Tetanus

Question 1

What is usually the first cause of death?

Answer 1

Respiratory muscle dysfunction leading to hypoxia, hypoventilation and death

Question 2

If patients survive the acute phase of the disease, what is the likely cause of death?

Answer 2

Autonomic dysfunction leading to dysrhythmias, MI, hypertension, hyperthermia

Question 3

What is the classic inciting event that leads to tetanus?

Answer 3

A penetrating wound, although sometimes this is such a minor event that the patient cannot recall an injury

Question 4

Apart from lacerations, abrasions, puncture wounds, what other scenarios can cause tetanus?

Answer 4

Childbirth, otitis media, corneal abrasions, dental procedures
Post-operative tetanus can occur because up to 10% of humans have C. tetani in the colon

Question 5

Where is C. tetani found in the world?

Answer 5

Ubiquitous in soil and also found in feces of humans and animals

Question 6

Is C. tetani aerobic or anearobic?

Answer 6

Obligate anaerobic

Question 7

Can germination and replication of C. tetani happen without clinical findings of an infected wound?

Answer 7

Yes

Question 8

What is the way that C. tetani causes disease?

Answer 8

Produces a neurotoxin that prevents vesicles from fusing to the presynaptic membrane and releasing inhibitory neurotransmitters such as glycine and GABA

Question 9

What is the name of the neurotoxin?

Answer 9

tetanospasmin

Question 10

How does tetanospasmin spread through the body?

Answer 10

Retrograde axonal transport and trans-synaptic spread to the CNS

Question 11

What are the first neurons affected?

Answer 11

Interneurons that are afferent to alpha motor neurons which leads to the classic muscle spasms of tetanus

Question 12

Are the effects of tetanospasmin reversible?

Answer 12

No, recovery only happens when a new axonal terminal is produced

Question 13

What is the incubation period of tetanus?

Answer 13

1 day to several months

Shorter incubation period has a worse prognosis

Question 14

What are the four types of tetanus clinical presentations?

Answer 14

Generalized: most common
Localized
Cephalic
Neonatal

Question 15

Describe generalized tetanus

Answer 15

Most common presentation
First presents with lockjaw in 50-75% of patients
Early symptoms: irritability, weakness, myalgias, muscle cramps, dysphagia, hydrophobia, drooling
More advanced disease: spasms triggered by even minor stimuli, laryngeal spasm leading to respiratory failure, autonomic dysfunction leading to unchecked sympathetic tone with hypertension, tachycardia, dysrhythmias, MI, hyperthermia
Patient remains lucid throughout

Question 16

How are tetanus and meningitis different?

Answer 16

Tetanus patients have no alteration in their mental state

Question 17

Describe cephalic tetanus

Answer 17

Rare variant
Usually an injury to the face or otitis media
Cranial nerve palsies usually precede spasms, making it easy to misdiagnose this
Most commonly involves CNVII, mimicking Bell’s Palsy
Will have trismus and palsies

Question 18

Describe neonatal tetanus

Answer 18

Generalized disease of the newborn
In developing countries where mom is not vaccinated or dirty instruments used on the umbilical cord
Symptoms in first week of life with irritability and poor feeding
Almost 100% fatal without intervention

Question 19

What are some of the complications of disease other than respiratory compromise and cardiovascular complications?

Answer 19

Fractures or dislocations from forceful contractures
Rhabdomyolysis and renal injury
Renal injury from dehydration and sympathetic overload
Hyperthermia
Peptic ulcers, ileus, intestinal perforation, constipation
SIADH
Hemolysis

Question 20

How is tetanus diagnosed?

Answer 20

Clinically
There are no lab tests
Wound cultures are not reliable
Other differential diagnoses are ruled out

Question 21

What is the spatula test?

Answer 21

Tongue depressor to the back of the throat
Gag and expulsion of the blade is negative
Reflex masseter spasm and biting the blade is positive
94% sensitive and 100% specific

Question 22

Poising from what substance has a similar presentation to tetanus?

Answer 22

Strychnine

Comes from rat poison, but can also be in street drugs

Question 23

What is another more likely cause of trismus?

Answer 23

Dental or intraoral infections

Question 24

Apart from intraoral infections, what other process can cause trismus and should be ruled out?

Answer 24

TMJ dislocation or TMJ syndrome

Question 25

What other diagnosis should be considered when a patient has dysphagia and respiratory dysfunction?

Answer 25

Rabies

Question 26

How is rabies unique from tetanus?

Answer 26

Rabies does not cause trismus

Question 27

What should be in the differential when a patient is presenting with CNVII palsy?

Answer 27

``` Tetanus Bell's palsy Stroke Botulism CN palsies Facial cellulitis with facial nerve compression ```

Question 28

What are the main treatment strategies for tetanus?

Answer 28

Supportive care Elimination of unbound toxin Active immunization Prevention of further toxin production

Question 29

How are spasms managed?

Answer 29

Avoid touch and sounds as these can trigger spasms Benzos are first line as they are GABA agonists (Diazepam most commonly used, but ativan and midazolam also good) Propofol infusion works Dantrolene can be adjunct as muscle relaxant Mg infusion often advocated but no evidence If no improvement with the above, paralyze, and intubate

Question 30

Which IV benzos can cause lactic acidosis and why?

Answer 30

IV lorazepam and diazepam have propylene glycol which can cause lactic acidosis at high doses

Question 31

What neuromuscular blocker should be used for paralysis?

Answer 31

Succinylcholine can be used in the first few days, but carries the risk of hyperkalemia and otherwise should be avoided Rocuronium/Vecuronium are good but require continuous infusion, they lack hemodynamic side effects Pancuronium is long acting but can worsen the autonomic instability because of catecholamine reuptake inhibition

Question 32

How is the autonomic and subsequent hemodynamic instability managed?

Answer 32

Combined alpha/beta blockers: labetalol or propranolol Beta blockers alone should be avoided (unopposed alpha) Clonidine has variable effect Morphine, Mg, or spinal baclofen can help Diuretics should be avoided (dehydration worsens autonomic instability) Bradydysrhythmias treated with pacing, not atropine, as there is already too much sympathetic tone

Question 33

How is elimination of unbound toxin achieved?

Answer 33

Give HTIG (human tetanus immune globulin) and immunize with Td

Question 34

How does HTIG work?

Answer 34

Binds and eliminates all free toxin and toxin at the inoculation site Does not bind toxin in the nervous system Does reduce mortality Does not treat any existing symptoms

Question 35

How and where should HTIG be given?

Answer 35

As soon as possible Separate site from Td Proximal to the wound is logical but not proven Not approved for intrathecal in the US

Question 36

Wound debridement and antibiotics can decrease future release of toxin, but should not be done until what else has been done first?

Answer 36

Must give HTIG first as debridement and antibiotics can cause a transient release of toxin

Question 37

What is the antibiotic of choice and why?

Answer 37

Metronidazole 500 Q6h | Better penetration into devitalized tissue and abscesses and superior in recovery time and mortality benefit

Question 38

Why is penicillin not a first choice antibiotic?

Answer 38

Has GABA antagonist activity and can potentiate the effects of tetanospasm

Question 39

Who gets a prophylactic Tdap shot in the ED?

Answer 39

Anyone with an unknown or less than full series of three shots regardless of the wound type

Question 40

When does a person with a completed Tdap series need a prophylactic Tdap in the ED?

Answer 40

Never, not even with more extensive wounds | But can consider updating if they are immune compromised, IV drug users, elderly, or long time since last booster

Question 41

When is HTIG given prophylactically?

Answer 41

Only to patients with high risk wounds and unknown or incomplete vaccination history

Question 42

What are high risk wounds for tetanus?

Answer 42

``` >6hrs old >1cm deep Stellate Contaminated Denervated Ischemic Infected ```

Question 43

What prophylactic medications are appropriate for pregnant patients?

Answer 43

Td and HTIG

Question 44

What should be given to patients that are reportedly allergic to tetanus?

Answer 44

Tetanus anaphylaxis is rare | But can give HTIG to these patients and should be referred to an allergist for immunization and further treatment