Vancomycin Monitoring and Acute Kidney Injury

In October 2024 the CBC published the story of Wendy Guimont, a piano teacher in her sixties whose death was attributed not to her metastatic pancreatic cancer but to acute kidney failure from vancomycin toxicity. The mechanism the family described to the CBC was a familiar one to anyone who works in medication-error litigation: vancomycin was prescribed, the antibiotic was administered, but the blood levels were not appropriately monitored. By the time the toxicity was identified, irreversible kidney injury had already occurred. The cancer was not the cause of death. The medication was.

The case is a useful starting point for thinking about a particular kind of medical malpractice claim that does not get as much public attention as the more dramatic categories. Birth injury, surgical error, and missed cancer diagnosis tend to dominate the public conversation about malpractice. Medication errors are quieter. They are also extremely common, sometimes catastrophic, and frequently rooted in identifiable system failures that the legal framework recognizes.

This post is not a comment on any reported court decision. There is no published Canadian decision named Guimont v anyone that I am aware of, and the analysis below proceeds on the basis of the publicly reported facts of Ms. Guimont’s case as a reference point for a broader discussion of vancomycin monitoring as a standard-of-care question. The substantive material applies generally to vancomycin nephrotoxicity claims and to the broader class of medication monitoring claims.

For more on medication error claims as a practice area, see the firm’s Medication Error Lawyer page. For a wider overview of how I evaluate any potential malpractice claim, see Suing for Medical Malpractice in Ontario: What You Need to Know.

What vancomycin is and why it is used

Vancomycin is a glycopeptide antibiotic that has been in clinical use since the 1950s. It is one of the most important antibiotics in modern hospital practice, used primarily for:

• Methicillin-resistant Staphylococcus aureus (MRSA) infections — bacteremia, endocarditis, pneumonia, skin and soft tissue infections, bone and joint infections
• Other gram-positive infections where alternative agents are not appropriate
• Clostridioides difficile colitis when given by mouth (the oral preparation is not absorbed and acts locally in the colon)
• Empiric coverage in serious infections where MRSA or other resistant gram-positive organisms are clinically plausible

Vancomycin is typically administered intravenously for systemic infections. The oral route is reserved for C. difficile because oral vancomycin is not absorbed and would not treat any infection outside the gut.

The drug has several pharmacological features that make appropriate monitoring critical:

It is primarily cleared by the kidneys. Approximately 80% to 90% of an intravenous dose is excreted unchanged in the urine. Renal function therefore directly determines how the drug accumulates in the body. A patient with normal renal function clears vancomycin steadily. A patient with reduced renal function accumulates the drug to higher and higher levels with each subsequent dose unless the dose is adjusted.

It is nephrotoxic at elevated levels. Vancomycin can cause both acute interstitial nephritis (an immune-mediated kidney injury) and acute tubular necrosis (direct toxic injury to the kidney tubules). The risk rises substantially with elevated serum levels, prolonged exposure, concurrent nephrotoxic drugs, and pre-existing renal impairment.

It has a narrow therapeutic window. The therapeutic concentration range is not wide. Below the effective range, the drug does not adequately treat the infection. Above the therapeutic range, the toxicity risk rises sharply. The clinical task is to keep the patient’s serum concentration inside the therapeutic range over time.

It is used for serious infections in patients who are often already vulnerable. The patients who require vancomycin tend to be hospitalized with significant illness. They often have multiple comorbidities, polypharmacy, intravenous access, and reduced physiological reserve. The margin for error in their care is thin.

Therapeutic drug monitoring as the standard of care

For vancomycin in serious infections in hospitalized patients, therapeutic drug monitoring (TDM) is the standard of care. The framework has several components.

Baseline renal function. Before vancomycin is started, the patient’s renal function should be assessed. The minimum is a serum creatinine and an estimated glomerular filtration rate (eGFR). Pre-existing renal impairment changes both the loading dose and the dosing interval and increases the importance of subsequent monitoring.

Initial dosing. The loading dose and maintenance dose should be calculated based on the patient’s body weight (typically actual body weight, with some adjustment in obese patients), the indication, and the renal function. In adults with normal renal function, loading doses of 25 to 30 mg per kilogram and maintenance doses of 15 to 20 mg per kilogram every 8 to 12 hours are typical. In renal impairment, the loading dose may be similar but the maintenance dose and the interval are adjusted to account for reduced clearance.

Therapeutic drug monitoring. The TDM framework has evolved over the last decade. The traditional approach used trough levels (a blood level drawn immediately before the next dose) targeted to 10 to 20 mg/L depending on indication. The more recent approach, endorsed in updated American and Canadian guidelines, targets a 24-hour area-under-the-curve (AUC) to minimum inhibitory concentration (MIC) ratio between 400 and 600. The AUC-based approach typically requires two blood levels rather than one and the use of pharmacokinetic software or Bayesian estimators.

Timing of first level. The first trough level is typically drawn immediately before the fourth dose (when steady state is approached) or earlier if there is concern about accumulation. AUC-based approaches may sample earlier and use software-driven dose adjustment. The principle is the same in either framework: the patient’s actual exposure to the drug is measured, and the dose is adjusted to maintain therapeutic levels without toxicity.

Ongoing monitoring. Daily monitoring of serum creatinine and eGFR is the standard of care during vancomycin therapy. Trough levels (or AUC-based assessments) are repeated periodically — typically every two to three days in patients with stable renal function, more frequently in patients with changing renal function or other risk factors.

Pharmacy-led dosing protocols. Most Ontario hospitals operate vancomycin dosing protocols led by clinical pharmacists. Under these protocols, the prescriber orders vancomycin and identifies the indication; the clinical pharmacist calculates the initial dose, orders the monitoring levels, interprets the results, and recommends or directly orders dose adjustments. The protocols are designed to standardize the TDM framework and reduce the variability that historically existed when individual physicians did their own monitoring.

Recognition of acute kidney injury. The KDIGO (Kidney Disease: Improving Global Outcomes) framework defines AKI as any of: an increase in serum creatinine by at least 0.3 mg/dL within 48 hours; an increase in serum creatinine to at least 1.5 times baseline within the prior 7 days; or a urine output below 0.5 mL/kg/hour for 6 hours. Each KDIGO stage corresponds to a defined level of injury severity. The clinical importance is that AKI on vancomycin is a clear trigger for dose reduction, dose holding, or discontinuation depending on the severity.

Documentation. Each step of the framework — the baseline assessment, the dosing calculation, the levels, the interpretations, the dose adjustments, the renal function trend — should be documented contemporaneously. The documentation is the operational record of the standard of care and the primary source of evidence in any subsequent dispute.

Risk factors for vancomycin-associated kidney injury

Several risk factors are well-recognized in the published clinical literature and in clinical practice guidelines. They include:

• Age 65 or older. Renal function declines with age and the margin for error narrows. Many published studies specifically identify age over 65 as a risk factor for vancomycin nephrotoxicity.
• Pre-existing chronic kidney disease. A patient with reduced baseline eGFR has reduced clearance and reduced reserve.
• Prolonged duration of therapy (greater than 7 days). The cumulative exposure to vancomycin correlates with nephrotoxicity risk. Courses beyond a week require particular vigilance.
• Concurrent nephrotoxic medications. NSAIDs, aminoglycosides (gentamicin, tobramycin, amikacin), intravenous contrast media, ACE inhibitors and angiotensin receptor blockers, calcineurin inhibitors (cyclosporine, tacrolimus), and several chemotherapy agents all interact with vancomycin to increase nephrotoxicity risk.
• Critical illness. ICU patients with hemodynamic instability, sepsis, or multi-organ dysfunction are at elevated risk for vancomycin-associated AKI.
• High trough or AUC targets. The higher the targeted exposure, the higher the toxicity risk. Patients targeted to the upper end of the therapeutic range for severe infections need particular attention.
• Hypovolemia or hypoperfusion. Any cause of reduced renal perfusion magnifies the toxicity risk.
• Underlying malignancy and chemotherapy. Cancer patients may have reduced renal reserve from disease, chemotherapy, or supportive medications.

The clinical task is to identify which risk factors apply to a given patient and to calibrate the monitoring intensity accordingly. A young patient with normal renal function on a short course of vancomycin may require minimal monitoring. An older patient with metastatic cancer, concurrent NSAIDs for symptom control, and a planned course of more than a week is at substantially higher risk and requires more frequent monitoring with a lower threshold for intervention.

The Guimont fact pattern and what it illustrates

The publicly reported facts of Wendy Guimont’s case, as covered by the CBC, illustrate several of these risk factors in combination:

• Age over 65 (she was reportedly in her sixties)
• Underlying serious illness (metastatic pancreatic cancer)
• The need for systemic antibiotic therapy
• A course of vancomycin that, on the family’s account, extended beyond the period where monitoring should have produced dose adjustment
• A delay in collecting a valid vancomycin level after the drug was administered
• Progression to toxic levels and acute kidney failure

The CBC story does not assert that civil litigation has been commenced; it reports the family’s account of the events and the family’s call for better drug monitoring in hospitals. I am not in a position to evaluate the underlying clinical record from public reporting alone, and the substantive analysis below is general rather than specific to Ms. Guimont’s case.

What the story does illustrate, on the family’s account, is the failure mode that medication monitoring frameworks are designed to prevent. When the TDM framework operates correctly, the vancomycin level is drawn at the right time, interpreted properly, and the dose is adjusted before toxicity develops. When the framework breaks down — when the level is not drawn, or is not drawn at the right time, or is drawn but not acted on — toxicity develops and the patient is harmed.

The story is also an illustration of the principle that the underlying disease is not always the cause of death. A patient who is admitted for one condition can be killed by a complication of treatment for that condition, by an iatrogenic injury during the admission, or by a medication error. The cause-of-death analysis is forensic; the legal analysis is whether the treatment fell below the standard of care and caused the death.

The legal framework for medication error claims

Medication error claims are part of the broader Canadian medical malpractice framework. The substantive law of negligence applies: duty of care, breach of the standard of care, causation, and compensable damages. The features that distinguish medication error claims from other malpractice areas:

The multi-defendant picture. Medication monitoring involves multiple professionals and the institutional context.

• The prescribing physician is responsible for the appropriate selection of the drug, the appropriate indication, the initial dose, and the orders for monitoring.
• The clinical pharmacist in a hospital with a pharmacy-led dosing protocol is responsible for the dose calculation, the TDM orders, the interpretation of levels, and the dose adjustments. Where there is no pharmacy-led protocol, the responsibility shifts back to the physician.
• The nursing staff is responsible for the administration of the drug, the documentation of administration, the drawing of monitoring levels per orders, and the recognition of clinical deterioration.
• The institution (the hospital) is responsible for the operational systems that support safe medication administration: the dosing protocols, the staffing levels, the laboratory turnaround times, the communication systems between pharmacy and the clinical teams, the electronic medical record and clinical decision support, the medication reconciliation processes.

In a fatal medication error claim, the analysis typically involves examining the conduct of each potential defendant. Liability may be joint and several or apportioned among multiple defendants, depending on the contributions to the failure.

Standard of care. The standard of care is the standard of a reasonably competent professional in the same circumstances. For the prescriber, that is the standard of a competent internal medicine specialist, hospitalist, or surgeon (depending on the clinical context) prescribing vancomycin. For the pharmacist, that is the standard of a competent clinical pharmacist. For the nurse, that is the standard of a competent registered nurse administering and monitoring intravenous medications. For the institution, that is the standard of a reasonably operated Canadian hospital. The published guidelines (Canadian and American) and hospital policies and procedures are typically the operative reference materials. Expert evidence from each profession is required.

Causation. The plaintiff must establish on the balance of probabilities that the breach caused the harm. In a vancomycin nephrotoxicity case, the causation question is typically whether the patient would have suffered the AKI and the consequent harm (which may include death) if the monitoring had been done appropriately and the dose adjusted in time. The Clements v Clements, 2012 SCC 32, but-for causation framework applies. Snell v Farrell, [1990] 2 SCR 311, the robust and pragmatic causation framework, may be needed where the precise mechanism is contested. The counterfactual analysis works through what would have happened with appropriate care: lower levels, adjusted dose, no toxicity, no AKI, recovery from the underlying infection, return to the patient’s baseline health trajectory.

Damages. In a death case, the heads of damage include:

• Family Law Act, RSO 1990, c F.3, s 61 damages for surviving spouses, children, parents, and siblings — including loss of guidance, care, and companionship; loss of services; and out-of-pocket expenses
• The deceased’s pain and suffering between the time of the negligence and the death, where there was a period of conscious suffering
• Funeral and burial expenses
• Loss of dependant income where the deceased was a financial contributor
• Management fees and contingencies on the awards

For a deceased patient with metastatic cancer, the damages analysis is calibrated by the underlying life expectancy. A patient with a life expectancy of months rather than years at the time of the negligence is in a different damages category from a patient with normal life expectancy. The legal point is that the patient is entitled to the life they would have had, not the life of a healthy person. Negligent care that shortens that life is still actionable, and the damages reflect the value of what was lost.

Limitations. Ontario’s Limitations Act, 2002, S.O. 2002, c 24, Sched B, applies. The basic limitation period is two years from when the surviving family member knew or ought to have known of the claim, subject to discoverability. The ultimate limitation under section 15 is fifteen years from the date of the act or omission. In death cases, the deceased’s estate may also have separate claims; the limitations analysis for estate claims has its own framework.

The Coroner’s investigation framework. Unexpected deaths in hospital that may involve negligence are typically reportable to the Office of the Chief Coroner under the Coroners Act, RSO 1990, c C.37. The Coroner may order an investigation, may convene a Coroner’s Inquest in appropriate cases, and may issue recommendations directed at preventing similar deaths in the future. The Coroner’s investigation operates separately from any civil litigation and produces information that can be useful to a family considering a claim. For more on the Coroner’s framework in the context of complaints, see A Patient’s Guide to Making Complaints About Health Care in Ontario.

The system pressure dimension

Medication errors are among the most common categories of preventable hospital harm tracked by the Canadian Institute for Health Information. The CIHI hospital harm framework specifically tracks “medication and electrolyte/fluid imbalance” as a top category of preventable harm. The most recent CIHI data covering 2024-2025 shows the rate of any preventable hospital harm has plateaued at 6.0 events per 100 hospitalizations for five consecutive years, with medication-related harm a substantial component of that total. For a fuller discussion, see Is Medical Malpractice on the Rise in Canada?.

The system pressures that contribute to medication monitoring failures include:

• Staffing shortages. Where pharmacy departments are understaffed, the pharmacy-led dosing protocols can lag. Where nursing is understaffed, the timely drawing of monitoring levels can be delayed.
• Laboratory turnaround. Vancomycin levels typically require several hours for processing. Where the laboratory is overloaded, the turnaround time stretches and the actionable information arrives later.
• Communication gaps. The pharmacist’s interpretation of a level needs to reach the prescribing physician quickly for dose adjustment to occur. Where the communication systems are not robust, the interpretation can sit unread.
• Electronic medical record issues. Decision-support alerts can be over- or under-tuned. Over-tuned alerts produce alert fatigue (the alerts are ignored). Under-tuned alerts miss the cases where intervention is needed.
• Handovers. Patients on prolonged vancomycin courses often see multiple teams across multiple shifts. Where handovers are inadequate, monitoring tasks can be dropped.

These system pressures are not a defence to negligence claims. The standard of care for an individual practitioner does not bend because the system is in crisis. The institution may bear some institutional responsibility for systemic failures, but each individual practitioner remains accountable to her own professional standard. The point I made in Hallway Medicine in Ontario: When Overcrowded Emergency Rooms Lead to Medical Malpractice about the ER context applies equally here: the standard of care for safe medication monitoring is not reduced by understaffing. It is simply harder to meet in those conditions, and the cases that go wrong are often the ones where the system was operating at the edge of its capacity.

Practical considerations for families

If you have lost a family member to what may have been a medication error, several practical steps matter.

Gather records promptly. The key records typically include:

• The complete hospital chart for the relevant admission
• The medication administration record (MAR)
• The pharmacy records, including the dosing calculation, the orders for monitoring, the level results, and any pharmacist interpretations or recommendations
• Laboratory records including all serum creatinine, eGFR, and vancomycin level results
• Nursing notes
• Physician progress notes
• Any consulting service notes (nephrology, infectious disease, internal medicine)
• The discharge summary or death summary
• Any incident or critical-incident reports produced by the hospital
• Coroner’s records, if applicable

You are entitled to your family member’s health records under the Personal Health Information Protection Act, 2004 (PHIPA) as the personal representative of the estate. The hospital is a health information custodian and must respond to records requests within statutory timelines.

Request a meeting with the hospital. Many Ontario hospitals will arrange a debrief or disclosure meeting with the family after an adverse event. This is not a substitute for legal investigation but it can provide useful context. Be cautious about anything you sign or commit to in this context without legal advice.

Consider whether to file a complaint. Complaints can be made to the College of Physicians and Surgeons of Ontario (for physicians), the Ontario College of Pharmacists (for pharmacists), the College of Nurses of Ontario (for nurses), or the hospital itself through patient relations. The Coroner may also be involved if the death was unexpected and may give rise to a public safety question. The complaint process and the civil litigation process operate independently and can run in parallel. For more on the complaint framework, see A Patient’s Guide to Making Complaints About Health Care in Ontario.

Get a legal opinion early. Medication error cases require expert evidence from multiple disciplines: clinical pharmacy, internal medicine, nephrology, and sometimes nursing. The records are voluminous. The investigation is resource-intensive. The earlier counsel can look at the file, the better the assessment. Limitation periods are short and run regardless of whether the family is ready to make a decision.

Manage expectations. Not every adverse drug event is malpractice. Vancomycin can cause kidney injury despite competent monitoring; the standard of care is monitoring, not the prevention of every adverse event. The question for legal purposes is whether the monitoring met the standard of care and whether the breach caused the harm. For more on how I evaluate cases, see Suing for Medical Malpractice in Ontario: What You Need to Know and Six Common Misunderstandings About Medical Malpractice in Ontario.

What this means for clinicians

A few observations from the other side of the file, for any clinicians reading this.

Document the monitoring framework explicitly. Each step — the baseline assessment, the dosing calculation, the level orders, the level interpretations, the dose adjustments, the renal function trend — should appear in the contemporaneous record. The documentation is the operational record of the standard of care.

The pharmacy-led dosing protocol is your friend. Hospitals with robust pharmacy-led TDM protocols have lower rates of vancomycin nephrotoxicity. If your hospital does not have one, advocating for one is a meaningful contribution to patient safety.

Recognize the high-risk patient. The patients most at risk of vancomycin nephrotoxicity are the ones with multiple risk factors stacked: older age, reduced baseline renal function, planned prolonged courses, concurrent nephrotoxins. Calibrate the monitoring frequency to the risk profile.

Act on AKI promptly. Once AKI is identified by the KDIGO criteria, dose holding, dose reduction, or discontinuation should occur without delay. Renal recovery is much more likely when the offending drug is removed early than when it is continued in the hope that the kidneys will recover.

Handover the monitoring expectations. When the patient transitions between teams or services, the active TDM plan should transfer with the patient. The receiving team should know that vancomycin levels are pending, when the next one is due, and what the current dose adjustment plan is.

Why this matters

Medication errors are a quiet category of medical malpractice. They do not produce the dramatic narratives of birth injury or surgical disaster. They produce, instead, the steady accumulation of preventable deaths and severe morbidity that the hospital harm data picks up at the population level and the individual file picks up at the family level. The cases that reach my office in this category often share the same structural features: a vulnerable patient, an appropriate indication for a high-risk medication, a monitoring framework that should have caught the developing toxicity, and a breakdown in the framework that allowed the toxicity to progress to a permanent and sometimes fatal outcome.

The legal framework treats these cases the same as any other medical malpractice claim. The standard of care is identified through expert evidence and through reference to published guidelines and institutional protocols. The breach is documented through the contemporaneous record and the expert analysis of where the framework failed. The causation is established through the counterfactual analysis of what would have happened with appropriate care. The damages reflect what the patient and the family actually lost.

If you have lost a family member to a medication error, or have suffered serious harm yourself from one, the first conversation about a possible claim is free and strictly confidential. The earlier we look at the records, the better.