Management of the brainstem-dead organ donor
Active organ donor management can increase the number of organs suitable for transplantation and allow planned and unhurried removal of organs. It is vital that active organ donor management is continued throughout the perioperative period. Good organ donor management should benefit all organs, and conflict should be avoided between strategies that aim to optimize thoracic or intra-abdominal organs.
1 Describe the perioperative critical care and anaesthetic management of the brainstem-dead heart-beating organ donor
2 Acknowledge the process and potential anaesthetic difficulties during organ retrieval surgery.
2C06
A 37-year-old man (Mr T), who sustained a subarachnoid haemorrhage 48 hours ago, has been confirmed brainstem-dead. You are the anaesthetic registrar on call and have been asked to provide anaesthetic support for a multiorgan retrieval procedure.
◆ A preceding period of rising ICP
◆ Compensatory arterial hypertension to attempt to restore CPP, the Cushing response, resulting in the stimulation of arterial baroreceptors and a vagally mediated bradycardia
◆ A ‘catecholamine storm’ immediately following brainstem death, with tachycardia and vasoconstriction
◆ Loss of vascular tone and hypotension following catecholamine storm
◆ Apnoea will occur if ventilation is not controlled.
◆ You should adopt a similar approach as you would for any other ventilated ICU patient requiring major body cavity surgery
◆ A thorough bedside ABC assessment, including assessment of the tracheal tube position, ventilator parameters, cardiovascular status, and inotrope requirement
◆ Collateral history from case-notes and ICU staff
◆ Review of recent blood results, including ABGs, FBC, coagulation profile, U&E, Cr, and LFTs
◆ Review of CXR
◆ Review of any cardiac investigations, e.g. echocardiography
◆ Review of paperwork relating to brainstem death tests and the authorization for organ donation.
Your patient has a predicted body weight of 70 kg. He is currently on volume-controlled ventilation of 700 mL at 12 breaths/min, with a PEEP of 5 cmH2O and an FiO2 of 0.5. His ABG shows PaO2 of 15 kPa, PaCO2 of 4.0 kPa, HCO3– of 20 mmol/L, and BE of –6.
◆ Lung-protective ventilation should be used, and his tidal volume should be reduced to 6–8 mL/kg; lung-protective ventilation as part of a package of care, has been shown to increase the number of transplantable lungs
◆ The lowest FiO2 to achieve normoxia should be used. Lowering the FiO2 may prevent bronchiolitis obliterans syndrome in the recipient
◆ Fluid balance management can be complex, and, whilst the circulating volume must be adequate, pulmonary oedema should be avoided.
Mr T has an arterial BP of 80/40 mmHg, a CVP of 5 mmHg, a lactate of 2 mmol/L, and warm peripheries. He is not currently receiving any inotropes.
◆ He is likely to need BP support in the form of a catecholamine infusion such as noradrenaline
◆ It can be very difficult to get a balance between an adequate intravascular volume and avoiding excessive extravascular lung water
◆ Cardiac output monitoring may be useful to guide fluid boluses; pulmonary artery catheters, oesophageal Doppler monitoring, and techniques based around arterial waveform analysis have all been used
◆ There is no good evidence to guide the type of fluid used for a fluid bolus; however, starch solutions have been associated with an increased incidence of renal dysfunction in some groups of critically ill patients.
You review Mr T’s ICU chart. He has been passing 500 mL/hour of urine for the last 3 hours. His Na+ has increased to 155 mmol/L.
◆ Mr T has developed central diabetes insipidus
◆ Posterior pituitary function is commonly lost
◆ Anterior pituitary function can be preserved or only partially lost
◆ Insulin secretion is decreased, and hyperglycaemia is common
◆ Hypothalamic temperature regulation is lost.
◆ Methylprednisolone is commonly given to brainstem-dead organ donors, to moderate the inflammatory response that occurs with brainstem death
◆ Glucose levels are often high; an infusion of a short-acting insulin should be given to target normoglycaemia
◆ Central diabetes insipidus may be treated with desmopressin or vasopressin. If the patient has a significant inotrope requirement, then adding vasopressin makes physiological sense
◆ Some organ retrieval teams also administer thyroid hormones, although this is not supported by a recent systematic review.
◆ Positioning: usually arms by side
◆ Large-bore IV access
◆ Arterial and central lines are mandatory
◆ Consider cardiac output monitoring
◆ A surgical pause should occur: you and the retrieval team may well not have worked together before. Issues to be discussed should include the timing of antibiotics, methylprednisolone, and heparin. The documentation relating to brainstem death and the authorization for organ donation should also be reviewed at this time.
◆ Reflex movements can occur, and muscle relaxation is necessary
◆ If hypertension and tachycardia occur, they can be well treated by the use of a volatile anaesthetic agent. There may also be a beneficial preconditioning effect in the transplanted organs.
◆ Laparotomy and an initial inspection of abdominal organs
◆ Median sternotomy: the organ donor should be disconnected from the ventilator during this, then reconnected with a recruitment manoeuvre
◆ Abdominal dissection continues with the aid of a sternal retractor
◆ The cardiothoracic team will inspect the heart
◆ If lung retrieval is planned, then a bronchoscopy will be performed, and differential blood gases from the right and left pulmonary veins will be taken
◆ The final stage is organ perfusion and retrieval. If the thoracic organs are not being retrieved, then the aorta will be cross-clamped, and perfusion of the abdominal organs commenced below the cross-clamp. Ventilation can be discontinued at this stage
◆ If the thoracic organs are being retrieved, then the heart will be arrested by the use of a cardioplegia solution. If lung retrieval is planned, pulmoplegia will follow this.
A systems approach is useful in active organ donor management. Lung-protective ventilation should be used. If lung retrieval is planned, then the lowest possible FiO2 to achieve a PaO2 of >10 kPa should be used. Fluid management can be challenging, with a difficult balance between an adequate intravascular volume and the avoidance of excess extravascular lung water. The use of a flow-directed fluid management strategy may be of benefit. The development of central diabetes insipidus is common, and this should be treated with vasopressin to prevent dehydration and electrolyte disturbances. Hypothermia and hyperglycaemia should be avoided. The timing of antibiotics, methylprednisolone, and heparin will be guided by the retrieval team.
Summary
Perioperative goals should be centred around maintaining good critical care with lung-protective ventilation and careful fluid balance. Intraoperatively, clear communication between the retrieval team and the anaesthetist is vital. Muscle relaxation is necessary, and volatile anaesthetic agents may be useful in treating hypertension, as well as having a potential beneficial preconditioning effect that is yet to be fully elucidated. The timing of antibiotics, methylprednisolone, and heparin will be guided by the retrieval team.
Brunkhorst FM, Engel C, Bloos F, et al. (2008). Intensive insulin therapy and pentastarch resuscitation in severe sepsis. New England Journal of Medicine, 358, 125–39.
Macdonald PS, Aneman A, Bhonagiri D, et al. (2012). A systematic review and meta-analysis of clinical trials of thyroid hormone administration to brain dead potential organ donors. Critical Care Medicine, 40, 1635–44.
McKeown DW. Guidelines for donor care during multiorgan retrieval procedures. Local guideline, Version 10, 2014. Obtained from personal communication with author.
McKeown DW, Bonser RS, and Kellum JA (2012). Management of the heartbeating brain-dead organ donor. British Journal of Anaesthesia, 108 (suppl 1), 96–107.
Perner A, Haase N, Guttormsen AB, et al. (2012). Hydroxyethyl starch 130/0.42 versus Ringer’s acetate in severe sepsis. New England Journal of Medicine, 367, 124–34.