CASE DISCUSSION
33 years old female, K/C/O HTN, CKD STAGE 3, loss to follow up for 1 year, admitted with A/CKD with H/O alternate drug intake. She had complaints of nausea, vomiting and breathlessness with serum creatinine value of 12.4 mg/dl and metabolic acidosis. She was started on haemodialysis with right IJV temporary DLC. She became stable after 2 cycles of haemodialysis. In follow-up she didn’t have improvement in urine output(Daily urine output <400 ml) and had persistent creatinine values >10 mg/dl. Her left RC AVF was created.
After maturation of AVF, haemodialysis was started through AVF with blood flow 250 ml/min. So the nephrologist asked the technician to remove the DLC at the end of the haemodialysis and he removed it. But after removing the DLC, the patient developed a sudden onset of breathlessness and chest pain. She was evaluated urgently and found to have severe hypotension with blood pressure 62/38 mm of Hg and SpO2 -74%.
Within minutes she became pulse less BP less. There was no access available and intracath insertion was not possible so urgent femoral central line was inserted and 500 ml bolus 0.9% NS was infused. Also 10 litre per minute of oxygen was started.
After that blood pressure came up to 92/74 mm of Hg and SPO2 -94%.
She was shifted to ICU setup after this.
So what are the possibilities that led to this emergency.
- Acute coronary syndrome
- Cerebrovascular accident(Stroke)
- Air embolism
- Post dialysis hypotension
DISCUSSION
An air embolism, also known as a gas embolism, is a blood vessel blockage caused by one or more bubbles of air or other gas in the circulatory system. Air embolism is an uncommon, but potentially catastrophic, event that occurs as a consequence of the entry of air into the vasculature.
Generally, small amounts of air are broken up in the capillary bed and absorbed from the circulation without producing symptoms. Traditionally, it has been estimated that more than 5 mL/kg of air displaced into the intravenous space is required for significant injury (shock or cardiac arrest) to occur.
2 or 3 mL of air into the cerebral circulation can be fatal, as little as 0.5 mL of air in the left anterior descending coronary artery has been shown to cause ventricular fibrillation, the closer the vein of entrainment is to the right heart, the smaller the lethal volume is.
SIGNS AND SYMPTOMS
Symptoms depend on the amount, speed, and site of introduced air, as well as the patient’s position.Tiny amounts of air in the bloodstream (microbubbles) may act like blood clots in patients’ organs.
Sitting Position-Venous Emboli in Cerebral Circulation
- Seizure, coma
Supine Position
- Impaired right ventricular function (decreased cardiac output and hypotension).
- Microemboli to pulmonary vasculature (dyspnea, dry cough, chest tightness or pain, hypoxia, respiratory failure).
- Sudden cardiac arrest (>50 mL).
Left Trendelenburg Position
- Lower extremity venous occlusion and arterial ischemia from increased outflow resistance.
CAUSE
It can be venous or less commonly, arterial. There are four vulnerable areas of air entry in dialysis patients:
- Between patient and blood pump (It can be through Arterial needle, Pre-pump arterial tubing segment (sampling port), Open venous catheter) due to high negative pressure and leaks in the circuit in this segment.
- Heparin line.
- Air in the dialysate fluid (uncommon, mostly gets trapped in the venous chamber). Very cold dialysate that releases a large amount of dissolved air when it is warmed.
- During central venous catheter insertion or removal. Upright body position and hypovolemia both reduce venous pressure and are significant contributing factors.
ACUTE MANAGEMENT
Clamp venous blood line.
Stop the blood pump.
Raise the patient’s feet above his/her head. (Trendelenburg position).
Monitor and stabilize vital signs. Attach a normal saline line to the arterial cannula or start a new IV for medicines. Give saline, if the patient is hypotensive.
Cardiovascular support (Give oxygen (8 L–10 L), Endotracheal intubation, Mechanical ventilation).
Do an ECG.
Aspirate air from the right ventricle using a percutaneously inserted needle.
PREVENTION
Secure all blood circuit connections.
Verify that catheters are clamped if the cap must be removed.
Inspect the venous bloodline for air before you connect it to the access.
Double clamp the saline line/all stagnant lines.
Keep the blood pump speed to a rate the access can deliver, so air is not pulled in.
Perform good priming of an extracorporeal circuit including dialyzer (there should be no residual air bubbles).
Avoid the use of the arterial line during dialysis for additional infusions.
During removal of dialysis catheter from neck veins, ask the patient to hold breath and strictly say no to breath in and also ask to avoid coughing.
Check the dialysis machine’s air detector.
Look at the venous bloodline from the air detector to the patient before you override an air alarm.
AIR DETECTOR: PREVENTS AIR EMBOLISM
Air detectors are devices that check for changes in a sound wave or light reflection sent through a cross-section of the blood path.
Two types of air-foam detectors are in use
- Ultrasonic
- Reflected light detectors
Ultrasonic type is currently being used in all new machines. Sound travels faster through air than liquid. Therefore, any air in the blood will raise the speed at which the sound wave passes through the blood, setting off an alarm.
The venous air trap and detector are very important for patient safety. The chamber traps any air that may have entered the blood line before the blood is returned to the patient.
Usually a level/air detector is placed around the top of the drip chamber; any increase in air (resulting in the drop of blood level) triggers an alarm. The power supply to the pump is then cut off and dialysis stops.
An additional safety device is a powerful clamp below the drip chamber through which the blood tubing returning the blood to the patient passes, and which is activated by the presence of air in the blood tubing. When activated, the clamp snaps shut and the blood pump is stopped; any air/blood mixture that may be present in the blood line is thereby prevented from passing back into the patient.
Article Courtesy – Dr. Jigar Shrimali
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