Perioperative Anaphylaxis Diagnosis and Management

Protocol for Tryptase Sampling

The American College of Anesthesiologists recommends obtaining serum tryptase immediately upon suspicion of perioperative anaphylaxis, following a protocol of three samples: during initial resuscitation, 1-2 hours after symptom onset, and at 24 hours or during convalescence to establish a baseline level 1
The first sample should be obtained as soon as possible during resuscitation, without delaying epinephrine treatment, and should include 5-10 mL of clotted blood 1
The second sample should be obtained between 30 minutes and 2 hours after symptom onset, as tryptase levels peak approximately 1 hour after anaphylaxis and have a half-life of 2 hours 2, 3
The third sample, obtained at 24 hours or during convalescence, is crucial for establishing a baseline level, as approximately 5-7% of the population has elevated baseline tryptase levels unrelated to anaphylaxis 1, 5, 6

The British Society of Anaesthetists recommends that an increase in acute tryptase levels greater than 1.2 times the baseline level plus 2 μg/L be considered clinically significant 5, 6
The variation from baseline is more useful than the absolute concentration for diagnosis, and a normal value does not rule out anaphylaxis 7, 8, 2

The Anaesthesia society notes that tryptase has limited sensitivity, as anaphylaxis can occur through basophil or complement activation, which does not elevate mast cell tryptase 7, 2, 8
The current assay has high specificity but relatively low sensitivity, and anaphylaxis should never be ruled out based solely on normal tryptase levels 7, 3
Factors such as IV fluid resuscitation can dilute blood and reduce measured tryptase concentrations, which should be considered when evaluating results in patients who received fluid resuscitation 7, 8, 3

The British Journal of Anaesthesia recommends that all samples be labeled with the exact time and date of collection to interpret tryptase kinetics correctly and determine if the sample was obtained within the optimal diagnostic window 1, 2, 3
The primary purpose of tryptase measurement is to confirm mast cell degranulation and help rule out or confirm mast cell disorders 5, 6
Elevated tryptase levels are associated with the severity of the reaction, and post-mortem tryptase measurement can be useful in suspected anaphylaxis-related deaths, although it has lower predictive value than samples taken during life 7, 5, 6