Other ergonomics assessment tools \200 The Assessment of repetitive tasks (ART) tool. Ava ilable at: M http:// www.hse.gov.uk/msd/uld/art/index.htm The Rapid Upper Limb Assessment (RULA) tool: original reference \200\224McAtamney L, Corlett EN (1993). RULA: a survey method for the investigation of work-related upper limb disorders, Appl Ergon , 24 , 91 \200\2239. download form \200\224M http://ergo.human.cornell.edu/ahRULA.html 38_Smedley_Chap38.indd 776 1/2/2013 1:04:37 PM CARRY OUT AN ERGONOMICS ASSESSMENT 777 Table 38.1 Monitoring and analysis techniques Method Advantages Disadvantages Quick to complete and inexpensive Subjective Con \201 ned to the items in the questionnaire; therefore d scope for recognizi ng new or unexpected risks Self-administered questionnaire or checklist about speci \201 c exposures or risk factors Interviewer administered questionnaire or checklist Opportunity for standardized explanation from interviewer Subjective Direct observation in the workplace, recording the exposures in real time. Computer technol ogy can be used to facilitate recording Objective Intrusive Dif \201 cult to check that all risks have been captured, as there is no permane nt record of the actual activity Video recording in the workplace, with later indirect observation and recording of exposure s Objective Repeatable measurements from a permanent record of the actual activity Intrusive Ethical issues around recording if sensitive subjects are inadvertently included on the video, e.g. when videoing a health care worker lifting and handling patients Observing experimental reconstructions of tasks under laboratory conditions Objective Allows closer measurements that might be too intrusive to be used in an actual wo rkplace (e.g. attachment of a spinal motion monitor, or use of an inclinometer) Always a \200\230proxy \200\231 for workplace exposures, so may not recreate the task or w orking environment accurately 38_Smedley_Chap38.indd 777 1/2/2013 1:04:37 PM CHAPTER 38 Non-clinical tasks and procedures 778 Carry out a noise assessment The noise assessment can be divided into three stages. Background information \200 De \201 ne purpose of the survey, e.g. collection of noise e xposure data for compliance with the Control of Noise at Work Regulations 2005 Gather background information: plan of work/layout to be assessed \200 tasks performed and patterns of work \200 time spent on speci \201 c tasks and variability in exposure time \200 previous records of no ise surveys/assessments \200 control measures available, e.g. ear muffs, noise refuge and control rooms, acoustic screens any recent relevant health concerns/reported symptoms. Preliminary site visit and static noise measurements \200 Systematically identify all noi se sources \200 Collect exposure information: who is exposed, when, for how long, and how often Identify control measures used and their effectiveness \200 Take measurements with a hand -held sound-level meter at workers \200\231 position(s) relative to a noise source Plot noise levels on a site map (noise mapping) showing position of machines and workers. T his helps to understand the distribution of noise levels for the area being assessed Estimate the LAeq for the job/task levels from information on tasks performed by workers and exposure time The LAeq for each job/task is then combined with its duration during the working day to determine the L EP , d . The calculation can be performed using t he electronic spreadsheet available on the HSE website M www.hse.gov.uk/noise Detailed noise survey: personal dosemetry \200 In certain situations the L EP , d and pea k sound pressure level are best determined by personal dosemetry: \200 \202 uctuating noise exposure levels \200 high exposure variability \200 sources of impulse noise Where L EP , d is likely to exceed the noise exposure limits, carry out octave band analysi s (noise frequency pattern) for tasks performed by the workers. These data will assist with the selection and design of control measures Identify steps needed to reduce noise exposure as far as reasonably practicable by examining in turn the noise source, the transmission of noise from the sourc e, and the individual exposed Keep records of assessment (see Table 38.2) and review. 38_Smedley_Chap38.indd 778 1/2/2013 1:04:37 PM CARRY OUT A NOISE ASSESSMENT 779 Table 38.2 Noise monitoring survey data form a. Premises \200\224name, address b. Survey \200\224conducted by, date of survey c. Survey equipment \200\224type, model, calibration, sound level meter settings e.g. weigh ting, response time d. Workplace \200\224layout, processes, noise sources e. Individuals exposed \200\224number, shift pattern, tasks conducted f. Ear defenders \200\224type available, actual use time, protection afforded by ear defend er Estimate of personal exposure levels Tasks and location Individual (name) Noise level LAeq Exposure duration L EP,d dB(A) Peak pressure (L Cpeak ) Octave band analysis \200\224dB levels at different frequencies Frequency 63Hz 125Hz 500Hz 1KHz 2KHz 4KHz 8KHz dB level 2 dB values, e.g. for a noise source (machine) need to measure using an octave band analyze r as part of the survey, and record on the form for each frequency. 38_Smedley_Chap38.indd 779 1/2/2013 1:04:37 PM CHAPTER 38 Non-clinical tasks and procedures 780 Carry out a display screen equipment assessment All organizations are likely to possess at least some equipment that falls under the terms of the Health and Safety (DSE) Regulations 1992 as amended (see b p. 528, Health and Safety (DSE) Regulations 1992). These regulations require that every employer shall perform an assess- ment of workstations to assess and re duce risk for DSE users. Procedure \200 The assessor should be trained regarding the requirements of the DSE regulations and how to undertake a DSE assessment Use a checklist or on-line questionnaire to gather operator feedback \200 Record the key \201 ndings for retention until the next DSE assessment. 2 A home worker \200\231s workst ation should be assessed even if the employer did not provide the workstation. Elements to be considered in a DSE assessment Equipment \200 Workstation should be of suf \201 cient size to permit adjustment of the equipment and should be non-re \202 ective Chair should be height adjustable with an adjustable backrest that offers good lumbar support A footrest should be provided if the user so desires \200 Display screen/monitor should g ive a clear image with adjustable contrast and brightness Keyboard should be adjustable, with suf \201 cient space in front of the keyboard to support wrists/arms Keys should be legible and the keyboard layout should facilitate use \200 Document holder should be provided where required \200 Keyboard and mouse should be regularly cleaned as a build-up of dirt i risk of work-related upper limb disorder Non-keyboard input devices (mouse/tracker ball, etc.) should be suitable for the task and the user. Environment \200 Adequate space \200 Keep workstation tidy and free from clutter \200 Adequate room/task lighting \200 No direct glare or re \202 ections on screen \200 Ad justable window blinds \200 Comfortable humidity levels \200 Low noise levels from equi pment \200 Avoid trailing cables. Equipment/user interface \200 Software should be \201 t for purpose \200 \200\230Help \200\231 functions should be provided \200 User m ust be adequately trained in: \200 use of equipment/software \200 setting up the workst ation correctly 38_Smedley_Chap38.indd 780 1/2/2013 1:04:37 PM CARRY OUT A DISPLAY SCREEN EQUIPMENT ASSESSMENT 781 Poor user posture i risk of musculoskeletal disorders (MSDs) (see b p. 256, Work-related up per limb disorders 1; b p. 258, Work-related upper limb disorders 2); \200 avoid slouchin g \200 avoid work at an angle \200 avoid very small fonts; use \200\230zoom \200\231 f unction \200 minimize keystrokes by use of \200\230macro \200\231 functions \200 regul ar breaks from keyboarding d fatigue \200 keyboarding skills course d risk of MSDs. Frequency of review The DSE assessment should be reviewed where: \200 The workstation is moved \200 The hardware or software is upgraded \200 There is a substantial change to t ask demands \200 The environment around the workstation is changed, e.g. new lighting \200 There is a change to the user \200\231s capacity/abilities due to injury or ill health. Relevant legislation and guidance HSE (2003). Work with Display Screen Equipment: Health an d Safety (Display Screen Equipment) Regulations 1992 as amended by the Health and Safety (M iscellaneous Amendments) Regulations 2002. Guidance on Regulations . L26, HSE Books, Sudbur y. 38_Smedley_Chap38.indd 781 1/2/2013 1:04:37 PM CHAPTER 38 Non-clinical tasks and procedures 782 Assess and interpret a research paper In order to make the best use of research evidence, a nd avoid being mis- led by poor science, it is advisable to appraise published original res earch papers critically. The majority of research papers in occupational medicine are observa- 1 A checklist for ide ntifying common problems with cohort tional studies. and case-control studies, divided by e ach main section of a paper, is given here. The list is intended for readers of single scie nti \201 c papers following publication, rather than as a guide for peer reviewers at the stage when a manuscript can be revised, or for those who are compiling evidence tables for guideline development. Introduction \200 Is the existing state of knowledge adequately described? \200 Is the study well justi \201 ed? \200 Is it relevant for your own practice? Methods Study sample \200 Are the target population and the sample well de \201 ned? \200 Is the sample suf \201 ciently large? ideally, a power calculation should be shown \200 wide con \201 dence intervals are an i mportant clue to inadequate sample size Are there any obvious sources of bias in the selection of subjects (e.g. volunteers, patients seen for medico-legal purposes)? Selection of controls Are the comparison groups appropriate? \200 Controls in case-contro l studies should be selected from the same population as the cases (e.g. clinic attenders f rom the same hospital catchment area) Care should be taken that unexposed groups in cohort studies are not inadvertently exposed, e.g. through proximity to exposed workers. Tools Are the methods of case ascertainment standardized? \200 Case de \201 nitions shou ld be stated clearly. It is useful if de \201 nitions are used widely, as the results are more easily compared with previous literature Methods should be valid and repeatable. It is not always possible to validate subjective ou tcomes, e.g. pain or mental ill health, as there is no gold standard. However, questionnair es and other tools should at least have acceptable repeatability Confounding: have possible confounding factors been considered, and attempts made to measur e them for inclusion (adjustment) in later analysis? 1 Randomized controlled trials (RCTs) are rare in occupational medicine research and are no t cov- ered here. Methods for assessing RCTs are available. Improving the quality of report ing of RCTs: The CONSORT statement. Available at: M http://www.biomedcentral.com/1471 \200 \2232288/1/2/ 38_Smedley_Chap38.indd 782 1/2/2013 1:04:37 PM ASSESS AND INTERPRET A RESEARCH PAPER 783 Exposure assessment Consider the quality and accuracy of exposure assessment. \200 Using job title as a proxy for exposure is common, but rather inaccurate Retrospective exposure assessment from hygiene records varies in quality Recalled exposure can be subject to bias if the subject has the disease of interest. Statistical methods Statistical techniques must be stated clearly (but not necessarily desc ribed in detail). Check that they are appropriate for the format of data presented. Results Response rates Rates >55% are desirable. Lower response rates are acceptable, but t he impact of response bias on the results should be discussed. Presentation of results \200 Look for an indication of the magnitude of effect or risk (o dds ratio, relative risk, prevalence rate ratio). Consider whether an increased risk is likely to be i mportant clinically Look for an estimate of statistical uncertainty (the likelihood that the results could have occurred by chance). Traditionally, P -values have been used to express statistical signi \201 cance, but they do not give a feel for the size of an effect. Con \201 dence interva ls around a risk estimate give more information about the scale of a \201 nding. Discussion and conclusions \200 Were limitations acknowledged and discussed? These must b e borne in mind when making the link to practice \200 Are the conclusions drawn appropriate? \200 Are the results related to other evidence from the existing literature? \200 If a s tudy has added new knowledge, is this generalizable to your local population? Do the results suggest that a change in practice is indicated? 38_Smedley_Chap38.indd 783 1/2/2013 1:04:37 PM CHAPTER 38 Non-clinical tasks and procedures 784 Writing a press release Purpose Press releases are issued to draw the attention of journali sts to new information which may be of interest to their readership/audience. They may be d irected at specialist publications (e.g. trade magazines) as well as the more general media (newspapers, radio, and television). They help to maximize publicity, and also give the in stigator some control over its timing. Sources of assistance Occupational health professionals normally issue press releases with assist- ance from experts in media relations, who can advise on their format, and optimize their circulation to journalists. Depending on the circumstances, assistance may come from: \200 The editorial staff of a scienti \201 c journal: many journals these days like to publicize their content beyond specialist readers, and have well-developed systems for promoting publicity Academic institutions: most major academic institutions have a press of \201 ce Conference organizers: it is common practice to highlight selected presentations at medical and scienti \201 c conferences, which may be of wider interest Media relations departments of employing companies: many larger companies have such departments Government press of \201 ces: relevant to occupational health professionals working for government departments, agencies, and advisory committees. Advance preparation In planning a press release, several questions should be considered. \200 What is the main message? \200 Who is the message for? This will in \202 uence bot h the content, and also the way in which the press release is circulated What will be the best timing? There may be little choice about this (e.g. because there is a need to coincide with publication of a paper or a presentation at a meeting). However, wh ere there is \202 exibility, factors to consider include the timing of other events that are likely to compete for media attention (e.g. a royal wedding) and the availability of an appropriate person to answer any follow-up questions from journalists (which usually come over several days). Format In compiling a press release, it is important to bear in mind the way in which journ alists work. Some may wish to interview the originators to get additional information, but others will prepare their piece simply from the content of the press release, perhaps suppl emented by readily available information from the internet. Requirements include: \200 An attention-grabbing headline \200 A clear statement of the main message in understandable language 38_Smedley_Chap38.indd 784 1/2/2013 1:04:37 PM WRITING A PRESS RELEASE 785 A short ampli \201 cation of the main message. It is often helpful to include attributable quotes that can be incorporated into articles Useful background information (e.g. brief details of the committee that has issued a report or the conference where paper will be presented) Useful references for further information (particularly to websites) \200 Contact details for someone who can give further information. Press conferences Where it is anticipated that new information will be of special interest to the general media, it may help to accompany a press release with a press conference. Suc h conferences are best organized by media professionals. The important thing for participat ing health professionals is to ensure that they are well prepared to answer questions. 38_Smedley_Chap38.indd 785 1/2/2013 1:04:37 PM CHAPTER 38 Non-clinical tasks and procedures 786 Conducting a media interview Circumstances The press may question occupational health profe ssionals because they are named as a contact in a press release, or are participants at a p ress conference. In addition, a journalist pursuing a story may approach them without advan ce warning. Contacts may take various forms: \200 Requests for non-attributable backgroun d information \200 Interviews to be used in the preparation of written articles \200 Li ve or recorded interviews on radio or television. Preparation As for a professional examination, when dealing with the media, it is impor- ta nt to be adequately prepared. In particular, it is essential to have a good understanding o f the relevant facts. If you get things wrong, you lose cred- ibility. Where media contact is expected (e.g. following a press release or because a newsworthy event has occurred), it is helpful to anticipate the questions that might be asked. And when an approach is receiv ed from a journalist, it is useful to establish at the outset the intended readership/ audi ence, and the planned scope and format of the communication. Talking to journalists from the written media \200 Assume that anything you say is \200 \230on record \200\230 and attributable, unless otherwise agreed (most journalists can be t rusted to respect such agreements) If you do not know the answer to a question, an offer to \201 nd out may be appreciated (but be sensitive to the journalist \200\231s deadline) If you are unable to answer a question (e.g. because of con \201 dentiality), try to explain why rather than simply decline to comment Most journalists are happy to let you check quotes that they wish to attribute to you (often they are paraphrases of what was actually said) \200 Where deadli nes allow, some journalists are happy to receive feedback on the draft text of their articl e (but remember that \201 nal responsibility for the content is theirs) Check that your name and af \201 liation are correctly noted \200 Remember that once you are quoted in one article, follow-up enquiries may come from other journalists. Broadcast interviews \200 Pre-recorded interviews have the advantage that if you lose you r thread you can start again. However, be mindful that your contribution may be edited and in terspersed with other material. Consider whether you trust the producer to do this sympathe tically Establish in advance the planned format of the program, including its length, who will be t he other participants, and in what capacity you are contributing (representing a group or g iving your personal view) \200 Think through your main message in advance, and try to ens ure that you get it across as early as possible in the interview Use language appropriate to the audience and do not talk too fast \200 Practical examples may help to illustrate theoretical points 38_Smedley_Chap38.indd 786 1/2/2013 1:04:38 PM CONDUCTING A MEDIA INTERVIEW 787 Avoid appearing defensive \200 Avoid saying things that you might regret, even after comp letion of the interview (if in doubt, assume that the tape is still running) Ensure that your name and af \201 liation have been correctly noted \200 Dress appropria tely for television appearances, (wear plain, muted, colors) Maintain eye contact with the interviewer and avoid \201 dgeting. Training Various courses are available for health professionals on interactions with the me dia. They provide a good opportunity to develop and practice tech- niques, and are strongly recommended for those who expect frequent or dif \201 cult media contacts. 38_Smedley_Chap38.indd 787 1/2/2013 1:04:38 PM This page intentionally left blank Section 12 Emergencies in occupational health 39 Acute poisoning 40 Non-chemical emergencies 41 Terrorism 791 813 827 39_Smedley_Chap39.indd 789 1/2/2013 1:36:06 PM This page intentionally left blank 791 Chapter 39 Acute poisoning General principles and contact details for specialist advice 792 Carbon monoxide poisoning 794 Cyanide 1: poisoning 796 Cyanide 2: treatment 798 Hydrogen su lfide poisoning 800 Organophosphate poisoning 802 Mercury poisoning 804 Phenol poisoning 80 6 Methaemoglobinaemia (acute treatment) 808 Hydro \202 uoric acid exposure 810 39_Smedley_Chap39.indd 791 1/2/2013 1:36:06 PM CHAPTER 39 Acute poisoning 792 General principles and contact details for specialist advice All substances are poisons: there is none which is not a poison. The right dose differentia tes a poison and a remedy. Paracelsus (1493 \200\2231541) Role of occupational health \200 Be aware of the general principles of \201 rst aid. OH should lead in this \200 In the workplace, adequate numbers of staff should be trained \201 rst aiders. This depends on the hazards identi \201 ed on site (see b p. 536, First Aid at Wor k Regulations 1981) It may be sensible to have staff trained in immediate life support (ILS) \200 Know your w orkplace/work area \200 Identify possible sources of chemical exposures/poisoning \200 Identify remedial actions needed \200 Liaise with nearest acute admitting hospitals for s peci \201 c hazards, e.g. cyanide, hydro \202 uoric acid Formulate and document immediate \201 rst aid/treatment protocols with respect to ambulance call-out times and transfer times to acute hospitals. Contact details for specialist advice \200 Telephone advice from NPIS if needed: UK NPIS \200\2240870 600 6266 \200 Ireland NPIC \200\224(01) 809 2566 Register with TOXBASE (the primary clinical toxicology database of the NPIS. Available a t: M http://www.toxbase.org/) Immediate management of poisoning in the workplace \200 Assess the situation: risk assess ment \200 Is it safe to approach the casualties? \200 1 Remove the casualties from furt her exposure if it is safe to do so \200 Contact the emergency services \200 Assess the route of exposure: inhalation \200 skin contamination/burns \200 eye contamination/burns \200 ingestion (unlikely in the occupational setting) \200 injection Assess the need for PPE \200 Start decontamination if necessary \200 Start \201 rst a id \200 With known or suspected case of exposure/poisoning instigate ABCs : airway \200 breathing \200 cardiac support. 39_Smedley_Chap39.indd 792 1/2/2013 1:36:06 PM PRINCIPLES AND CONTACT DETAILS FOR SPECIALIST ADVICE 793 Management of chemical exposures to the eye 1 Chemicals splashed or sprayed into the eyes a re an emergency. Features \200 Pain, blepharospasm, lacrimation, conjunctivitis, palpebra l oedema, and photophobia Acidic and alkaline solutions may cause corneal burns \200 Alkaline solutions may penetra te all layers of the eye and cause: iritis \200 anterior and posterior synechia \200 corneal opaci \201 cation \200 cata racts \200 glaucoma \200 retinal atrophy. 1 Alkali burns to the eyes are an ophthalmic emergency. Management of chemical exposures to the eye \200 Remove contact lenses if necessary and i mmediately irrigate the affected eye thoroughly with water or 0.9% saline for at least 10 \200\22315min. Continue until the conjunctival sac pH is normal (7.5 \200\2238.0). Use pH-s ensitive paper, retest after 20min, and re-irrigate if necessary Any particles lodged in the conjunctival recesses should be removed \200 Repeated instill ation of local anesthetics (e.g. amethocaine) may reduce discomfort and help more thorough decontamination \200 Corneal damage may be detected by instillation of \202 uorescein \200 Mydriatic and cycloplegic agents (e.g. cyclopentolate, tropicamide) may reduce discom fort. Do not use in patients with glaucoma Patients with corneal damage, exposed to strong acids or alkalis and those whose symptoms d o not resolve rapidly should be referred for ophthalmological assessment. 39_Smedley_Chap39.indd 793 1/2/2013 1:36:06 PM CHAPTER 39 Acute poisoning 794 Carbon monoxide poisoning Properties \200 Colorless odorless gas \200 Unlikely to be en countered in the occupational setting in isolation \200 Product of incomplete combustion including diesel oils, petroleum products and domestic gas. 2 Leaks of domestic gas do not involve CO. Mechanism of toxicity \200 CO combines with hemoglobin to d oxygen-carrying capacity of t he blood This causes the oxyhaemoglobin dissociation curve (see Fig. 24.1) to shift to the left, impairing tissue oxygen delivery CO may also inhibit cytochrome oxidase \200 The short-term exposure limit is 200ppm (232m g/m 3 ) \200 The long-term exposure limit is 30ppm (35mg/m 3 ). Poisoning features Immediate features \200 Headache \200 Nausea \200 Irritability \200 Weakness \200 Tachypnoea. Intermediate features \200 Dizziness \200 Ataxia \200 Agitation \200 Impairment of consciousness \200 Respiratory failure. 2 Cerebral o edema and metabolic acidosis may develop in serious cases. Less common features include ski n blisters, rhabdomyolysis, acute renal failure, pulmonary oedema, myocardial infarction, r etinal hemorrhages, cortical blindness, choreoathetosis, and mutism. Late features \200 The majority recover uneventfully. \200 Rarely, neuropsychiatric fea tures after periods of several weeks free of symptoms. More common in those >40 years age a nd includes memory impairment, disorientation, apathy, mutism, irritability, inability to c oncentrate, personality change, parkinsonism, and parietal lobe lesions. Urinary and/or fec al incontinence and gait disturbance are common. Fortunately, the great majority will recov er completely or to a considerable extent within a year. Indication of severity \200 Severity increases with one or more of the following \200 A ny new objective acute neurological signs, e.g. i tone, upgoing plantar re \202 exes 39_Smedley_Chap39.indd 794 1/2/2013 1:36:06 PM CARBON MONOXIDE POISONING 795 Coma \200 Need for ventilation \200 ECG indication of infarction or ischaemia \200 Cl inically signi \201 cant acidosis \200 Initial carboxyhaemoglobin > 30% 2 The link betwe en carboxyhaemoglobin level and clinical outcome is weak. Management of carbon monoxide poisoning \200 Remove from exposure \200 Maintain a clear airway and adequate ventilation \200 Give oxygen in as high a concentration as possible \200 Transfer to hospital if severely compromised \200 Correct metabolic acidosis by in creasing oxygen delivery to the tissues Give mannitol 1g/kg (as 20%) IV over 20min if cerebral oedema suspected Monitor the heart rhythm \200 Measure the carboxyhaemoglobin concentration as an emergenc y. A carboxyhaemoglobin percentage of 30% indicates severe exposure. However, concentration s less than this do not exclude signi \201 cant poisoning, and the relationship between ca rboxyhaemoglobin and severity of poisoning and/or clinical outcome is poor In patients who have been unconscious look for extrapyramidal features and retinal hemorrha ges to assess the severity of CNS toxicity The role of hyperbaric oxygen therapy is controversial. Further information Heath Protection Agency (2009). Diagnosing poisoning: carbon monoxide ( CO) (amended October 2010). Available at: M http://www.hpa.org.uk/webc/HPAwebFile/HPAweb_C/ 1236845874045 Department of Health (2010). Carbon monoxide poisoning: needless deaths, unne ces- sary injury, Letter from the Chief Medical Of \201 cer/Chief Nursing Of \201 cer. Av ailable at: M http://www.dh.gov.uk/en/Publicationsandstatistics/Lettersandcirculars/Profess ionalletters/ Chiefmedicalof \201 cerletters/DH_121502 39_Smedley_Chap39.indd 795 1/2/2013 1:36:07 PM CHAPTER 39 Acute poisoning 796 Cyanide 1: poisoning Properties \200 Naturally occurring toxin in a variety of forms \200 Important examples are hydrogen cyanide (HCN) gas, salts, e.g. potassium and sodium cyanide (KCN, NaCN), and nitriles (R \200\223CN), which are used widel y as solvents and in the manufacture of plastics. Sources of exposure \200 Industrial: metal treatment and ore processing, printing, electr oplating, photoengraving, electronics, production of acrylics, plastics, and nylon, petroch emical industry \200 Fumigants and rodenticides \200 Acrylic nail remover and metal pol ishes \200 Fires: combustion of polyurethane, rubber, nylon, etc. \200 Tobacco smoke \200 Drugs, e.g. sodium nitroprusside \200 Natural sources: cassava, some grasses, \202 ax, lima beans, linseed. Toxicity \200 Highly toxic by inhalation, ingestion, or dermal or eye exposure \200 Sol uble cyanide salts (e.g. Na, K, Ca, NH 3 ) are more toxic than lower- solubility salts (mercury, gold, copper, and silver cyanide). Onset of toxicity \200 Toxicity can occur within a few seconds of HCN gas inhalation, wit h death occurring within minutes Ingestion of soluble cyanide salts can cause toxicity within minutes, but continued absorption can cause toxicity for several hours Toxicity from skin exposure requires a large surface area to be affected. Onset of toxicity may be delayed for several hours. Estimated lethal doses \200 Hydrocyanic acid, 50mg \200 NaCN/KCN ingestion, 150 \200 \223300mg ( 7 3mg/kg) \200 Median lethal dose for skin contamination, 100mg/kg. UK short- term occupational exposure limits (15min) HCN, 10 ppm (11mg/m 3 ) Cyanogen chloride 0.3 ppm (0.77mg/m 3 ) UK long-term occupational exposure limits (8-h TWA) Cyanogen, 10ppm (22mg/m 3 ) Other cyanides, except HCN and cyanogen chloride 5mg/m 3 . Clinical \201 ndings \200 Rapid respiration \200 Hypotension \200 Convulsions \200 Coma. 1 It can be dif \201 cult to diagnose cyanide poisoning. 39_Smedley_Chap39.indd 796 1/2/2013 1:36:07 PM CYANIDE 1: POISONING 797 Acute poisoning Cyanide, cyanogen chloride, acetonitrile, and other cyanide releasing subst ances. Ingestion or inhalation of large amounts Cyanide concentration > 3mg/L (>114 mol/L) \200 Immediate unconsciousness \200 Convulsions \200 Death within 1 \200\22315min. Ingestio n, inhalation, or skin absorption of moderate amounts Cyanide concentration 1 \200\2233mg/L (38 \200\223114 mol/L) \200 Dizziness \200 Rapid respiration \200 Vomiting \200 F lushing \200 Headache \200 Drowsiness \200 Hypotension \200 Rapid pulse \200 Unco nsciousness \200 Death in convulsions within 4h except sodium nitroprusside where death may be delayed for 12h. Ingestion, inhalation, or skin absorption of small amounts Cyanide concentration < 1mg/L (< 38 mol/L) \200 Nausea \200 Dizziness \200 Drowsiness \200 Hyperventilation \200 Anxiety. Acute poisoning: acrylonitrile Inhalation \200 Nausea and vomiting \200 Diarrh ea \200 Weakness \200 Headache \200 Jaundice. Note that skin contact can cause epider mal necrosis. 39_Smedley_Chap39.indd 797 1/2/2013 1:36:07 PM CHAPTER 39 Acute poisoning 798 Cyanide 2: treatment 1 Rescuers should not put themselves at risk. Moisture on some cyanide salts can liberate HCN. Immediate \201 rst aid \200 Maintain clear airway and adequate ventilation \200 Give 100% oxygen to all patients \200 Monitor pulse, blood pressure, respiratory rate, oxygen saturation, and cardiac rhythm Transfer all de \201 nite cases to hospital as rapidly as possible \200 Consider startin g treatment on site if transfer to hospital is likely to be prolonged, and depending on severity of exposure. Diagnosis In the absence of a blood cyanide concentration the following features suggest cy anide poisoning: \200 Lactate >7 mmol/L \200 Elevated anion gap acidosis \200 Reduced arteriovenous oxygen gradient. Mild poisoning \200 Observe asymptomatic and mildly symptomatic patients for at least 6 h ours after ingestion of cyanide salt and at least 12h after ingestion of acetonitrile Give 50mL of 25% sodium thiosulphate (12.5g) IV over 10min. Moderate and severe poisoning \200 Patients with moderate or severe poisoning should be m anaged in a critical care environment Treatment with antidote therapy is necessary in all cases \200 It is important that the a dmitting hospital is informed if any antidote therapy has been given in the pre-hospital setting since repeat doses of some antidotes can cause unwanted side effects 1 If treatment is started on site the doctor should accompany the casualties to the admitting hospital Give 20mL of 1.5% dicobalt edetate solution (300mg) IV over 1min followed immediately by 50 mL of 50% dextrose. If there is only a partial response to dicobalt edetate 300mg or the pa tient relapses after recovery, a further dose of dicobalt edetate 300mg should be given. If a second dose of dicobalt edetate is administered, there is a danger of inducing cobalt to xicity, if the diagnosis is not cyanide poisoning In addition, the administration of 50mL of 25% sodium thiosulphate (12.5g) IV over 10min may be bene \201 cial Or , if dicobalt edetate is not available, give 10mL of 3% sodium nitrite solution (300mg) IV over 5 \200\22320min and 50mL of 25% sodium thiosulphate (12.5g ) IV over 10min 39_Smedley_Chap39.indd 798 1/2/2013 1:36:07 PM CYANIDE 2: TREATMENT 799 A further dose of sodium thiosulphate 12.5g IV over 10min may be needed. A second dose of sodium nitrite should not be given because of the risk of excessiv e methaemoglobinaemia Response to treatment in the pre-hospital setting can be assessed by improved haemodynamic status Single brief convulsions do not require treatment. If frequent or prolonged, control with IV diazepam (10 \200\22320mg) or lorazepam (4mg) Correct hypotension by raising the legs of the patient and/or expanding the intravascular volume. 39_Smedley_Chap39.indd 799 1/2/2013 1:36:07 PM CHAPTER 39 Acute poisoning 800 Hydrogen sulfide poisoning Properties \200 Colorless gas with characteristic \200\230rot ten egg \200\231 smell \200 CAS Number 7783 \200\22306 \200\2234 \200 UN 1053. Synonyms \200 Sulphuretted hydrogen \200 Sulfur hydride \200 Hydrosulphuric acid. Toxicity \200 Irritant gas with systemic asphyxiant effects \200 Reversibly inhibits cy tochrome oxidase, which impairs cell respiration \200 Rapidly absorbed by inhalation \200 Little absorption occurs through the skin \200 Irritating to the eyes \200 Occupa tional short-term exposure limit is 10ppm (14mg/m 3 ) \200 Long-term exposure limit is 5p pm (7mg/m 3 ). 0.02 \200\2230.025ppm Odor threshold 10ppm Unpleasant smell, sore eyes 100ppm Loss of smell after 3 \200\22315min, eyes, and throat sting 250ppm Prolonged exposure \200\224pulmonary oedema 1000ppm Rapid collapse, respiratory paralysis, coma, and death within minutes Features Prolonged exposure causes: Respiratory tract irritation \200 Rhinitis \200 Pharyngitis Bronchitis \200 Dyspnoea \200 Pulmonary oedema Systemic effects \200 Vomiting \200 Diarrhea \200 Headache \200 Nystagmus \200 Di zziness \200 Agitation Drowsiness \200 Tremor \200 Muscular weakness \200 Seizures \200 Tachycardia \200 Hypotension 39_Smedley_Chap39.indd 800 1/2/2013 1:36:07 PM HYDROGEN sulfide POISONING 801 Inhalation of high concentrations Leads rapidly to: \200 Collapse \200 Respiratory para lysis \200 Cyanosis \200 Convulsions Coma \200 Cardiac arrhythmias \200 Death within minutes Eye effects May be delayed and include: \200 Irritation \200 In \202 ammation \200 L acrimation \200 Conjunctival hyperaemia Photophobia \200 Conjunctivitis \200 Keratitis \200 Blepharospasm Recovery is usually complete, but there may be permanent damage. Skin effects \200 Skin discoloration \200 Pain, itching, erythema \200 Local frostbit e. Management of H 2 S poisoning \200 Remove from exposure (rescuers must wear PPE) \200 O xygen in as high a concentration as possible, if necessary via an endotracheal tube Skin decontamination is usually not necessary because it is a gas. Removing patient \200\231s clothing and washing the skin with water and a mild detergent ma y reduce the risk of odor-related complaints in rescuers, but this is not a priority if dea ling with a critically ill patient Maintain a clear airway and adequate ventilation \200 Monitor pulse, blood pressure, and oxygen saturation \200 If the patient has clinical features of bronchospasm treat conventionally with nebulized bronchodilators and steroids Transfer to hospital \200 Correct hypotension with IV \202 uids \200 Convulsions are unlikely to require treatment by the time the patient reaches medical care but IV diazepam 10 \200\22320mg could be given if necessary. 39_Smedley_Chap39.indd 801 1/2/2013 1:36:07 PM CHAPTER 39 Acute poisoning 802 Organophosphate poisoning See also b p. 298. Immediate management and decontamination \200 1 Avoid contaminating yourself: organophosp hates are rapidly absorbed through skin Wear appropriate protective clothing \200 Supportive measures are vitally important. 2 Mo st products are dissolved in hydrocarbon solvents. Aspiration of these products will cause severe aspiration pneumonia with high mortality, and for this reason gastric aspiration sho uld be avoided. Management of organophosphate poisoning \200 Prevent further absorption according to rout e of exposure: \200 remove to fresh air \200 remove soiled clothing and wash contaminat ed skin with washing-up liquid in water (see b p. 803) \200 Consider hospital transfer early \200 Protect the a irway \200 Gain IV access \200 Monitor BP and pulse \200 In symptomatic patients esta blish intravenous access \200 Collect blood samples in an EDTA tube for measurement of erythrocyte and plasma cholinesterase activities to con \201 rm the diagnosis If bronchorrhoea develops, administer atropine 0.6 \200\2232mg IV every 10 \200\22315min until secretions are minimal and the patient is atropinized (dry skin and sinus tachycardia). In severe cases very large doses of atropine may be required if hospita l admission is likely to be delayed Moderately or severely poisoned patients should be given pralidoxime mesilate 2g IV over 4min to reactivate phosphorylated enzyme IV diazepam 5 \200\22310mg is useful in controlling apprehension, agitation, fasciculation, and convulsions. The dose may be repeated as required. 39_Smedley_Chap39.indd 802 1/2/2013 1:36:08 PM ORGANOPHOSPHATE POISONING 803 Skin decontamination: pesticides \200 1 Safety \201 rst \200 Avoid contaminating your self \200 Wear protective clothing \200 Do NOT allow smoking nearby. There may be a ris k of \201 re if a solvent is involved Carry out decontamination in a well-ventilated area, preferably with its own ventilation system The patient should remove soiled clothing and wash him/herself if possible Put soiled clothing in a sealed container to prevent escape of volatile substances Wash hair and all contaminated skin with liberal amounts of water (preferably warm) and soap