Studies

South Africa (Western Cape Province)
Müller 1993: 42 scorpion stings with a severe course of envenoming. Identification: 15 of the scorpions that caused the stings were brought in for identification: P. granulatus 14/15, P. capensis 1/15; children <13 years 19/42; patients ≥13 years 23/42.

Zimbabwe

Bergman 1997: 17 P. transvaalicus stings with a severe course of envenoming. Identification: all scorpions were brought to the hospital and morpholoically identified.

Case reports

South Africa (Cape Province)
Smith et al. 1983: 1 scorpion sting with a severe course of envenoming. Identification: Parabuthus spp.

Botswana
Petersen 1987: 1 scorpion sting with a severe course of envenoming. Identification: P. granulosus.

Signs & symptoms

Autopharmacological effects

Experimental and clinical observations suggest that the major systemic effects of envenoming are caused by endogenous catecholamines and acetylcholine, which are released in response to scorpion venom. As these are transmitters in the sympathetic, parasympathetic and somatic nervous systems, the resulting clinical symptoms of envenoming are dealt with in the section "Neurological effects".

However, scorpion venoms are also believed to lead to other indirect effects that are caused by the release of autopharmacologically active substances (such as kinins, prostaglandins and slow-reacting substances). The pathophysiological effects of these substances overlap to a great extent. This makes it difficult to be certain about aetiology. In particular with regard to pulmonary oedema, there has been discussion concerning the effects of mediators on vascular permeability, which might constitute a non-cardiac component of the pulmonary oedema. Peripheral blood pressure regulation is also responsive to a variety of different mediators that might be released.

However, according to the available descriptions of patients suffering from Parabuthus stings, pulmonary oedema and myocardial damage appear to play at most a very minor role or none at all (Müller 1993). This is in contrast to Mesobuthus (= Hottentotta), Leiurus and Tityus stings.

Local effects

Children (<13 years): local pain 15/19, paraesthesias 2/19; patients ≥13 years: local pain 22/23, paraesthesias 17/23 (Müller 1993).

Local pain, often intense, lasting over 24h 8/17 (Bergman 1997).

Neurological effects (autonomic and somatic nervous system)

In contrast to Mesobuthus (= Hottentotta), Leiurus and Tityus venoms, Parabuthus venom appears to cause mainly neuromuscular effects.

Stimulation of the autonomic nervous system through the release of endogenous catecholamines and acetylcholine, as observed following Mesobuthus (= Hottentotta), Leiurus and Tityus stings, is not as marked with Parabuthus stings. Transient early cholinergic effects, such as vomiting, profuse sweating, hypersalivation and arterial hypotension, and later occurring, longer-lasting adrenergic effects, such as arterial hypertension and tachycardia, have been described. In contrast to Mesobuthus (= Hottentotta), Leiurus and Tityus stings, pulmonary oedema and myocardial damage do not seem to be characteristic for Parabuthus stings. The same is true for priapism (Müller 1993).

Children (<13 years)

Symptoms: difficulty in swallowing 5/19, general feeling of weakness 5/19, generalised muscle pain and cramps 2/19, trembling 1/19, hyperaesthesia 1/19, hypersalivation 12/19, anxiety 13/19, visual disturbances 1/19, respiratory disturbances 8/19, sweating 0/19, nausea, vomiting, diarrhoea 0/19, headache 1/19.

Findings: dysphagia, dysarthria 9/19, tremor, involuntary movements 6/19, obvious puncture site 6/19, arterial hypertension (140/90–200/130 mmHg) 6/19, increased deep tendon reflexes 1/19, reduced grip and pinch strength 5/19, raised temperature 6/19, impaired coordination/ataxia 8/19, hyperactivity/restlessness 16/19, hypersalivation 13/19, sweating 1/19, ptosis 3/19, respiratory depression 10/19, urine retention 2/19, tachycardia 8/19, pharyngeal reflex absent 4/19 (Müller 1993).

Patients ≥13 years

Symptoms: difficulty in swallowing 16/23, general feeling of weakness 14/23, generalised muscle pain and cramps 13/23, trembling 12/23, hyperaesthesia 10/23, hypersalivation 7/23, anxiety 6/23, visual disturbances 6/23, respiratory disturbances 5/23, sweating 5/23, nausea, vomiting, diarrhoea 2/23, headache 2/23.

Findings: dysphagia, dysarthria 16/23, tremor, involuntary movements 13/23, obvious puncture site 13/23, arterial hypertension (140/90–200/130 mmHg) 11/23, increased deep tendon reflexes 11/23, reduced grip and pinch strength 10/23, raised temperature 10/23, impaired coordination/ataxia 9/23, hyperactivity/restlessness 9/23, hypersalivation 8/23, sweating 6/23, ptosis 6/23, respiratory depression 6/23, urine retention 5/23, tachycardia 5/23, pharyngeal reflex absent 2/23.

Onset of symptoms and first occurrence of findings within 4 h after the sting in most of the 42 patients; in adults, however, often only after 4–12 h (Müller 1993).

Respiratory failure, endotracheal intubation and artificial respiration necessary for a period of 4 days, bulbar symptoms, arterial hypertension (onset of symptoms 8 h after the sting) (Smith et al. 1983).

Clinical features of envenoming primarily neuromuscular in 17 patients with P. transvaalicus stings with a severe course of envenoming (muscular weakness, ptosis, fasciculation of the tongue and sceletal muscles). Absence of adrenergic effects. Cholinergic effects have been observed (hypersalivation, sweating, bradycardia, lacrimation, urinary bladder distension with difficulties passing urine (Bergman 1997).

Cardiac effects

The pathogenesis of the myocardial damage has not been conclusively resolved. The myocardial and vascular effects of endogenous catecholamines, release of which is elicited by scorpion venom, are one – and probably the most vital – component (see above "Neurological effects"). Direct toxic effects of components of scorpion venom are also possible.

According to the available descriptions of patients suffering from Parabuthus stings, pulmonary oedema and myocardial damage appear to play at most a very minor role or none at all (Müller 1993). This is in contrast to Mesobuthus (= Hottentotta), Leiurus and Tityus stings.

Case fatality rate

4/42. All 4 were children; cause of death most probably respiratory failure in all 4; the 4 patients who died were among the 7/42 patients who did not receive antivenom (Müller 1993).

1/1. Child; death occurred approx. 1 h after the sting; autopsy: severe pulmonary oedema (Peterson 1987).

Laboratory and physical investigations

1. ECG
ECG was performed in 10/42 patients with severe envenoming: pathological findings 0/10 (Müller 1993).

2. CPK
CPK was determined in 6/42 patients with severe envenoming: elevated 4/6 (Müller 1993).

3. Blood sugar
Blood sugar was determined in 13/42 patients with severe envenoming: elevated 8/13 (Müller 1993).

4. Leucocytes
Leucocyte count determined in 22/42 patients with severe envenoming: leucocytosis (11,000–24,000/mm³) 7/22 (Müller 1993).

5. Chest X-ray
8/42 patients with severe envenoming were ventilated. 4 of these 8 patients had radiological signs of aspiration pneumonia (Müller 1993).

Treatment (symptomatic)

1. Monitoring of patients
For 12–24 h after a scorpion sting (Müller 1993, Smith et al. 1983).
All patients with systemic envenoming should be hospitalised and monitored in an intensive care unit if available.

2. Local pain
Infiltration with a local anaesthetic (Müller 1993).

3.  Respiratory failure
Artificial respiration.
16/42 patients with severe envenoming had respiratory problems, 14 of them had signs and symptoms of bulbar paralysis, 9 were ventilated for between 10 and 144 h (Müller 1993).

4. Contra-indicated medications and medications to be avoided
Pethidine, morphine, barbiturates, beta-blockers, calcium, anti-inflammatory drugs, including corticosteroids, atropine (Ismail 1993, Gueron et al. 1993, Müller 1993).

Treatment (specific)

Antivenom
Scorpion antivenom (SAIMR, Johannesburg, South Africa). Produced using venom from the medically less important species P. transvaalicus.

Müller 1993: this antivenom was administered to 35/42 patients; average dose 10 ml i.m.; time interval between the sting and antivenom administration: within 6 h 22/35, within 24 h 11/35, within 48 h 1/35, after 5 days 1/35.

Assessment of the value of antivenom in the treatment of scorpion stings

None of the 35 patients who received antivenom showed dramatic improvement after the administration of antivenom. It is thus not possible to distinguish this from the spontaneous course of envenoming. The 4 children who died were among the 7 patients who did not receive antivenom. It is recommended to administer antivenom (10 ml i.m.) to all patients with signs of systemic envenoming. In light of the general principles of antivenom administration, it must be asked why the method of administration of this scorpion antivenom is not changed from i.m. to i.v. in the package insert. This is also an issue because one of the factors that can cause a lack of efficacy is the method of administration.

P. granulatus venom should be included in the production of the antivenom (Müller 1993).