醫學筆記匯整 ED Notes

 Epidemiology 
 - Worldwide incidence 1 million cases per year
 -  Mortality rate 20-30%
 -  第三類法定傳染病 (一週內通報)
 - 台灣每年通報 < 20例

 

 Clostridium tetani 破傷風桿菌 
 - Anaerobic Spore forming gram-positive rod (GPB)
 - Soil, Animal feces
 - Incubation period : ranges from < 24hr to > 1 month
 - Wound
    * 70 % related to acute wound : 厭氧環境!
      Puncture (生鏽鐵釘), Contaminated, Infected or devitalized wounds 
    * Less common : 
       Chronic wounds, ulcers, Wounds in DM, Dental abscesses, 
       Injection drug abuser, Neonate umbilical stump
    * 10% patients with tetanus : no wound

 - Exotoxins
   1.  Tetanolysin
   2.  Tetanospasmin : Neurotoxin
        - Doesn’t cross BBB, but Retrograde intraneuronal transport to CNS
        - Prevents the release of the inhibitory neurotransmitters : Glycine + GABA
          from presynaptic nerve terminals
       - Sympathetic overactivity
       - Generalized muscular rigidity, Violent muscular contractions, ANS instability
 



- 3 types of Tetanus

  1.  Generalized : 80%
       - Neonatal tetanus : Unsterile treatment of the umbilical cord
          Weak, irritable, inability to suck

  2.  Cephalic : injuries to the head or occasionally otitis media, Dysfunction of CN7
  3.  Local : Rigidity proximal to the injury site 

 Generalized tetenus 
 - Pain and stiffness in masseter : Lockjaw, Trismus牙關緊閉, 張口困難
 - Stiffness -> Rigidity : Risus sardonicus, Sardonic smile痙笑

 - Nerves with short axons affected first 
    * Descending progression : Face, Neck, Trunk, Extremities
    * Dysphagia
    * Opisthotonos : flexing of the arms, Clenching of the fists, Extension of the lower extremities


 

 - Mental status is normal ! 
 - Rhabdomyolysis, long-bone fractures
 - Respiratory compromise
    * Laryngospasm
    * Respiratory muscles contraction
 - Hypersympathetic state : 2nd week
    * Tachycardia, labile hypertension, profuse sweating, hyperpyrexia

Strychnine poisoning 番木鱉鹼 is most closely mimics !
 

 Diagnosis 
 - Tetanus is diagnosed clinically
 - No laboratory tests to diagnose
 - Wound culture is of limited value
 

 Treatment 
 -  Immunotherapy
     * Human tetanus immunoglobulin (TIG) : neutralizes circulating tetanospasmin and toxin in wound
     * Around the wound, before debridement

< TIG 是被動免疫 >

- Wound : debridement 
- Antibiotics : limited value but are traditionally administered
     * Parenteral metronidazole
     * Do not give penicillin, may potentiate tetanospasmin 

 - Neuromuscular blockade : Prolonged neuromuscular blockade
 - Muscle relaxant : midazolam 
 - Autonomic dysfunction

 
 - Immunization : infection does not confer immunity
   recover from tetanus must receive active immunization
   破傷風病癒後並不會產生終身免疫, 仍有可能二次感染, 因此病癒後仍需進行預防注射

DTaP-Hib-IPV : 2, 4, 6, 18個月
Tdap-IPV : 5歲至國小入學前接受一劑

感染 :  TIG + Toxoid (Present + 6W + 6M)
暴露後預防 :
  - 基本上都有注射 > 3 次類毒素, 所以不需要 TIG 
  - 疫苗效力 10 年, 乾淨傷口15 歲以下不太需要考慮
    髒的傷口 10 歲要考慮

　髒的傷口 :　
　* Wounds > 6 hours old
　* Contaminated by soil, saliva, feces, dirt
　* Puncture or crush wounds
　* Avulsions
　* Wounds from missiles, burns, or frostbite.
 

-  Contraindications
   *  Serious allergic reaction, Encephalopathy, Guillain-Barré syndrome ≤6 weeks
       Arthus hypersensitivity reaction

      =  Passive immunization with tetanus immunoglobulin

主動免疫疫苗：  
(1) DTaP-Hib-IPV 五合一疫苗  
(2) DT 白喉, 破傷風混合疫苗 
(3) Td 破傷風, 減量白喉混合疫苗 
(4) Toxoid 單一破傷風類毒素 
 

被動免疫血清：
(1) TAT 破傷風抗毒素 : 馬血清來源, 應注意過敏
(2) TIG 破傷風免疫球蛋白