急診 VBG 可否取代 ABG？

VBG or ABG analysis in Emergency Care? from Sun Yai-Cheng

Can VBG analysis replace ABG analysis in emergency care?

Blood Gas Analysis 臨床主要用來評估病患的 Respiratory or Metabolic conditions:
病患是否缺氧、呼吸衰竭、需呼吸器，有無/何種酸鹼異常，對治療有無反應… 

VBG 的 PvO2 無臨床價值。除此之外，PvCO2, venous pH & HCO3 可用來評估 ventilation and/or acid-base status；SvO2 可用在 severe sepsis or septic shock (EGDT) 治療指引。

VBG 轉換 ABG 校正：

	Central	Peripheral
pH	＋ 0.03 to 0.05	＋ 0.02 to 0.04
pCO2	－ 4 to 5 mmHg	－ 3 to 8 mmHg
HCO3	＝	－ 1 to 2 meq/L

 

CASE 1:

26歲女性，DM病史。上吐下瀉兩天，急診就醫
Pulse 120, BP 100, RR 30. PE 無明顯異常
Bedside glucose show ‘Hi’
VBG: pH 7.26, pCO2 16, HCO3 7.1, K 3.8, BE −14, lactate 7.2
pH↓, pCO2↓, HCO3 ↓ →metabolic acidosis
加上 glucose ‘Hi’ 可診斷 DKA

CASE 2:

74歲男性，COPD病史。「感冒」後 呼吸急促，急診就醫。
休息時會喘，僅能講簡短字句。
Pulse 125, BP 140, RR 35, SpO2 86% on air
Chest examination: generally reduced breath sounds with scattered rhonchi
VBG: pH 7.16, pCO2 82.6, HCO3 28.8

pH↓, pCO2↑, HCO3 near normal
診斷：COPD with acute hypercarbia and respiratory failure
治療：ventilatory support with non-invasive ventilation.

CASE 2: A VARIATION

Symptoms/Signs are the same
Pulse 110, BP 140, RR 30 with SpO2 86% on air
VBG: pH 7.45, pCO2 42 and HCO3 28.7 

VBG pCO2< 45 mmHg 可排除臨床有意義的 hypercarbia
Sensitivity 100% (95% CI 97% to 100%) & NPV 100% (97% to 100%)

此病患沒有acute respiratory failure 也沒有 significantly hypercarbia

VBG 的臨床侷限

血壓不穩或休克病患，仍以 ABG優先

若 VBG data 無法解釋臨床症狀，抽 ABG 確認

【摘要】

• VBG 的 PvCO2, pH & HCO3 與 ABG 差異不大，可用來評估 ventilation 和 acid-base status
• VBG pCO2< 45 mmHg 可排除臨床有意義的 hypercarbia
• VBG的 PvO2 無臨床價值，但可用 pulse oximerty 來評估 oxygenation (O2 saturation)
• venous 與 artery 的 CO-Hb 差異 < ±2%，可相互取代
• 大部分的臨床情況下，可以根據 VBG 決定病患的診斷與處置。除非病患血壓不穩/休克，或 VBG data 無法解釋臨床症狀，需再抽 ABG 確認

Reference:

• Emerg Med J 2014;0:1–3. Can VBG analysis replace ABG analysis in emergency care?
• UpToDate. VBG and other alternatives to ABG. Literature review current through: Sep 2016. This topic last updated: Feb 29, 2016.
• Ann Emerg Med 1995;33:105-109. Relationship between venous and arterial carboxyhemoglobin levels in patients with suspected carbon monoxide poisoning.
• AliEM PV card. ABG vs VBG

Resuscitation Fluids

Resuscitation Fluids from Sun YaiCheng

Critical Care Medicine
Resuscitation Fluids

N Engl J Med 2013;369:1243-51.

The Ideal Resuscitation Fluid

• produces a predictable and sustained increase in intravascular volume
• has a chemical composition as close as possible to that of extracellular fluid
• is metabolized and completely excreted without accumulation in tissues
• does not produce adverse metabolic or systemic effects
• is cost-effective in terms of improving patient outcomes
• Currently, there is no such fluid available for clinical use

• colloid solutions: more effective in expanding intravascular volume
• 1:3 ratio of colloids to crystalloids to maintain intravascular volume
• semisynthetic colloids have a shorter duration of effect than human albumin solutions
• crystalloids: resuscitation fluids

Specific Considerations Apply To Different Categories Of Patients

1. Bleeding patients require control of hemorrhage and transfusion with red cells and blood components as indicated.
2. Isotonic, balanced salt solutions are a pragmatic initial resuscitation fluid for the majority of acutely ill patients.
3. Consider saline in patients with hypovolemia and alkalosis.
4. Consider albumin during the early resuscitation of patients with severe sepsis.
5. Saline or isotonic crystalloids are indicated in patients with traumatic brain injury.
6. Albumin is not indicated in patients with traumatic brain injury.
7. Hydroxyethyl starch is not indicated in patients with sepsis or those at risk for acute kidney injury.
8. The safety of other semisynthetic colloids has not been established, so the use of these solutions is not recommended.
9. The safety of hypertonic saline has not been established.
10. The appropriate type and dose of resuscitation fluid in patients with burns has not been determined.

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【摘要小結】

• Colloid 與 crystalloid solution 兩種復甦溶液對於升壓的效果並無差異。
• Albumin 是Colloid 代表溶液，其價格限制了其使用性。Albumin 使用在大部分急重症病患復甦是安全的，特別是嚴重敗血症患者的早期復甦。然而創傷性腦損傷的病患，Albumin 使用會增加死亡率。
• ICU 病患使用Hydroxyethyl starch (HES) 會增加急性腎傷害及洗腎的風險！

急診低血鈉的處置

Hyponatremia from Sun YaiCheng

Hyponatremia 定義：[Na⁺] < 135 mEq/L

• Clinical Signs of Hyponatrema: Nausea, vomiting, anorexia, muscle cramps, confusion, and lethargy, and culminate ultimately in seizures and coma. 
• Seizures are quite likely at [Na⁺] of 113 mEq/L or less.

Effects of Hyponatremia on the Brain and Adaptive Responses

Causes of Hyponatremia

Hypertonic Hyponatremia (Osmotic Pressure >295)

• Hyperglycemia
• Mannitol excess
• Glycerol therapy

Isotonic Hyponatremia (Osmotic Pressure 275 to 295)

• Hyperlipidemia
• Hyperproteinemia (e.g., multiple myeloma, Waldenström macroglobulinemia)

Hypotonic Hyponatremia (Osmotic Pressure < 275) 

• Hypovolemic 

Renal

Diuretic use
Salt-wasting nephropathy (renal tubular acidosis, chronic renal failure, interstitial nephritis)
Osmotic diuresis (glucose, urea, mannitol, hyperproteinemia)
Mineralocorticoid (aldosterone) deficiency 

Extrarenal

Volume replacement with hypotonic fluids
GI loss (vomiting, diarrhea, fistula, tube suction)
Third-space loss (e.g., burns, hemorrhagic pancreatitis, peritonitis) 

• Hypervolemic 

Urinary [Na⁺] >20 mEq/L

Renal failure

Urinary [Na⁺] < 20  mEq/L

Congestive heart failure
Nephrotic syndrome  
Cirrhosis

• Euvolemic

Urine [Na+] usually > 20 mEq/L

SIADH
Hypothyroidism (possible increased ADH or deceased glomerular filtration rate)
Pain, stress, nausea, psychosis (stimulates ADH)
Drugs: ADH, nicotine, sulfonylureas, morphine, barbiturates, NSAIDs, acetaminophen, carbamazepine, phenothiazines, tricyclic antidepressants, colchicine, clofibrate, cyclophosphamide, isoproterenol, tolbutamide, vincristine, MAOI.
Water intoxication
Glucocorticoid deficiency
Positive pressure ventilation
Porphyria
Essential (reset osmostat or sick cell syndrome—usually in the elderly)

Total Body [Na⁺] Deficit

= (desired plasma [Na⁺]－measured plasma [Na⁺]) ×TBW

Emergency Treatment of Severe Hyponatremia

• In the ED, there is generally little urgency to address the hyponatremia immediately when [Na+] is 120 mEq/L.
• Urine electrolytes are useful only before beginning treatment and therefore should be collected in the ED. 
• The rise in [Na+] should be no greater than 0.5 to 1.0 mEq/L per hour

相關文章： 急診高血鈉的處置

急診高血鈉的處置

Hypernatremia from Sun YaiCheng

 

Hypernatremia 定義：[Na+] > 150 mEq/L

Clinical Signs of Hypernatremic States Related to Serum Osmolality:

Osmolality (mOsm/kg) Manifestations

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350–375                                    Restlessness, irritability
375–400                                    Tremulousness, ataxia
400–430                                    Hyperreflexia, twitching, spasticity
>430                                         Seizures and death

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Causes of Hypernatremia *Likely or important ED diagnostic considerations.

Inadequate water intake*

• Inability to obtain or swallow water
• Impaired thirst drive
• Increased insensible loss

Excessive sodium

• Iatrogenic sodium administration  

Sodium bicarbonate
Hypertonic saline

• Accidental/deliberate ingestion of large quantities of sodium  

Substitution of salt for sugar in infant formula or tube feedings
Salt water ingestion or drowning

• Mineralocorticoid or glucocorticoid excess*  

Primary aldosteronism
Cushing syndrome
Ectopic ACTH production

• Peritoneal dialysis  

Loss of water in excess of sodium

GI loss*  

• Vomiting, diarrhea, intestinal fistula

Renal loss  

• Central diabetes insipidus  
• Impaired renal concentrating ability  
• Osmotic diuresis (multiple causes)*     

Hypercalcemia
Decreased protein intake
Prolonged, excessive water intake
Sickle cell disease
Multiple myeloma
Amyloidosis
Sarcoidosis
Sjögren syndrome
Nephrogenic diabetes insipidus
Congenital

Drugs/medications

• Alcohol, lithium, phenytoin, propoxyphene, sulfonylureas, amphotericin, colchicine

Skin loss  

• Burns, sweating

Essential hypernatremia


急診病人高血鈉最常見的原因是「嚴重水分不足 severe volume loss」

Treatment

1. The cornerstone of treatment is volume repletion.
2. Volume should be replaced first with NS or lactated Ringer's solution.
3. Some practitioners inappropriately fear using NS solution from concern that an [Na+] of 154 mEq/L exceeds normal serum [Na+]. However, in most hypernatremic states, there is a total body [Na+] deficit, and the use of NS allows a more gradual decrease in serum [Na+].
4. Once perfusion has been established, the solution should be converted to 0.45% saline or another hypotonic solution until the urine output is at least 0.5 mL/kg/h.
5. The reduction in [Na+] should not exceed 10~15 mEq/L per day.

• 原則：先處理水分缺損，再來矯正高血鈉
• 輸液選擇：先以 N/S 矯正水分缺損後，再用 half saline or D5W 矯正高血鈉
• 血鈉變化應每天小於 10~15 mEq/L

Free Water Deficit 計算

公式一 (Washington manual)

公式二 (Harrison, ICU Book,Tintinalli, Rosen )

Free Water Deficit

Replacement Volume = TBW deficit × 1/(1－X)

X= [Na+] of resuscitation fluid / [Na+] of isotonic saline

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70 公斤的成人，抽血發現 [Na+] 160 mEq/L

計算式：

TBW deficit = 0.6 ×70× [160/140－1]= 6 L
若使用 0.45NaCl 做為輸液
Replacement volume = 6 × 1/ (1－½)=12 L
水分缺損要在 48小時 補足
點滴速度約每小時 250 mL

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