The estimated snakebite mortality in Papua New Guinea (3.5/100 000 population per year) is about 100-fold higher than in Australia.1 There are concerns that this rate is increasing, perhaps because of inadequate antivenom supplies — an international problem that is particularly acute in the Indo-Pacific region.2-4 Detailed studies of the problems of snakebite in PNG were last carried out a decade ago; however, such investigations were generally restricted to patients receiving antivenom and were not specifically focused on mortality.1,5-11

Port Moresby General Hospital (PMGH) has the largest caseload of seriously envenomed patients in PNG. Between 1990 and 1992, snakebite is said to have accounted for about 50% of all patients requiring ventilation at this hospital.5 Enzyme-linked immunoassays attributed 94% of serious snakebites to two species: 83.2% to Papuan taipans (Oxyuranus scutellatus canni) and 10.8% to death adders (Acanthophis spp.).1

The aim of our study was to investigate snakebite mortality at PMGH as a means of identifying factors that currently contribute to poor clinical outcomes after snakebite. This should provide the basis for developing sustainable initiatives to improve the prognosis for snakebite across PNG.

We conducted a retrospective analysis of snakebite admissions to PMGH between 1 January 1992 and 31 December 2001. Our focus was on snakebite mortality within the intensive care unit (ICU).

This is the first study that specifically examined snakebite mortality in PNG. Previous reports on this subject have overwhelmingly focused on morbidity among patients receiving antivenom in an era of lower antivenom prices.1,5-11 Unfortunately, the reality over the past decade has changed from a situation where most snakebite patients received antivenom to one of restricted antivenom availability and its delayed administration.13

Financial constraints mean that many investigations considered routine for snakebite in Australia are often unavailable at PMGH, and cultural factors result in low autopsy rates.14,15 One consequence is that studies such as ours are limited to information available in medical notes. Moreover, hospital records are not always readily available, impeding access to meaningful data. Despite these limitations, we were able to demonstrate that envenomation places a greater burden on PMGH ICU ventilators than all other conditions and that the duration of dependency for snakebite was significantly longer than for other diagnoses, undoubtedly adding to treatment costs. This represents the highest proportional ventilator load reported for snakebite in any hospital worldwide.

The second major finding of our study related to the worsening outcomes for children. A study during the 1980s found that 29.6% of children admitted to PMGH ICU with envenomation required intubation, 91% received antivenom, and the case-fatality rate was 7.7%.6 In contrast, in our study, 85.4% of children admitted to the ICU were intubated and ventilated, antivenom use was only documented for 50% of the children who died, and the paediatric case-fatality rate was 14.6%. Ventilation was also a key feature in the management of the adult ICU admissions.

Increased reliance on ventilation may be a consequence of inadequate antivenom supplies due to rising costs, influenced partly by the floating of the kina and its subsequent devaluation against the Australian dollar.2,3,16 The cost issue is even more extreme when considering direct antivenom purchases from Port Moresby pharmacies by individuals when PMGH stocks have been depleted. However, comparison of year 2000 GDP/capita antivenom costs shows that antivenoms cost less in India (which produces its own antivenoms) than in Australia, indicating that not all developing nations suffer the same fate as PNG.17 Since 1998, PNG has purchased antivenom from a wholesaler instead of directly from the manufacturer.18 Direct purchasing from CSL of less expensive monovalent antivenoms in combination with appropriate diagnostic use of the simple 20WBCT and CSL’s VDK should not only generate significant unit cost savings, but also result in increased stock availability.

Previous studies have found that delays in the administration of antivenom significantly increase the necessity to intubate snakebite patients at PMGH.7,9 Patients who received antivenom within 4 hours of being bitten were three times less likely to require intubation, exhibited more rapid resolution of neurotoxicity, and had shorter hospital stays.7 Unfortunately, even though many patients in our study arrived at a health facility (either a peripheral clinic or PMGH) within 4 hours of the bite, very few received antivenom within that period (Box 2).

Despite clear guidelines for appropriate antivenom administration, their relevance becomes questionable in the absence of adequate antivenom supplies. Consequently, antivenom is often reserved for moribund patients, and its use may be delayed until significant deterioration has occurred.19,20 During the 1960s, patients who developed paralysis often received up to four ampoules each.21,22 Since then, antivenom use has become more frugal, although in the 1980s and early 1990s most patients received at least one ampoule.5,9 This study shows that the treatment focus has switched from high antivenom availability and use with lower rates of ventilation to one of low antivenom availability and consequent high rates of ventilation. This is despite clear advice that snakebite deaths in PNG may be prevented by more widespread availability of antivenom.23

This is the first study to detail the use of blood products in envenomed patients in PNG. Given the concern about intracranial haemorrhage in the context of a bleeding diathesis, use of products such as fresh frozen plasma might appear reasonable. However, blood products are scarce and expensive, their value in the treatment of snakebite coagulopathy is unclear, and they are potentially hazardous. Moreover, previous studies have demonstrated that systemic bleeding generally resolves rapidly after administration of appropriate amounts of specific antivenom.9

Previous studies have found that the positive predictive value (PPV) of a 20WBCT ≥ 20 minutes for diagnosis of Papuan taipan envenoming is 96%.7 In our study, 75% of patients had a 20WBCT ≥ 20 minutes, but only 25% of those who received antivenom received taipan monovalent. Given the gap between the cost of polyvalent and monovalent antivenoms, the recommendations that all envenomed PMGH patients with incoagulable blood should receive monovalent taipan antivenom, and that CSL Venom Detection Kits be used to enable monovalent antivenom selection in cases without coagulopathy, remain relevant.7 Such protocols should significantly reduce per-patient antivenom costs and increase overall antivenom availability.

Our study confirms previous findings that about 20% of snakebite patients present to hospital more than 10 hours after the bite.7 While some of these patients may consult traditional healers before seeking medical services, transportation difficulties on poorly maintained roads are probably a more important factor, with many rural health centres lacking functioning ambulances and communications infrastructure.24,25 Potentially dangerous first aid techniques, such as scarification, also persist in PNG and are reported more frequently than the application of pressure bandaging.9,24,25 Infrequent use of pressure immobilisation is a continuing challenge for community education in Australia and PNG, but it is encouraging to note an apparent reduction in tourniquet use reported at PMGH since the 1980s.1,5,26

System failures and equipment deficiencies contributed to several of the deaths, and included ICU bed and staff shortages that led to intubated patients spending lengthy periods in the emergency department, where they could not be adequately monitored and, on occasion, self-extubated as a result. Ventilator shortages often resulted in relatives being required to rotate hand-ventilation of paralysed patients. Even in a well-equipped Australian ICU, snakebite can be a challenging condition to manage. The difficulties of managing venom-induced multisystem failures are compounded in PNG by precarious health infrastructure20 and increasing antivenom costs, which are further exacerbated by economic instability and a devaluing currency.

Development of protocols that increase availability of less expensive monovalent antivenoms, in conjunction with appropriate diagnostic criteria for their use, may improve prognoses; however, resources also need to be committed to ensuring that adequate life support facilities and other infrastructure are available. We reinforce recent calls for wider public snakebite first aid education, and the development and implementation of appropriate snakebite management protocols for both rural clinics and urban hospitals.2-5,9

4 Ventilator bed-days: snakebite compared with all other causes

Data were extracted from Port Moresby General Hospital Intensive Care Unit logbooks.