Clinical features of organophosphate poisoning: A review of different classification systems and approaches

Abstract

Purpose: The typical toxidrome in organophosphate (OP) poisoning comprises of the Salivation, Lacrimation, Urination, Defecation, Gastric cramps, Emesis (SLUDGE) symptoms. However, several other manifestations are described. We review the spectrum of symptoms and signs in OP poisoning as well as the different approaches to clinical features in these patients.

Materials and methods: Articles were obtained by electronic search of PubMed(®) between 1966 and April 2014 using the search terms organophosphorus compounds or phosphoric acid esters AND poison or poisoning AND manifestations.

Results: Of the 5026 articles on OP poisoning, 2584 articles pertained to human poisoning; 452 articles focusing on clinical manifestations in human OP poisoning were retrieved for detailed evaluation. In addition to the traditional approach of symptoms and signs of OP poisoning as peripheral (muscarinic, nicotinic) and central nervous system receptor stimulation, symptoms were alternatively approached using a time-based classification. In this, symptom onset was categorized as acute (within 24-h), delayed (24-h to 2-week) or late (beyond 2-week). Although most symptoms occur with minutes or hours following acute exposure, delayed onset symptoms occurring after a period of minimal or mild symptoms, may impact treatment and timing of the discharge following acute exposure. Symptoms and signs were also viewed as an organ specific as cardiovascular, respiratory or neurological manifestations. An organ specific approach enables focused management of individual organ dysfunction that may vary with different OP compounds.

Conclusions: Different approaches to the symptoms and signs in OP poisoning may better our understanding of the underlying mechanism that in turn may assist with the management of acutely poisoned patients.

Keywords: Intermediate syndrome; manifestations; organophosphate; poisoning.

Figure 1

The cholinergic system - cholinergic synapses are present in the central nervous system (CNS) and the peripheral nervous system (PNS). Both nicotinic and muscarinic receptors are found in the CNS. The peripheral nicotinic receptors are present in the neuromuscular junction, adrenal medulla and the sympathetic and parasympathetic ganglia of the PNS. Peripheral parasympathetic muscarinic innervation is postganglionic to the heart, exocrine glands and smooth muscle and sympathetic postganglionic fibres innervate the sweat glands

Figure 2

Subtypes of muscarinic and nicotinic receptors - the peripheral nicotinic receptors at the neuromuscular junction are of the N1 or Nm type and the central nicotinic receptors are of the neuronal nicotinic acetylcholinesterase subtype (Nn or N2). All five (M1 to M5) muscarinic receptor subunits are present in the central nervous system. The peripheral muscarinic receptors are predominantly of the M3 subunit although the M2 subunit is also represented in the heart and exocrine glands

Figure 3

Spectrum of delayed manifestations in organophosphate poisoning - delayed onset cholinergic symptoms are reported to occur 40-48 h following poisoning (a). Intermediate syndrome (b) typically occurs 24-96 h following poisoning although it may be delayed up to 114-h (c). Delayed onset coma or encephalopathy (d) occurs about 4-day after poisoning, generally after a period of normal conscious state. Cerebellar ataxia (e) has been reported to occur 8-day after poisoning and extrapyramidal manifestations (f) after 5-15 days (reproduced with permission)