Abstract
Background:
We previously reported in a small case series that THAM improves acid-base balance in severe ARDS complicated by profound acidosis, whereas sodium bicarbonate therapy resulted in acute deterioration in arterial blood gases (ABG). 1 THAM's effectiveness is attributable to its high pK (7.8), direct binding of CO2 without producing CO2 and renal excretion that obviates increasing minute ventilation (VE); thus making THAM a useful buffer for LPV. THAM was our buffer of choice until its availability in the United States ceased in 2016. This summary describes our use of THAM during LPV over the last 10 years of the drugs availability.
Methods:
The SFGH ARDS quality assurance database tracks LPV practices and was queried to identify subjects treated with THAM. From September 2006-August 2016, 97 subjects were identified, of whom 82 met inclusion criteria: 1) standard bolus infusion of at least 1 full dose of THAM (150 mmol), 2) pre/post ABGs done < 4 h of therapy initiation/completion respectively, and 3) no adjustments in either VE or tidal volume (VT). Data are presented as median [IQR]. Paired comparisons were made using the Wilcoxon Signed-Rank Test. Alpha was set at 0.05.
Results:
A total of 143 discreet treatments met inclusion criteria. Infusion of THAM at 2.04 [1.61, 2.36] mmol/kg/h over 60 [60, 60] min, significantly increased arterial pH and bicarbonate (HCO3); decreased arterial carbon dioxide tension (PaCO2), base deficit (BD), and anion gap (Table). These changes occurred despite extraordinarily elevated dead-space fraction of 0.80 [0.72, 0.85]. Oxygenation was unaffected.
Conclusions:
This study confirms our previous findings that THAM improves pH and lowers PaCO2 without alterations in VE. Decreased PaCO2 is attributable to THAM's capacity to directly bind CO2 with subsequent renal excretion (or removal during dialysis). These properties make THAM a useful buffer to maintain LPV in ARDS complicated by severe acidosis and markedly elevated dead-space.
1. Kallet RH, Jasmer RM, Luce JM, et al. The treatment of acidosis in acute lung injury with tris-hydroxymethyl aminomethane (THAM). Am J Respir Crit Care Med 2000;161:1149-1153.
PBW = predicted body weight View all access options for this article.
Pre-THAM
Post-THAM
P
pH
7.17 [7.08,7.21]
7.22 [7.16,7.28]
<0.001
PaCO2 (mm Hg)
50 [39,62]
47 [38,58]
<0.001
HCO3 (mEq/L)
17.8 [13.3,22.9]
19.1 [15.5,24.8]
<0.001
BD (mEq/L)
11.5 [16.9,5.5]
8.5 [13.2,2.3]
<0.001
Anion Gap (mEq/L)
16.2 [11.8,24.9]
14.8 [10.8,20.8]
<0.001
VE (L/m)
14.5 [12.3,17.2]
14.4 [12.0,17.2]
0.86
VT (mL/kg PBW)
7.2 [6.1,8.1]
7.2 [6.1,8.1]
0.15
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