An 83 year old man developed persistent hiccoughs and later became confused. He was admitted to hospital the next day. Mild tenderness was noted in the left upper quadrant.
Biochemistry results were: Na+ 128, K+ 5.7, creatinine 0.202, urea 12.7 (All in mmol/l). Bilirubin was elevated. Amylase was normal. [Hb] 115 g/l, WCC 15.2. He became febrile (T 38.9C) and an ultrasound the next day diagnosed acute cholecystitis with a large calculus in the neck of the gallbladder.
A subtotal cholecystectomy and exploration of common bile duct was performed the next day (4th).
Postop arterial gases in the Recovery Room on high flow oxygen by mask were collected (Gas 1)
Three days postop (7th), he became very confused and pulled out his T-tube. This was reinserted at laparotomy later the same day. He was reversed and extubated (at 1055 hrs) but remained unconscious and respiratory effort was poor. Naloxone IV was given without effect. Blood gases at 1209hrs (Gas 2) in theatre showed respiratory failure. He was reintubated and ventilated and gases were checked at 1242hrs (Gas 3). He was transferred ventilated to Intensive Care Unit at 1300hrs. Gas 4 and Gas 5 are later in the Intensive Care Unit.
|Serial Blood Gas Results for Case 22|
|Number:||Gas 1||Gas 2||Gas 3||Gas 4||Gas 5|
|Place:||Recovery Room||Op Theatre||Op Theatre||ICU||ICU|
|[HCO 3 ]||18||22.0||17.5||18.7||18.4|
He slowly improved and after a prolonged time in the Rehabilitation Unit was discharged to a Nursing Home
If you have reached this case after proceeding through all the previous ones then you are well-placed to analyse this one yourself.
As an exercise, try your hand at doing this yourself (in a systematic way) before reading the comments below.
Gas (1) shows a mild metabolic acidosis with appropriate respiratory compensation. Hyponatraemia is noted and could be contributing to his confusion.
Gas (2) shows a severe respiratory acidosis due to prolonged hypoventilation in theatre. The acute effect of this is to cause an elevation in bicarbonate level. However the actual bicarbonate level is lower than 24mmol/l so a significant metabolic acidosis is also present. Severe hyponatraemia is noted. The continued unconsciousness and probable difficulty with reversal of neuromuscular blockage is explained by the known biochemical disorders. Any associated hypothermia will also contribute.
In Gas (3), the respiratory acidosis has been corrected by institution of adequate ventilation. The magnitude of the metabolic acidosis is now apparent. As ventilation is controlled, then the pCO2 value is not due to compensation but is dependent on the level of ventilation set by the Anaesthetist.
Chronic renal failure with a creatinine level of 0.2mmol/l would not by itself cause any metabolic acidosis.