The interpretation of abnormally high serum amylase activity is not always straightforward. The usual reason for measuring serum amylase level is to confirm or exclude the diagnosis of pancreatitis.3
Acute pancreatitis was unlikely in this patient who had only discrete abdominal pain and no radiological changes of the pancreas.4
Thus, the Atlanta-criteria for diagnosing acute pancreatitis were not fulfilled. Moreover, the patient had no history of alcohol abuse or gallstones.
However, very high serum total amylase levels may also occur in patients with acidosis. In lactic acidosis, the hyperamylasemia typically results from the presence of excessive salivary-type isoamylase.3
It has been reported that acute hypoxaemia may alone or in combination with other factors raise serum total amylase level possibly through ischaemic injury to the pancreas or salivary glands.5
Tissue hypoxia, according to this hypothesis, produces hyper-permeability of cell membranes, allowing intracellular amylase to leak out, resulting in high serum total amylase levels.6
This might be the mechanism producing hyperamylasemia in shock,7
carbon monoxide poisoning,6
and open heart surgery.9
Experimental studies suggest that vascular disturbance alone or in conjunction with pancreatic duct obstruction can lead to elevation of serum amylase.10
Thus, in our case, the very high level of serum total amylase was most likely due to hypoxaemia and lactic acidosis. This seems to be in accordance with the patient's fast recovery where the serum total amylase levels were gradually falling as the acidosis was corrected. Such correlation has been described in the literature where the lower the level of consciousness and the greater the degree of acidosis, the higher the level of amylase.6
It has been mentioned that morphine and codeine can cause hyperamylasemia in the absence of pancreatic or salivary gland disease, which might be due to spasm of the sphincter of Oddi, and, subsequently, elevation of pancreatic isoamylase.5 11–13
According to the product description sheet for Tramadol, an increase in liver enzymes has been reported in a few isolated cases. Pancreatitis is not mentioned as a side effect or a sign of toxicity.14
Anyhow, the elevation of amylase and liver enzymes in opioid overdoses is unlikely to be more than 10 times the upper limit of normal, and this elevation is usually associated with CT scan verified pancreatitis.11–13
Kameya et al
analysed 91 hyperamylasemic sera and traced the patients’ records finding that more than half of the patients had a salivary-type isoamylase.7
The association between hyperamylasemia and non-pancreatic abdominal pain in patients visiting the emergency room was also reported in other studies.15 16
Isoamylase analysis can be of value in differentiating acute abdominal pain. The pancreatic isoamylase (P type) arises only from the pancreas, while salivary isoamylase (S type) is secreted by many different tissues.7
Furthermore, the ratio of P type to S type can also be used as a diagnostic tool. A study in patients in the intensive care unit showed that 51% had hyperamylasemia. When isoamylase analysis was done, it showed that the P/S ratio was high in those who had a disorder related to the pancreas, low in patients with extra-pancreatic disorders and normal in patients with renal failure.10
- Increases in serum total amylase levels most commonly, but not always, signify pancreatitis.
- Many patients are erroneously labelled as having pancreatitis despite the absence of clinical features to support this diagnosis.
- Hyperamylasemia can occur due to hypoxaemia and lactic acidosis and it is usually the salivary amylase that increases.
- Isoamylase enzyme analysis is recommended for diagnosing conditions other than pancreatitis as a cause of hyperamylasemia.