A stumble may prevent a fall

A 50-yo man presented to the ED confused complaining of vomiting. Time of onset and frequency couldn’t be determined with certainty, but he noted worsening of symptoms two weeks ago. Admission lab-tests showed S-Na 109mmol/l, CRP 28 and WBC 9,5. Past medical history was significant for laparoscopic appendectomy and cholecystectomy two years previously. He was currently being treated with sertralin, a SSRI, due to depression.

Vital signs were stable except for a sinus tachycardia of 115 BPM. The patient noted he’d tried to stay hydrated drinking water. Serum-osmolality was 233 mosmol/kg (norm 285-295) and urine-osmolality 325 mosmol/kg (norm >800). The kidneys weren’t making a case to concentrate the urine very well and it seemed that he was diluted. This looked to be a clear-cut case of chronic hyponatremia secondary to SIADH, a known side-effect of SSRI. The patient was admitted and a slow IV-drip infusion of sodiumchlorid 0,9% started at the rate 80ml/h with a correction-goal of 8-10mmol /24hours (0,5mmol/hour).

Several hours had passed and I first saw the patient at the ward after he’d had a severe bout of vomiting. Perceived much older than his biological age, there was something out of the ordinary about him. With intermittent facial contractions my thoughts immediately went to tetany and hypocalcaemia. Positive Chvostek (YouTube) and Trousseau (YouTube) signs strenghtened my suspicions. This was most probably a severely dehydrated patient that demanded immediate IV fluid and electrolyte substitution. More about this relation later. His face reminded me of a raisin I’d leave in the box for last; his tongue was shrunk and hiding like a little turtles head; the eyes were sunken as if they’d seen to much. Abdominal peristaltics were reduced! Upon palpation there was slight tenderness, diffuse resistances, but no signs of peritonitis. There had hardly been any diuresis since admission! As the examination was being performed, the patient had another episode of vomitus and became dyspneic. His respiratory rate increased to 40/min, oxygen saturation and BP dropped to 75% and 90/60 respectively. Stabilization was initiated with oxygen and IV bolus of Ringer Acetate. An arterial blood gas was drawn. From nowhere an ultrasound probe appeared in my hand. I tripped onto the patient landing the probe onto his subcostal window.

Subcostal view trying to identify a collapsed inferior vena cava. Even though evident by the physical examination, this just reinforces how severely dehydrated the patient was. What was I to do but apply some more mixed sonographic arts.

Right lateral lung- and abdominal view is significant for lung consolidations. Due to the larger caliber and more vertical orientation of the right mainstem bronchus, there is a high suspicion of aspiration and aspiration pneumonitis/pneumonia.

Ultrasound probe dropped straight onto the abdomen. All abdominal views could identify the same pathologic state. Small bowel loops are dilated beyond 2,5cm and hence there is a high suspicion of ileus. Additional IV crystalloids were administered. A nasogastric tube was placed draining about 750ml of light-brown fluid.

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Even though the patient didn’t complain of severe abdominal pain, the computed tomography raised a high suspicion of mechanical small intestinal ileus. The contrast didn’t reach past the distal ileum. In effect the patient was taken to surgery and an exploratory laparotomy performed, identifying an adherence/bride at the distal ileum as the culprit obstruction.

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Hypochloremic metabolic alkalosis partly compensated by elevated PCO2. A patient with persistent vomiting may loose in excess of 2 liters of HCl-rich fluid per day. The fluid contains a high level of protons at a concentration of about 100mmol/L. For every H+ secreted a bicarbonate molecule (HCO3-) is generated. In effect the body must rid itself of 200mmol of HCO3- through the kidneys. Initial this works, but as the vomiting persist intravascular volume is drained and glomerular filtration rate is decreased, hence resulting in elevated HCO3- levels and pH. In addition to losing sodium through the GI-tract, maintainance of steady-state relationship between chloride and sodium transmembrane electrochemical potential differences is kept by natriuresis. Chloride is reduced, sodium follows. GFR is reduced, HCO3- and pH is elevated. All is maintained by protracted vomiting! And last but not least, how is the vomiting related to tetany? As pH is elevated, albumin develops a higher affinity for calcium. Hence free calcium-ion levels are lowered.
In conclusion, despite the present medical history being a rare mineral called unobtanium, the case could have been partly solved by taking a good look at the blood-gas. Fortunately, ultrasound was available bedside, reinforcing suspicions and saving yet another day.

References
1. Small bowel obstruction. Introduction to Bedside Ultrasound: Volume 2 by Matthew Dawson och Mike Mallin (free at Itunes)