alfentanil and raised intracranial pressure

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Page 1: Alfentanil and raised intracranial pressure

1008 Correspondence

Alfentanil and raised intracranial pressure

We read with interest the report by Dr Moss (Anaesthesia 1992; 47: 134-136) concerning increases in intracranial pressure associated with the use of alfentanil in patients with normal pressure hydrocephalus and wish to describe a similar event in a child with a head injury.

A 30 kg, 8-year-old boy suffered a head injury while riding his bicycle. His trachea was intubated and his lungs ventilated. A CT scan showed a left parietal contusion, a small left subdural haematoma with a slight mass effect and a small amount of subarachnoid blood. A subdural catheter was inserted through a frontal burr hole and the child transported to the intensive care unit for sedation, ventilation and intracranial pressure (ICP) monitoring. Infusions of morphine and midazolam were used for sedation and atracurium for neuromuscular blockade. His lungs were hyperventilated to a Pacoz of 3.5 to 4.0 kPa. ICP remained steady at 10 to 12 mmHg. Several hours later, during a nursing procedure, his pulse and blood pressure rose, although ICP remained steady. His level of sedation was considered inadequate and therefore a 0.5 mg bolus of alfentanil was given to provide a short period of increased sedation. Immediately following this, the ICP showed a brisk rise from 10 to 27 mmHg which lasted for 20 min. Mean arterial pressure (MAP) fell from 85 to 75 mmHg and pulse rate from 110 to 90 beat.min.-’. This resulted in a decrease of cerebral perfusion pressure from 75 to 47 mmHg. Two hours later, a rise of ICP from 10 to 30 mmHg followed a further bolus of 0.5 mg alfentanil, which required treatment with mannitol. Following this, fentanyl was substituted for alfentanil. Two doses of 50 pg were used for sedation; these had no effect on ICP despite evidence of an overall steady decrease in intracranial compliance.

As Dr Moss reports, the effects of alfentanil on cerebral vasculature are not clear. Marx et al. [l] described an increase in cerebrospinal fluid pressure associated with the use of alfentanil, which also caused a significant decrease in MAP. Fentanyl did not exhibit this action. It was unclear whether the increase in ICP was due to a direct cerebral vasodilator effect or secondary to the decrease in MAP. Cuillerier and colleagues [2], however, did not show any difference between alfentanil, fentanyl and sufentanil in ICP or cerebral perfusion pressure.

In two of Dr Moss’s patients, the increase in ICP was not associated with a significant reduction in MAP, and preceded it. It seems more likely, therefore, that the rise in ICP is due to a direct effect on cerebral vasculature rather than a compensatory response to a decrease in MAP. Like Dr Moss, we would also advise caution with the use of alfentanil when intracranial compliance is compromised.

Shackleton Department of D.M. HARGREAVES Anaesthetics, J. HANDEL

Southampton General Hospital. Southampton SO9 4XY

References [I] MARX W, SHAH N, LONG C, ARBIT E, GALICICH J, MASCOTT C.

MALLYA K, BEDFORD R. Sufentanil, alfentanil and fentanyl: impact on CSF pressure in patients with brain tumors. Anesthesiology 1988; 6 9 A627.

[2] CUILLERIER D, MANNINEN P, GELB A. Alfentanil, sufentanil and fentanyl: effect on cerebral perfusion pressure. Anesthesia and Analgesia 1990; 7 0 S75.

Patientcontrolled analgesia-a serious incident

Drs Grover and Heath (Anaesthesia 1992; 47: 402-4) mention their use of a Vygon ‘one-way valve’ to prevent reflux of opioid into the gravity feed intravenous infusion. However, it appears that they did not use an ‘antisyphon’ valve to prevent the syphoning of opioid out of the syringe in the PCA pump. This would have prevented the incident that they describe. ‘Y’ connector sets that incorporate both antireflux and antisyphon valves are available, cheap and have been standard practice in our hospital for several years. The incident brings to six the number of known episodes of malfunction of a PCA pump leading to serious morbidity or mortality [l], but must be seen against the extensive worldwide use of the technique, the fact that all equipment will malfunction at some time, and that all routes of opioid administration carry risks that are largely undetermined [2]. It is significant that five out of the six patients survived.

The authors go on to discuss the problems of monitoring of patients, commenting on previous work from this hospital [3]. They state ‘it is not surprising if busy nurses accord a low priority to quantifying an event which apparently provokes little response from the medical team’. Here we always recognise that respiratory rate is a poor indicator of respiratory function, (except when very low or very high). However, at present there is no other simple measure of monitoring respiratory activity that can be used easily on ordinary wards. Nurses in this hospital always have a positive response from anaesthetists on reporting possible respiratory problems, even if no active

intervention is needed. Monitoring of respiration is deemed mandatory and not an option that could be given a ‘priority’.

From time to time we see failure to monitor or failure to act on behalf of patients who have clearly deranged physiological parameters. Our nursing colleagues must take up the issue of the provision of a safe environment for patients who are recovering from major surgery. Surgeons and anaesthetists are now auditing their morbidity and mortality. Nurses too must take on this type of audit and show that if they change their practice (e.g. team nursing) and move away from the traditional graded and progressive care (i.e. the illest patients in one area) then they must demonstrate that there is an improvement in safety and a reduction in morbidity.

James Paget Hospital. Great Yarmouth. Norfolk NR31 6LA

W.G. NOTCUTT R. KALDAS

References NOTCUTT WG, KNOWLES P, KALDAS R. Overdose of opioid from patient controlled analgesia pumps. British Journal of Anaesthesia 1992; 6 9 95-7. NOTCUTT WG. Patient controlled analgesia-the need for caution. Anaesthesia 1989; e4: 268. NOTCUTT WG, MORGAN RJM. Introducing patient controlled analgesia for postoperative pain control with a district general hospital. Anaesthesia 1990; 45: 401 -6.