelial; 31˚C Dermamtophytoses; 32˚C Candidiasis; 38˚C Yeast, Rickettsia;37˚C Typhus;

38˚C Q fever. Viral: 29˚C plantar warts; 33-34˚C Variola, rhinovirus, varicella-zoster; 36˚C Influenza; 37˚C hepatitis; 38˚C Rabies, poliomyelitis. Parasitic: 33˚C Leischmanisias (muccocutaneous); 36˚C Faliciparum malaria; 37˚C Leishmaniasis (visceral); 38-39˚C Toxoplasmosis, Entamoeba.

82 fever,” that food intake affected the immune system by increasing levels of gamma interferon production, while food deprivation stimulated interleukin-4 release.

3.3.13.3 Staying warm so as not ‘To catch your death of cold?’

Getting cold has been associated with catching a cold for hundreds of years.

Rather than assuming that folk medical beliefs which caution that ‘getting cold gives you a cold’ are merely ignorant of germ theory, it is possible to consider instead that there could be truth underlying this extremely widespread belief.

Medics have commonly thought that lay people who follow these beliefs may simply not understand the pathogenic source of the common cold. It may instead be the case, however, that the lay belief is informed by an understanding of the way in which cold depresses the immune system long enough for an infection to take hold. Preliminary evidence for this has been gathered, although studies are not conclusive. Johnson and Eccles (2005) found participants whose feet were chilled experienced more cold symptoms afterwards. Fleming and colleagues (2006) found that infants who slept in colder night-time conditions were more prone to infections. He noted that “infants who showed the highest incidence of respiratory infections during the course of the study were most commonly cared for in lower environmental temperatures and with less bedding and wrapping – thus seeming to support the belief ‘if you get cold, you catch a cold” (Fleming and colleagues 2006:

9A).

Again, this may not be simply due to colder temperature in the child’s

microenvironment, but may have more to do with the effect of thermal stress on the individual. For example, Anderson and Stenfors (1997) found that peak rates of infection of Otitis media seemed to be related to relatively minor seasonal shifts in temperature.¹⁶ This may have something to do with thermal stress on the body as opposed to actual environmental temperatures.

16 40% of the patients in Anderson and Stenfor’s (1997) study were under 6 years of age.

The average temperature was -5˚C and the range was -14˚C to +6˚C.

83 Knowledge that the immune system can be enhanced at higher body

temperatures has been useful in improving the results of cancer therapy (Steiner and Luiz 2001; Van Haaren 2007), and increasing body temperature through layers of clothing has been shown to support the immune functioning of patients with HIV/AIDS (University of Texas 1998). Identifying the optimum temperatures for various bacteria and viruses has been useful for developing methods to store these pathogens, and has also informed strategies for keeping the cold-adapted flu virus from invading the lower respiratory tract (Yannarell and colleagues 2002).

A context-specific understanding of infant thermoregulation and thermal comfort is therefore essential to the prevention of SIDS (including understanding of how respiratory infections contribute to SIDS risk), as well as for the prevention of infections which kill millions of infants worldwide.