Baseline tests and monitoring
Recommended baseline tests and ongoing monitoring are described in Table 2. There may be slight local variations in these guidelines. As well as biochemical monitoring it is important to look for and educate patents about physical signs and symptoms associated with adverse effects and toxicity. These include tremor, tiredness, lethargy, nausea, vomiting and diarrhoea, dehydration, polydipsia, polyuria and nocturia. Although baseline tests will be carried out when lithium is initiated by a specialist, check that the results are complete and readily available for reference.
Table 2 Lithium baseline tests and monitoring.6,9 (adapted from Livingstone 2006, Waitemata DHB 2006)
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Baseline |
Routine maintenance |
Comments |
| Serum lithium concentrations |
Important to establish reliable steady state concentration associated with therapeutic response |
3-monthly |
Monitor more frequently in high risk patients, e.g. those on potentially interacting drugs, poor compliance, elderly, unstable renal function, physical illness |
| Thyroid Function |
Baseline thyroid function (T4, TSH) |
TSH 3 months after initiation and then 6-monthly |
T4 not routinely required. Monitor for symptoms of hypothyroidism |
| Electrolytes |
Baseline |
Check with lithium serum levels every 3 months |
Particularly important to monitor sodium as it competes for reabsorption in proximal renal tubule |
| Serum creatinine and renal function |
Exclude renal disease. Baseline creatinine and estimation of renal function |
Check at same time as lithium levels, at least every 3 months |
Estimate renal function using the Cockcroft and Gault Equation* based on ideal body weight |
| Serum calcium and magnesium |
Baseline |
Check every 2 years |
Lithium may rarely cause hypercalcaemia and hypermagnesium |
| Parathyroid Hormone (PTH) |
|
|
Measure only if serum calcium is elevated. PTH must be interpreted relative to serum calcium measurement on the same specimen |
| Weight |
Baseline weight |
Monthly, reduce frequency after 6-12 months if weight is stable |
Encourage self-monitoring and weight control measures |
| Pregnancy Test |
Baseline in women of childbearing age |
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| ECG |
Baseline in patients with cardiac problems or aged over 45 years |
12-monthly in patients with cardiac problems or aged over 45 years |
Conduct more frequently if clinically indicated |
| *The bpac creatine clearance calculator is based on the Cockroft-Gault equation |
 For correspondence regarding baseline ECG for lithium patients, see "Correspondence: Aspirin in children", BPJ 13 (May, 2008).
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