Propofol Infusion Syndrome

A 28-year-old man was involved in a high-speed road traffic accident suffering severe head injury (diffuse axonal injury) with bilateral haemopneumothoraces and pulmonary contusions. He was transferred intubated and ventilated to the neurointensive care unit from a district general hospital for intra-cranial pressure (ICP) monitoring.

He was initially managed with bilateral chest drains and conservative neuroprotective measures for difficult to control ICP. He was heavily sedated on propofol (300mg/hr), midazolam (30mg/hr) and fentanyl (300mcg/hr).

Over the next few days his temperature increased and he became increasingly hypoxic. He subsequently developed ECG changes and a echocardiogram showed right heart failure. A diagnosis of pulmonary embolism, which was confirmed on CTPA a few days later which showed evidence of a small PE. He was not anticoagulated due to neurosurgical concern regarding his head injury.

Over the next few days he developed renal failure requiring renal replacement therapy and acute liver failure with hypoglycaemia and lactic acidosis. He developed severe cardiovascular failure requiring multiple inotropes and pulmonary artery catheter guided therapy. Lipids were found to be elevated, with creatine kinase >50,000 and myoglobin found in the urine. Propofol infusion syndrome was diagnosed. Sedation was stopped and he started to make a recovery.

What are the clinical features of propofol infusion syndrome?

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Extracorporeal CO2 removal

A 42 year old man presented with a week-long history of increasing shortness of breath, cough  (productive of purulent sputum) and fevers on a background of significant chronic lung disease. He had a ten year history of interstitial lung disease and was on the waiting list for a lung transplant. He used oxygen at a rate of 2 litres per minute at home, 24 hours a day. His usual exercise tolerance of 200 metres had been significantly reduced for the past week. His regular medications included seretide and salbutamol inhalers, lansoprazole, azathioprine, prednisolone alendronate.

On arrival in hospital, he was alert and orientated. He had a patent airway, but was tachypnoeic (rate of 50/minute) using his respiratory accessory muscles and a tracheal tug was evident. An arterial blood gas revealed type two respiratory failure (pH 7.26; pO2 8.14, pCO2 7.52 on 15 liters/min of face mask oxygen). He was hypotensive (80/40mmHg) and tachycardic (130/minute, sinus rhythm). A pyrexia of 39.2°C was recorded. Blood results showed normal renal function, a slightly elevated white cell count of 14.

The patient was admitted to the high dependency for close monitoring in view of his history and presentation. He was commenced on treatment for a presumed infection (viral or bacterial) with oseltamivir, co-amoxiclav and clarithromycin and given three “pulsed” doses (750mg) of methylprednisolone. He remained stable for the next twelve hours.

Early the next morning, he became very hypoxic (oxygen saturations less than 50%), bradycardic (<35 beats per minute) and had a brief hypoxic respiratory arrest. He received 1 cycle of cardiopulmonary resuscitation and was intubated. There was subsequently a return of spontaneous circulation.

The next 24 hours involved a period of difficulty with ventilation. His peak airway pressures were very high, despite being paralysed and a low volume/high respiratory rate strategy being employed. He was discussed with a tertiary respiratory centre and it was decided that he should be transferred for insertion of a pumpless arteriovenous interventional lung assist (for extracorporeal carbon dioxide removal) as a bridge prior to lung transplantation. He had formal ultrasound measurement of his femoral arteries. His left common femoral artery was widely patent (AP and transverse diameter of 8-9mm throughout), but the right was only 4-5mm throughout.

In the meantime, his peak airway pressures were consistently between 35 and 40cmH2O, despite tidal volumes of 230ml, 3.8ml/kg). With a rate of 32-35 breaths per minute, his pH was  initially maintained above 7.2, with a pCO2 of 9-11kPa. Over the course of the next few hours, this became increasingly difficult to achieve. His oxygen requirements did not escalate (an FiO2 of 0.6 provided a pO2 of 8-9kPa). When his pCO2 increased to 15.4kPa and his pH dropped to 7.17, further adjustments were made and the PEEP decreased to 5cmH2O from 10cmH2O. His noradrenaline requirements were increasing and with the aid of the cardiac output monitoring, he was cautiously given fluid with a good response.

He was transferred to the centre in which a lung transplant could be performed within hours of the referral. A Novalung device was inserted and he underwent a bilateral lobar lung transplant several days later. He was in hospital for 6 weeks and made a very good long-term recovery. At six months, he was extremely well and was undertaking his activities of daily living completely normally with stable lung function. He even managed to complete an eight mile bike ride.

What is the rationale for extracorporeal lung assist?
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Management of Inhalational Injury

A 30-year-old man with no significant past medical history was admitted to ED from a house fire started by a piece of faulty electrical equipment. There were superficial skin burns only but some evidence of a possible inhalation injury with singed nasal hairs and a hoarse voice. Coughing resulted in expectoration of carbonaceous sputum with some haemoptysis. Arterial blood gas analysis revealed a PaO2 of 10.4 kPa on 40% oxygen a carboxyhaemoglobin level of 18%.

Semi-elective endotracheal intubation was performed using an uncut orotracheal tube. Ventilatory parameters were adjusted to give a tidal volume of 6-8 ml/kg and plateau pressure of less than 30 cmH20. Recruitment manouveres were performed to give an optimum compliance in the region of 40-50 ml/cmH20 with a positive end-expiratory pressure of 8 H20. The inspired fraction of oxygen was kept high (i.e. greater than 60%) until there was a fall of the carboxyhaemoglobin level to less than 5% at which point downwards titration was performed as guided by a target SpO2 of 94%.

Fibreoptic bronchoscopy was performed approximately six hours after admission to intensive care which demonstrated carbonaceous colonisation of the lower respiratory tract and areas of erythematous and denuded epithelium. Within 12 hours of intubation significant oedema of the face and upper airway had developed. A restrictive fluid regimen was instituted and there was gradual resolution of this swelling over the next 3 days. At this time, gas exchange was satisfactory and the patient was successfully extubated before being discharged to the high-dependency unit.

How is inhalational injury managed on the ICU?Read More »

Use of Bicarbonate in Lactic Acidosis

Five days post emergency colorectal surgery, an elderly woman, following a brief period of chest pain a few hours earlier, developed progressive hypotension and tachycardia on the ward. She had a background of hypertension, type 2 diabetes and a chronic left foot ulcer. On examination she was found to be clammy, mottled and peripherally vasoconstricted with a GCS of 15/15. Her abdomen was soft and non-tender. Her initial ECG had showed no ischaemic changes and subsequent ECGs showed only a sinus tachycardia.

Initial blood gas analysis showed a metabolic acidosis (pH 7.21 Lactate 2.8mmol/l, HCO3 11.1mmol/l with a pCO2 of 2.7kPa).  A starting differential diagnosis of a cardiac event, a pulmonary embolism, critical ischaemia or sepsis related to a hip or foot ulcer were made. Urgent orthopaedic and vascular review were obtained, and it was deemed that neither the hip, ulcer or vascular insufficiency were a likely source for the deterioration. Initially it was planned to transfer her for a CTPA, however she became progressively unstable, was no longer fluid responsive, and was intubated on the ward and transferred to the intensive care unit (ICU) for stabilisation.

On arrival on ICU she continued to deteriorate, and in addition to fluid resuscitation required a high dose noradrenaline infusion to maintain her blood pressure. Broad spectrum antibiotics were started, a bedside echocardiogram and blood tests performed and hydrocortisone started. Her metabolic acidosis continued to deteriorate, subsequent arterial blood gas showed a pH 6.91, Lactate of 13.7mmol/l, HCO3 7.7mmol/l, base excess -25mmol/l with a pCO2 of 5.4kPa. It was decided to correct this acidosis with a bicarbonate infusion and initially 200ml of 8.4% was given over an hour, based on correcting half the calculated bicarbonate deficit (bicarbonate deficit (mmol) = base deficit 0.3xbodyweight(kg)1).  The blood gas following this infusion showed improvement in the metabolic acidosis despite the increasing Lactate (pH 7.07, Lac 14.0mmol/l, HCO3 10mmol/l, BE -18.6mmol/l with a pCO2 of 4.85kPa). She continued to deteriorate and the results from her blood tests, troponin and bedside echo suggested a primary myocardial infarction to cause this decline. She was too unstable for primary coronary intervention and her condition continued to deteriorate. She died 6 hours post admission.

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Ethylene Glycol Poisoning

Ethylene Glycol Poisoning

A 50 year old man was found by the roadside by paramedics with a GCS of 13. On arrival he had a patent airway, but a GCS of 5 (E1 M3 V1). He had an elevated respiratory rate (30/min) and a profound metabolic acidosis (pH 6.97 pO2 16.8 pCO2 1.68 HCO3 2.8 BXS -30.8 COHb 0). The lactate was too high to be measured by the blood gas analyser and there was an elevated anion gap [(147+5.5) – (2.8+ 109) = 40.7] He was cardiovascularly stable with warm peripheries. His ECG revealed a prolonged QTc. He was intubated and 8.4% sodium bicarbonate was administered. His initial laboratory bloods showed CRP 11, white cell count 29.5 CK 2539 creatinine 213. Ethanol levels were <10 and Paracetamol and salicylate levels were within normal limits. He was given a dose of intravenous cefotaxime and his urine was sent for organic acids screening which revealed an enormous peak of glycolic acid and small increase in oxalic acid, consistent with an overdose of ethylene glycol.

After arrival in intensive care, the sodium bicarbonate had improved the pH to 7.2, with a residual lactaemia (15 as measured in the laboratory, without any interference from glycolic acid). CVVHDF was commenced. In order to inhibit futher metabolism of the ethylene glycol, 10% ethanol was commenced until fomepizole was available (an initial bolus of 800ml, followed by an infusion at 180ml/hr). Ethanol levels were monitored. Fomepizole was administered later that day abd the ethanol stopped (15mg/kg loading and 1mg/kg/hr). The renal function deteriorated despite CVVHDF (peaked at urea 28, creatinine 724 on day 4), which was continued for 5 days. Treatment for aspiration pneumonia was started in day 1 and cardiovascular support was continued (noradrenaline). Intermittent boluses of glycopyrolate were required to treat the bradycardia associated with fomepizole. A gradual improvement occurred and he had made a full neurological recovery within 2 weeks, with much improved renal function. He later admitted to drinking 250ml of antifreeze.

What are the clinical features and management of ethylene glycol poisoning?Read More »

Obesity Hypoventilation Syndrome

Obesity Hypoventilation Syndrome

 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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Haemofiltration in Sepsis

Haemofiltration in Sepsis

A young IV drug user was admitted with septic shock secondary to staphylococcal sepsis with bilateral shadowing on CXR. He rapidly required intubation due to hypoxia, and institution of vasopressor support. He had a significant metabolic acidosis and consequently was commenced on haemofiltration. Transthoracic echocardiography revealed a large tricuspid vegetation. After 48 hours of haemofiltration, his acidosis haf normalised, and pressor requirements had reduced. He had a prolonged respiratory wean before being transferred to a cardiothoracic centre.

What is the role of haemofiltration (or other modes of renal replacement therapy) in severe sepsis and septic shock?
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Sodium Bicarbonate in Amitriptyline Overdose

Sodium Bicarbonate in Amitriptyline Overdose

A 40 year old man with pre-existing mental health problems presented after an overdose of 6g of amitriptyline. He was deeply unconscious and required invasive ventilation. He was commenced on bicarbonate therapy and hyperventilated to pH 7.5. Around 12 hours after admission he developed tonic-clonic seizures, a broad complex tachycardia and subsequently suffered a cardiac arrest that was refractory to defibrillation, adrenaline and amiodarone. He was given additional 8.4% bicarbonate and further defibrillation attempts and was successfully resuscitated after 90 minutes.

What is the rationale for the use of sodium bicarbonate in the management of amitriptyline overdose?Read More »