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Arterial blood gas analysis in patient evaluation
oRIGINAL CONTRIBUTION
Arterial Blood Gas Analysis in Patient Evaluation Steven J. Morris, MD* John H. Stone, MDt Atlanta, Georgia
The u s e o f a r t e r i a l b l o o d g a s e s i n a n e m e r g e n c y d e p a r t m e n t w a s studied b y r e v i e w i n g , r e t r o s p e c t i v e l y , 5,000 c o n s e c u t i v e p a t i e n t s . Of these, 169 (3.38%) h a d a r t e r i a l b l o o d g a s e s done; 150 (85%) m a n i f e s t e d at least o n e a b n o r m a l i t y ; 58 (35%) w e r e h o s p i t a l i z e d . A t o t a l o f 35 d i f f e r e n t diagnoses was made among those patients who had arterial blood gases done. P n e u m o n i a w a s the m o s t c o m m o n (34), f o l l o w e d b y c h e s t p a i n (14). H y p o x i a , the m o s t f r e q u e n t a b n o r m a l i t y , w a s f o u n d in 124 (75%) o f all t e s t e d p a t i e n t s . In an e m e r g e n c y d e p a r t m e n t , w h e r e r a p i d a c c u m u l a tion of d a t a is n e c e s s a r y , a r t e r i a l b l o o d g a s e s p l a y a v i t a l role in p a t i e n t evaluation. A b n o r m a l i t i e s are f r e q u e n t a n d a s i g n i f i c a n t p e r c e n t o f admissions m a y result.
Morris SJ, Stone JH: Arterial blood gas analysis. JACEP 6:85-88, March, 1977. blood gas analysis, diagnosis. INTRODUCTION A p p r o x i m a t e l y 300 y e a r s ago, Hook a n d B o y l e u s e d a v a c u u m pump to f i r s t s e p a r a t e a i r f r o m blood.~ It took almost 200 y e a r s for Gustav Magnus, in 1840, to analyze the c o m p o n e n t s of blood t h a t h a d been n a m e d " f i x e d a i r " ( c a r b o n ~ dioxide) by Black a n d "dephlogisticated a i r " ( o x y g e n ) by P r i e s t l e y . 2 Magnus was the first to note t h a t arterial blood c o n t a i n e d more oxygen than venous-blood.
From the Department of Medicine, Emory Uaiversity Affiliated Hospitals Program,* aad the Emergency Medicine Program (I)irector),t Grady Memorial Hospital, aad Emory University School of Medicine,t Atlanta, Georgia. Address for reprints: John H. Stone, MD, ThOmas K. Glenn Building, 69 Butler Street, SE, Atlanta, Georgia 30303.
J ~ V ) 6:3 (Mar)1977
Since the mid-1960s technological a d v a n c e s h a v e m a d e a r t e r i a l blood gas a n a l y s i s more a v a i l a b l e to the clinician. A t present, a r t e r i a l blood gas a n a l y s i s is available 24 hours a day, seven d a y s a week, in most hospitals. As w i t h m a n y new, p o p u l a r procedures, a r t e r i a l blood gas a n a l y sis has evoked the criticisms of overuse, misuse, cost, and morbidity. This s t u d y was done to discover 1) how often blood gases are used in an e m e r g e n c y d e p a r t m e n t ; 2) for w h a t reasons; 3) w h a t a b n o r m a l i t i e s are uncovered, and 4) w h a t assistance is afforded in the e v a l u a t i o n and care of the patients. MATERIALS AND METHODS Grady Memorial Hospital, an a c u t e care, c o u n t y f a c i l i t y , is t h e p r i n c i p a l t e a c h i n g hospital of E m o r y U n i v e r s i t y School of Medicine. Its
e m e r g e n c y d e p a r t m e n t is subdivided into m e d i c a l , surgical, gynecologyobstetrics, and pediatric units. Five t h o u s a n d p a t i e n t s were seen in the medical u n i t d u r i n g a 30-day period ( J a n u a r y - F e b r u a r y , 1974) and t h e i r e m e r g e n c y records were reviewed_ All arterial blood gases were d r a w n by the house officers for the sole purpose of assisting t h e i r diagnostic w o r k - u p and/or t h e r a p y . Arter i a l blood was t a k e n with the p a t i e n t b r e a t h i n g room air, and most were d r a w n from t h e r a d i a l artery, w i t h the brachial next most frequently used. A r t e r i a l blood was placed' on ice and t a k e n to a special blood gas laboratory. A n a l y s e s were performed by t r a i n e d t e c h n i c i a n s using a Radiometer (Copenhagen) BMS 3MK 2 Blood Micro system. This machine was s t a n d a r d i z e d three times daily (preceding each shift) and two m a c h i n e s were a v a i l a b l e if one malfunctioned. R e s u l t s of blood g a s e s w e r e recorded by the house officers. Impressions of t h e p a t i e n t ' s major problem were a l w a y s recorded to the h i g h e s t l e v e l of r e s o l u t i o n t h a t c o u l d be achieved. The decision as to w h e t h e r to a d m i t a p a t i e n t was a function of the r e s i d e n t in charge and was made, of course, in light of the overall clinical context of t h a t patient. T h r o u g h o u t t h i s paper, reference will be m a d e to n o r m a l and abnorreal values. For the p a r t i a l pressure 85/23
of oxygen (PO2) a value below 80 m m Hg on room air will be considered abnormal. However, for patients over 60 years of age we have subtracted 1 m m Hg/year to obtain their "normal" v a l u e 2 For PC02 a n d pH, we are u s i n g an i n t e r p r e t i v e r a t h e r t h a n a strict r a n g e of normal. 2 PC02 will be considered n o r m a l within the 30 to 50 m m Hg range, and pH from 7.30 to 7.50 units.
RESULTS Of 5,000 consecutive patients seen, 169 p a t i e n t s (3.38%) b a d a r t e r i a l blood gas analyses performed while i n the e m e r g e n c y d e p a r t m e n t . A t o t a l of 191 a r t e r i a l blood gas analyses was done; 17 p a t i e n t s had two and two patients, three determinations. Of these 169 patients, 150 (85%) m a n i f e s t e d at least one abn o r m a l i t y in their POe, PC02 or pH. A total of 58 patients, 35% of all pat i e n t s who had a r t e r i a l blood gases d e t e r m i n e d , were a d m i t t e d to the hospital. A total of 35 different diagnoses was reached in the cases h a v i n g art e r i a l blood gases done (Table 1). Diagnoses ranged in degree of resol u t i o n from the less specific chest p a i n to s u b d u r a l h e m a t o m a . The most f r e q u e n t use of arterial blood gases was in the e v a l u a t i o n of pneumonia. To f u r t h e r assess how blood gases were used in the e v a l u a t i o n of a specific e n t i t y , we a n a l y z e d t h e two most frequent diagnoses: p n e u m o n i a and chest pain. A total of 24 p a t i e n t s with p n e u m o n i a had arterial blood gas analysis (15 m e n and 9 women; m e a n age of 51). Of these, 23 (96%) had an a b n o r m a l blood gas; all showing hypoxemia. F u r t h e r m o r e , 15 of the 24 (62%) were hospitalized. Duri n g t h i s s a m e period, 57 p a t i e n t s with a diagnosis of pneumonia, but without a n a r t e r i a l blood gas determ i n a t i o n , were seen. O n l y 2 (3%) were hospitalized. All p a t i e n t s with PO2 less t h a n 50 m m Hg were a d m i t t e d to the hospital. Of those w i t h PO2 between 50 and 60 m m Hg, there was an equal d i s t r i b u t i o n between those admitted a n d those n o t a d m i t t e d . Of those w i t h PO2 above .60, most were not admitted (Tabl6 2). The n u m b e r s in
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Table 1 DIAGNOSES ASSOCIATED WITH ARTERIAL BLOOD GAS ANALYSIS (n =169) Diagnosis
No.
%
Diagnosis
No.
%
Pneumonia
24
14.2
Seizures
3
1.8
Diabetic ketoacidosis Chest pain
18 14
10.7 8.3
Hypoxemia Pneumothorax
3 3
1.8 1.8
Chronic obstructive pulmonary disease
13
7.7
Chlorox inhalation
2
1.2
Asthma
8
4.8
Flu syndrome
2
1,2
Delirium tremens
2
Altered mental status
8
1,2
4.8
Acute bronchitis
Pancreatitis
1
0.6
8
4.8
Gastroenteritis
1
0.6
Hyperventilation syndrome
8
4.8
Shortness of breath
8
4.8
Salicylism
1
0.6
Alcoholic ketoacidosis
1
0.6
Phlebitis
1
0.6
Alcoholic cardiomyopathy
1
0.6
Dehydration
1
0.6
Pyeloneph ritis
1
0.6
1
0,6
2.4
Febrile illness Hyperglycemic nonketotic coma
1
0.6
2.4
Sarcoid
1
0.6
Neoplastic pulmonary disease
5
3.0
Pulmonary edema
5
3.0
Chronic renal failure
4
2.4
Pulmonary embolus
4
2.4
Smoke inhalation
4
2.4
Pleurisy
4
Pulmonary infiltrates
4
Overdose
3
1.8
Table 2 PATIENTS WITH PNEUMONIA: RELATION OF P02 AND ADMISSION PO= 40-49
Tolal No.
3 (12%)
0
5 (19%) 11 (42%) 3 (12%) 2 (8%) 24
No, Admitted
3
0
5
6
1
2
17 (65%)
No. Not Admitted
0
0
0
5
2
~2
9 (35%)
In the category of chest pain, 14 arterial blood gases were done on six m e n and eight women (average age, 46). F o u r of these p a t i e n t s (28_6%) were a d m i t t e d to the hospital (two with the diagnosis of myocardial infarction; two w i t h the diagnosis of p u l m o n a r y embolus). All four of the a d m i t t e d p a t i e n t s h a d grossly abn o r m a l blood gases. Of the ten pat i e n t s not admitted, seven had norm a l blood gases and three had mild
60-69
Total
30-39
this latter category are too small to have statistical significance.
50-59
70-79
< 30
a b n o r m a l i t i e s i n their PO2 ranging between 70 and 79.
P02 Measurements Looking at specific parameters of blood gas analysis, the majority of a b n o r m a l i t i e s were of the P02 measu r e m e n t s ; ' 1 2 4 p a t i e n t s had abnormal PO2 m e a s u r e m e n t s after appro" priate correction for age (75% of all blood gases d r a w n ) . F i f t y - s e v e n of these 124 p a t i e n t s were admitted to the hospital - - 45% of all patients with a b n o r m a l PO2.
6:3 (Mar) 1977 , ~ P
It was i n t e r e s t i n g t h a t five paiie~ts with PO2 less t h a n 40 were not ~draitted; four of these p a t i e n t s had :hronic o b s t r u c t i v e p u l m o n a r y disease of long standing. Many of the patients w i t h a b n o r m a l PO2 were placed on oxygen and repeat blood gases showed improvement (Table 3).
Table 3 ABNORMAl PO2 (n=125) PO2 (mm Hg)
Number
< 30
4 (3%)
30-39
10 (8%)
pCO= Measurements
40-49
21 (17%)
Seven p a t i e n t s had hypercarbia defined as a PCO2 g r e a t e r t h a n 50_ Three of these patients had chronic obstructive l u n g disease with longstanding h y p e r c a r b i a and were not admitted. One p a t i e n t with chronic obstructive p u l m o n a r y disease a n d acute respiratory failure was admitIed. Of the other three patients, all were a s t h m a t i c s a n d were hospitalized; two r e q u i r e d i n t u b a t i o n later on the e v e n i n g of admission. There were 80 patients whose PCO2 was less t h a n 30 (hypocarbia). Of these, 64 fell in the 20 to 30 m m Hg range, e v o k e d l i t t l e c o n c e r n , a n d prompted the observation t h a t most patients h y p e r v e n t i l a t e d either prior Lo or d u r i n g the d r a w i n g of blood samples, s t a r t i n g of i n t r a v e n o u s fluids, or receiving injections, making this value by itself difficult to interpret. However, when hypocarbia was associated w i t h hypoxemia, it made the lowered PO2 all the more d i s t u r b i n g . F i f t e e n p a t i e n t s were found to have PCO2 of less t h a n 20, a finding t h a t usually reflects an approximate q u a d r u p l i n g of the respiratory rate. a E l e v e n of t h e s e 15 patients were h o s p i t a l i z e d . S e v e n were also found to be acidotic and three had associated severe hypoxemia. In one p a t i e n t with p u l m o n a r y embolus, the lowered PCO2 was the lone abnormality.
50-59
34 (27%)
60-69
32 (26%)
70-79
24 (19%)
pH In a n a l y z i n g the acid-base abnorraalities uncovered by arterial blood gases, we should state in our hospital ~ve use a large n u m b e r of venous pH d e t e r m i n a t i o n s , e s p e c i a l l y in the rapid e v a l u a t i o n of simple diabetic ketoacidosis. T w e n t y - t w o p a t i e n t s had an arterial pH less t h a n 7.30 and 18 of these were hospitalized. Table 4 shows the d i a g n o s e s i n those p a t i e n t s w i t h a c i d o s i s , associated hypoxemia or hypercarbia, and whether or not the p a t i e n t was admitted to the hospital. J~P
6:3 (Mar)1977
Number Hospitalized
4 5 13 16 11 8
(100%) (50%) (62%) (47%) (34%) (33%)
Table 4 ARTERIAL BLOOD GASES AND ACID-BASE ABNORMALITY pH < 7.20
pH 7.20-7.30
Associated Abnormality
Disposition
Diabetic ketoacidosis
2
6
1 pt.-hypoxemia
8 admitted
Chronic renal failure
1
1
Altered mental status
0
3
1 pt.-hypoxemia
2 admitted
Congestive heart failure
1
1
2 pt.-hypoxemia
2 ad m itted
Asthma
1
1
2 pt.-hypoxemia 2 pt.-hypercarbia
2 admitted
Chronic obstructive pulmonary disease
1
1
2 pt.-hypoxemia 1 pt.-hypercarbia
1 admitted
Pneumonia
0
2
2 pt.-hypoxemia
1 admitted
Seizures
0
1
1 pt.-hy.poxemia
0 admitted
Alcoholic ketoacidosis
0
1
0
1 admitted
Diagnosis
DISCUSSION We h a v e looked at blood gas a n a l y s e s in the setting of a medical emergency d e p a r t m e n t where rapid a c c u m u l a t i o n of all p e r t i n e n t data - historical, physical e x a m i n a t i o n and l a b o r a t o r y - - is r e q u i r e d for t h e physician to appropriately decide pat i e n t disposition. Arterial blood gases can be obtained in our hospital in a m a t t e r of m i n u t e s . I n c o n t r a s t , s e r u m electrolyte analysis often requires over one hour. Of the 5,000 patients seen, arterial blood gases were performed on 3.4%. Almost 85% of these a r t e r i a l blood gases were abnormal. First, this appears to be a reasonable, c e r t a i n l y n o t overzealous, use of these tests. Second, there is a very high yield if
1 admitted
one is a t t e m p t i n g to gather concrete data on a possible a b n o r m a l and lifet h r e a t e n i n g condition. Third, the fact t h a t one t h i r d of these p a t i e n t s were e v e n t u a l l y admitted to the hospital attests to the fact that arterial blood gases were c e r t a i n l y d r a w n on the sickest, and more difficult patients. A d i s t u r b i n g q u e s t i o n is s i m u l t a n e o u s l y raised, however. The limit a t i o n s of physical e x a m i n a t i o n in the e v a l u a t i o n of h y p o x e m i a a n d h y p e r c a r b i a are well known. ~ In our s t u d y , 60% of those p a t i e n t s w i t h p n e u m o n i a who had a r t e r i a l blood gases done were admitted to the bospital. In contrast, only 3.7c~ of all other p a t i e n t s with p n e u m o n i a , but without an arterial blood gas determ i n a t i o n , were admitted to the hos87/25
pital. All other clinical criteria notw i t h s t a n d i n g , one still must wonder w h e t h e r s i g n i f i c a n t hypoxemia was missed or u n d e r e s t i m a t e d in this latter group. The u l t i m a t e usefulness of a n arterial blood gas, as with any test, lies i n the a b i l i t y of the p h y s i c i a n to properly i n t e r p r e t the test and act
26/88
accordingly. In this study, it is app a r e n t t h a t the physicians involved found t h a t a b n o r m a l a r t e r i a l blood gas values were highly significant in the u l t i m a t e decision as to hospitalization of the patient.
REFERENCES 1. Respiration, in Handbook of Physiology, section 3. Washington, American
Physiological Society, 1964, p 17. 2. Breathnach CS: The development ~ blood gas analysis. Med Hist 16:51-62 1972. 3. Shapiro B: C l i n i c a l A p p l i c a t i o n of Blood Gases. Chicago, Year Book Medical Publishers, 1973, pp90-92. 4. Comroe JH Jr: The unreliability ~[ cyanosis in the recognition of anoxemia. A m J Med Sci 214:1-6, 1947.
6:3 (Mar) 1977 ~]~P
Arterial Blood Gas Analysis in Patient Evaluation Steven J. Morris, MD* John H. Stone, MDt Atlanta, Georgia
The u s e o f a r t e r i a l b l o o d g a s e s i n a n e m e r g e n c y d e p a r t m e n t w a s studied b y r e v i e w i n g , r e t r o s p e c t i v e l y , 5,000 c o n s e c u t i v e p a t i e n t s . Of these, 169 (3.38%) h a d a r t e r i a l b l o o d g a s e s done; 150 (85%) m a n i f e s t e d at least o n e a b n o r m a l i t y ; 58 (35%) w e r e h o s p i t a l i z e d . A t o t a l o f 35 d i f f e r e n t diagnoses was made among those patients who had arterial blood gases done. P n e u m o n i a w a s the m o s t c o m m o n (34), f o l l o w e d b y c h e s t p a i n (14). H y p o x i a , the m o s t f r e q u e n t a b n o r m a l i t y , w a s f o u n d in 124 (75%) o f all t e s t e d p a t i e n t s . In an e m e r g e n c y d e p a r t m e n t , w h e r e r a p i d a c c u m u l a tion of d a t a is n e c e s s a r y , a r t e r i a l b l o o d g a s e s p l a y a v i t a l role in p a t i e n t evaluation. A b n o r m a l i t i e s are f r e q u e n t a n d a s i g n i f i c a n t p e r c e n t o f admissions m a y result.
Morris SJ, Stone JH: Arterial blood gas analysis. JACEP 6:85-88, March, 1977. blood gas analysis, diagnosis. INTRODUCTION A p p r o x i m a t e l y 300 y e a r s ago, Hook a n d B o y l e u s e d a v a c u u m pump to f i r s t s e p a r a t e a i r f r o m blood.~ It took almost 200 y e a r s for Gustav Magnus, in 1840, to analyze the c o m p o n e n t s of blood t h a t h a d been n a m e d " f i x e d a i r " ( c a r b o n ~ dioxide) by Black a n d "dephlogisticated a i r " ( o x y g e n ) by P r i e s t l e y . 2 Magnus was the first to note t h a t arterial blood c o n t a i n e d more oxygen than venous-blood.
From the Department of Medicine, Emory Uaiversity Affiliated Hospitals Program,* aad the Emergency Medicine Program (I)irector),t Grady Memorial Hospital, aad Emory University School of Medicine,t Atlanta, Georgia. Address for reprints: John H. Stone, MD, ThOmas K. Glenn Building, 69 Butler Street, SE, Atlanta, Georgia 30303.
J ~ V ) 6:3 (Mar)1977
Since the mid-1960s technological a d v a n c e s h a v e m a d e a r t e r i a l blood gas a n a l y s i s more a v a i l a b l e to the clinician. A t present, a r t e r i a l blood gas a n a l y s i s is available 24 hours a day, seven d a y s a week, in most hospitals. As w i t h m a n y new, p o p u l a r procedures, a r t e r i a l blood gas a n a l y sis has evoked the criticisms of overuse, misuse, cost, and morbidity. This s t u d y was done to discover 1) how often blood gases are used in an e m e r g e n c y d e p a r t m e n t ; 2) for w h a t reasons; 3) w h a t a b n o r m a l i t i e s are uncovered, and 4) w h a t assistance is afforded in the e v a l u a t i o n and care of the patients. MATERIALS AND METHODS Grady Memorial Hospital, an a c u t e care, c o u n t y f a c i l i t y , is t h e p r i n c i p a l t e a c h i n g hospital of E m o r y U n i v e r s i t y School of Medicine. Its
e m e r g e n c y d e p a r t m e n t is subdivided into m e d i c a l , surgical, gynecologyobstetrics, and pediatric units. Five t h o u s a n d p a t i e n t s were seen in the medical u n i t d u r i n g a 30-day period ( J a n u a r y - F e b r u a r y , 1974) and t h e i r e m e r g e n c y records were reviewed_ All arterial blood gases were d r a w n by the house officers for the sole purpose of assisting t h e i r diagnostic w o r k - u p and/or t h e r a p y . Arter i a l blood was t a k e n with the p a t i e n t b r e a t h i n g room air, and most were d r a w n from t h e r a d i a l artery, w i t h the brachial next most frequently used. A r t e r i a l blood was placed' on ice and t a k e n to a special blood gas laboratory. A n a l y s e s were performed by t r a i n e d t e c h n i c i a n s using a Radiometer (Copenhagen) BMS 3MK 2 Blood Micro system. This machine was s t a n d a r d i z e d three times daily (preceding each shift) and two m a c h i n e s were a v a i l a b l e if one malfunctioned. R e s u l t s of blood g a s e s w e r e recorded by the house officers. Impressions of t h e p a t i e n t ' s major problem were a l w a y s recorded to the h i g h e s t l e v e l of r e s o l u t i o n t h a t c o u l d be achieved. The decision as to w h e t h e r to a d m i t a p a t i e n t was a function of the r e s i d e n t in charge and was made, of course, in light of the overall clinical context of t h a t patient. T h r o u g h o u t t h i s paper, reference will be m a d e to n o r m a l and abnorreal values. For the p a r t i a l pressure 85/23
of oxygen (PO2) a value below 80 m m Hg on room air will be considered abnormal. However, for patients over 60 years of age we have subtracted 1 m m Hg/year to obtain their "normal" v a l u e 2 For PC02 a n d pH, we are u s i n g an i n t e r p r e t i v e r a t h e r t h a n a strict r a n g e of normal. 2 PC02 will be considered n o r m a l within the 30 to 50 m m Hg range, and pH from 7.30 to 7.50 units.
RESULTS Of 5,000 consecutive patients seen, 169 p a t i e n t s (3.38%) b a d a r t e r i a l blood gas analyses performed while i n the e m e r g e n c y d e p a r t m e n t . A t o t a l of 191 a r t e r i a l blood gas analyses was done; 17 p a t i e n t s had two and two patients, three determinations. Of these 169 patients, 150 (85%) m a n i f e s t e d at least one abn o r m a l i t y in their POe, PC02 or pH. A total of 58 patients, 35% of all pat i e n t s who had a r t e r i a l blood gases d e t e r m i n e d , were a d m i t t e d to the hospital. A total of 35 different diagnoses was reached in the cases h a v i n g art e r i a l blood gases done (Table 1). Diagnoses ranged in degree of resol u t i o n from the less specific chest p a i n to s u b d u r a l h e m a t o m a . The most f r e q u e n t use of arterial blood gases was in the e v a l u a t i o n of pneumonia. To f u r t h e r assess how blood gases were used in the e v a l u a t i o n of a specific e n t i t y , we a n a l y z e d t h e two most frequent diagnoses: p n e u m o n i a and chest pain. A total of 24 p a t i e n t s with p n e u m o n i a had arterial blood gas analysis (15 m e n and 9 women; m e a n age of 51). Of these, 23 (96%) had an a b n o r m a l blood gas; all showing hypoxemia. F u r t h e r m o r e , 15 of the 24 (62%) were hospitalized. Duri n g t h i s s a m e period, 57 p a t i e n t s with a diagnosis of pneumonia, but without a n a r t e r i a l blood gas determ i n a t i o n , were seen. O n l y 2 (3%) were hospitalized. All p a t i e n t s with PO2 less t h a n 50 m m Hg were a d m i t t e d to the hospital. Of those w i t h PO2 between 50 and 60 m m Hg, there was an equal d i s t r i b u t i o n between those admitted a n d those n o t a d m i t t e d . Of those w i t h PO2 above .60, most were not admitted (Tabl6 2). The n u m b e r s in
24/86
Table 1 DIAGNOSES ASSOCIATED WITH ARTERIAL BLOOD GAS ANALYSIS (n =169) Diagnosis
No.
%
Diagnosis
No.
%
Pneumonia
24
14.2
Seizures
3
1.8
Diabetic ketoacidosis Chest pain
18 14
10.7 8.3
Hypoxemia Pneumothorax
3 3
1.8 1.8
Chronic obstructive pulmonary disease
13
7.7
Chlorox inhalation
2
1.2
Asthma
8
4.8
Flu syndrome
2
1,2
Delirium tremens
2
Altered mental status
8
1,2
4.8
Acute bronchitis
Pancreatitis
1
0.6
8
4.8
Gastroenteritis
1
0.6
Hyperventilation syndrome
8
4.8
Shortness of breath
8
4.8
Salicylism
1
0.6
Alcoholic ketoacidosis
1
0.6
Phlebitis
1
0.6
Alcoholic cardiomyopathy
1
0.6
Dehydration
1
0.6
Pyeloneph ritis
1
0.6
1
0,6
2.4
Febrile illness Hyperglycemic nonketotic coma
1
0.6
2.4
Sarcoid
1
0.6
Neoplastic pulmonary disease
5
3.0
Pulmonary edema
5
3.0
Chronic renal failure
4
2.4
Pulmonary embolus
4
2.4
Smoke inhalation
4
2.4
Pleurisy
4
Pulmonary infiltrates
4
Overdose
3
1.8
Table 2 PATIENTS WITH PNEUMONIA: RELATION OF P02 AND ADMISSION PO= 40-49
Tolal No.
3 (12%)
0
5 (19%) 11 (42%) 3 (12%) 2 (8%) 24
No, Admitted
3
0
5
6
1
2
17 (65%)
No. Not Admitted
0
0
0
5
2
~2
9 (35%)
In the category of chest pain, 14 arterial blood gases were done on six m e n and eight women (average age, 46). F o u r of these p a t i e n t s (28_6%) were a d m i t t e d to the hospital (two with the diagnosis of myocardial infarction; two w i t h the diagnosis of p u l m o n a r y embolus). All four of the a d m i t t e d p a t i e n t s h a d grossly abn o r m a l blood gases. Of the ten pat i e n t s not admitted, seven had norm a l blood gases and three had mild
60-69
Total
30-39
this latter category are too small to have statistical significance.
50-59
70-79
< 30
a b n o r m a l i t i e s i n their PO2 ranging between 70 and 79.
P02 Measurements Looking at specific parameters of blood gas analysis, the majority of a b n o r m a l i t i e s were of the P02 measu r e m e n t s ; ' 1 2 4 p a t i e n t s had abnormal PO2 m e a s u r e m e n t s after appro" priate correction for age (75% of all blood gases d r a w n ) . F i f t y - s e v e n of these 124 p a t i e n t s were admitted to the hospital - - 45% of all patients with a b n o r m a l PO2.
6:3 (Mar) 1977 , ~ P
It was i n t e r e s t i n g t h a t five paiie~ts with PO2 less t h a n 40 were not ~draitted; four of these p a t i e n t s had :hronic o b s t r u c t i v e p u l m o n a r y disease of long standing. Many of the patients w i t h a b n o r m a l PO2 were placed on oxygen and repeat blood gases showed improvement (Table 3).
Table 3 ABNORMAl PO2 (n=125) PO2 (mm Hg)
Number
< 30
4 (3%)
30-39
10 (8%)
pCO= Measurements
40-49
21 (17%)
Seven p a t i e n t s had hypercarbia defined as a PCO2 g r e a t e r t h a n 50_ Three of these patients had chronic obstructive l u n g disease with longstanding h y p e r c a r b i a and were not admitted. One p a t i e n t with chronic obstructive p u l m o n a r y disease a n d acute respiratory failure was admitIed. Of the other three patients, all were a s t h m a t i c s a n d were hospitalized; two r e q u i r e d i n t u b a t i o n later on the e v e n i n g of admission. There were 80 patients whose PCO2 was less t h a n 30 (hypocarbia). Of these, 64 fell in the 20 to 30 m m Hg range, e v o k e d l i t t l e c o n c e r n , a n d prompted the observation t h a t most patients h y p e r v e n t i l a t e d either prior Lo or d u r i n g the d r a w i n g of blood samples, s t a r t i n g of i n t r a v e n o u s fluids, or receiving injections, making this value by itself difficult to interpret. However, when hypocarbia was associated w i t h hypoxemia, it made the lowered PO2 all the more d i s t u r b i n g . F i f t e e n p a t i e n t s were found to have PCO2 of less t h a n 20, a finding t h a t usually reflects an approximate q u a d r u p l i n g of the respiratory rate. a E l e v e n of t h e s e 15 patients were h o s p i t a l i z e d . S e v e n were also found to be acidotic and three had associated severe hypoxemia. In one p a t i e n t with p u l m o n a r y embolus, the lowered PCO2 was the lone abnormality.
50-59
34 (27%)
60-69
32 (26%)
70-79
24 (19%)
pH In a n a l y z i n g the acid-base abnorraalities uncovered by arterial blood gases, we should state in our hospital ~ve use a large n u m b e r of venous pH d e t e r m i n a t i o n s , e s p e c i a l l y in the rapid e v a l u a t i o n of simple diabetic ketoacidosis. T w e n t y - t w o p a t i e n t s had an arterial pH less t h a n 7.30 and 18 of these were hospitalized. Table 4 shows the d i a g n o s e s i n those p a t i e n t s w i t h a c i d o s i s , associated hypoxemia or hypercarbia, and whether or not the p a t i e n t was admitted to the hospital. J~P
6:3 (Mar)1977
Number Hospitalized
4 5 13 16 11 8
(100%) (50%) (62%) (47%) (34%) (33%)
Table 4 ARTERIAL BLOOD GASES AND ACID-BASE ABNORMALITY pH < 7.20
pH 7.20-7.30
Associated Abnormality
Disposition
Diabetic ketoacidosis
2
6
1 pt.-hypoxemia
8 admitted
Chronic renal failure
1
1
Altered mental status
0
3
1 pt.-hypoxemia
2 admitted
Congestive heart failure
1
1
2 pt.-hypoxemia
2 ad m itted
Asthma
1
1
2 pt.-hypoxemia 2 pt.-hypercarbia
2 admitted
Chronic obstructive pulmonary disease
1
1
2 pt.-hypoxemia 1 pt.-hypercarbia
1 admitted
Pneumonia
0
2
2 pt.-hypoxemia
1 admitted
Seizures
0
1
1 pt.-hy.poxemia
0 admitted
Alcoholic ketoacidosis
0
1
0
1 admitted
Diagnosis
DISCUSSION We h a v e looked at blood gas a n a l y s e s in the setting of a medical emergency d e p a r t m e n t where rapid a c c u m u l a t i o n of all p e r t i n e n t data - historical, physical e x a m i n a t i o n and l a b o r a t o r y - - is r e q u i r e d for t h e physician to appropriately decide pat i e n t disposition. Arterial blood gases can be obtained in our hospital in a m a t t e r of m i n u t e s . I n c o n t r a s t , s e r u m electrolyte analysis often requires over one hour. Of the 5,000 patients seen, arterial blood gases were performed on 3.4%. Almost 85% of these a r t e r i a l blood gases were abnormal. First, this appears to be a reasonable, c e r t a i n l y n o t overzealous, use of these tests. Second, there is a very high yield if
1 admitted
one is a t t e m p t i n g to gather concrete data on a possible a b n o r m a l and lifet h r e a t e n i n g condition. Third, the fact t h a t one t h i r d of these p a t i e n t s were e v e n t u a l l y admitted to the hospital attests to the fact that arterial blood gases were c e r t a i n l y d r a w n on the sickest, and more difficult patients. A d i s t u r b i n g q u e s t i o n is s i m u l t a n e o u s l y raised, however. The limit a t i o n s of physical e x a m i n a t i o n in the e v a l u a t i o n of h y p o x e m i a a n d h y p e r c a r b i a are well known. ~ In our s t u d y , 60% of those p a t i e n t s w i t h p n e u m o n i a who had a r t e r i a l blood gases done were admitted to the bospital. In contrast, only 3.7c~ of all other p a t i e n t s with p n e u m o n i a , but without an arterial blood gas determ i n a t i o n , were admitted to the hos87/25
pital. All other clinical criteria notw i t h s t a n d i n g , one still must wonder w h e t h e r s i g n i f i c a n t hypoxemia was missed or u n d e r e s t i m a t e d in this latter group. The u l t i m a t e usefulness of a n arterial blood gas, as with any test, lies i n the a b i l i t y of the p h y s i c i a n to properly i n t e r p r e t the test and act
26/88
accordingly. In this study, it is app a r e n t t h a t the physicians involved found t h a t a b n o r m a l a r t e r i a l blood gas values were highly significant in the u l t i m a t e decision as to hospitalization of the patient.
REFERENCES 1. Respiration, in Handbook of Physiology, section 3. Washington, American
Physiological Society, 1964, p 17. 2. Breathnach CS: The development ~ blood gas analysis. Med Hist 16:51-62 1972. 3. Shapiro B: C l i n i c a l A p p l i c a t i o n of Blood Gases. Chicago, Year Book Medical Publishers, 1973, pp90-92. 4. Comroe JH Jr: The unreliability ~[ cyanosis in the recognition of anoxemia. A m J Med Sci 214:1-6, 1947.
6:3 (Mar) 1977 ~]~P