Neobook — clinical reference

PART A - Algorithm
PART B - Introduction and Description

Contact numbers

TBH Poison Centre: 021-9316129
South African Antivenom Unit 011-386 6016

Level of Training needed: Doctor to administer antivenom personally.

Part A Algorithm

Part B Algorithm

Introduction/Description

It may be difficult to identify the snake. DON'T bother - IDENTIFY THE VENOM.
An accurate diagnosis can be made on clinical signs and symptoms.
Venomous snakes in South Africa result in mainly neurotoxic, cytotoxic or haemotoxic effects.
The polyvalent antiserum (PVA = SAIMR Polyvalent Antiserum) covers many neurotoxic and cytotoxic venoms. A separate antiserum exists for the boomslang, which is haemotoxic. (MVA = Monovalent Boomslang Antiserum).
There are numerous South African snakes that cause minor symptoms of envenomation, are not lethal and for which antivenom is not necessary. (Skaapstekers, Night adders, Horned Adders)
95 % of Western Cape envenomations are Puff Adder or Cape Cobra.
Snake Handlers who get bitten can usually accurately identify the offending snake.

VENOM CATEGORIES	Snakes native to the Western Cape	South African Snakes not native to the Western Cape	Exotic Snakes (Kept by herpeto- philes)
NEUROTOXIC	Cape Cobra * Rinkals * Berg Adder **	Black Mamba * Green Mamba * Egyptian Cobra * Forest Cobra *	Coral Snake **
CYTOTOXIC	Puff Adder * Black-Necked Spitting Cobra *	Gaboon Viper * Mozambique Spitting Cobra (Mfezi) * Night Adder Stiletto Snake	Rattlesnake Group # Rattlesnakes Cottonmouth Copperhead
HAEMOTOXIC	Boomslang ***	Vine Snake **

* Covered by PVA = SAIMR Ployvalent Antiserum
** No antivenom
***Covered by MVA = Monovalent Boomslang Antiserum
# Ovine-based antiserum, FAB AV; available on enquiry

Diagnosis of problem and differential diagnosis

There have been cases of allergy to snake VENOM itself, amongst snake handlers. Consider anaphylaxis in the setting of a snake handler presenting in shock.

ASK FOUR IMPORTANT QUESTIONS

Has envenomation occurred?
- NO: No marks on skin AND asymptomatic for an hour post-bite
- Suspected but not obvious: Marks on Skin BUT Asymptomatic
- YES: Bite Marks AND/OR Symptomatic
Are there clinical symptoms consistent with one of the three main types of envenomation in the Western Cape?
- Neurotoxic: Weakness - Paraesthesia – Ptosis; Paralysis; Respiratory Failure (May be delayed onset)
- Cytotoxic: Severe pain, Bruising and Swelling at bite site. Extends to regional lymph nodes
- Haemotoxic: Bleeding from wound site; Ecchymoses; Haematuria; DIC; Renal failure
Is there an antivenom to cover this clinical picture?
Are the symptoms severe enough to warrant antivenom?

Triage

TRIAGE patient using SATS: ALL PATIENTS WITH ENVENOMATION ARE AT LEAST ORANGE (VERY URGENT SIGN: POISONING, BUT MAY BE RED DEPENDING ON THE TEWS SCORE.

Management (based on severity)

Use a standard ABCDE approach: Assess - Intervene - Reassess: Assessment and Management occur in tandem

Immediate action: Stabilise ABC's. O2; IV line; Attach monitors

Non-drug treatment:

FIRST AID

Immobilise the body part
Pressure dressings are controversial
DO NOT apply a tourniquet
DO NOT incise the wound
DO NOT administer antivenom out side the hospital setting
Eye envenomation: Copious irrigation with water

No envenomation:

Discharge.
Advise to return if symptoms develop

Suspected but not obvious:

Admit overnight.
Observe.
Elevate limb.
If no progressions of symptoms: Discharge the next day

Envenomation:

Admit.
Give antiserum if symptoms severe enough to warrant this.
Observe. Elevate limb.
Discharge once symptoms resolved.

Drug treatment

ANTIVENOM:

Insert an IV line
Doctor to administer antivenom personally.
No test dose or pretreatment needed BUT WATCH FOR ANAPHYLAXIS (Itching; Wheezing; Urticaria; Perioral anaesthesia). If any of these occur:
STOP the injection
Give: 0.3 mg IM Adrenaline; 200 mg IV Hydrocotisone; 25 mg IV Phenergan

Dose chart

POLYVALENT ANTISERUM (10ml vials)
- 40-80 mls (4-8 vials) Slow IV injection
- Titrate to symptoms
- Assess for improvement every 30 minutes
- Give ADEQUATE DOSE( Especially with Puff Adder bites)
MONOVALENT ANTIVENOM (10mls vials)
- Start at 40 mls (4-8 vials) Slow IV injection
- Monitor haematological parameters
- Repeat dose if needed
- ANALGESIA
- MORPHINE IV 10mg in 10ml Water
- Bolus 2-5 mg every 30 minutes
- Titrate to analgesic effect
- Watch BP, LOC, RR

Monitoring chart

History

DMIST Handover from Ambulance
SAMPLE HISTORY
Signs and Symptoms: Cytotoxic; Neurotoxic; Haemotoxic
Allergies
Medications
Past Medical history
Last Meal
Events: Geographic area. Type of snake. Associated trauma.

Examination

A: Airway - may be unable to clear secretions and exhibit hypersalivation
B: Breathing may be compromised by respiratory muscle weakness
C: Assess for shock and signs of unusual bleeding (haematuria/oozing from wound)
D: Neurological examination and cranial nerves
E: Neurovascular status of limb, swelling and dermal necrosis
Measure and Record Vital Signs
Fingerprick Haemoglobin

Investigations

Depend on the clinical scenario: Hb, Platelets, CK, Renal Function, DIC screen

Referral Criteria (L1/2/3)

Critical patients need ICU admission
Neurotoxic and Haematoxic envenomations are managed by the medical team
Cytotoxic envenomations are managed by the surgical team

Discharge and Admission Criteria/Checklist

No envenomation: Discharge. Advise to return if symptoms develop
Suspected but not obvious: Admit overnight. Observe. Elevate limb. If no progressions of symptoms: Discharge the next day
Yes: Admit. Give antiserum if symptoms severe enough to warrant this. Observe. Elevate limb.

References

Rosens Emergency Medicine 7th ed.
Tintinallis 4th ed.
Roger Blalock: The identification and syndromic management of snakebite in South Africa (SA Fam Pract 2005; 47 (9): 48-53))
Darryl Wood: Severe snakebites in northern KwaZulu-Natal: treatment modalities and outcomes. S Afr Med J. 2009 Nov; 99 (11): 814-8.
Wood D1, Webb C, DeMeyer J.

Snakebite Emergencies

Drugs mentioned