| GUIDELINES FOR PATHOLOGY
REQUESTING IN PATIENTS ON TOTAL PARENTERAL NUTRITION
INTRODUCTION
| Pathology tests may be required for: |
Initial assessment of patient |
|
Monitoring response to treatment |
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Detection and management of complications |
INITIAL ASSESSMENT
Generalised Malnutrition
Clinical biochemistry tests (e.g. Albumin Urine Creatinine.) are not as specific as clinical
assessment e.g. clinical history, body mass index, physical examination, skin fold
thickness.
Specific nutrient deficiency - Minerals
Magnesium, Zinc, Iron (Hb level) should be measured to assess whether additional amounts
need to be provided. Zinc levels are affected by the acute phase response (reduced) and
should be interpreted in conjunction with c-reactive protein level.
Specific nutrient deficiency - Vitamins
Unnecessary to assess water soluble vitamin status. Vitamin A and E deficiency rare and
additional amounts can be added safely. Vitamin D can be asessed indirectly by calcium,
phosphate, alkaline phosphate and if necessary PTH levels. Vitamin K levels may be
assessed by prothrombin time.
Other concurrent disease
The patients electrolyte balance, renal and hepatic function should be assessed before
starting TPN so that major metabolic imbalances can be corrected first.
|
If not already known initial
assessment should consist of: |
|
|
U&E |
- sodium, potassium, urea,
creatinine |
|
GS |
- glucose |
|
LFT |
- total prot., alb.,
bilirubin, ALT, alkaline phosphatase |
|
GGT |
- gamma-GT |
|
CA |
- calcium |
|
PI |
- phosphate |
|
MG |
- magnesium |
|
FBC |
- full blood count |
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Urine electrolytes
and urea may provide useful information. |
|
MONITORING (Minimum Frequency)
ROUTINE CLINICAL TESTS
Tests |
During 1st Week or
until metabolically stable |
After 1 week or when
metabolically stable |
| Serum |
|
|
| Na,K,Urea,Creatinine |
Daily |
Monday + Thursday |
| Phosphate |
Monday |
Monday |
| Calcium |
Monday |
Monday |
| Magnesium |
Monday |
Monday |
| LFT’s |
Monday |
Monday |
| Gamma -GT |
Monday |
Monday |
| Full Blood Count (FBC) |
Monday |
Monday |
| Zinc (with CRP) |
As required |
As required |
| Glucose |
As required |
As required |
| Total C02 (Bicarb.) |
As required |
As required |
| Urine |
|
|
| Electrolytes (Spot) |
Monday |
Monday |
| Urea (24 hr.) |
As required |
As required |
| Glucose (Spot) |
As required |
As required |
OTHER TRACE ELEMENTS
Deficiencies of trace elements other than magnesium and zinc may occur, particularly in
long term TPN. However, serum levels are not available locally and are not a reliable
guide to the body’s requirements. Deficiency of these elements should always be borne
in mind and treated by addition to feeds on an empirical basis.
For example:
Colbalt - reduced vitamin B levels
Copper - hypochromic anaemia, leukopenia
Selinium - cardiomyopathy
Molybdenum - ?amino acid intolerance, marked hypouricaemia
Chromium - glucose intolerance
REQUESTING
In order to facilitate requesting for patients the TPN1
profile should be used to request initial and weekly blood tests:-
MONDAYS OR PART OF INITIAL ASSESSMENT
| Profile |
Tests |
Collection Tubes |
| TPN1 |
Na, K, Urea, Creatinine |
} |
| |
Phosphate |
} |
| |
Calcium |
} SST tube (yellow top) |
| |
Magnesium |
} |
| |
LFTs |
} |
| |
Gamma-GT |
} |
| |
Full Blood Count |
EDTA tube (purple top) |
THURSDAYS OR DAILY DURING 1ST WEEK OR UNTIL METABOLICALLY STABLE
| Profile |
Tests |
Collection Tube |
| UE |
Na, K, Urea, Creatinine |
SST tube (yellow top) |
OTHER
| Other |
Tests |
Collection Tubes |
| Weekly |
Urine Electrolytes |
Spot urine (plain universal) |
| As Required |
Blood Gases |
Arterial sample |
| |
Total C02 (Bicarbonate) |
} |
| |
Zinc (with CRP) |
} Plain tube (red top) |
| |
Glucose |
} |
| |
Urine Urea |
24hr collection |
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