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高ナトリウム血症鑑別の概略

uOsm:尿浸透圧、uSG:尿比重
出典
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1: 著者提供

細胞外液量減少における各指標の感度、特異度および尤度(LR*)

出典
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1: The rational clinical examination. Is this patient hypovolemic?
著者: McGee S, Abernethy WB 3rd, Simel DL.
雑誌名: JAMA. 1999 Mar 17;281(11):1022-9. doi: 10.1001/jama.281.11.1022.
Abstract/Text: OBJECTIVE: To review, systematically, the physical diagnosis of hypovolemia in adults.
METHODS: We searched MEDLINE (January 1966-November 1997), personal files, and bibliographies of textbooks on physical diagnosis and identified 10 studies investigating postural vital signs or the capillary refill time of healthy volunteers, some of whom underwent phlebotomy of up to 1150 mL of blood, and 4 studies of patients presenting to emergency departments with suspected hypovolemia, usually due to vomiting, diarrhea, or decreased oral intake.
RESULTS: When clinicians evaluate adults with suspected blood loss, the most helpful physical findings are either severe postural dizziness (preventing measurement of upright vital signs) or a postural pulse increment of 30 beats/min or more. The presence of either finding has a sensitivity for moderate blood loss of only 22% (95% confidence interval [CI], 6%-48%) but a much greater sensitivity for large blood loss of 97% (95% CI, 91%-100%); the corresponding specificity is 98% (95% CI, 97%-99%). Supine hypotension and tachycardia are frequently absent, even after up to 1150 mL of blood loss (sensitivity, 33%; 95% CI, 21%-47%, for supine hypotension). The finding of mild postural dizziness has no proven value. In patients with vomiting, diarrhea, or decreased oral intake, the presence of a dry axilla supports the diagnosis of hypovolemia (positive likelihood ratio, 2.8; 95% CI, 1.4-5.4), and moist mucous membranes and a tongue without furrows argue against it (negative likelihood ratio, 0.3; 95% CI, 0.1-0.6 for both findings). In adults, the capillary refill time and poor skin turgor have no proven diagnostic value.
CONCLUSIONS: A large postural pulse change (> or =30 beats/min) or severe postural dizziness is required to clinically diagnose hypovolemia due to blood loss, although these findings are often absent after moderate amounts of blood loss. In patients with vomiting, diarrhea, or decreased oral intake, few findings have proven utility, and clinicians should measure serum electrolytes, serum blood urea nitrogen, and creatinine levels when diagnostic certainty is required.
JAMA. 1999 Mar 17;281(11):1022-9. doi: 10.1001/jama.281.11.1022.

体内水分量とNaの二重調節

体内の水分量とNaは図に示すように、血漿浸透圧-ADH-腎を介した主に水の調節系と血圧-循環血漿量-レニンアンジオテンシンアルドステロン(RAAS)系-心房性Na利尿ペプチドを介した主にNa調節系の2つの系によって調節されている。

血漿浸透圧(Posm)と血中ADH濃度(PADH)との関係および尿流量(UF)と尿浸透圧(Uosm)との関係

出典
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1: 太田昌宏編. SIADHの長期予後、ホルモンと臨牀. 医学の世界社, 1998; 46(8): 697-703, 図4.

高ナトリウム血症の考え方(口渇感により自由な飲水行動が可能な場合)

高Na血症の病態を水分量とNa量との関係から考えると図のように3つに分けられる。
A.体液量減少を伴う高Na血症:水分量もNa量も減少しているが水分喪失のほうが大きい場合。
B.体液量正常の高Na血症:Na量は正常で水分喪失のみがある場合。
C.体液量増加を伴う高Na血症:水分量もNa量も増加しているがNaの増加のほうが大きい場合。
 
Aの病態では水分、Naともに失われるがその原因として、腎性に失われる場合はマニトール投与時や高血糖時にみられる浸透圧利尿が挙げられる。さらに水利尿薬であるトルバプタン使用時には、水喪失による高Na血症を呈する。特にループ利尿薬やサイアザイド系利尿薬などを併用されていることが多く、水分、Naとも喪失する病態となり注意が必要である。また、腎外性に失われる場合は嘔吐や下痢、発汗によるものが多い。この両者の鑑別には尿中Na濃度が有用であり腎性喪失の場合UNa>20 mEq/L、腎外性喪失の場合UNa<20 mEq/Lとなることが多い。
Bの病態では主に水分が失われるが、その代表疾患は尿崩症と本態性高Na血症である。尿崩症では抗利尿ホルモン(ADH)の分泌が低下する中枢性尿崩症と腎集合管でのADH-V2受容体の異常による腎性尿崩症があるが、いずれの場合でも尿浸透圧は低張で多尿を呈する。
しかし、口渇感が正常で飲水が可能であれば著明な高Na血症を呈することは少ない。
Cの病態では体内へのNa貯留により高Na血症を呈する。一般に体内に過剰のNaが貯留されるのは、過剰の塩分投与、重炭酸塩の投与、高張液による血液透析など医原性のことが多い。疾患としては原発性アルドステロン症やCushing症候群のようにミネラルコルチコイドの作用により体内へNa貯留が起こる場合である。
出典
img
1: 著者提供

高ナトリウム血症鑑別の概略

uOsm:尿浸透圧、uSG:尿比重
出典
img
1: 著者提供

細胞外液量減少における各指標の感度、特異度および尤度(LR*)

出典
imgimg
1: The rational clinical examination. Is this patient hypovolemic?
著者: McGee S, Abernethy WB 3rd, Simel DL.
雑誌名: JAMA. 1999 Mar 17;281(11):1022-9. doi: 10.1001/jama.281.11.1022.
Abstract/Text: OBJECTIVE: To review, systematically, the physical diagnosis of hypovolemia in adults.
METHODS: We searched MEDLINE (January 1966-November 1997), personal files, and bibliographies of textbooks on physical diagnosis and identified 10 studies investigating postural vital signs or the capillary refill time of healthy volunteers, some of whom underwent phlebotomy of up to 1150 mL of blood, and 4 studies of patients presenting to emergency departments with suspected hypovolemia, usually due to vomiting, diarrhea, or decreased oral intake.
RESULTS: When clinicians evaluate adults with suspected blood loss, the most helpful physical findings are either severe postural dizziness (preventing measurement of upright vital signs) or a postural pulse increment of 30 beats/min or more. The presence of either finding has a sensitivity for moderate blood loss of only 22% (95% confidence interval [CI], 6%-48%) but a much greater sensitivity for large blood loss of 97% (95% CI, 91%-100%); the corresponding specificity is 98% (95% CI, 97%-99%). Supine hypotension and tachycardia are frequently absent, even after up to 1150 mL of blood loss (sensitivity, 33%; 95% CI, 21%-47%, for supine hypotension). The finding of mild postural dizziness has no proven value. In patients with vomiting, diarrhea, or decreased oral intake, the presence of a dry axilla supports the diagnosis of hypovolemia (positive likelihood ratio, 2.8; 95% CI, 1.4-5.4), and moist mucous membranes and a tongue without furrows argue against it (negative likelihood ratio, 0.3; 95% CI, 0.1-0.6 for both findings). In adults, the capillary refill time and poor skin turgor have no proven diagnostic value.
CONCLUSIONS: A large postural pulse change (> or =30 beats/min) or severe postural dizziness is required to clinically diagnose hypovolemia due to blood loss, although these findings are often absent after moderate amounts of blood loss. In patients with vomiting, diarrhea, or decreased oral intake, few findings have proven utility, and clinicians should measure serum electrolytes, serum blood urea nitrogen, and creatinine levels when diagnostic certainty is required.
JAMA. 1999 Mar 17;281(11):1022-9. doi: 10.1001/jama.281.11.1022.