ORIGINAL ARTICLE. Abstract. Introduction. Materials and Methods

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1 ORIGINAL ARTICLE Effects of Cardiac Hemodynamics on Agreement in the ph, HCO3- and Lactate Levels between Arterial and Venous Blood Samples in Patients with Known or Suspected Chronic Heart Failure Satoshi Kurisu, Noriaki Watanabe, Hiroki Ikenaga, Tadanao Higaki, Takashi Shimonaga, Toshitaka Iwasaki, Ken Ishibashi, Yoshihiro Dohi, Yukihiro Fukuda and Yasuki Kihara Abstract Objective Analyses of arterial blood gas parameters, including ph, HCO3- and lactate, play an important role in assessing the clinical status of patients with heart failure. In the present study, we evaluated the degree of agreement in the ph, HCO3- and lactate levels between arterial and venous blood samples according to the subset of the Forrester classification. Methods The study population consisted of 128 patients with known or suspected heart failure. The subjects were divided into four groups based on the Forrester classification. Arterial blood samples were drawn from the radial or brachial artery, and venous blood samples were drawn from the pulmonary artery. Results There were 59 patients with a Forrester subset I status, 32 patients with a subset II status, 21 patients with a subset III status and 16 patients with a subset IV status. The ph and HCO3- levels were similar between the four subsets. In all subsets, the ph values were significantly higher and the HCO3- values were significantly lower in the arterial blood samples than in the venous blood samples. There was good correlation and agreement in the ph and HCO3- levels between the arterial and venous blood samples. In contrast, there was a significant difference in the lactate levels in both the arterial and venous blood samples between the four subsets, and the lactate levels were highest in subset IV. In all subsets, there was good correlation and agreement in the lactate levels between the arterial and venous blood samples. Conclusion These data suggest that the venous ph, HCO3- and lactate levels are acceptable substitutes for arterial parameters, regardless of the cardiac hemodynamics. Key words: heart failure, blood gas, lactate, agreement () () Introduction Analyses of arterial blood gas parameters, including the ph, HCO3- and lactate levels (1-4), as well as pulmonary artery catheterization (5), play an important role in determining the clinical status of patients with heart failure. The arterial values are the standard criteria (6); however, it is not always practical to obtain arterial blood samples. Previous studies have shown that arterial values correlate well with peripheral, mixed or central venous values (1-4). In the present study, we retrospectively evaluated the degree of agreement in the ph, HCO3- and lactate levels between arterial and venous blood samples for each subset of the Forrester classification (7, 8). Patients Materials and Methods The study population consisted of 128 patients with known or suspected heart failure admitted to Hiroshima Uni- Department of Cardiovascular Medicine, Hiroshima University Graduate School of Biomedical and Health Sciences, Japan Received for publication August 27, 2014; Accepted for publication December 21, 2014 Correspondence to Dr. Satoshi Kurisu, skurisu@nifty.com 1841

2 Table 1. Patient Characteristics. Number of patients 128 Male gender 76 (59%) Age (years) 68.2±12.6 NYHA classification Functional class I or II 78 (61%) Functional class III or IV 50 (39%) Systolic blood pressure (mmhg) 127.5±22.7 Heart rate (bpm) 70.7±13.6 Pulmonary capillary wedge pressure (mmhg) 15.7±7.8 Cardiac index (L/min 2 ) 2.67±0.77 Arterial blood sample ph 7.43±0.03 O 2 (mmhg) 87.7±16.4 CO 2 (mmhg) 37.9±4.6 HCO - 3 (mmol/l) 25.2±2.2 Base excess (mmol/l) 1.26±2.17 Lactate (mmol/l) 0.77±0.32 Venous blood sample ph 7.40±0.03 O 2 (mmhg) 39.4±5.3 CO 2 (mmhg) 43.1±5.5 HCO - 3 (mmol/l) 26.2±2.3 Base excess (mmol/l) 1.96±2.07 Lactate (mmol/l) 0.74±0.31 Difference between arterial and venous blood samples ph 0.03±0.02 HCO - 3 (mmol/l) -1.0±1.2 Lactate (mmol/l) 0.03±0.09 Arterial blood samples were drawn from the radial or brachial artery for measurement of ph, gases, HCO3-, base excess and lactate. As close to simultaneously as possible, venous blood samples were drawn from the pulmonary artery for measurement of the cardiac output according to the Fick method. The ph, HCO3- and lactate levels in the venous blood samples were also obtained. The blood was drawn into blood gas syringes, and the samples were analyzed as soon as possible after collection using the same blood gas analyzer (Radiometer ABL 700). Statistical analysis All data are expressed as the mean ± SD. An analysis of variance was performed to test for differences among values between the four groups. The Student s paired t-test was used to evaluate differences in the ph, HCO3- and lactate levels between the arterial and venous blood samples in each group. Pearson s correlation coefficient and a regression analysis were used to evaluate the correlations between two samples, and Bland-Altman plots were applied to assess the degree of agreement between two samples. Differences were considered to be significant for p values of <0.05. Results Patient characteristics versity Hospital in the period from April 2010 to March All patients had clinical signs and/or symptoms suggestive of heart failure and underwent pulmonary artery catheterization in stable condition. Individuals treated with inotropic agents were excluded from this study, as were patients with renal insufficiency (serum creatinine >2.0 mg/ dl), acute coronary syndrome or cardiogenic shock. The study protocol was approved by the institutional ethics committee, and written informed consent was obtained from all patients. Cardiac hemodynamics A 5-Fr Swan-Ganz thermodilution catheter was inserted percutaneously via the internal jugular vein and positioned in the pulmonary artery. Hemodynamic measurements were obtained, including the pulmonary artery pressure, right atrial pressure and pulmonary capillary wedge pressure (PCWP). Cardiac output was determined via thermodilution as well as the Fick method (9). The cardiac output derived using the thermodilution method was divided by the body surface area to obtain the cardiac index (CI). The patients were classified into the following four groups according to the Forrester classification (7, 8): (1) subset I, PCWP <18 and CI 2.2; (2) subset II, PCWP 18 and CI 2.2; (3) subset III, PCWP <18 and CI <2.2; and (4) subset IV, PCWP 18 and CI <2.2. Blood samples The patient characteristics are summarized in Table 1. There were 76 men and 52 women, with a mean age of 68.2±12.6 years. The systolic blood pressure and heart rate were 127.5±22.7 mmhg and 70.7±13.6 bpm, respectively, and the PCWP and CI values were 15.7±7.8 mmhg and 2.67±0.77 L/min, respectively. The ph (p<0.01) and lactate (p<0.01) levels were significantly higher and the HCO3- levels (p<0.01) were significantly lower in the arterial blood samples than in the venous blood samples. The differences in the ph, HCO3- and lactate levels between the arterial and venous blood samples were 0.03, -1.0 mmol/l and 0.03 mmol/l, respectively. There was good correlation in the ph (r=0.82, p<0.01), HCO3- (r=0.87, p<0.01) and lactate (r= 0.96, p<0.01) levels between the arterial and venous blood samples. Effects of cardiac hemodynamics on the correlations and degree of agreement There were 59 patients with a Forrester subset I status, 32 patients with a subset II status, 21 patients with a subset III status and 16 patients with a subset IV status (Table 2). The ph and HCO3- levels were similar between the four subsets. In all subsets, the ph levels were significantly higher and the HCO3- levels were significantly lower in the arterial blood samples than in the venous blood samples. The differences in the ph and HCO3- levels between the arterial and venous blood samples were minimal but manifest in all subsets, especially in subset IV. In all subsets, there was good correlation and agreement in the ph (Fig. 1, 2) and HCO3- (Fig. 3, 4) levels between the arterial and venous blood samples. 1842

3 Table 2. Arterial and Venous Blood Samples in 4 Groups Stratified According to Cardiac Hemodynamics. Subset I Subset II Subset III Subset IV p value (n=59) (n=32) (n=21) (n=16) Male gender 34 (58%) 19 (59%) 15 (71%) 8 (50%) ns Age (years) 67.7± ± ± ±18.8 ns Systolic blood pressure (mmhg) 128.2± ± ± ±32.4 ns Heart rate (bpm) 73.1± ±12.4* 66.4±16.3* 76.2±8.0 <0.05 Pulmonary capillary wedge pressure (mmhg) 11.0± ±4.2** 10.7± ±9.3** <0.01 Cardiac index (L/min 2 ) 2.91± ±0.77* 1.90±0.18** 1.82±0.22** <0.01 Arterial blood sample ph 7.43±0.03## 7.44±0.03## 7.44±0.03## 7.45±0.04## ns O 2 (mmhg) 85.7± ± ± ±14.6 ns CO 2 (mmhg) 38.7± ± ± ±5.5 ns HCO - 3 (mmol/l) 25.3±2.0## 25.1±2.5## 24.8±1.8## 25.2±3.0## ns Base excess (mmol/l) 1.28± ± ± ±2.60 ns Lactate (mmol/l) 0.67± ±0.33** 0.83±0.26*# 0.93±0.38**# <0.05 Venous blood sample ph 7.40± ± ± ±0.03 ns O 2 (mmhg) 40.8± ± ±3.9** 33.9±2.9** <0.01 CO 2 (mmhg) 43.7± ± ± ±5.5 ns HCO - 3 (mmol/l) 26.1± ± ± ±3.2 ns Base excess (mmol/l) 1.86± ± ± ±2.54 ns Lactate (mmol/l) 0.66± ±0.30* 0.79± ±0.37** <0.01 Difference between arterial and venous blood samples ph 0.03± ± ±0.02* 0.04±0.02** <0.05 HCO - 3 (mmol/l) -0.8± ± ± ±1.3** <0.01 Lactate (mmol/l) 0.01± ± ± ±0.09 ns * p<0.05, **p<0.01 vs. subset I # p<0.05, ##p<0.01 vs. venous blood sample There was a significant difference in the lactate levels in both the arterial and venous blood samples between the four subsets, and the lactate levels were highest in subset IV. The differences in the lactate levels between the arterial and venous blood samples were similar between the four subsets. In all subsets, there was good correlation and agreement in the lactate levels between the arterial and venous blood samples(fig.5,6). Discussion The current study showed good correlation and agreement in the ph, HCO3- and lactate levels between arterial and venous blood samples, regardless of the cardiac hemodynamics, in patients with known or suspected heart failure. Assessing the levels of ph, HCO3- and lactate plays an important role in determining the clinical status of critically ill patients. Analyses of arterial blood samples constitute the standard method for assessing these variables. However, arterial puncture is painful and sometimes associated with vascular complications. Several studies have evaluated whether venous blood samples may be used as alternatives to arterial blood samples. Regarding ph and HCO3-, the differences in these values between arterial and venous blood samples have been reported to range from to 0.04 (1, 2) and to 0.52 (3, 4), respectively. In the current study, these differences were minimal and within the ranges noted in previous reports, indicating that the venous ph and HCO3- levels are in sufficient agreement with the arterial ph and HCO3- levels to be acceptable alternatives. Measurements of single, peak and/or serial blood lactate levels are used to assess the peripheral circulatory status, predict mortality and guide resuscitation (10-12). Middleton et al. measured the arterial and central venous lactate levels in patients requiring intensive care and showed that the venous lactate values were in sufficient agreement with the arterial lactate values (3). In addition, Mikami et al. measured the arterial and peripheral venous lactate levels in emergency patients and obtained similar results (13). In the current study, the differences in the lactate levels were also minimal, and there was good correlation and agreement between the arterial and venous blood samples. Low cardiac output is a condition involving inadequate tissue perfusion that results in increased anaerobic metabolism and lactate production as a consequence of regional hypoxia. Several clinical studies have shown the usefulness of the lactate level as a diagnostic, therapeutic and prognostic marker in patients with acute circulatory failure or an advanced Killip class status. In the present study, the lactate levels were higher in the patients with worse cardiac hemodynamics and the arterial lactate levels correlated well with the venous lactate levels, regardless of cardiac hemodynamics, in the patients with known or suspected heart failure. These results suggest that the venous lactate levels may be used in place of the arterial lactate levels serially as a therapeutic marker for assessing the clinical status in patients undergoing pulmonary artery catheter placement. There are several limitations associated with the current study. First, this study included only patients in stable condition and excluded those with renal insufficiency, acute 1843

4 Figure 1. Correlations in ph between the arterial and venous blood samples in the four subsets according to the Forrester classification. Figure 2. Agreement in ph between the arterial and venous blood samples in the four subsets. coronary syndrome or cardiogenic shock. Second, only 25 of the 128 patients had an arterial lactate level of >1.0 mmol/l, and we were unable to fully assess the correlation with high lactate levels. Third, venous blood samples drawn from the pulmonary artery are not necessarily representative of peripheral venous samples. Finally, the small sample size, especially in subsets III and IV, is a major limitation of this study. Further studies are required to clarify the effects of 1844

5 Figure 3. Correlations in the HCO3- levels between the arterial and venous blood samples in the four subsets. Figure 4. Agreement in the HCO3- levels between the arterial and venous blood samples in the four subsets. inotropic agents in patients in unstable condition. In conclusion, the present data suggest that the venous ph, HCO3- and lactate levels are acceptable substitutes for the corresponding arterial parameters, regardless of cardiac hemodynamics. 1845

6 Figure 5. Correlations in the lactate levels between the arterial and venous blood samples in the four subsets. Figure 6. Agreement in the lactate levels between the arterial and venous blood samples in the four subsets. The authors state that they have no Conflict of Interest (COI). References 1. Gokel Y, Paydas S, Koseoglu Z, Alparslan N, Seydaoglu G. Com- 1846

7 parison of blood gas and acid-base measurements in arterial and venous blood samples in patients with uremic acidosis and diabetic ketoacidosis in the emergency room. Am J Nephrol 20: , Ma OJ, Rush MD, Godfrey MM, Gaddis G. Arterial blood gas results rarely influence emergency physician management of patients with suspected diabetic ketoacidosis. Acad Emerg Med 10: , Middleton P, Kelly AM, Brown J, Robertson M. Agreement between arterial and central venous values for ph, bicarbonate, base excess, and lactate. Emerg Med J 23: , Ak A, Ogun CO, Bayir A, Kayis SA, Koylu R. Prediction of arterial blood gas values from venous blood gas values in patients with acute exacerbation of chronic obstructive pulmonary disease. Tohoku J Exp Med 210: , Zion MM, Balkin J, Rosenmann D, et al. Use of pulmonary artery catheters in patients with acute myocardial infarction. Analysis of experience in 5,841 patients in the SPRINT Registry. SPRINT Study Group. Chest 98: , Shirakabe A, Hata N, Kobayashi N, et al. Clinical significance of acid-base balance in an emergency setting in patients with acute heart failure. J Cardiol 60: , Ganz W, Donoso R, Marcus HS, Forrester JS, Swan HJ. A new technique for measurement of cardiac output by thermodilution in man. Am J Cardiol 27: , Forrester JS, Ganz W, Diamond G, McHugh T, Chonette DW, Swan HJ. Thermodilution cardiac output determination with a single flow-directed catheter. Am Heart J 83: , Venkataraman K, De Guzman MF, Hafeez Khan A, Haywood LJ. Cardiac output measurement: a comparison of direct Fick, dye dilution and thermodilution methods in stable and acutely Ill patients. J Natl Med Assoc 68: , Cowan BN, Burns HJ, Boyle P, Ledingham IM. The relative prognostic value of lactate and haemodynamic measurements in early shock. Anaesthesia 39: , Astiz ME, Rackow EC. Assessing perfusion failure during circulatory shock. Crit Care Clin 9: , Lazzeri C, Valente S, Chiostri M, Picariello C, Gensini GF. Lactate in the acute phase of ST-elevation myocardial infarction treated with mechanical revascularization: a single-center experience. Am J Emerg Med 30: 92-96, Mikami A, Ohde S, Deshpande GA, Mochizuki T, Otani N, Ishimatsu S. Can we predict arterial lactate from venous lactate in the ED? Am J Emerg Med 31: , The Japanese Society of Internal Medicine