Category: Basic Sciences

Invasive Ventilation of Life-Threatening Asthma

Invasive Ventilation in Life-Threatening Asthma

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An 18-year-old known asthmatic presented with a two-day history of increasing shortness of breath on a background of a recent coryzal illness. She had a background of reasonably poor control and had been admitted to the intensive care unit for mechanical ventilation twice as a child. Her current medication included regular inhaled serotide 250, montelukast 10mg and theophylline MR 450mg BD. At presentation she was in extremis; pulse rate was 65 per minute, blood pressure 75/54 mmHg and respiratory rate 14 per minute. Arterial blood gas analysis demonstrated a PaCO2 of 11 kPa and PaO2 of 7.6 kPa with associated respiratory acidosis. Nebulised salbutamol and intravenous magnesium sulphate therapy was administered. along with 200mg of intravenous hydrocortisone. On arrival of the intensive care team, the patient’s respiratory rate deteriorated to a rate of 4 per minute. Assisted ventilation with a self-inflating bag and 100% oxygen was performed; rapid-sequence intubation was performed using ketamine and rocuronium.

Following intubation, immediate difficulties were experienced with mechanical ventilation. High airway pressures in excess of 40 cmH2O with tidal volumes of less than 200 ml were observed. Immediate chest radiography confirmed correct positioning of the endotracheal tube and excluded a pneumothorax. Adequate sedation and neuromuscular blockade were confirmed. Auscultation confirmed severe, widespread wheeze with limited air entry. Further nebulised salbutamol was administered and an aminophylline infusion initiated. The patient was transferred to the intensive care unit where magnesium, ketamine and vecuronium by infusion were added. Various modes of mechanical ventilation were tried including volume and pressure triggered with varying success; this included lengthening the I:E ratio, frequent disconnections to allow deflation and adjustment of PEEP to maximum compliance. Continuous salbutamol was administered via an ultrasonic nebuliser. Airway pressures remained high and there was little improvement in her acidosis. 2 hours after admission the patient suffered a PEA cardiac arrest from which she could not be resuscitated.

What are the difficulties in ventilating severe asthmatics, and what strategies can we use to overcome them?

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Major Haemorrhage and Recombinant Factor VIIa Concentrate

Major Haemorrhage and Recombinant Factor VIIa Concentrate

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A 40-year-old female intravenous drug user presented with a diffusely swollen right lower leg. She had injected heroin into her right thigh one week previously. The swelling started 3 days later. Initial observations revealed T 39.6, HR 135, NIBP 100/87, RR 32, Sats 96% on air. On examination, she was pale and sweaty. She had a swollen right lower leg with mottling of her foot and poor pedal pulses. Following initial fluid resuscitation, chest X-ray, cultures and broad-spectrum antibiotics (Flucloxacillin, Metronidazole and Gentamicin), she underwent CT angiogram of her lower limbs which showed oedematous and expanded muscle compartments of the thigh and calf but patent arterial flow to the feet. There was also right common femoral vein thrombosis with some vessel patency. Initial labs revealed neutrophilia (9.2), thrombocytopaenia (16) and deranged coagulation (PT 16, APPT 33, Fib 2.6). CK was 57000. She underwent right leg fasciotomies and was brought to ICU ventilated and on Noradrenaline to maintain MAP >65. She commenced Immunoglobulin IV 1gram/kg per day for 2 days for suspected Streptococcus Group A sepsis. That night she had massive transfusion requirements due to ongoing haemoserous ooze from her fasciotomy sites, losing up to 1 litre of haemoserous fluid per hour. Overnight she received 10 units RCC, 8 x FFP, 6 x Platelets and 2 x Cryoprecipitate, as well as Vitamin K (guided by Hb on ABG, formal lab results and thromboelastography). She was discussed with the Haematology Consultant and it was decided that, if rapid blood loss continued despite full correction of her clotting factors, fibrinogen and platelets then Factor VII could be given. However, over the next 2 hours, losses were much reduced following product replacement, and since she already had clot in her femoral vein, Factor VII Concentrate was not given.

What is the role of Recombinant Factor VIIa in major haemorrhage?

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High Frequency Oscillatory Ventilation in ARDS

High Frequency Oscillatory Ventilation in ARDS

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A 45 year old female presented to A&E with a 5 day history of worsening SOB, cough productive of green sputum, lethargy, anorexia, fever and rigors. She had no co- morbidities and was active and independent with a good exercise tolerance. On examination she looked unwell, clammy and drowsy. Her respiratory rate was 35 breaths per minute and SpO2 of 84% on 15 Litres of oxygen via a non-rebreathing mask. Her blood pressure was 88/40 mmHg with a heart rate of 140 per minute despite having received 3 litres of fluid. Arterial blood gas showed PaO2 6.0kPa, pH 7.28, PaCO2 7.1 kPa, Bicarbonate 14 mmol/l, BE -11 and Lactate 8.6 mmol/l. Chest radiograph demonstrated significant bilateral consolidation with infiltrates consistent with ARDS. PaO2:FiO2 was calculated as 15 indicating severe ARDS presumed secondary to CAP.

She was managed as per sepsis guidelines. Oxygen therapy was continued and CPAP was initiated due to the hypoxia whilst an ICU bed was being prepared for admission. Noradrenaline was commenced at 0.2mcg/kg/min which continued to increase. Repeat arterial blood gases confirmed worsening type 2 respiratory failure and the patient was clinically exhausted. A modified rapid sequence induction was performed and IPPV commenced. Her oxygenation remained a problem and despite a FiO2 of 1.0 and PEEP of 20 his SpO2 remained 85% and PaO2 6kPa. The patients’ sedation was deepened and muscle relaxant administered. Lung protective ventilation was continued however arterial blood gases continued to worsen. The decision was made to convert the patient from conventional ventilation (CV) to High-Frequency Oscillator Ventilation (HFOV). The initial ABGs after an hour of HFOV showed an improvement as did subsequent numbers. This mode of ventilation was continued for a further 48 hours and then converted to CV. Gas exchange continued to improve. Over the course of the following 4 weeks the patient had a tracheostomy performed to aid weaning. She subsequently developed a Ventilator Associated Pneumonia and worsening ARDS required a further period of HFOV. Improvement continued and the patient was successfully decannulated and discharged from ICU.

What is the evidence base for high frequency oscillatory ventilation in ARDS?

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Secondary Complications of Subarachnoid Haemorrhage

Secondary Complications of Subarachnoid Haemorrhage

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A thirty eight year old female smoker was admitted via A+E following sudden onset occipital headache with visual disturbance and collapse with loss of consciousness lasting approximately five minutes. She had complained of unusual headaches a week prior to this event, but these were short lived and not associated with any neurology. On arrival in resus she had recovered to a Glasgow coma score (GCS) of 14/15. She demonstrated neck stiffness and photophobia, as well as general irritability. Plain computerised tomography
scan (CT) performed showed a subarachnoid haemorrage in the region of the middle cerebral artery, with the presence of blood in the sylvian fissure.

She was transferred to the ITU for monitoring and blood pressure control with invasive arterial and central venous pressure monitoring. She was treated with nimodipine to prevent vasospasm. Contrast CT performed showed an aneurysm at the bifurcation of the middle cerebral artery, and this was felt to be the origin of the bleed. She underwent uneventful endovascular coiling of this aneurysm the following day under general anesthesia, and was discharged to the neurosurgical team for ongoing care afterwards.

What are the secondary complications of subarachnoid haemorrhage and how are they managed?

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Steroids in Cervical Spine Injury

Steroids in Cervical Spine Injury

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A previously fit and well 46 year-old was admitted via the emergency department having sustained a neck injury whilst horse riding. She was unable to move her arms and legs immediately after the fall. On arrival to the Emergency Department, she was alert and orientated. Examination of the cardiovascular and respiratory system was unremarkable although there was evidence of diaphragmatic breathing.

Examination of her neurological system revealed:

•A sensory level at C6
•Absent upper limb reflexes except for brisk bicep reflex bilaterally
•⅖ power in shoulder abductors bilaterally
•Flaccid paralysis of her lower limbs
•No anal tone

She was initially managed in a hard neck collar with full spinal immobilisation. CT brain was reported to be normal. CT neck showed an obviously displaced fracture of C5 and C6 vertebral bodies. She was transferred to the intensive care unit for cardiovascular, respiratory and neurological monitoring while a definitive treatment plan was being considered. After discussions with the orthopaedic surgeons, it was decided not to commence high-dose steroids. This decision was reinforced after discussion with the local neurosurgical and spinal units. It was also decided not to surgically stabilise the c-spine due to the higher risk of respiratory complications. She was transferred to the spinal rehabilitation unit after 2 days.

What is the role of steroids in cervical spine injury?Read More »

Glutamine in Critical Illness

Glutamine in Critical Illness

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A forty-year-old motorcyclist was admitted to the ITU following a road traffic accident involving a stationary vehicle. She sustained a fractured right distal radius and multiple left sided rib fractures, involving ribs 2 to 9, with a free floating flail segment. She developed respiratory distress due to underlying lung contusions and a haemopneumothorax and was treated with two left sided intercostal drains, endotracheal intubation and invasive ventilation. She developed ARDS with bilateral infiltrates and PF ratio of <200mmHg, with normal cardiac function on transthoracic echocardiography. She was tracheostomised on day 12, and had a protracted ventilatory wean further complicated by a ventilator associated pneumonia. She was enterally fed during this period but began to develop an ileus and gut dysmotility, resistant to prokinetic treatment, leading to large volume gastric aspirates. She became visibly malnourished and was commenced temporarily on parenteral nutrition and IV glutamine. The ileus resolved over the following week and weaning recommenced, having ceased due to diaphragmatic splinting. She eventually weaned from the ventilator and was discharged from the ITU on day 40. She was profoundly weak due to a critical illness acquired weakness.

What is the role of glutamine supplementation in critical illness?Read More »

Obesity Hypoventilation Syndrome

Obesity Hypoventilation Syndrome

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 A 66 year old man was brought by ambulance to ED after becoming acutely dyspnoeic at home, and his wife had struggled to wake him after an afternoon sleep. He had a moderate smoking history of 20 pack years and quit 20 years ago, and drank approximately 20 units of alcohol as beer per week. There were no preceding prodromal respiratory or infective symptoms reported. On examination, he was obese with a weight of 120 kg. He was snoring, which eased with a chin-lift or jaw thrust, but he would not tolerate an airway adjunct. His respiratory rate was 8 and shallow, producing SpO2 84% on high flow oxygen. He was flushed and veno-dilated peripherally, with a tachycardia of 110 bpm sinus rhythm. Most notably, he was difficult to rouse, with a GCS of 9 (E2 M5 V2). Arterial blood sampling revealed a profound hypercapnoeic respiratory acidosis with no degree of compensation. Chest X-ray showed poorly expanded lungs with bilateral basal atelectasis and prominent pulmonary vasculature. Empiric naloxone was ineffective and he was commenced on non-invasive ventilation (NIV). The working diagnosis was an acute non-infective exacerbation of previously undiagnosed chronic obstructive pulmonary disease (COPD). Treatment involved bronchodilators, steroids and bilevel pressure support non- invasive ventilation.
One hour after NIV had been established, the patient’s respiratory acidosis was worse and his clinical picture was unchanged. He was intubated then transferred to Intensive Care. CTPA ruled out significant pulmonary emboli but was suggestive of pulmonary hypertension. Ventilation was not difficult, with near normal inspiratory pressures, and his minimal wheeze resolved quickly. As his respiratory acidosis normalised, his GCS rapidly improved to the point of safe extubation after just 48 hours. Given his obesity he was extubated to non-invasive pressure support ventilation immediately. After a further 24 hours, his gas exchange began to deteriorate again. Increasing inspiratory pressure improved his tidal volumes but his intrinsic rate of breathing slowed such that his minute ventilation remained static. He eventually found a stable equilibrium using nocturnal bilevel pressure support with a high mandatory backup rate (pressure control), which maintained a normal minute ventilation. Although he developed hypercapnoea each night, this was mild and eventually compensated. With the NIV, he did not obstruct, have hypopnoeic events or desaturated overnight, which markedly improved his daytime somnolence and effort of breathing.

What are the clinical features and approaches to management of obesity hypoventilation syndrome?

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Scoring Systems for Acute Hepatic Dysfunction

Scoring Systems for Acute Hepatic Dysfunction

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A 40 year old was admitted to hospital with his first presentation of alcoholic liver disease with symptoms of jaundice (bilirubin 248), poor mobility, hallucinations and passing of black stool. On admission to hospital, he was lethargic with features of Grade II encephalopathy, was coagulopathic (INR 3.1), had deranged electrolytes (sodium 114, potassium 2.9), but a normal creatinine (54) and a raised white cell count (15.9). He was haemodynamically stable and had a haemoglobin of 119g/L with no signs of active bleeding. His abdomen was distended (ascites), he was visibly jaundiced and had spider naevi on his chest. An abdominal ultrasound was performed that showed liver cirrhosis, borderline splenomegaly, small volume ascites and normal kidneys. A full liver screen revealed no infective cause and his AST:ALT ratio suggested alcoholic liver disease. His prognostic indicator scores were all suggestive of severe alcoholic liver hepatitis (Maddrey score: 131; Childs: C; Lille Score: 1; GAHS: 10; MELD: 29). His serum ammonia level was 170. He was commenced on terlipressin, prednisolone and pentoxyphylline and thiamine. Despite this, his encephalopathy progressed to grade 4 and he required intubation and ventilation for airway protection and a presumed aspiration pneumonia. His liver function and coagulopathy continued to worsen, and he developed an acute kidney injury necessitating commencement of renal replacement therapy. He required noradrenaline to support his blood pressure. Ascitic tap ruled out spontaneous bacterial peritonitis. He was discussed with regional liver centres, but was not felt to be a transplant candidate. His liver and renal function continued to deteriorate and eventually treatment was withdrawn nearly 3 weeks into his admission.

Describe the scoring systems for assessing the severity of acute hepatic dysfunction.

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Coiling versus Clipping Subarachnoid Haemorrhages

Coiling versus Clipping Subarachnoid Haemorrhages

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A 40 year old female presented with a severe sudden onset headache, and deteriorated in the emergency department with worsening agitation and confusion requiring intubation and ventilation for her own safety. A CT scan diagnosed a Fisher Grade 4 subarachnoid haemorrhage and obstructive hydrocephalus. Clinical presentation was scored as Hunt and Hess grade 4 or World Federation of Neurosurgeons grade 4. The patient was transferred to the local tertiary Neurocritical care unit where an extra-ventricular drain was inserted overnight. The following day the patient underwent coiling of her right middle cerebral artery aneurysm in the radiology suite. A Magnesium infusion and Nimodipine therapy were commenced to reduce the risk of vasospasm. On initial sedation hold she woke up agitated so she had an early tracheostomy placed to allow controlled wake up. She had a straightforward respiratory wean from the ventilator over the next few days. Neurological recovery was good (Glasgow coma score improved to 14/15) and the patient was discharged to the ward for on-going neuro rehabilitation and repatriation to the base hospital.

What are the risks of clipping vs coiling subarachnoid haemorrhages?Read More »

When to Initiate Parenteral Nutrition

When to Initiate Parenteral Nutrition

Steve Mathieu2 Comments

A 19 year old man presented to the surgical team complaining of abdominal pain. He underwent a laparoscopic appendicectomy and a perforated appendix was removed. He returned to the surgical ward and three days later was ready for discharge. Unfortunately he then developed worsening abdominal pain, fevers and breathlessness. He underwent a CT scan and this demonstrated multiple collections of infected matter within his abdomen in addition to bi-basal atelectasis. He was admitted to the intensive care unit for haemodynamic monitoring, oxygen therapy and broad spectrum antibiotics. He underwent three intra-abdominal washouts of infected material over an eight day admission. During this time he had attempted enteral feeding via a nasogastric tube but had very high gastric aspirates, with no absorption, as a result of a prolonged ileus. He was started on parenteral nutrition on day eight of his ICU admission.

When should parenteral nutrition be initiated in those that are failing to meet caloric targets with enteral feeding alone?

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