Organ donation management

Contents

Brain Death Physiology

After brainstem death, the body undergoes profound physiological derangements that threaten organ viability before retrieval. Understanding the pathophysiology is the basis of donor management.

The Autonomic Storm

At the moment of cerebral herniation, a massive sympathetic surge ("catecholamine storm") occurs:

  • Extreme hypertension and tachycardia — may cause neurogenic myocardial injury (contraction band necrosis, Takotsubo-like cardiomyopathy), ↑ troponin, ECG changes, LV dysfunction
  • Followed by autonomic collapse: loss of sympathetic tone → vasodilation → hypotension
  • This is why donors often present with haemodynamic instability despite being otherwise "stable"

Loss of Hypothalamic-Pituitary Function

After brainstem death:

  • Central diabetes insipidus (DI): loss of ADH secretion → massive dilute polyuria, hypernatraemia, hypovolaemia
  • Central hypothyroidism: TSH falls; T₃ levels decline rapidly (↓ T₄→T₃ conversion); contributes to myocardial dysfunction and vasodilation
  • Loss of ACTH: cortisol production falls → relative adrenal insufficiency, vasopressor dependence
  • Insulin resistance and hyperglycaemia
  • Hypothermia: loss of hypothalamic temperature regulation → heat loss → core temperature falls

Inflammatory Response

Brain death triggers systemic inflammation — release of brain-derived cytokines (TNF-α, IL-6, IL-1β) → inflammatory injury to donor organs. The shorter the time from brain death to retrieval, the lower the inflammatory burden.

Haemodynamic Instability in the DBD Donor

Haemodynamic instability (hypotension, arrhythmias) is the most common reason for organ loss post-brain death. The goal is maintaining adequate perfusion to all organs while minimising additional injury.

Haemodynamic Targets

Parameter Target
MAP 60–80 mmHg
CVP 6–10 cmH₂O
SBP >90 mmHg
Urine output 0.5–3 mL/kg/h
SpO₂ >95%
Temperature >35°C

Causes of Hypotension in the DBD Donor

  1. Hypovolaemia — DI-related polyuria, prior osmotic therapy (mannitol), resuscitation deficits
  2. Vasodilation — loss of sympathetic tone; reduced catecholamine and cortisol
  3. Myocardial dysfunction — neurogenic cardiomyopathy from autonomic storm
  4. Hypothyroidism — reduced T₃ → impaired cardiac function and vasomotor tone
  5. Hypothermia — impairs cardiac contractility and vasomotor response

Vasopressor Strategy

  • Vasopressin (also called ADH): first-line vasopressor in brain-dead donors
    • Rationale: endogenous vasopressin is depleted after brain death; replacement provides vasopressor effect AND treats diabetes insipidus
    • Dose: 0.5–2.4 units/hour (higher than normal vasopressor dosing — titrated to urine output AND MAP)
    • Key advantage: does not cause renal vasoconstriction at these doses; also reduces vasopressor requirements, allowing lower catecholamine doses
  • Noradrenaline: second-line or adjunct; risk of renal, mesenteric, and coronary vasoconstriction at high doses — minimise dose
  • Dopamine: historical use as first-line; now largely replaced by vasopressin

Hormonal Resuscitation

The hypothalamic-pituitary-adrenal and hypothalamic-pituitary-thyroid axes fail after brain death. Hormonal resuscitation (also called thyroid hormone therapy) aims to correct these deficiencies and improve organ quality.

Standard Hormonal Bundle (varies by protocol)

  1. Methylprednisolone 15 mg/kg IV — anti-inflammatory; reduces cytokine-mediated organ injury; also covers relative adrenal insufficiency
  2. T₃ (triiodothyronine) 4 mcg IV bolus → 3 mcg/hour infusion OR T₄ (thyroxine) 20 mcg IV bolus → 10 mcg/hour — corrects cellular hypothyroidism; improves myocardial function and vasomotor tone
  3. Vasopressin 1 unit/hour (as above) — replaces depleted ADH
  4. Insulin — maintains normoglycaemia; protects cardiac and other organs from hyperglycaemia-related injury

Evidence for Hormonal Resuscitation

  • Multiple observational studies show improvement in haemodynamic stability, reduced vasopressor requirements, and increased number of organs transplanted per donor
  • Randomised evidence is limited; however, hormonal resuscitation is endorsed by NHSBT and is standard UK practice
  • Particularly beneficial for cardiac donation: T₃ therapy restores myocardial function → increases donor heart suitability and transplant numbers

Diabetes Insipidus Management

  • Vasopressin infusion is both vasopressor and ADH replacement — treats DI and hypotension simultaneously
  • If vasopressin infusion insufficient to control polyuria alone: desmopressin (DDAVP) 0.5–2 mcg IV 6-8-hourly
  • Target urine output 0.5–3 mL/kg/h; replace urine losses volume for volume with 0.45% NaCl or crystalloid
  • Correct hypernatraemia (targets Na <155 mmol/L — hypernatraemia damages kidneys and liver)

Organ-Specific Management

Heart

  • Echo to assess LV function: EF <40% does not automatically exclude donation — hormonal resuscitation often recovers function
  • Aim MAP 60–80 mmHg; avoid extreme tachycardia (>120); treat with β-blockers if sustained
  • Troponin elevation does not automatically exclude cardiac donation
  • Liaise with transplant cardiology team for assessment

Kidneys

  • Maintain UO 0.5–2 mL/kg/h; avoid prolonged hypotension
  • Avoid high-dose noradrenaline (↓ renal blood flow); vasopressin preferred
  • Correct electrolytes (hypernatraemia, hypokalaemia common)

Liver

  • Avoid hypernatraemia (Na >155 mmol/L significantly increases primary non-function in liver grafts)
  • Normalise glucose; avoid hypoglycaemia
  • Minimise vasopressor dose; maintain adequate flow

Lungs

  • Target FiO₂ as low as possible (0.4 if possible) to reduce oxygen toxicity
  • PEEP 5–8 cmH₂O; tidal volume 6 mL/kg ideal body weight
  • Recruitment manoeuvres if compliance poor
  • Suction, bronchoscopic toilet — clear secretions; treat aspiration if occurred

Consent and Referral

Referral Obligations

All patients who meet criteria for brain death should be referred to the Specialist Nurse in Organ Donation (SNOD) before the first set of brainstem death tests. This is a professional obligation (NHSBT/GMC guidance) and does not commit to donation — it ensures that the family receives accurate information at an appropriate time.

Consent

  • England (Max and Keira's Law 2020): opt-out/deemed consent system; ODR registration is first-person authorisation
  • Family approach must be compassionate, timely, and separate from the WLST conversation (for DBD, families are being supported through an unexpected brain death — most are not expecting the donation conversation)
  • SNOD leads the donation conversation with family; ICU team provides ongoing clinical care and support
  • Explicit family refusal can in practice prevent donation in England, even where patient was registered

Viva Questions

1. Explain the physiological consequences of brain death that threaten organ viability and how they guide your management.

Brain death produces several simultaneous physiological crises. The initial autonomic storm causes a catecholamine surge — hypertension, tachycardia, and neurogenic myocardial injury that may leave the donor with a stunned or damaged heart. This is followed by autonomic collapse: loss of sympathetic tone causes vasodilation and hypotension. Loss of hypothalamic function means ADH secretion ceases → central diabetes insipidus, massive polyuria, hypovolaemia, and hypernatraemia. Loss of TRH/TSH → falling T₃ levels → reduced myocardial contractility and further vasodilation. Loss of ACTH → relative adrenal insufficiency → vasopressor dependence. Hypothermia follows as the thermoregulatory centre fails. Together, these derangements cause haemodynamic instability, hypernatraemia, hyperglycaemia, and inflammatory organ injury from brain-derived cytokines. Management therefore targets each of these: vasopressin (combined vasopressor and ADH replacement), hormonal resuscitation (methylprednisolone + T₃/T₄), normoglycaemia with insulin, careful fluid management to maintain euvolaemia, temperature warming, and targeted vasopressors to maintain MAP 60–80 mmHg.

2. Why is vasopressin the preferred first-line vasopressor in the brain-dead donor, and how is it dosed differently to septic shock?

In brain-dead donors, endogenous vasopressin (ADH) is depleted after loss of hypothalamic function. Exogenous vasopressin therefore serves a dual role: vasopressor (V1 receptor → vasoconstriction) and ADH replacement (V2 receptor → water reabsorption in collecting duct → reduces polyuria from diabetes insipidus). This addresses two simultaneous problems — hypotension and DI — with one agent, reducing the need for high-dose catecholamines. High-dose noradrenaline causes renal, mesenteric, and coronary vasoconstriction that damages donor organs; vasopressin has a much lower risk of organ ischaemia at donor management doses. Dosing: in septic shock, vasopressin is typically 0.01–0.04 units/min (0.6–2.4 units/hour) as a fixed dose. In donor management, doses up to 2.4 units/hour are used and titrated to both MAP (60–80 mmHg) and urine output (0.5–3 mL/kg/h) — adjusting for the concurrent DI treatment requirement.

3. The family of a brain-dead patient who is registered on the Organ Donor Register refuses consent to donation. How do you approach this?

This is a sensitive and ethically complex situation. Under Max and Keira's Law (2020), a first-person registration on the ODR constitutes legal authorisation for donation in England — the family cannot legally override this. However, clinical practice recognises the profound impact of overriding a bereaved family's wishes. My approach: I would ensure the SNOD is fully involved and leads the family discussion. I would ensure the family fully understands the patient's wishes and why those wishes are legally valid. I would explore their specific concerns — fear of disfigurement, religious or cultural concerns, distrust of the process — and address each directly with accurate information. I would not rush the family, and I would give them time to process. If the family remains firm in their refusal despite these conversations, the clinician has to weigh the patient's registered wish against the family relationship and the practical realities. In most UK centres, explicit family refusal in this context would in practice lead to donation not proceeding — clinicians exercise discretion, and there is no legal enforcement mechanism. The SNOD, the ICU consultant, and potentially the Trust's ethics advisor would all be involved in a decision of this gravity.