REVIEW ARTICLE 혈역학감시의일반적원칙 연세대학교원주의과대학외과학교실 권혜연ㆍ장지영ㆍ배금석ㆍ심홍진 General Principles in Hemodynamic Monitoring Hye Youn Kwon, M.D., Ji Young Jang, M.D., Keum Seok Bae, M.D., Ph.D., Hongjin Shim, M.D. Department of Surgery, Yonsei University Wonju College of Medicine, Wonju, Korea Correspondence to: Hongjin Shim, M.D. Trauma and Surgical Critical Care, Department of Surgery, Yonsei University Wonju College of Medicine, 20 Ilsan-ro, Wonju 26426, Korea Tel: +82-31-741-0990 Fax: +82-31-741-0574 E-mail: simong3@yonsei.ac.kr Hemodynamic monitoring continuously checks hemodynamic variables for problems so that the clinician can treat them when a patient s vital signs are unstable. There are many different monitoring systems, and many new technologies were developed over the past three decades. It is challenging to understand the many monitoring system in the intensive care units, for example. However, all such monitoring systems are based on the general principle of monitoring oxygen transport to a peripheral organ. In this review, from conventional to recent principles, general concepts and paradigm shifts of hemodynamic monitoring will be discussed. (J Acute Care Surg 2017;7:2-8) Key Words: Hemodynamic monitoring, Intensive care units Received September 19, 2016, Revised April 12, 2017, Accepted April 14, 2017 Copyright 2017 by Korean Society of Acute Care Surgery cc This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. ISSN 2288-5862(Print), ISSN 2288-9582(Online) https://doi.org/10.17479/jacs.2017.7.1.2 서론 혈역학적감시 (hemodynamic monitoring) 란혈역학적불안정성을보이는중증환자에서진단과치료를목적으로혈역학지표들을지속적으로확인하는것을말한다 [1]. 혈압, 맥박수, 중심정맥압 (central venous pressure, CVP), 말초산소포화도등의기본적인방법부터일회박출량변동 (stroke volume variation, SVV), 맥박압변동 (pulse pressure variation, PPV), 심초음파 (echocardiography), 비침습적생체임피던스 (bioimpedence) 등다양한방법들이혈역학적감시에이용되고있다. 외상및패혈증등의중증환자에서산소의공급과전달, 소비가적절히이루어지도록하는것이치료의궁극적인목적이므로이를파악하기위해산소전달의시작점이되는심폐기능과산소전달의매개가되는혈장량, 그리고 말초에서산소의교환이이루어지는관류 (perfusion), 이세가지가모두감시의대상이되어야한다. 과거에는폐동맥카테터 (pulmonary artery catheter, PAC) 와같은침습적방법이심박출량및호흡기능을평가하는데주로사용되었다면, 현재는비침습적방법들이선호되고있는데최근이론적발달과기술적발전으로심폐기능뿐아니라혈장량및관류지표에있어서도유용하게평가받고있다. 본글에서는현재임상에서사용되는기본적인혈역학적감시방법의이론적인배경과원리에대해알아보고자한다. 2 J Acute Care Surg Vol. 7 No. 1, April 2017
Hye Youn Kwon, et al: Hemodynamic Monitoring 본론 혈압측정에서의동맥압파형 (arterial pressure waveform) 과평균동맥압 (mean arterial presure, MAP) 혈압은중환자의감시에가장기본이되는혈역학적지표로, 혈압의측정은비침습적혈압측정 (non-invasive blood pressure) 과동맥혈관에카테터삽입을통해지속적으로동맥혈압을측정할수있는침습적혈압감시방법이있다. 동맥혈관을이용한침습적혈압감시방법은비침습적인방법보다더정확한것으로알려져있으며중환자실에서주로사용되는방법이다. 지속적동맥혈압을보면일정한파형을볼수있는데이것을동맥압파형이라고한다. 이는측정부위에따라다르게나타나고심장위치에서의상완동맥압 (brachial arterial pressure) 이가장정확한것으로알려져있다. 동맥압파형은각절흔 (dicrotic notch) 을중심으로두부분으로나눌수있는데앞부분이심장의수축기파형을, 뒷부분이이완기파형을나타낸다. 동맥압파형은말초로이동할수록동맥이분지하면서직경이감소하여수축기압력이증가하고수축기파형부분이좁아진다. 최대수축기압력은증가하고수축기압파형이좁아지면서이둘이서로상쇄되어 MAP는일정한값을유지하게된다. MAP 는수축기와이완기의두가지요소를포함하고있기때문에중심대동맥압을좀더정확히대변한다고할수있고측정위치에상관없이일정하기때문에체순환을유지시키는근본적인힘으로 간주된다. MAP값을얻는방법은계산하는방법과측정하는방법, 두가지가있다. MAP 계산값 (= 이완기혈압 + ( 수축기혈압-이완기혈압 )) 은심장박동수가 60회 / 분이었을때이완기시간이심장박동의 3분의 2를차지하는것에근거하고있으므로중증환자에서심장박동수가 60회 / 분이상으로증가하는경우, 계산에의한 MAP보다는직접측정한값이더욱정확하다 [2]. 특별한장치없이일반적으로사용되는중환자실모니터에나타나는 MAP는계산된값이다. 심폐상호작용 (heart-lung interaction) 을이용한수액반응성의평가 1) 심폐상호작용흉강내의인접한기관인심장, 폐, 대동맥과대정맥은흉강내압의영향을같이받으며상호간에영향을미친다. 특히인공호흡을통해양압환기를받고있는중증환자의경우흉강내압의변화에따라복귀정맥혈과말초저항이변하기때문에이변화를통해환자의혈장량과수액반응성 (fluid response) 을예측할수있다. 흉강내압이상승하면우심장의관점에서는복귀정맥혈이감소하고후부하 (afterload) 가증가하지만, 좌심장의관점에서는복귀정맥혈이증가 (squeeze of pulmonary blood) 하고후부하는감소한다. 우심방의혈류량은좌심방에영향을미치기때문에호흡주기에따라동맥압과복귀정맥혈은일정한증감의흐름을 Fig. 1. The hemodynamic effects of positive pressure ventilation on heart-lung interactions. www.jacs.or.kr 3
J Acute Care Surg Vol. 7, No. 1, Apr. 2017 보이게된다 (Fig. 1) [3]. 이러한변화는 Frank-Starling의법칙에따라혈장량이충분할때에는잘나타나지않지만, 혈장량이부족하여전부하 (preload) 가감소한경우뚜렷이나타난다 (Fig. 2) [4,5]. 2) 일회박출량변동 (SVV) 과맥박압변동 (PVV) 앞서언급된바와같이심폐상호작용에의한혈역학적변화는 SVV를발생시키며이는혈역학적감시에서측정되는여러가지지표들즉, PPV, 최고대동맥혈류속도변동 (peak aortic blood flow velocity variation), 대정맥직경의호흡성변이 (respiratory variation of vena cava diameter) 등의이론적배경이된다. 이러한변화의정도를나타내는역동적지표들은 MAP나 CVP 등의정적인지표들에비해환자의합병증및사망률과더많은연관성을보인다 [1]. 동맥압파형에서보이는주기적인변화의폭을계산하여 PPV 를알수있는데 (Table 1, Fig. 3) [6], 이지표를통해혈관내혈장량이충분한지와, 수액공급을했을때나타나는혈역학적반응을예측할수있다. PPV는양압환기를시행하는환자에서적용하여야하며일회호흡량이적지않고 (<8 12 ml/kg), 자발호흡이없는규칙적인인공호흡환자에서정확한혈역학지표를나타낸다. 호흡수가너무빠르거나부정맥이있는환자, 복압이증가되어있는환자에서는정확도가낮은것으로보고된다 [3]. PPV의절단값 (cut off value) 은 13% 로, 이이상으로측정되는경우에는혈장량이충분하지않은것을의미하므로수액을공급의적응증이된다. 이외에도심폐상호작용을이용한혈역학적지표들은여러가지가있으며이중 PPV가가장신뢰도가높다 (Table 2) [4]. 3) 수액반응성혈장량에대한평가는조직의산소공급을위한기초적인평가 인데, 패혈증과같은중증환자에서수액의과다공급으로인한폐부종, 심부전과같은합병증을피하면서정확한수액효과를알아볼수있는좋은방법이수액반응성을평가하는것이다 [4,5]. 수액반응성은일반적으로수액유발 (fluid challenge) 을하였을때심박출량이나일회박출량이 10 11% 이상증가하는것으로정의된다. 수액반응성은심-폐상호작용에의한혈역학적변화에근거하며다음의몇가지검사를통해알아볼수있다. (1) 수동적하지거상법 (passive leg raising test): 수동적하지거상법은수액반응성을평가하기위해임상에서가장많이사용되고있는방법으로 semi-fowler 자세를앙와위자세로변경한후하지를 45도올리는검사이다. 이런자세의변경은하지와복강의혈장액을흉강안으로들어가게하여일시적으로복귀정맥혈을증가시키는효과를가져온다. Frank-Starling 곡선에서수액투여후심장의전부하가의미있게증가하는군을수액반응군으로규정할때, 하지거상법은수액을투여하지않고수액반응군과비반응군을구별할수있는좋은방법이다. 하지거상법은심장박출지수가환자의기저치보다 10 11% 이상증가했을때수액 Table 1. How to measure PPV Check that cardiac rhythm is regular Raise the tidal volume to 10 ml/kg of predicted body weight Ensure that the patient is receiving ventilation passively or adjust further the rate, tidal volume, or degree of sedation to achieve this Display or pint the arterial pressure waveform for 30 s Measure the minimum and maximum pulse pressure Calculate PPV (PP max-pp min)/([pp max+pp min]/2) 100% A value 13% predicts fluid responsiveness Reproduced from the article of Durairaj and Schmidt (Chest 2008;133:252-63) [6]. PPV: pulse pressure variation, PP: pulse pressure, PP max: maximal PP, PP min: minimal PP, PP mean: mean PP. Fig. 2. Functional hemodynamic monitoring for assessing the Frank- Starling relationship in patients with spontaneous breathing activity and/or cardiac arrhythmias and/or low tidal volume and/or low lung compliance. PPV: pulse pressure variation, SVV: stroke volume variation, PLR: passive leg raising test, EEO: endexpiratory occlusion, VE: volume expansion. 4 www.jacs.or.kr
Hye Youn Kwon, et al: Hemodynamic Monitoring Fig. 3. Relationship of arterial pressure wave and passive respiration. PP max: maximal pulse pressure, PP min: minimal pulse pressure. Table 2. Predictable value of techniques used to determine fluid responsiveness Method Technology AUC a) Pulse pressure variation (PPV) Arterial waveform 0.94 (0.93 0.95) Systolic pressure variation (SPV) Arterial waveform 0.86 (0.82 0.90) Stroke volume variation (SVV) Pulse contour analysis 0.84 (0.78 0.88) Left ventricular end- diastolic area (LVEDA) Echocardiography 0.64 (0.53 0.74) Global end-diastolic volume (GEDV) Transpulmonary thermodilution 0.56 (0.37 0.67) Central venous pressure Central venous catheter 0.55 (0.48 0.62) Reproduced from the article of Marik et al. (Ann Intensive Care 2011;1:1) [4]. a) AUC: area under the curve with 95% confidence intervals. 반응이있는것으로정의한다. 8개임상연구를대상으로한메타분석에서정확성에대해보고하고있으며 [7] 경식도초음파와같은침습적측정방법을융합하여맥박압이아닌대동맥혈류량을직접측정하면자발호흡이있는환자에서도수액반응성을정확히예측할수있다 [8]. 하지만복압이 16 mmhg 이상으로증가되어있거나하지혈장용적이적은환자에서는정확하지않다. (2) 호기말호흡폐쇄법 (end-expiratory occlusion test): 호기말호흡폐쇄법은인공호흡을하는환자에서적용할수있는방법으로심장과폐의상호작용에의해발생하는복귀정맥혈의변화를최소화하기위해잠시호기말에인공호흡을중지하는방법이다 (Fig. 4). 맥박압과심장박출지수의증가를결과지표로하였을때역치 5% 에서각각 area under the curve 0.957, 0.972로정확한예측도를보였으며자발호흡이있는인공호흡환자에서도 PPV, SVV 를결과지표로하였을때높은민감도를보였다 [9]. (3) 최소수액유발검사 (mini fluid challenge): 최소수액유발검사는 100 ml의콜로이드를 1분동안투여하여적은수액으로최대용적확대효과를보려는방법으로경흉부심초음파를이용하여 sub-aortic velocity time index (SVT) 를측정한다. 10% 이상 SVT index가증가했을때민감도는 95%, 특이도는 78% 이다. 이검사는다량의수액이축적되지않고검사를여러번시행할수있다는장점이있지만측정장비를준비해야하는단점이 있다 [10]. 이상의수액반응성을평가하기위한방법들은모두심폐상호작용에의한혈역학변이에근거하고있기때문에정확한평가를위해각각의상황과적응증에맞는방법을적용하는것이필요하다 (Fig. 5). 혈역학적감시방법의종류현재임상에서사용하고있는혈역학적감시방법은여러가지가있는데, 침습적방법으로는식도 Doppler를이용하여하행대동맥의혈류량과혈류속도를측정하는 Cardio-Q R 와동맥내혈압감시장치인 PiCCO R 가있으며, 최소침습적동맥내혈압감시장치로는 Flotrac R, LiDCO R, ProAQT R 가있다. 비침습적방법으로 Doppler 초음파 USCOM R 과 non-invasive bioreactance measurements (NICOM R ), 손가락의커프를이용한 non-invasive continuous arterial blood pressure measurement (Nexfin R, Finapres R ) 등이있다. 최근에는침습적인방법보다는사용하기간편하고안전하게적용할수있는비침습적방법으로선호되는경향을보인다. 비침습적감시방법들의정확도는혈역학감시장치의기초라고할수있는 PAC와비교하였을때유사한결과를보이고있으나 [11] 아직대규모연구가부족하고경증환자를대상으로한연구가대부분이어서중증환자에서전적으로신뢰하기는어렵다. 또한비용-효율을고려하였을때일반적으로상용화하기 www.jacs.or.kr 5
J Acute Care Surg Vol. 7, No. 1, Apr. 2017 Fig. 4. End-expiratory occlusion test. The end-expiratory occlusion (EEO) test consists in interrupting mechanical ventilation at the end of expiration during 15 seconds. Fig. 5. Decision-making process of fluid administration. SVV: stroke volume variation. Table 3. Hemodynamic monitoring devices for the perioperative setting Device Technique Invasive Continuous measurements SV/CO SVV PPV Ward Cardio-Q R Doppler + + + - - - PiCCO R Thermodilution/arterial line + +/- + + + - Flotrac R /LiDCO R /ProAQT R Arterial line + + + + + - USCOM R Doppler - - + + - + NICOM R Bioreactance - + + + - + Nexfin R Finger cuff - + + - - + Reproduced from Perioperative monitoring of tissue perfusion: new developments. Annual update in intensive care and emergency medicine 2013 (Berline: Springer; 2013. p.291-9) [12]. SV: stroke volume, CO: cardiac output, SVV: stroke volume variation, PPV: pulse pressure variation, ward: general surgical ward. 6 www.jacs.or.kr
Hye Youn Kwon, et al: Hemodynamic Monitoring 에는제한점이있다 [12]. 혈역학적감시에이용되는기기의종류와특징은 Table 3과같다 [12]. 산소전달과조직관류의평가심박출량과혈장량은조직으로의산소전달과관류를위한기본적인조건으로알려져있지만, 절대적인인과관계를보이는것은아니다. 수액반응군에서산소전달 (DO 2) 이증가하여도이들중일부에서만산소소비량이증가된연구결과들을볼때, 충분히혈장량이증가하였다고해서조직에적절한관류가이루어졌다고보기는어렵다 [13]. 조직의관류을평가하기위해서산소소비량을나타내는지표들을이용해야하며실제로젖산 (lactate), 염기결핍 (base deficit), 혼합정맥산소포화도 (mixed venous oxygen saturation, SmvO 2) 등이이용되고있다. 젖산은무산소대상의결과물로이것의증가를통해부적절한관류가이루어지고있음을예측할수있다. 하지만, 간기능부전과같이젖산의제거능력이저하된환자의경우에는결과해석에주의해야한다. 염기결핍에의한 ph의변화는조직관류를평가할수있는좋은지표가될수있지만, 변화에따른반응속도가느린편이어서제한점이있다. 최근에는위장관점막과설하점막에서이산화탄소의분압 (PCO 2) 및 ph의변화를측정하는방법들이소개되어내장순환 (splanchnic circulation) 이나말초조직의관류를평가하기도한다. SmvO 2 는체순환의산소전달및산소소비량을평가할수있는지표로, PAC를통해폐동맥에서채혈하여측정한다. 산소소비량은급격한대사변화가없는한크게변하지않으므로 SmvO 2 는산소전달능력을평가할때간접적으로사용된다. 하지만이값은산소소비량에대한평가가배제된값이므로조직관류를평가하기에는한계가있다 [14]. 중심정맥에서측정하는중심정맥산소포화도 (ScvO 2) 는 SmvO 2 보다 5 10% 정도낮게측정되지만, SmvO 2 를예측할수있어대체적인지표로쓰이기도한다 [14]. 위와같은방법들이산소전달과조직관류의평가에이용되고있다. 하지만, 순환장애가산소전달과정중어느단계에서발생하였는지알수없다는것이현재이용되고있는지표들의한계이다. 결론 혈역학적감시는관류의적절성을평가하는것이며심폐기능, 혈장량및산소전달과소비까지이루어져야완성되었다고할수있다. 이것을적절히평가하기위하여다양한방법들이개발되 어오고있으며이러한다양한혈역학적감시방법을적절히이용하기위해서는혈역학과심폐상호작용에대한전반적인이해가뒷받침되어야한다. Conflicts of Interest No potential conflict of interest relevant to this article was reported. References 1. Park CM. Noninvasive hemodynamic monitoring. In: Proceedings of the 1st Korean Society of Surgical Critical Care Symposium; 2011 Sep 17; Seoul: ROKa: Press; 2011. p.17-21. 2. Marino PL. Arterial blood pressure. In: Marino PL. The ICU book: hemodynamic monitoring. 3rd ed. New York: Williams & Wilkins; 2007. p.151-61. 3. Ramos FJS, Costa ELV, Amato MBP. Bedside monitoring of heart-lung interactions. Annual update in intensive care and emergency medicine 2013. Berline: Springer; 2013. p. 373-84. 4. Marik PE, Monnet X, Teboul JL. Hemodynamic parameters to guide fluid therapy. Ann Intensive Care 2011;1:1. 5. Monnet X, Teboul JL. Assessment of volume responsivenss during mechanical ventilation: recent advances. Annual update in intensive care and emergency medicine 2013. Berline: Springer; 2013. p.385-96. 6. Durairaj L, Schmidt GA. Fluid therapy in resuscitated sepsis: less is more. Chest 2008;133:252-63. 7. Cavallaro F, Sandroni C, Marano C, La Torre G, Mannocci A, De Waure C, et al. Diagnostic accuracy of passive leg raising for prediction of fluid responsiveness in adults: systematic review and meta-analysis of clinical studies. Intensive Care Med 2010;36:1475-83. 8. Monnet X, Rienzo M, Osman D, Anguel N, Richard C, Pinsky MR, et al. Passive leg raising predicts fluid responsiveness in the critically ill. Crit Care Med 2006;34: 1402-7. 9. Monnet X, Osman D, Ridel C, Lamia B, Richard C, Teboul JL. Predicting volume responsiveness by using the end-expiratory occlusion in mechanically ventilated intensive care unit patients. Crit Care Med 2009;37:951-6. 10. Muller L, Toumi M, Bousquet PJ, Riu-Poulenc B, Louart G, Candela D, et al. An increase in aortic blood flow after an infusion of 100 ml colloid over 1 minute can predict fluid responsiveness: the mini-fluid challenge study. Anesthesiology 2011;115:541-7. 11. Vincent JL, Rhodes A, Perel A, Martin GS, Della Rocca G, Vallet B, et al. Clinical review: update on hemodynamic monitoring--a consensus of 16. Crit Care 2011;15:229. 12. Boer C. Perioperative monitoring of tissue perfusion: new www.jacs.or.kr 7
J Acute Care Surg Vol. 7, No. 1, Apr. 2017 developments. Annual update in intensive care and emergency medicine 2013. Berline: Springer; 2013. p.291-9. 13. Monnet X, Julien F, Ait-Hamou N, Lequoy M, Gosset C, Jozwiak M, et al. Lactate and venoarterial carbon dioxide difference/arterial-venous oxygen difference ratio, but not central venous oxygen saturation, predict increase in oxygen consumption in fluid responders. Crit Care Med 2013;41: 1412-20. 14. Andrew JG, Ednan KB, Atul M. Minimal invasive monitoring. In: Richard SI, James MR. Irwin & Rippe's intensive care medicine. 7th ed. Philadelphia: LWW; 2012. p.245-57. 8 www.jacs.or.kr