Page 630 - ACCCN's Critical Care Nursing

Emergency Presentations 607

Clinical manifestations anaphylactic reaction, although this is rare. An IV cannula
Envenomation by a redback spider is known as latrodec- is inserted and adrenaline 1 : 1000 is prepared for the
tism, as the venom contains excitatory neurotoxins that possiblity of anaphylaxis.
stimulate release of catecholamines from sympathetic The initial dose of Red Back Spider Antivenom is two
nerves and acetylcholine from motor nerve endings. 152,156 ampoules administered IM (500 units; approx 1.5 mL
Signs and symptoms associated with a significant enven- each ampoule), and symptoms should subside over the
omation are distinctive, and diagnosis is by clinical find- next 30–60 minutes. Complete resolution of symptoms
ings; initially a minor sting at the bite site, where the requires no specific further treatment. If there has not
spider may or may not have been seen. Over the first hour been complete resolution of symptoms after 2 hours a
the bite becomes progressively painful to severe, spread- further 2 doses of antinvenom are given. If after a further
ing proximally with and involving swollen and tender 2 hours there is incomplete resolution of symptoms or
local lymph nodes. Localised sweating at the bite site or no discernable response after 4 ampoules of antivenom,
limb or generalised sweating may appear, associated with expert advice should be sought via the local poison infor-
hypertension and malaise. Pain eventually becomes gen- mation centre. Patients who are symptom-free after 6
eralised and may be expressed as chest, abdominal, head hours of observation or the administration of antivenom
or neck pain suggestive of other acute conditions such as can be discharged home with instructions to represent
myocardial infarction. 155 should any symptoms return. Antivenom may be effective
Progression of symptoms generally occurs in less than 6 days after the bite (and possibly longer) however a larger
152,156
hours but may take up to 24 hours, while people with amount of antivenom is usually required.
minor untreated bites may experience symptoms for IV administration has been advocated in severe cases or
several weeks. 152,156 Other less common signs and symp- where there is poor response to IM administration. 152,156
toms include local piloerection, nausea, vomiting, head- The manufacturer recommends that for life-threatening
ache, fever, restlessness/insomnia, tachycardia, and envenomation the IV route may be used after first dilut-
neurological symptoms such as muscle weakness or ing the antivenom to 1 : 10 with Hartmann’s solution and
twitching. 152,157 administered over 20 minutes. 156,159 IV administration is
160
safe with reactions uncommon (less than 5%). No
Assessment significant benefit of IV administration over IM adminis-
Patients presenting with pain from a bite who have the tration was demonstrated in a randomised controlled
offending spider with them are straightforward in terms trial, so there is little evidence to justify one route of
of initial assessment. Identification of the spider is con- administration over another. 160 Redback spider antive-
firmed and a history of the event obtained, including the nom administration in various stages of pregnancy has
time of the bite and any first aid initiated. A brief assess- not been associated with direct or indirect harmful effects
ment of the bite site and the involved limb is undertaken, to the fetus. 152
including the extent of pain, presence of sweating and
painful tender lymph nodes, and a baseline set of vital
signs. Patients are then placed in a suitable area for Practice tip
medical assessment and ongoing observation. 157
Observations for the development or progression of symptoms
Adult patients presenting with vague limb pain, or pre- for a redback envenomation focuses on development of
verbal children who are ‘distressed’ and ‘cannot be local pain that spreads proximally and increases in intensity,
settled’, may be unaware that they have been bitten by a development of sweating either local or generalised and
redback. The pain may not have been felt at the time and hypertension.
no spider may have been seen. Thorough history-taking,
physical assessment and knowledge of latrodectism’s
effects enable detection of a suspected spider bite. 157 Funnel-web Spider Bite
Management Description and incidence
There is no recommended definitive first aid for a redback Funnel-web spiders are the most venomous spiders to
157,159,161
spider bite. Application of cold packs to the bite site and humans worldwide, and Australian funnel-web
administration of simple analgesia (e.g. paracetamol) spiders (Atrax or Hadronyche genera) are found primarily
may assist with local pain relief. The use of a pressure along the east coast. The Sydney funnel-web spider (Atrax
immobilisation bandage is not necessary, as symptom robustus) is found mainly within a 160 km radius of
progression is slow and not life-threatening, 152,156-158 and Sydney, while other species are found in eastern New
will cause further pain only in the affected limb. Remove South Wales and central and southern Queensland. The
any pressure bandage that was applied during first aid spider is large, black or dark brown, and approximately
after identification of the spider is confirmed. 152 3 cm long in the body. The cephalothorax is oval, smooth
and shiny, and the eyes are closely grouped. The abdomen
Presence of the above symptoms indicates systemic is similar in size to the thorax and is dull and hairy with
envenomation, requiring administration of redback spinnerets, that project noticeably behind the body. The
spider antivenom. 152,156 Prior to administration, the legs are moderately long and are black or dark plum in
patient should be placed in a clinical area with colour. Male spiders have longer legs, smaller abdomens
readily available resuscitation equipment to treat any and are significantly more toxic than females. 161