Transport to Hospital Times and Survival: The Case of Snake Bite

High-income countries have well developed ambulance services. However, investment in acquiring and maintaining effective systems of transport for sick and injured patients does not seem to have been a priority for many low- and middle-income countries (LMICs).  In some settings, for example post conflict states, lack of ambulance services is understandable; what is the point of transferring people to non-functioning or non-existent hospitals? But most LMICs do have a network of hospitals providing emergency care. The point must be reached where the opportunity costs of further improvements in fixed facilities is less than those of providing transport to reach the facilities in the first place.

There are many types of transport: motorised ambulance, motorbike ambulance, bicycle ambulance, and private vehicles. These different types of transport operate with or without trained clinical staff to accompany the patient. Moreover, there are many different types of clinical scenario where rapid transport may be required, from a very sick child to major trauma. There are also many different settings, rural vs. urban for example. The cost-effectiveness of different forms of transport will vary considerably between these different types of vehicle, different staff configurations, different clinical scenarios, and different geographical settings. Thus, the cost-effectiveness of a given type of transport, staffed in a given way and dealing with a particular clinical scenario, may have different effects and costs in different geographic and social contexts.

However, there is one unifying variable that underpins all cost-effectiveness calculations: this is the function that relates marginal changes in transport times in reaching a facility to the contingent marginal changes in outcome. In many circumstances death is the primary outcome of interest. Then, given an estimate of the relationship between time delay and survival, a local decision-maker can populate a cost-effectiveness model with context specific data. In this way it is possible to calibrate the anticipated benefit of a proposed transport system through its effect on reducing time to treatment.

In a forthcoming paper we will develop the model that relates transfer time to survival, taking into account costs, baseline survival rates, and whether or not treatment is administered in association with transport. To illustrate the model we will populate it with data for one particular scenario: snake bite. We use snake bite as the example, not only for its (considerable) intrinsic interest, but also because the best data we can find for transport time vs. survival rates, relates to snake bite. Our purpose is to illustrate the methodology so that it can be applied more generally. The case for ambulance services, of any particular type and in any setting, turns on its use across all emergency conditions. The investment case certainly could not be made on the basis of just one condition, least of all an uncommon scenario such as snake bite. Nevertheless, the model we propose could be used across a range of common scenarios to build up a case for a particular type of transport in a particular context.

— Richard Lilford, CLAHRC WM Director

Transport to Place of Care

Availability of emergency transport is taken for granted in high-income countries. The debate in such countries relates to such matters as the marginal advantages of helicopters over vehicle ambulances, and what to do when the emergency team arrives at the scene of an accident. But in low- or low-middle-income countries, the situation is very different – in Malawi, for example, there is no pretence that a comprehensive ambulance system exists. The subject of transport does not seem to get attention commensurate with its importance. Researchers love to study the easy stuff – role of particulates in lung disease; prevalence of diabetes in urban vs. rural areas; effectiveness of vaccines. But study selection should not depend solely on tractability – the scientific spotlight should also encompass topics that are more difficult to pin down, but which are critically important. Transport of critically ill patients falls into this category.[1]

Time is of the essence for many conditions. Maternity care is an archetypal example,[2] where delayed treatment in conditions such as placental abruption, eclampsia, ruptured uterus, and obstructed labour can be fatal for mother and child. The same applies to acute infections (most notably meningococcal meningitis) and trauma where time is critical (even if there is no abrupt cut-off following the so called ‘golden hour’).[3] The outcome for many surgical conditions is affected by delay during which, by way of example, an infected viscus may rupture, an incarcerated hernia may become gangrenous, or a patient with a ruptured tubal pregnancy might exsanguinate. However, in many low-income countries less than one patient in fifty has access to an ambulance service.[4] What is to be done?

The subject has been reviewed by Wilson and colleagues in a maternity care context.[5] Their review revealed a number of papers based on qualitative research. They find the theory that one might have anticipated – long delays, lack of infrastructure, and so on. They also make some less intuitive findings. People think that having an emergency vehicle at the ready could bring bad luck, and that it is shameful to expose oneself when experiencing vaginal bleeding.

Quite a lot of work has been done on the use of satellites to develop isochrones based on distances,[6] gradients, and road provision. But working out how long it should take to reach a hospital does not say much about how long it takes in the absence of a service for the transport of acutely sick patients.

We start from the premise that, for the time being at least, a fully-fledged ambulance service is beyond the affordability threshold for many low-income countries. However, we note that many people make it to hospital in an emergency even when no ambulance is available. This finding makes one think of ‘grass-roots’ solutions; finding ways to release the capacity inherent in communities in order to provide more rapid transfers. An interesting finding in Wilson’s paper is that few people, even very poor people, could not find the money for transfer to a place of care in a dire emergency. However, this does not square with work on acutely ill children in Malawi (Nicola Desmond, personal communication), nor work done by CLAHRC WM researchers showing the large effects that user fees have in supressing demand, especially for children, in the Neno province of Malawi.[7] In any event, a grass roots solution should be sought, pending the day when all injured or acutely ill people have access to an ambulance. Possible solutions include community risk-sharing schemes, incentives to promote local enterprises to transport sick people, and automatic credit transfer arrangements to reimburse those who provide emergency transport.

I am leading a work package for the NIHR Global Surgery Unit, based at the University of Birmingham, concerned with access to care. We will describe current practice across purposively sampled countries, work with local people to design a ‘solution’, conduct geographical and cost-benefit analyses, and then work with decision-makers to implement affordable and acceptable improvement programmes. These are likely to involve a system of local risk-sharing (community insurance), IT facilitated transfer of funds, promotion of local transport enterprises, community engagement, and awareness raising. We are very keen to collaborate with others who may be planning work on this important topic.

— Richard Lilford, CLAHRC WM Director

References:

1. United Nations. The Millennium Development Goals Report 2007. New York: United Nations; 2007.
2. Forster G, Simfukew V, Barber C. Use of intermediate mode of transport for patient transport: a literature review contrasted with the findings of Transaid Bicycle Ambulance project in Eastern Zambia. London: Transaid; 2009.
3. Lord JM, Midwinter MJ, Chen Y-F, Belli A, Brohi K, Kovacs EJ, Koenderman L, Kubes P, Lilford RJ. The systemic immune response to trauma: an overview of pathophysiology and treatment. Lancet. 2014; 384(9952): 1455-65.
4. Nyamandi V, Zibengwa E. Mobility and Health. 2007. In: Wilson A, Hillman S, Rosato M, Costello A, Hussein J, MacArthur C, Coomarasamy A. A systematic review and thematic synthesis of qualitative studies on maternal emergency transport in low- and middle-income countries. Int J Gynaecol Obstet. 2013; 122(3): 192-201.
5. Wilson A, Hillman S, Rosato M, Skelton J, Costello A, Hussein J, MacArthur C, Coomarasamy A. A systematic review and thematic synthesis of qualitative studies on maternal emergency transport in low- and middle-income countries. Int J Gynaecol Obstet. 2013; 122(3): 192-201.
6. Frew R, Higgs G, Harding J, Langford M. Investigating geospatial data usability from a health geography perspective using sensitivity analysis: The example of potential accessibility to primary healthcare. J Transp Health 2017 (In Press).
7. Watson SI, Wroe EB, Dunbar EL, Mukherjee J, Squire SB, Nazimera L, Dullie L, Lilford RJ. The impact of user fees on health services utilization and infectious disease diagnoses in Neno District, Malawi: a longitudinal, quasi-experimental study. BMC Health Serv Res. 2016; 16(1): 595.