Anaerobic Spore Forming Gram +Ve Bacillus

Tetanus

3/9/10

PY Mindmaps

A-Z

- caused by toxin from Clostridium tetani -> able to survive in the environment as highly resistant spores

- anaerobic Spore Forming Gram +ve Bacillus

- once in a suitable environment -> spores germinate -> bacteria multiply -> toxin release

- toxin taken up by motor nerves or haematogenous spread to CNS

- toxin disrupts synaptic transmission by preventing release of neurotransmitters (zinc endopeptisdase)

- the toxin preferentially prevents discharge from GABA inhibitory interneurons -> to interneurons in spinal cord and brainstem -> unrestricted motor nerve activity and autonomic instability

CLINICAL FEATURES

- minor laceration or umbilical stump in neonates

- 2/52 incubation period

- muscle stiffness (trismus, dysphagia, increased tone in trunk muscles – greater on side of injury initially)

- spasms (spontaneous or provoked by physical or emotional stimuli, laryngospasm)

- opisthotonos = severe spasm in which the back arches and the head bends back and heels flex toward the back

- rigid muscles

- spasms

- autonomic disturbance (tachycardia, hypertension)

INVESTIGATIONS

- urinary strychnine to exclude this as a cause (it is a glycine agonist that can produce a similar picture)

- CK for rhabdomyolysis

MANAGEMENT

- diagnosis = based on history and examination

- differential: oropharyngeal infections causing trimus, dystonic reactions, psychogenic illness

- quiet environment

Resuscitate

A - intubate as requires large doses of sedatives to control muscle spasm + laryngospasm,

B - at risk of aspiration and have copious bronchial secretions requiring frequent suctioning, often ventilated for 2-3 weeks until spasms subside

C – autonomic dysfunction necessitate monitoring in a critical care environment, fluctuant haemodynamics so use short acting agents

D – benzodiazepines in large doses -> non-depolarsing NMBD

Electrolyte and Acid-base Abnormalities

- Mg to 2-4mmol/L as useful in spasm treatment and limits autonomic instability

Antidote

- metronidazole (first choice)

- penicillin used throughout most of the world

- anti-tetanus immunoglobulin: 100-300IU/kg of human Ig IM, 500IU/kg of equine – higher incidence of anaphylaxis

- dantrolene

Underlying cause

- clean and debride wounds

- immunize (infection does not confer immunity) – Q10 yearly

COMPLICATIONS

- ARF from rhabdomyolysis

- dehydration

- tendon avulsions

- vertebral fractures secondary to muscle spasm

- GI bleeding

- VTE

PROGNOSIS

- untreated: mortality >60% in neonates

- treated well: 10-25%

- adverse prognostic features:

1. incubation of < 7 days

2. period of onset < 48 hours

3. portal of entry from umbilicus, uterus, burns, open # or IM injection

4. presence of spasms

5. temperature > 38.4

6. HR > 120 (adults), > 150 (neonates)

Jeremy Fernando (2011)