Relative bradycardia and constipation in typhoid fever

Two of the buzzwords in typhoid that are oft-mentioned in clinical setting as well as in many literature are 1) relative bradycardia and 2) constipation.


Relative bradycardia (Faget sign):

But what exactly is relative bradycardia?

Cunha (2000) commented that this term has been vaguely described in a variety of literature and by many healthcare professionals leading to confusion.

Physiologically, for every one degree increase in Fahrenheit (read: Fahrenheit), heart rate increases by 10 beats/min.  Therefore, as 1 degree celcius equals to 9/5 (or 1.8 degrees) Fahrenheit, therefore the increase of every one degree celcius should be resulting in 18 beats/min. In some internet sources, this is allegedly known as the Leibermeister's rule.

In his editorial, Cunha (2000) also commented that relative bradycardia should only be applied to patients with temperature in excess of 102 F (or approx 39C).

The following criteria for relative bradycardia mentioned in the article:
1) Patient's age>13 years old
2) Temperature >102 deg Fahrenheit or 39 celcius
3) pulse must be taken simultaneously with the temperature elevation

Exclude patients with heart diseases such as AV nodal block, bradyarrhythmias, or patients on beta-blocker.

NOTE: Only Beta-blocker can interfere with the pulse-temperature relationship (meaning resulting in relative bradycardia) but not ACE inhibitors (A), calcium channel blockers (C) or digoxins (D) (which means: among the A-B-C-D, A, C and D does not cause relative bradycardia, only 'B' causes bradycarida) (Cunha, 2000).

But one thing for sure: FEVER + RELATIVE BRADCARDIA does not equal to typhoid as so often I have heard (even then, the term relative bradycardia has been misused so many times) as there are many other causes of relative bradycardia.

Causes of relative bradycardia include:

Infective causes

1. Typhoid fever
2. Dengue fever
3. Malaria
4. Leptospirosis
5. Typhus
6. Legionella
7. Psittacosis  
8. Q fever
9. Yellow fever
10. Babesiosis
11. Rocky Mountain spotted fever
12. Viral hemorrhagic fevers

Non-infective causes

1. Beta-blockers
2. CNS lesions (tumors, bleeds)
3. Lymphomas 
4. Drug fever
5. Fictitious fever

Constipation:
Constipation is another buzzword often mentioned in literature on typhoid.
WHO website mentions that constipation as a symptom of typhoid is more common than diarrhoeain adults and older children.

But in a response in BMJ titled "Constipation in Typhoid fever", it is commented that "there appears to be little recent evidence" that typhoid more often causes constipation than diarrhea. In that short comment, the author cited a number of small retrospective studies (and I quote):

Dimitrov et al (2007)
A retrospective analysis in Kuwait of 135 blood culture positive for S. typhi (101 cases, 74.8%) or S. paratyphi A (34 cases, 25.2%) over 4 years:

• diarrhoea occurred in 52.6% of cases vs
• constipation in only 3.7% of case 

Khan et al (1999) 
102 patients positive for S. typhi in Durban, South Africa:

• 16 (28.6%) of female patients and 10 (21.7%) of males patients had diarrhea
• Only 1 female had constipation

Deshmukh et al (1994)
Retrospective study

• Diarrhoea occured in 8 out of 28 Indian children (28.6%) diagnosed with a positive blood culture, Widal test or electrophoresis for S. typhi antigen. 
• No mention of constipation at all. 

Chowta et al (2005)
44 adult patients with typhoid fever hospitalized patients in an Indian Teaching Hospital in Manipal (1999 - 2001):

• 20.4% were reported to have diarrhoea
• only 9.09% constipation

Based on these studies, a large, systematic review of the incidence of constipation in typhoid fever is called for but in my anecdotal experience, I tend to agree with the above comment. I think constipation as a symptom of typhoid fever has really been over-estimated than it really is. I think it is another one of those stuffs which are good to test students in exam but in actual cases, they are not as common as mentioned in textbooks.

Update: 
Nobody knows for sure why constipation can occur in typhoid fever but Medscape emedicine.com explains that in typhoid fever:

"Monocytic infiltration inflames Peyer patches and narrows the bowel lumen, causing constipation that lasts the duration of the illness."(Brusch et al. Typhoid Fever. In: Medscape. Available at URL: http://emedicine.medscape.com/article/231135-clinical Accessed 21 September 2015)

Reference:

1. Cunha BA. The diagnostic significance of relative bradycardia in infectious disease. Clin Microbiol Infect 2000;6(12):633-4.