Category: Physiology & Biochemistry

Decompressive Craniotomy in Traumatic Brain Injury

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A 20 year-old man was admitted to his local district hospital with a severe head injury following an assault. On arrival in the Emergency Department he was agitated with a reduced conscious level, with evidence of blunt trauma to the head and neck. Prior to intubation, his Glasgow Coma Score (GCS) was recorded as 7 (E1V2M4), and with cervical spine precautions he underwent intubation with subsequent mechanical ventilation and sedation.

An urgent CT brain and cervical spine revealed early evidence of intracerebral contusions with diffuse areas of petechial intracerebral haemorrhage identified. Nasal and maxillary fractures were also seen, with no cervical spine pathology identified. He was transferred to the regional neurological centre for assessment and ongoing management.

On arrival in the Neurosurgical Intensive Care unit the patient underwent insertion of an intracranial pressure monitor revealing an intracranial pressure (ICP) of between 30-35 mmHg. Pupil reactivity was sluggish bilaterally. Sedation was changed to infusions of propofol, fentanyl and midazolam, positioning was optimised with 20 degree head-up tilt, endotracheal tube ties were replaced and targeted mechanical ventilation to EtCO2 4- 4.5kPa. Central venous access was established and an infusion of Noradrenaline was used to target cerebral perfusion pressure to 70mmHg.

Initial medical management stabilised ICP below 25mmHg, but within the next 12 hours this began to rise despite neuromuscular blockade and infusion of hypertonic saline. Further CT imaging revealed progression of the intracerebral contusions with developing oedema. The patient was transferred to the operating theatre for insertion of an external ventricular drain. CSF drainage resulted in an immediate but small improvement in ICP but again over the next 12 hours it began to rise, and decision was made for bifrontal decompressive craniectomy.

Subsequent recovery was slow and was complicated by ventilator-associated pneumonia, a protracted tracheostomy wean and severe agitation. The patient underwent intensive neuro-rehabilitation and had been decannulated, but was left with persistent cognitive impairment, seizures and depression.

What is the rationale for performing decompressive craniotomy in TBI?

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Sleep Deprivation on the ICU

ICM Case Summaries1 Comment

A 70-year-old lady was admitted to the Intensive Care Unit (ICU) with respiratory failure and septic shock secondary to pneumococcal pneumonia. She developed multi- organ failure, requiring a prolonged period of mechanical ventilation and weaning, and also developed acute kidney injury requiring haemofiltration. Once a tracheostomy was performed and sedative infusions weaned, she was noted to be acutely delirious. Her sleep pattern was severely disrupted, with extended periods of nighttime wakefulness and sleep fragmentation, increased daytime sleep and difficulty with sleep initiation requiring pharmacological intervention.

Following exclusion of organic causes including CT brain imaging, the delirium was managed with a combination of antipsychotic medications including haloperidol, mirtazapine and quetiapine. Benzodiazepine-based night sedation was used but found to be ineffective in establishing sustained sleep.

A trial of night sedation with infusion of Propofol did not have any ongoing or long-lasting benefit other than the immediate sedative effects and providing control of agitation. A trial of Dexmedetomidine infusion also yielded similar results, although a more sustained daytime anxiolytic effect was noted. Benzodiazepine therapy was changed to supplementation of Melatonin. At around this time, the delirium began to resolve and the patient was able to more actively engage in physiotherapy and patient care. By the time of ICU discharge over thirty days later, and following successful weaning and decannulation, the patient’s sleep pattern had improved significantly.

What are the implications of sleep deprivation in the critically ill patient and how can it be managed?

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ICP Monitoring and Acute Liver Failure

ICP Monitoring and Acute Liver Failure

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A 28-year-old lady presented to the medical team jaundiced with cramping upper abdominal pain and multiple episodes of vomiting over the previous day. She admitted ingesting Paracetamol 8 grams 3 days previously (staggered throughout the day) ostensibly to treat a frontal headache. She had been commenced on Citalopram 1 week previously for depression but denied taking any intentional overdose. On examination, she was slightly drowsy but GCS 15. HR 109, BP 136/92. Sats 98%on air. Her chest was clear, she was warm peripherally but jaundiced with some epigastric and RUQ tenderness on palpation. Her urine output was 10-20ml/hr.

Full Blood Count revealed Hb 152, WCC 24.7, Plats 301. She was in acute liver failure with Bil 189, AST 22970, ALT 13040, ALP 426 and coagulopathic with PT 82, APTT 72, Fib 0.7 Urea 5.7, Cr 193. Paracetamol and Salicylate were not detected. She was not acidotic with H+ 35, OCI2 3.7, pO2 17, Bic 20, BE –3. Lactate 7.1.

She was commenced on N-acetylcysteine and transferred to Critical Care. She was reviewed by the Hepatobiliary surgical team and placed on the super-urgent list for liver transplant. 

On Day 2, she became encephalopathic with GCS E3M5V5 and she was intubated and ventilated.Her PT had increased to 168 (INR >15) and she became anuric. She commenced FFP and Cryoprecipitate transfusions that improved her PT to 17, APTT 34 and Fibrinogen 1.5. An Intracranial Pressure (ICP) monitor was inserted and an opening pressure of 19mmHg was found. 2 hours post-insertion, it was noticed that her right pupil had increased in size from 2mm to 4mm and was poorly reactive. ICP remained at 16 and pCO2 4.1.

A brain CT showed a large haematoma in the right frontal region around the ICP bolt (which was not in the brain parenchyma but sitting in the skull) and mass effect with 5mm midline shift. There was also some lack of grey-white matter differentiation and sulcal effacement in keeping with diffuse oedema and mass effect.

INR was 1.7 and so further FFP was given. She was discussed with the neurosurgical registrar (in a separate hospital) who advised they would not drain at present but he would discuss with his Consultant and call back. 

Soon after, her right pupil increased to 8mm and the left to 7mm. Repeat CT brain showed slightly increased right frontal haematoma with 6mm midline shift and global oedematous cortical changes but no herniation. The ICP readings were thought to be inaccurate due to proximal placement and she was medically treated for raised ICP with hypertonic saline, mannitol and then therapeutic hypothermia. Despite this treatment, her pupils were fixed and dilated and so a thiopentone infusion was commenced.

The neurosurgeons advised that they would insert a further ICP monitor when INR <1.3 and so further FFP was given. An ICP bolt was inserted and the opening pressure was >120.

Discussions between the ICU, hepatobiliary and neurosurgical teams confirmed that she had a non-survivable injury and so this was discussed with her family. She was rewarmed, paralysis and then sedation were discontinued, brain stem death testing took place and she was extubated in the presence of her family. She died on Day 3 and was referred to the Coroner for further investigation.

What is the rationale for measuring ICP in acute liver failure?

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Enteral vs Parenteral Feeding on ICU

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A 70-year-old man had been an inpatient on the intensive care unit for nearly 40 days after a complicated recovery following mitral valve replacement. He was being gradually weaned from the ventilator via tracheostomy but required no other invasive organ support. His intensive care unit stay had been complicated by recurrent respiratory sepsis treated with antibiotics and aggressive physiotherapy. Up until this point he had been fed by a nasogastric tube but began to exhibit signs suggestive of impaired absorption including large nasogastric aspirates and a requirement for higher levels of parenteral electrolyte administration.

Prokinetic treatment with metoclopramide 10mg TDS for 24 hours failed to improve the high aspirate levels which remained in excess of 300ml every four hours. Erythromycin 250mg BD was added with little improvement. Following discussion with gastroenterology colleagues an agreement to place a post-pyloric nasojejunal feeding tube was made; unfortunately this procedure was delayed by a further 48 hours as no endoscopist was free to attend. Parenteral feeding was initiated at this point in order to maintain calorific intake.

Compare enteral and parental nutrition.Read More »

Albumin Use in Critical Illness

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A 70-year-old woman was admitted to the surgical ward with abdominal pain. CT scans showed some dilated loops of small bowel. She remained on the surgical ward for 5 days with minimal resolution of her symptoms. She was taken to theatre for exploratory laparotomy where she was diagnosed with faecal peritonitis from a perforated diverticulum. She had a washout and a Hartmanns procedure was performed.
She became unstable during her laparotomy requiring vasopressors and was taken to the intensive care unit postoperatively.  She was left with a laparostomy with a VAC dressing applied. She was treated with lung protective ventilation and remained cardiovascularly unstable. Two days later she was taken back to theatre for a further washout and closure of her abdomen. She developed an ileus and was then started on total parenteral nutrition. An oesophageal doppler monitor was placed to help guide her fluid status. She was extubated on day 4 post op but her filling status remained a problem to gauge. Her fluid balance became very positive and she became very oedematous. Her albumin level dropped significantly. It was then decided to give her daily intravenous albumin.
What evidence is there for the use of albumin in critically ill patients?

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Management of Refractory Intracranial Hypertension

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A young man with no significant past medical history was admitted to the Emergency Department following an assault. His Glasgow Coma Score on arrival was 8 with a motor score of 4 and there was evidence of an external head injury. Pupils were symmetrically reactive. He was intubated to facilitate further management. Both primary and secondary surveys were unremarkable apart from multiple contusions to the face and scalp. Multi-slice CT showed no intrabdominal or intrathoracic injury but significant intracranial pathology with subarachnoid and intraventricular blood and multiple, principally frontal contusions. No associated neuraxial fracture was seen.

Urgent neurosurgical opinion was sought which confirmed no immediate target for surgical intervention. The patient was transferred to the intensive care unit where appropriate monitoring was established including the insertion of a fibreoptic subdural intracranial pressure bolt. Initial intracranial pressure was measured at 18 mmHg. Sedation with propofol and alfentanil infusions was titrated to a RASS score of -3, ventilation adjusted to a PaO2 > 13 kPa and PaCO2 4.5-5.0 kPa as per the Brain Trauma Foundation guidelines and an infusion of noradrenaline started to achieve a cerebral perfusion pressure of 60 mmHg. The patient was nursed 30° head-up and although active cooling was not undertaken, temperature maintained at less 35-37.5°C.

There was initial stability but approximately 24 hours after admission sustained rises in intracranial pressure (ICP) in excess of 25 mmHg were seen, necessitating boluses of sedation, the addition of atracurium by infusion, administration of hypertonic saline, cooling to 35°C and brief periods of hyperventilation to a PaCO2 4.0-4.5 kPa albeit without significant control. Urgent repeat CT brain was undertaken which showed evolution of the contusions with signifiant oedema and loss of both the lateral ventricles and basal cisterns.

On further consultation, neurosurgical colleagues again felt that no immediate surgical option was viable; in particular that attempts to insert and external ventricular drain were unlikely to be successful and that contusionectomy would produce significant disability. The patient was randomised into the RESCUEicp trial and thiopentone infusion started at a rate to produce isoelectrical activity on three lead electroencephalogram.

What are the management options for refractory intracranial hypertension?
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Post Operative Cognitive Deficit after Cardiac Surgery

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A middle-aged  man underwent an elective re-do aortic arch replacement for a 6.1cm ascending aortic aneurysm distal to a pre-existing composite graft. Past medical history included a Bentall procedure (metallic aortic valve replacement, aortic root and ascending aorta replacement with coronary re-implantation into the composite graft) 20 years ago. Preoperative echocardiogram showed a well seated AVR and good biventricular function. Drug history included Warfarin (target INR 2-3) and Atenolol.

Anaesthetic induction and re-sternotomy were uneventful. Cerebral oximetry (rSO2) monitoring was utilized in this case. Cardiopulmonary bypass (CPB) was achieved uneventfully and deep hypothermic circulatory arrest (DHCA) was instituted. The patient was cooled to 18°C using CPB and icepacks. Prior to CPB and DHCA being commenced, intravenous thiopentone and methylprednisolone were administered for neuroprotection. Total DHCA time was 40 minutes and selective anterograde perfusion via the right axillary artery (chosen as it is relatively free of atheroma) was employed when rSO2 dropped to <40% and they remained >40% for the remainder of DHCA. Total CPB time was 105 minutes.

Following successful insertion of a new graft, the patient was carefully rewarmed to normothermia and weaned off CPB uneventfully, only requiring minimal vasopressor support. The patient was transferred to the cardiothoracic critical care unit.

After optimization of cardiorespiratory physiology, correcting coagulopathy and maintaining normothermia, with strict avoidance of hyperthermia, the patient was extubated the following day. For the first 48-72 hours postoperatively, delirium was the most active medical issues and this was managed according to conventional treatment. There was no focal upper or lower limb neurology. The patient did not require any other organ system support.

Following resolution of his delirium the patient was discharged to the ward to continue his rehabilitation. Prior to discharge, at approximately postoperative days 7-10, he was complaining of loss of short-term memory, reduced attention span and difficulty with finding words. A neurology review attributed this to cognitive dysfunction but no formal tests were carried out. A neurology clinic follow-up and an outpatient MRI scan were arranged.

What are the neurological complications after cardiac surgery?Read More »

Heparin Induced Thrombocytopaenia

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A 75 year old was admitted to the Cardiac Intensive Care Unit following aortic valve replacement for severe aortic stenosis. He had no other significant past medical history. He remained intubated and ventilated overnight until cardiovascularly stable, and was extubated the following morning. He suffered bleeding into the pericardial drains, and went back to theatre on day 3. He remained intubated on his return from theatre. On day 7 it was noticed that he had developed thrombocytopenia, with a platelet count of 34, reducing from 103 the previous day. A heparin induced thrombocytopenia (HIT) screen was sent, and he was changed to alternative anticoagulation.

The HIT screen was positive. His platelet count fell further and he continued to bleed slowly from any puncture sites and from around his mouth and gums. He remained intubated and ventilated and developed a requirement for inotropic support. Transfusions of platelets were required for any intervention. He was anticoagulated with lepirudin to prevent thrombosis. His platelet count continued to remain in single figures over the next 10 days despite treatment with steroids. Unfortunately he deteriorated, suffering an arterial thrombosis in his arm, renal failure and developed a necrotic skin rash all over his body, likely to be related to the HIT. Following discussions with his family, who felt he was suffering and would not want a poor quality of life, treatment was withdrawn on day 26 of his intensive care stay and she died.

What are the clinical implications of heparin-induced thrombocytopaenia?Read More »

Transplantation After Brainstem Death

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A 38-year-old previously fit man suffered a grade five subarachnoid haemorrhage. Attempts at coiling failed and he suffered a catastrophic rebleed on-table whereupon his pupils became fixed and dilated. After a suitable sedation washout period he underwent testing which confirmed brainstem death at which point he was referred to the specialist nurse for organ donation. Following counselling of the family and appropriate assessment, donation of his kidneys, liver and heart was agreed.

Upon confirmation of brainstem death, mechanical ventilation was continued to ensure PaO2 greater than 10 kPa and limit peak inflation pressure to less than 30 cmH20. Vasoactive support was switched from noradrenaline to vasopressin 0.02 iu/kg/min. Methylprednisolone and intravenous triiodothyronine were administered whilst awaiting harvest. Blood antibody testing for HIV1+2, Hepatitis B and C, HTLV-1 and CMV IgG were all negative. A transthoracic echocardiogram confirmed good biventricular function; following discussion with the transplant retrieval team a pulmonary artery catheter was floated. Clinical measurements of cardiac output and mixed venous oxygen saturation were satisfactory. Adequate hydration was maintained with crystalloid by infusion and glucose control optimised in the range 8-10 mmol/L with insulin. The dedicated retrieval team performed the organ retrieval eighteen hours after confirmation of brainstem death.

How can we optimise organ function for organ donation?Read More »

Refractory Status Epilepticus

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A middle aged man presented with seizures. For 4 days he had been feeling unwell with coryzal symptoms, frontal headache and dizziness. He had ‘not been himself’ for some months. He had no previous medical history and had never had a seizure before. The ambulance crew noted that he was confused and witnessed a generalised tonic-clonic seizure. On arrival in hospital he was severely agitated and uncooperative and received IV lorazepam.

He was not adequately protecting his airway, saturations were 100% on high flow oxygen, temperature was 37.8, his pulse was 88, BP 129/90mmHg, blood sugar was 7.7. Clinical examination did not reveal any abnormality except for diminished level of consciousness. A presumptive diagnosis of meningitis / encephalitis was made. His trachea was intubated, he received fluids, parenteral vitamins, IV ceftriaxone and acyclovir. A CT head (with contrast) was obtained and a lumbar puncture were normal. His blood tests, CXR, urinary toxicology screen, and ECG were non-contributory. Arterial blood gas analysis revealed changes consistent with being post ictal and then (whilst ventilated) normalised.

His sedation was weaned and once extubated he remained very drowsy, even 18 hours after his last sedation. A Glasgow Coma Score (GCS) was recorded at E1V1M5 (7/15). His pupils were equal and reactive, and he was moving all 4 limbs. Both plantar responses were down-going, and tone and reflexes were symmetrical. He had myoclonic jerking of his left hand but no rhythmical muscle activity was evident. To protect his airway he required reintubation of his trachea and re-institution of ventilation.

In addition to sedation with propofol and alfentanil he received therapeutic phenytoin. An electroencephalogram (EEG) performed on his second day, off sedation, revealed continuous periodic sharp and slow wave complexes at around 1Hz with intermittent high amplitude waves in the left temporal region and bursts of rhythmical activity in the right temporal region. At the time of the EEG he had some abnormal motor activity – continuous movement of his fingers and twitching of an eyelid and rhythmical jerking of both of his arms. An MRI of his brain was normal.

In this clinical context the EEG was interpreted as being consistent with encephalitis and non-convulsive status epilepticus.  Phenobarbitone was started in addition to the phenytoin. Normothermia and normoglycemia was maintained. To improve the management of his non convulsive status we continuously monitored his cerebral electrical activity with a bispectral index (BIS) monitor and bitemporal EEGs. We targeted a burst suppression of 20-50%. Propofol was ineffective at reducing the BIS without causing limiting hypotension but midazolam was effective.

Further investigations did not further our search for the primary diagnosis. A further EEG was performed 24 hours later, off midazolam but whilst on 350mg/hr of propofol. He developed some rhythmical motor activity and his EEG revealed ongoing abnormal electric activity, consistent with continued non-convulsive status, which resolved in response to a bolus of propofol. A possible diagnosis of limbic encephalitis was considered and methylprednisolone (1g IV) was administered.

A repeat MRI showed increased abnormal signal changes in the amygdala and hippocampus, which is supportive of the diagnosis of limbic encephalitis.

Despite optimal medical treatment his EEG showed more severe and continued abnormal electrical activity. Thiopentone was added to his anti-seizure regime. By the 19th day from initial presentation multiorgan failure had developed. He required ventilation with high airway pressures and high inspired oxygen concentrations for lung injury due to ventilator associated pneumonia, vasoactive drugs to support his cardiovascular system through the associated sepsis, haemofiltration for renal failure and had ileus with failure of enteral feeding. There were still signs of seizure activity despite concurrent administration of propofol, midazolam, phenytoin, levetiracetam, phenobarbitone and sodium valproate. Supportive treatment was withdrawn following diagnosis of brain-stem death. His family did not permit a post mortem examination.Read More »