What is THAM and How Does it Work?
Tromethamine (THAM) is an alkalinizing agent designed to treat metabolic acidosis, a condition where the blood becomes too acidic, often due to underlying critical illnesses like sepsis, respiratory failure, or cardiac arrest.
Mechanism of Action: THAM acts as a proton acceptor. It binds with hydrogen ions (H+), a key component of acid, to produce bicarbonate. This helps neutralize excess acid, restoring blood pH to normal levels (7.35-7.45) [1,2]. Unlike sodium bicarbonate, THAM does not produce carbon dioxide, making it suitable for patients with impaired respiratory function [2,3].
Osmotic Diuretic: THAM also acts as a mild diuretic, encouraging the kidneys to excrete excess acid through urine. This dual mechanism helps manage metabolic acidosis more comprehensively [1,2].
When is THAM Used?
THAM is typically employed in scenarios where traditional options, like sodium bicarbonate, are less effective or contraindicated. Common indications include:
- Severe metabolic acidosis unresponsive to standard treatments.
- Acidosis associated with cardiac bypass surgery or cardiac arrest [2].
- Situations where sodium loading (from bicarbonate) must be avoided, such as in fluid-overloaded or hypernatremic patients [2].
- Cases involving renal or respiratory compromise where carbon dioxide retention from bicarbonate could exacerbate the condition [2,3].
How is THAM Administered?
THAM is administered intravenously, preferably via a central line to minimize the risk of tissue damage (extravasation). Dosage is carefully calculated based on body weight and the severity of acidosis [1,2]:
Dose (mL) = Body Weight (kg) x Base Deficit (mEq/L) x 1.1
It is crucial to administer slowly (over at least 1 hour) to reduce adverse effects such as hypoglycemia or fluid overload [2].
The pH of THAM is 8.6, because of which must be kept in a glass container [5].
Advantages of THAM Over Sodium Bicarbonate
Avoids Carbon Dioxide Production: Unlike sodium bicarbonate, THAM does not generate carbon dioxide as a byproduct, reducing the risk of respiratory acidosis, particularly in patients with compromised ventilation [3,5].
Remember that when Sodium Bicarbonate is administered it is converted to Carbonic acid, which ultimately is converted to CO2 and H2O [3].
Sodium-Free: THAM does not introduce additional sodium into the bloodstream, making it a safer option for patients with hypernatremia or fluid overload [1,3].
Enhanced Intracellular Buffering: THAM’s ability to penetrate cells allows it to correct intracellular acidosis more effectively than sodium bicarbonate, which primarily acts in the extracellular space [3].
Improved Use in Hypercapnic Conditions: By lowering partial pressure of carbon dioxide (PaCO2), THAM is particularly advantageous in hypercapnic respiratory failure [1,4].
Key Side Effects to Watch For
While THAM is effective, it’s not without risks. Here are the major side effects and how to monitor for them:
Hypoglycemia (Low Blood Sugar): THAM can lower blood glucose levels, especially if given rapidly or in large doses [1,2].
- Monitor: Check blood glucose levels before, during, and after administration.
- Action: Be prepared to administer dextrose if hypoglycemia develops.
Fluid Overload: Rapid infusion or high doses can lead to overhydration, pulmonary edema, or congestive states [1,2].
- Monitor: Assess fluid status and watch for signs of respiratory distress or worsening edema.
Hyperkalemia (High Potassium): Impaired excretion in patients with kidney dysfunction can lead to elevated potassium levels [1].
- Monitor: Regularly check serum potassium levels.
Respiratory Depression: Excessive doses can raise blood pH too high, reducing the drive to breathe [1,2].
- Monitor: Ensure proper ventilation, especially in non-intubated patients.
Vesicant Properties: Extravasation can cause severe tissue damage [2].
- Prevention: Use a central line or a large peripheral vein with careful placement.
THAM in Action
Presenting Information
65yo Female; 50kg
Hx:
- Chron’s Disease
- Hyperlipidemia
- Pancytopenia
Chief Complaint:
Presented to the ER for nausea, vomiting, fever, and fatigue. Concern for Pneumocystis Jiroveci Pneumonia (PJP) due to long term steroid use for Chron’s disease. Pt’s was hypoxic and respiratory status decreased until pt was ultimately intubated.
Assessment:
Neuro
- Pupils equal and reactive; 3mm
- Sedated with Fentantyl and Propofol
- Unresponsive; RASS -5
Cardiovascular
- Normal Sinus Rhythm
- Radial pulses +2; Dorsalis Pedis +1
- Capillary refill 2-4 seconds
- Afebrile; 36.9 C
- Edema noted in lower extremities
Respiratory
- Intubated; 8.0mm ETT at 24cm
- Breath sounds diminished
- Ventilator assisted breaths
Ventilator Settings
- Volume control/ Assist control
- FiO2- 85%
- Peep- 11 cmH20
- Tidal Volume- 400 ml
- Respiratory Rate- 18 bpm
- Minute Ventilation- 7.2 Lpm
- Peak Inspiratory Pressure- 24 cmH20
Current Infusions:
- Propofol- 50 mcg/kg/min
- Fentanyl- 300 mcg/hr
- Levophed- 0.09 mcg/kg/min
- D5 NS -75 ml/hr
Critical Care Transport Crew arrived and placed the pt on their monitor. They placed in-line end tidal CO2 (EtCO2) on the ETT which read 33 mmHg. The crew placed the patient on their ventilator and matched the OSH’s ventilator settings.
Transport Ventilator Settings:
- Volume control/ Assist control
- FiO2- 85%
- Peep- 11 cmH20
- Tidal Volume- 400 ml
- Respiratory Rate- 18 bpm
- Minute Ventilation- 7.65 Lpm
- Peak Inspiratory Pressure- 25 cmH20
The crew noticed the EtCO2 was increasing, currently 44 mmHg prompting them to draw an ABG.
- pH-7.03
- PaCO2- 65
- PaO2- 82
- HCO3- 16
Based on the uncompensated mixed acidosis, they slowly increased the respiratory rate to 28. As the respiratory rate increased, the EtCO2 was slowly decreasing to 35 mmHg.
Adjusted Ventilator Settings
- Volume control/ Assist control
- FiO2- 85%
- Peep- 11 cmH20
- Tidal Volume- 400 ml
- Respiratory Rate- 28 bpm
- Minute Ventilation- 11.2 Lpm
- Peak Inspiratory Pressure- 29 cmH20
- Autopeep- 2 cmH2O
The crew performed a repeat ABG.
- pH-7.14
- PaCO2- 47
- PaO2- 86
- HCO3- 16
Based on the persistent uncompensated metabolic acidosis, the crew decided to administer THAM. Per their protocol, 500ml of THAM was administered over 1hr.
After the THAM infusion was completed, the flight crew performed a repeat ABG.
- pH-7.24
- PaCO2- 45
- PaO2- 82
- HCO3- 17
The administration of THAM allowed for improved patient acid/base balance and safer transport. The pt was safely dropped off in the ICU and continued to receive care.
Contact US
Help up improve the Crit Bit Corner. Follow the link below to help us improve the newsletter or suggest future Crit Bit topics!
References
- Clinical Guideline: Management of Adult Patients with Acute Alveolar Injury or Disease (ARDS). Revised May 2024.
- Tromethamine (THAM): Drug Information. UpToDate. Updated January 2025.
- EMCrit 380: Tris-Hydroxymethyl Aminomethane (THAM) for Acidosis. Published July 2024.
- Planta M, et al. Effects of Tromethamine and Sodium Bicarbonate Buffers During Cardiac Resuscitation. J Clin Pharmacol. 1988;28:594-599.
- Pfizer. Tham Solution Package Insert. Updated February 2020.
Credits:
Created with images by Matt Gush - "An ambulance races to respond to the scene of an emergency." • KL 1981 - "Emergency Medical First aid kit bags of first aid team service for an accident in work of worker loss of function in limbs, First aid training to transfer patient" • hedgehog94 - "Emergency medical service at work.,Paramedic is pulling stretcher with senior man with serious heart attack to the ambulance car.,Help on the road.,Drivers assistance concept." • Gorodenkoff - "Team of EMS Paramedics React Quick to Bring Injured Patient to Healthcare Hospital and Get Him Out of Ambulance on a Stretcher.,Emergency Care Assistants Help Young Man to Stay Alive After Accident." • Peakstock - "Cardiac monitoring on stroke female patient hospitalized in intensive care unit.,Neurovascular unit" • Matt Gush - "An ambulance races to respond to the scene of an emergency."