The spectre of medical errors is a critically important subject, one that is as old as organised medical practice itself. What is striking, however, is not merely their longevity but their alarming frequency.
Estimating the true scale of medical errors remains difficult because of varying definitions, underreporting, institutional concealment, and differences in study methodologies.
In this essay, we examine what is known, beginning from the earliest period of organised healthcare, and briefly outline key findings from major studies and official reports.
The World Health Organisation estimates that one in every 10 patients is harmed while receiving hospital care in high-income countries.
In low- and middle-income countries, the risk is significantly higher, with an estimated 134 million adverse events each year contributing to about 2.6 million deaths.
In the United States, figures often cited come from a 2016 study by Johns Hopkins University, which concluded that medical errors constitute the third-leading cause of death, accounting for more than 250,000 deaths annually.
These errors include failures in diagnosis, medication, communication and systems of care.
Earlier, in 1999, the Institute of Medicine published its landmark report, To Err Is Human, estimating that between 44,000 and 98,000 people died annually in U.S. hospitals due to medical errors.
Though conservative, the report served as a wake-up call and catalysed global patient-safety movements.
Subsequent studies suggest the figures may be much higher, with estimates ranging between 210,000 and 440,000 preventable deaths each year among hospitalised patients.
These statistics, however, largely emerge from societies with the resources, institutional curiosity and transparency required to study failures within their health systems. In resource-poor settings such as ours, where healthcare workers are overwhelmed by shortages of personnel, equipment and basic utilities, systematic investigations into medical errors are rare.
Conducting such studies often requires external funding and publication fees in foreign currency, further discouraging inquiry.
Nevertheless, despite wide variations in reported figures, there is broad consensus that medical errors are far too common and represent a major public-health challenge. In this sense, medical errors are not a modern aberration; they are as old as medicine itself.
Medical errors remain a leading cause of death and injury worldwide, yet many are preventable through improvements in systems, technology and organisational culture.
They are not abstract statistics but one of the most direct threats to achieving favourable treatment outcomes.
All medical interventions carry inherent risks. Surgery carries the risk of infection; chemotherapy carries severe side effects, including secondary cancers and death.
These risks are known, communicated and accepted as trade-offs in pursuit of greater benefit, which is why informed consent is central to ethical practice.
The errors that concern us most, however, do not arise from accepted risk but from failure, sometimes despite the best efforts of highly trained professionals. Some errors occur simply because doctors and nurses are human, and therefore fallible.
As noted earlier, some of the earliest and most instructive examples of medical error arose from what is now a routine hospital procedure: blood transfusion. The earliest attempts at transfusion, from the 17th to the early 19th centuries, form a grim but revealing chapter in medical history.
These efforts were marked by bold experimentation, scientific curiosity and catastrophic failure, driven by a profound ignorance of basic physiology.
The idea of blood transfusion emerged in the 1600s, influenced by alchemy, humoral theory and the belief that blood carried a person’s “vital spirit.” Some believed transfusion could rejuvenate the elderly, calm the mentally ill or even alter personality. In 1665, the English scientist Richard Lower performed the first documented successful transfusion between two dogs, using quills as cannulas, demonstrating that life could be sustained by another’s blood. Encouraged by these results, early transfusions in humans were performed using animal blood.
In 1667, French physician Jean-Baptiste Denis transfused lamb’s blood into a young man suffering from fever, who reportedly survived.
He later transfused calf’s blood into a mentally ill patient who initially appeared to improve but died after a second procedure.
Denis was charged with murder but acquitted after it was determined that the man had likely died from arsenic poisoning administered by his wife. Nonetheless, the scandal, alongside other deaths, led to bans on blood transfusion in France and England by 1670.
These early practitioners were operating in near-total ignorance of critical biological principles. Blood groups were unknown until Karl Landsteiner’s discovery of the ABO system more than two centuries later.
Transfusing incompatible blood triggers fatal immune reactions, causing red blood cells to clump and rupture in a process known as haemolysis.
There was also little understanding of blood circulation, blood pressure, clotting mechanisms or the role of the circulatory system. Equally absent was any knowledge of germs or sepsis.
Instruments and procedures were far from sterile, leading to rampant infections. Knowledge of blood clotting and its importance was minimal. Using animal blood, the preferred method for early transfusions, introduced massive incompatibility problems and severe toxic reactions.
Outcomes were often predictably disastrous: patients suffered violent chills, back pain, black urine from ruptured red blood cells, kidney failure, shock, and frequently death.
The procedure quickly gained a reputation for being more lethal than the diseases it sought to treat.
Following these early failures and bans, blood transfusion was largely abandoned for nearly 150 years, becoming a disreputable, fringe practice.
It was not until the rise of hospital-based obstetrics in the early 1800s, amid the desperate need to treat fatal postpartum haemorrhage, that interest in transfusion between humans was revived. In 1818, British obstetrician James Blundell performed the first successful human-to-human transfusions.
Blundell designed instruments, called “gravitators,” to connect the donor and patient directly via syringe and tubing. He insisted on human donors and applied transfusions exclusively to women bleeding after childbirth.
Outcomes were mixed: while some patients survived, mortality remained high at around 50 per cent, largely due to unresolved issues of incompatibility and sepsis.
The earliest transfusions were perilous leaps in the dark, guided more by symbolic ideas than scientific understanding, often with horrifying consequences.
It was only after the foundational discoveries of blood typing, anticoagulation, and aseptic technique in the early 20th century that transfusion evolved into the life-saving, routine procedure it is today.
The journey from lamb’s blood to modern blood banks is a dramatic story of medical trial, error, and eventual triumph. Three critical milestones stand out:
- Joseph Lister’s work on antisepsis (1860s): Introduced cleaner, safer procedures, reducing infection risks in transfusions and surgery.
- Sodium citrate anticoagulation: Enabled blood to be stored and transfused indirectly, paving the way for modern blood banks, which proved pivotal in saving lives during the First World War.
- Karl Landsteiner’s discovery of blood groups (1901): Identification of the ABO blood types explained why some transfusions worked while others proved fatal, allowing compatibility testing.
Despite these advances, blood transfusion remains a treatment with inherent risks. Adverse reactions still occur today, usually due to clerical errors, such as mislabelled samples or mismatched blood, rather than negligence.
When such errors happen, or indeed when any medical error occurs, certain predictable events unfold, which we will examine in a subsequent essay.
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