Dr Nigel Watson describes an audit of patients on lithium therapy in his practice which prompted the development of an action plan to improve monitoring


   

Lithium can be a difficult drug to use. Although it is effective in the management of bipolar depression and recurrent depression, the unwanted side-effects are troublesome. The dose of lithium needs to be adjusted with reference to the serum levels to minimise the risks.

Once stabilised on lithium the patient can be monitored safely in general practice. The specialist and the GP need to agree specific responsibilities for the shared care.1

Serum lithium levels should be monitored every 6 months once the patient is stable, but would need more frequent monitoring in the first few weeks.2

Lithium has a very narrow therapeutic range. Serum lithium levels should be maintained between 0.5 and 1.2mmol/l. Levels should be measured 12 hours after the last dose. If levels rise above 1.5mmol/l, tremor, ataxia, dysarthria, nystagmus, renal failure, convulsions and, rarely, death can occur.

At therapeutic serum levels the most common side-effects are dry mouth, weight gain, polyuria and fatigue.3

Lithium may have an adverse effect on renal function.4 Depletion of sodium can exacerbate lithium toxicity.

In some patients, lithium therapy can cause clinical hypothyroidism.5 It is therefore recommended that thyroid function be monitored annually.

The aim of this audit was to show the level of monitoring of this drug in our practice.

Standard medical advice is that any patient on lithium therapy should have the following monitoring:

  • Six-monthly serum lithium level
  • Annual thyroid function tests
  • Annual serum urea & electrolytes.

The practice has 12 200 patients registered. The target was all patients currently prescribed lithium. Using the practice clinical computer, we identified 12 patients on long-term lithium therapy.

All of these patients had been started on lithium therapy by the psychiatrist. Thereafter, either the psychiatrist or the community psychiatric nurse (CPN), in the main, was responsible for ongoing care. Repeat prescribing of lithium has increasingly passed to the GP.

The CPN initially arranged the follow-up blood tests, but increasingly this task has also passed to the GP.

For all patients on lithium therapy:

  • Serum lithium level to be measured every 6 months
  • Thyroid function test to be performed every 12 months
  • Serum urea and electrolytes to be measured every 12 months.
  • 100% of patients to have had a serum lithium level measured in the last 6 months.
  • 100% of patients to have had a thyroid function test in the last 12 months.
  • 100% of patients to have had serum urea and electrolytes measured in the last 12 months.

The results are shown in Figure 1. They show that the actions taken between 1994 and January 1999 to improve the monitoring of patients on lithium therapy were largely ineffective. We attributed this to the fact that with some patients it was unclear who was responsible for monitoring – the GP or the CPN.

Figure 1: Percentage acheiving the standards for monitoring lithium between 1994 and 1999
  1994
1995
1996
1997
1998
1999
(Jan)
1999
(July)
Serum lithium levels in last 6 months (%)
81
62
30
84
60
66
100
Thyroid function tests in last 12 months (%)
36
85
60
50
30
60
92
Serum urea & electrolytes in last 12 months (%)
18
62
70
50
40
66
100
bar chart

Following the audit in January 1999, the action plan outlined below was instigated.

  • Discuss audit with partners and agree the action plan.
  • Confirm with the CPNs who will monitor blood tests for each patient, so that the patient, GP and CPN are all aware of their responsibilities.
  • Ensure that the results of all blood tests performed by the CPN are sent to the practice.
  • Identify a member of staff to take responsibility for monitoring blood tests for patients on lithium therapy. Remove this task from the GP.
  • Establish a database that clearly identifies when the next test is required and the person identified would be responsible for chasing up non-attenders.

The practice has struggled for a number of years to provide adequate monitoring for this small group of patients. This is clearly demonstrated in Figure 1. Implementation of the agreed action plan has had dramatic results (see July 1999 results in Figure 1).

The only patient who is currently overdue for a blood test is in hospital and has not had a thyroid function test performed in the last 12 months. The hospital has been asked to action this as she is likely to be an inpatient for some time.

References

  1. Kehoe RF, Mander AJ. Lithium treatment: prescribing and monitoring habits in hospital and general practice. Br Med J 1992; 304: 552-4.
  2. Drug and Therapeutics Bulletin 1999; 37(3): 22-4.
  3. Gitlin MJ, Cochran SD, Redfield Jameson K. Maintenance lithium treatment: side effects and compliance. J Clin Psychiatry 1989; 50:127-31.
  4. Bendz H, Sjodin I, Aurell M. Renal function on and off lithium in patients treated on lithium for more than 15 years. Nephrol Dial Transplant 1996; 11: 457-60.
  5. Bocchetta A, Cherchi A, Loviselli A. Six year follow up of thyroid function in patients during lithium treatment. Acta Psychiatr Scand 1996; 94: 45-8.

Guidelines in Practice, August/September 1999, Volume 2
© 1999 MGP Ltd
further information | subscribe