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| Journal of the New Zealand Medical Association,
15-April-2005, Vol 118 No 1213
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Near death episode after exposure to toxic gases from liquid
manure
Louise Couch, Laura Martin, Nigel Rankin
Liquid manure is used in New Zealand as a nitrogen source in
mushroom production. During its formation, toxic gases including hydrogen
sulphide (H2S), methane, and carbon monoxide are
generated. In a confined space, potentially lethal concentrations can arise.
This paper illustrates an under-recognised hazard in New Zealand.
Case reportA 26-year-old mushroom farm worker
(Patient A) collapsed after stirring chicken manure slurry contained inside a
water tank. A 49-year-old coworker (Patient B) attempted a rescue but was also
overcome. Both men were pulled free through a hole cut in the side of the tank
(Figure 1).
Figure 1. The tank in which
the victims were overwhelmed
 Bystanders performed cardiopulmonary resuscitation (CPR) on
Patient A for 2 minutes. On ambulance arrival, he had a Glasgow Coma Score
(GCS) of ‘4’ with decerebrated posturing. He was intubated at the
scene. Patient B was unresponsive when rescued but quickly roused to a GCS of
‘14’. Both men were transported to hospital by helicopter.
Patient A filled the emergency department with a
‘rotten eggs’smell. Coarse bilateral crepitations were auscultated,
and his oxygen saturation was 91% on 10 L. Copious amounts of foul smelling
material were suctioned from the endotracheal tube.
Sodium Nitrite 3% at 0.3 ml/kg was administered for presumed
H2S poisoning. Hyperbaric oxygen therapy was
considered, but the patient was too unstable to transfer. In the ICU, Patient A
initially required 100% oxygen. He was given
imipenem for aspiration pneumonia and topical chloramphenicol for bilateral
corneal burns. On day 2, his GCS was E1 VT M5. A small right-sided pneumothorax
with surgical emphysema was noted. This was treated conservatively.
Patient A was orientated and extubated on day 3, and
discharged home on day 6. He required ENT follow-up for otitis externa and
sinusitis.
Patient B’s GCS had deteriorated from 15 to 3 during
transfer, however he improved rapidly when given high-flow oxygen. He also was
given sodium nitrite and treated for aspiration pneumonia and painful corneal
burns. In addition, he suffered a foul post-nasal drip and nasal discharge. This
was managed with oral antibiotics and nasal douches. One year later, both
patients had returned to work.
Occupational Safety and Health Service (OSH) conducted
studies of the gases emitted from the tank. (Table 1)
Table 1. Gases in the tank
*ppm=parts per million.
DiscussionThis report illustrates how
dangerous H2S exposure can be. It also
demonstrates that a good outcome can occur despite an initially poor
presentation. In the previous 5 years, there have been two deaths reported in
New Zealand’s agricultural industry that were associated with ‘toxic
fumes’.1 The ‘near miss’ rate
is unknown.
H2S is a colourless,
odiferous gas formed during anaerobic degradation of
protein.2 It can be found naturally occurring
in sewers, septic tanks, slurry stores, and mines
3, and is also a byproduct of processes
involving sulphur-containing compounds. Exposures typically occur at sites some
distance from emergency services.4
At a concentration of 20–30 ppm,
H2S has a characteristic malodorous scent of
‘rotten eggs’. At a higher concentration, olfactory paralysis can
occur and so both victims and rescuers maybe unaware of their
exposure.5,6 The toxic effects occur rapidly.
H2S binds to cytochrome oxidase inhibiting
oxidative phosphorylation. H2S can cause
bronchospasm6,7 and secondary hypoxia may
develop due to respiratory paralysis and pulmonary oedema. Other effects are
listed in Table 2.
Table 2. Effects of H2S
(from references 3 and 6)
*ppm=parts per
million.
Management includes rapid removal from the source,
decontamination, high-flow oxygen, nitrite therapy, and consideration of
hyperbaric oxygen.3,7,8 Nitrite therapy
produces methaemaglobin to which the H2S
preferentially binds releasing
haemoglobin.5
Liquid manure when agitated in a confined space is a
potential hazard.9 The testing done by OSH
(Table 1) found H2S concentrations were above the
maximum allowed for short (15 ppm) and prolonged exposure (10 ppm). This was a
simulation and probably underestimates the true levels of
H2S to which the patients were exposed.
Information about the risks of exposure to toxic gases is
briefly covered in the OSH handbook (under the
Working in Confined Spaces
section).10 It is vital that rescuers recognise
this danger, and use respiratory apparatus and protective clothing to avoid
further casualties.
Author information:
Louise Couch, Emergency Medicine Registrar; Laura Martin, Emergency
Medicine Registrar; Nigel Rankin, Intensivist, Middlemore Hospital, Counties
Manukau District Health Board, Auckland
Correspondence: Dr
Nigel Rankin, Department of Intensive Care Medicine, Middlemore Hospital,
Private Bag 93311, Otahuhu, Auckland. Email: nrankin@middlemore.co.nz
References:
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