December 1975
The Journal o f P E D I A T R I C S
973
Leg growth following umbilical artery catheter-associated thrombus formation: A 4-yearfollow-up Fourteen children were re-examined 4 years following the radiographic demonstration o f umbilical artery catheter associated thrombus formation. Positive correlations couM not be established between radiographically determined femoral and~or tibial lengths, length differences, pulse pressure differences, and the location of thrombi noted on the 1971 aortograms.
Stephen J. Boros, M.D.,* J a n e t F. N y s t r o m , R.N., M.Ed., T h e o d o r e R. Thompson, M.D., J o h n W. Reynolds, M.D., and H u g h J. Williams, M.D., Minneapolis, Minn.
TrIE EFFECT of excessive blood flow to growing limbs is well known. The overgrowth of extremities harboring large hemangiomas or arteriovenous fistulas are classic examples of this phenomenon. The effect of the converse problem, arterial insufficiency, is less well known. In 1964, Harris and associates 1 noted that children who had Blaloek-Taussig procedures performed for the palliation of tetralogy of Fallot frequently developed short arms on the side of the ligated artery. These findings were confirmed and expanded by Curranino and Engle. ~ In 1968 Basset and associates 3 and White and associates' each reported significant discrepancies of leg length in children years following cardiac catheterizations performed through femoral arteries. Collectively, these observations suggest that a compromise of arterial blood supply to a growing extremity may indeed reduce its ultimate size. At this institution, in 1971, Neal and colleagues ~ radiographically demonstrated arterial thrombus formation in 95% of infants with polyvinyl chloride umbilical artery catheters. In several cases fragmentation of thrombi with embolization into iliac and femoral vessels was observed. From Children's Hospital and the Department of Pediatrics, University of Minnesota. Supported by St. Paul Children's Hospital Research and Education Fund. *Reprint address: Children's Hospital, 311 Pleasant Ave., St. Paul, Minn. 55102.
Although, by the time of discharge, all infants appeared to have clinically normal lower extremity circulation, the ultimate consequence of the lowel~extremity emboli was unknown and was a genuine concern. The present paper describes the re-examination of those children originally studied by Neal and associates at 4 years of age. It attempts to correlate physical findings with earlier aortography findings. Symptoms, gait, leg lengths, and pulse pressures were evaluated. METHODS
AND RESULTS
Of the original 21 patients studied in 197l, two died during infancy. One died at 2 weeks of age following a superior mesenteric artery thrombosis (noted in the original report), and the other, at 2 months of age following abdominal surgery. At postmortem examination the second patient had a large, organized, previously unsuspected thrombus of the renal artery. Five of the remaining subjects had either moved, out of state or could not be located. Fourteen children, ranging in age from 3.7 to 4.3 years, were re-examined. Parents were questioned regarding any complaints by their children of leg pain, especially during or following exercise, or any noticeable limping. A general physical examination was performed. Ranges of motion, leg lengths, and leg circumferences were determined and walking and running gaits were evaluated. Femoral, popliteal, and dorsalis pedis pulses were palpated bilaterally and compared. Auscultatory
Vol. 87, No. 6, part L pp. 973-976
Boros et al.
974
The Journal of Pediatrics December 1975
Table I. Clinical data on patients
Radiologically measured bone lengths (cm)
Clinically measured circumference differences (em)
Normal range*
Total femur and tibia length difference
19.0
(16.6-21.2)
+ 0.2 L
0
0
+2R
18.1
18.1
(16.4-20.6)
0
+0.5 R
0
+2L
(21.0-26.0)
18.1
18.1
(16.2-20.8)
0
+0.2 R
0
+10R
24.9 23.3 24.1
(21.0-25.8) (20.8-25.6) (21.0-26.0)
20.4 18.9 19.1
20.9 19.1 19.3
(16.4-20.6) (16.2-20.5) (16.2-20.8)
+ 0.4 L + 0.2 L + 0.5 L
+I.0R +0.5 R 0
0 0 0
+8R +4L +2R
22.2
22.1
(20.8-25.6)
18.8
18.8
(16.2-20.5)
+ 0.1 R
+0.5 R
0
+2R
3.8 3.8 4.0
24.6 21.9 24.5
24.5 21.6 24.5
(20.8-25.6) (21.0-26.0) (21.2-26.0)
19.9 18.8 19.5
19.8 19.2 19.5
(16.2-20.5) (16.2-20.8) (16.4-20.8)
+ 0.2 R +0.I L 0
+ 0.5 L 0 + 0.5 R
0 0 0
+2R +4 R 0
M M M
3.6 4.0 4.1
23.3 23.5 19.7
23.5 23.6 19.9
(20.0-24.8) (21.2-26.0) (21.4-26.3)
18.9 19.5 16.7
18.9 19.5 16.5
(15.8-19.8) (16.4-20.8) (16.7-21.0)
+0.2 L + 0.1 L 0
+0.5 L 0 + 2.0 R
0 t 0
+4 L 0 +4L
M
4.3
21.7
21.6
(21.6-26.6)
20.0
19.7
(16.9-21.3)
+ 0.4 L
+ 0.3 L
0
+3R
Patient
Sex
Age at time of exam (yr)
1
F
4.0
22.2
22.4
(21.2-26.6)
19.0
2
M
3.9
22.5
22.5
(21.0-25.8)
3
F
3.8
22.6
22.6
4 5 6
M M F
3.9 3.8 3.8
25.0 23.3 23.8
7
M
3.8
8 9 10
M F M
11 12 13
14
Tibia
Femur I
Right I Left
R = right; L = left; C I A = c o m m o n
Normal range*
iliac a r t e r y ; A o = a o r t a ;
Right I Left
SMA = superior mesenteric
artery;
FA = femoral artery;
Ph
Thigh [ Calf
pre,5 diffe, ~mm ~g)
S F A = s u p e r f i c i a l f e m o r a l artery;
* _+ 2 S D f r o m t h e m e a n for a g e a n d sex. ~ tNot measured.
popliteal blood pressures were measured using standard, appropriate-sized, blood pressure cuffs. F e m o r a l and tibial lengths were measured radiologically using the techniques of Green and associates? Bone lengths were then compared to a normal range of values for sex and age taken from the femoral and tibial growth charts of Anderson and associates. 7 The results of these measurements are listed in the Table I. Measurements of bone length of only two subjects were outside the normal range. One girl had a tibial measurement slightly larger than the upper limit for age (0.3 cm). The other child, a boy, had previously undiagnosed Noonan syndrome and had overall growth retardation. Differences in measured leg lengths of subjects' femurs ranged from 0 to 0.3 cm with a m e a n difference of 0.1 cm. Tibial length differences varied from 0 to 0.5 cm (mean 0.1 cm). Overall leg length differentials measured from 0 to 0.5 cm with a m e a n difference of 0.2 cm. Clinically
measured thigh circumference differences varied from 0 to 2 em, the mean differential being 0.5 cm. Popliteal pulse pressures were obtained by subtracting the auscultated popliteal diastolic pressure from the auscultated systolic pressure. Differences between opposite extremities varied from 0 to 10 m m Hg, the m e a n difference being 3.4 mm Hg. Since measurements of blood pressure were obtained using a s p h y g m o m a n o m e t e r and standard auscultatory techniques, such small differences are probably not significant. Positive correlations could not be established between either femoral a n d / o r tibial length differences and pulse pressure differences. Neither did positive correlations exist between measured bone lengths (tibial and femoral) and the position of the catheter-related thrombus noted on the 1971 aortogram. The overall differences in all the measurements appeared to be distributed in a nonconsistent fashion.
Volume 87 Number 6, part 1
Leg growth following thrombus formation
f
1971 catheter position
1975 physical exam Normal
RUA T-7
Normal
RUA T-8
Normal
RUA T-3
Normal Normal Psychomotor retardation Normal
RUA T-9 RUA T-9 RUA T-8
Normal Normal Normal
LUA T-10 RUA T- 12 RUA T-9
Normal Normal Noonan syndrome
LUA T-7 RUA T-6 LUA T-4
Normal
RUA T-6
LUA T- 10
1971 aortography findings Clot in Ao, both CIA, migration down RCIA Clot in Ao with temporary block of SMA Large clot in Ao, migration down LCIA Technically unsatisfactory Technically unsatisfactory Large clot in distal Ao Large clot in distal Ao, total occlusion of RCIA, clot migration down LFA No clot Large clot at Ao bifurcation Clot in Ao, both CIA, migration down LFA Clot in distal Ao and LCIA Large clot in Ao Large clot in distal Ao, and LCIA, total occlusion of LSFA Clot in distal Ao, RCIA, and RHA
HA = hypogastricartery; UA = umbilicalartery.
DISCUSSION The effects of umbilical artery catheter-associated thrombi, with and without embolization, have legitimately concerned pediatricians. The demonstration of ubiquitious umbilical catheter associated thrombi by Neal and associates ~ and later by Strauss and associates 8 has caused some. neonatologists to plead for more restraint in the use of such catheters, and others to search for a less thrombogenic catheter material?, 10 The serious acute consequences of emboli origina.ting from umbilical artery catheters have been well described. Gangrene, 11 infarction of abdominal viscera, 1~renal artery thrombi with resultant hypertension, la and paraplegia, TM ~ have all been reported. The possibility of late appearing ill effects from seemingly innocent umbilical catheter-associated thrombi has been a persisting question. Interference with lower extremity blood flow by catheter-associated emboli leading
975
to a disturbance of extremity growth might be expected because of evidence for leg length inequalities following cardiac catheterizations through femoral arteries, "~,4 and u p p e r extremity shortening following Blalock-Taussig procedures?. ~ The incidence of such sequelae following radiographically localized umbilical artery catheter-associated emboli has not been examined previously. Recently, however, Powers and Swyer, l! using v e n o u s occlusion plethysmography, measured lower extremity blood flow in a group of infants 29 to 135 days after umbilical artery catheterization. They found no significant difference in blood flows between legs in which the iliac arteries had been catheterized and the opposite, noncatheterized extremities. In 1972, Tooley 9 described a follow-up study of 693 children who had umbilical artery catheters as infants. He observed no difference in gaits or clinically measured leg lengths or circumferences. Our re-examination of 14 children, ten of w h o m as neonates had umbilical catheter-associated arterial thrombi demonstrated by pull-out aortography, also failed to demonstrate any long-term sequelae. Gaits, radiologically determined leg lengths, clinically measured leg circumferences, and pulse pressures were not significantly different from one extremity to another, and could not be correlated with earlier aortography findings. In addition, femoral and tibial bone lengths were within the normal range for age with the exception of one child with Noonan syndrome. We presume that the activation of fibrinolytic systems and perhaps the recruitment of collateral arterial channels combine to ensure extremity blood flow adequate to allow normal growth. Our observations and those of Powers and Swyer TM and Tooley '~ suggest that the ever-present umbilical artery catheter-associated thrombus has little long-term effect on lower extremity blood flow or size. REFERENCES
1. Harris AM, Segel N, and Bishop JM: Blalock-Taussig anastomosis for tetralogy of Fallot: A ten-to-fifteen year follow-up, Br Heart J 26:266, 1964. 2. Curranino G, and Engle MA: The effects of ligation of the subclavian artery on the bones and soft tissues of the arms, J P~mATR 67:808, 1965. 3. Bassett FH, Lincoln CR, King TD, and Canent RV: Inequality in the size of the lower extremity following cardiac catheterization, South Med J 61:1013, 1968. 4. White JJ, Talbert JL, and Haller JA: Peripheral arterial injuries in infants and children, Ann Surg 167:757, 1968. 5. Neal WA, Reynolds JW, Jarvis CW, and Williams H J: Umbilical artery catheterization: Demonstrations of arterial thrombosis by aortography, Pediatrics 50:6, 1972. 6. Green WT, Wyatt GM, and Anderson M: Orthoroentgenography as a method of measuring the bones of the lower extremity, J Bone Joint Surg 28:61, 1946. 7. Anderson M, Messner MB, and Green WT: Distribution of
976
8.
9. 10.
11.
Boros et al.
lengths of the normal femur and tibia in children from one to eighteen years of age, J Bone Joint Surg 46-A:1197, 1964. Strauss AW, Escobedo M, and Goldring D: Continuous monitoring of arterial oxygen tension in the newborn infant, J PEDIATR 85:254, 1974. Tooley WH: What is the risk of an umbilical artery catheter? Pediatrics 50:1, t972. Boros SJ, Thompson TR, Reynolds JW, Jarvis CW, and Williams HJ: Reduced thrombus formation with silicone rubber (silastic) umbilical artery catheters, Pediatrics (in press). Rudolph N, Wang H, and Dragutsky D: Gangrene of the
The Journal of Pediatrics December 1975
12.
13.
14. 15. 16.
buttock: A complication of umbilical artery catheterization, Pediatrics 53:106, 1974. Wigger HJ, Bransilver BR, and Blanc WA: Thrombosis due to catheterization in infants and children, J PEOIATR 76:1, 1970. Ford KT, Teplick SK, and Clark RE: Renal artery embolism causing neonatal hypertension: A complication of umbilical artery catheterization, Radiology 113:169,. 1974. Aziz EM, and Robertson AF: Paraplegia: A complication of umbilical artery catheterization, J PEDIATR 82:1051, 1973. Winter RB: Personal communication. Powers WF, and Swyer PR: Limb blood flow following umbilical artery catheterization, Pediatrics 55:248, 1975.
The Journal o f P E D I A T R I C S
973
Leg growth following umbilical artery catheter-associated thrombus formation: A 4-yearfollow-up Fourteen children were re-examined 4 years following the radiographic demonstration o f umbilical artery catheter associated thrombus formation. Positive correlations couM not be established between radiographically determined femoral and~or tibial lengths, length differences, pulse pressure differences, and the location of thrombi noted on the 1971 aortograms.
Stephen J. Boros, M.D.,* J a n e t F. N y s t r o m , R.N., M.Ed., T h e o d o r e R. Thompson, M.D., J o h n W. Reynolds, M.D., and H u g h J. Williams, M.D., Minneapolis, Minn.
TrIE EFFECT of excessive blood flow to growing limbs is well known. The overgrowth of extremities harboring large hemangiomas or arteriovenous fistulas are classic examples of this phenomenon. The effect of the converse problem, arterial insufficiency, is less well known. In 1964, Harris and associates 1 noted that children who had Blaloek-Taussig procedures performed for the palliation of tetralogy of Fallot frequently developed short arms on the side of the ligated artery. These findings were confirmed and expanded by Curranino and Engle. ~ In 1968 Basset and associates 3 and White and associates' each reported significant discrepancies of leg length in children years following cardiac catheterizations performed through femoral arteries. Collectively, these observations suggest that a compromise of arterial blood supply to a growing extremity may indeed reduce its ultimate size. At this institution, in 1971, Neal and colleagues ~ radiographically demonstrated arterial thrombus formation in 95% of infants with polyvinyl chloride umbilical artery catheters. In several cases fragmentation of thrombi with embolization into iliac and femoral vessels was observed. From Children's Hospital and the Department of Pediatrics, University of Minnesota. Supported by St. Paul Children's Hospital Research and Education Fund. *Reprint address: Children's Hospital, 311 Pleasant Ave., St. Paul, Minn. 55102.
Although, by the time of discharge, all infants appeared to have clinically normal lower extremity circulation, the ultimate consequence of the lowel~extremity emboli was unknown and was a genuine concern. The present paper describes the re-examination of those children originally studied by Neal and associates at 4 years of age. It attempts to correlate physical findings with earlier aortography findings. Symptoms, gait, leg lengths, and pulse pressures were evaluated. METHODS
AND RESULTS
Of the original 21 patients studied in 197l, two died during infancy. One died at 2 weeks of age following a superior mesenteric artery thrombosis (noted in the original report), and the other, at 2 months of age following abdominal surgery. At postmortem examination the second patient had a large, organized, previously unsuspected thrombus of the renal artery. Five of the remaining subjects had either moved, out of state or could not be located. Fourteen children, ranging in age from 3.7 to 4.3 years, were re-examined. Parents were questioned regarding any complaints by their children of leg pain, especially during or following exercise, or any noticeable limping. A general physical examination was performed. Ranges of motion, leg lengths, and leg circumferences were determined and walking and running gaits were evaluated. Femoral, popliteal, and dorsalis pedis pulses were palpated bilaterally and compared. Auscultatory
Vol. 87, No. 6, part L pp. 973-976
Boros et al.
974
The Journal of Pediatrics December 1975
Table I. Clinical data on patients
Radiologically measured bone lengths (cm)
Clinically measured circumference differences (em)
Normal range*
Total femur and tibia length difference
19.0
(16.6-21.2)
+ 0.2 L
0
0
+2R
18.1
18.1
(16.4-20.6)
0
+0.5 R
0
+2L
(21.0-26.0)
18.1
18.1
(16.2-20.8)
0
+0.2 R
0
+10R
24.9 23.3 24.1
(21.0-25.8) (20.8-25.6) (21.0-26.0)
20.4 18.9 19.1
20.9 19.1 19.3
(16.4-20.6) (16.2-20.5) (16.2-20.8)
+ 0.4 L + 0.2 L + 0.5 L
+I.0R +0.5 R 0
0 0 0
+8R +4L +2R
22.2
22.1
(20.8-25.6)
18.8
18.8
(16.2-20.5)
+ 0.1 R
+0.5 R
0
+2R
3.8 3.8 4.0
24.6 21.9 24.5
24.5 21.6 24.5
(20.8-25.6) (21.0-26.0) (21.2-26.0)
19.9 18.8 19.5
19.8 19.2 19.5
(16.2-20.5) (16.2-20.8) (16.4-20.8)
+ 0.2 R +0.I L 0
+ 0.5 L 0 + 0.5 R
0 0 0
+2R +4 R 0
M M M
3.6 4.0 4.1
23.3 23.5 19.7
23.5 23.6 19.9
(20.0-24.8) (21.2-26.0) (21.4-26.3)
18.9 19.5 16.7
18.9 19.5 16.5
(15.8-19.8) (16.4-20.8) (16.7-21.0)
+0.2 L + 0.1 L 0
+0.5 L 0 + 2.0 R
0 t 0
+4 L 0 +4L
M
4.3
21.7
21.6
(21.6-26.6)
20.0
19.7
(16.9-21.3)
+ 0.4 L
+ 0.3 L
0
+3R
Patient
Sex
Age at time of exam (yr)
1
F
4.0
22.2
22.4
(21.2-26.6)
19.0
2
M
3.9
22.5
22.5
(21.0-25.8)
3
F
3.8
22.6
22.6
4 5 6
M M F
3.9 3.8 3.8
25.0 23.3 23.8
7
M
3.8
8 9 10
M F M
11 12 13
14
Tibia
Femur I
Right I Left
R = right; L = left; C I A = c o m m o n
Normal range*
iliac a r t e r y ; A o = a o r t a ;
Right I Left
SMA = superior mesenteric
artery;
FA = femoral artery;
Ph
Thigh [ Calf
pre,5 diffe, ~mm ~g)
S F A = s u p e r f i c i a l f e m o r a l artery;
* _+ 2 S D f r o m t h e m e a n for a g e a n d sex. ~ tNot measured.
popliteal blood pressures were measured using standard, appropriate-sized, blood pressure cuffs. F e m o r a l and tibial lengths were measured radiologically using the techniques of Green and associates? Bone lengths were then compared to a normal range of values for sex and age taken from the femoral and tibial growth charts of Anderson and associates. 7 The results of these measurements are listed in the Table I. Measurements of bone length of only two subjects were outside the normal range. One girl had a tibial measurement slightly larger than the upper limit for age (0.3 cm). The other child, a boy, had previously undiagnosed Noonan syndrome and had overall growth retardation. Differences in measured leg lengths of subjects' femurs ranged from 0 to 0.3 cm with a m e a n difference of 0.1 cm. Tibial length differences varied from 0 to 0.5 cm (mean 0.1 cm). Overall leg length differentials measured from 0 to 0.5 cm with a m e a n difference of 0.2 cm. Clinically
measured thigh circumference differences varied from 0 to 2 em, the mean differential being 0.5 cm. Popliteal pulse pressures were obtained by subtracting the auscultated popliteal diastolic pressure from the auscultated systolic pressure. Differences between opposite extremities varied from 0 to 10 m m Hg, the m e a n difference being 3.4 mm Hg. Since measurements of blood pressure were obtained using a s p h y g m o m a n o m e t e r and standard auscultatory techniques, such small differences are probably not significant. Positive correlations could not be established between either femoral a n d / o r tibial length differences and pulse pressure differences. Neither did positive correlations exist between measured bone lengths (tibial and femoral) and the position of the catheter-related thrombus noted on the 1971 aortogram. The overall differences in all the measurements appeared to be distributed in a nonconsistent fashion.
Volume 87 Number 6, part 1
Leg growth following thrombus formation
f
1971 catheter position
1975 physical exam Normal
RUA T-7
Normal
RUA T-8
Normal
RUA T-3
Normal Normal Psychomotor retardation Normal
RUA T-9 RUA T-9 RUA T-8
Normal Normal Normal
LUA T-10 RUA T- 12 RUA T-9
Normal Normal Noonan syndrome
LUA T-7 RUA T-6 LUA T-4
Normal
RUA T-6
LUA T- 10
1971 aortography findings Clot in Ao, both CIA, migration down RCIA Clot in Ao with temporary block of SMA Large clot in Ao, migration down LCIA Technically unsatisfactory Technically unsatisfactory Large clot in distal Ao Large clot in distal Ao, total occlusion of RCIA, clot migration down LFA No clot Large clot at Ao bifurcation Clot in Ao, both CIA, migration down LFA Clot in distal Ao and LCIA Large clot in Ao Large clot in distal Ao, and LCIA, total occlusion of LSFA Clot in distal Ao, RCIA, and RHA
HA = hypogastricartery; UA = umbilicalartery.
DISCUSSION The effects of umbilical artery catheter-associated thrombi, with and without embolization, have legitimately concerned pediatricians. The demonstration of ubiquitious umbilical catheter associated thrombi by Neal and associates ~ and later by Strauss and associates 8 has caused some. neonatologists to plead for more restraint in the use of such catheters, and others to search for a less thrombogenic catheter material?, 10 The serious acute consequences of emboli origina.ting from umbilical artery catheters have been well described. Gangrene, 11 infarction of abdominal viscera, 1~renal artery thrombi with resultant hypertension, la and paraplegia, TM ~ have all been reported. The possibility of late appearing ill effects from seemingly innocent umbilical catheter-associated thrombi has been a persisting question. Interference with lower extremity blood flow by catheter-associated emboli leading
975
to a disturbance of extremity growth might be expected because of evidence for leg length inequalities following cardiac catheterizations through femoral arteries, "~,4 and u p p e r extremity shortening following Blalock-Taussig procedures?. ~ The incidence of such sequelae following radiographically localized umbilical artery catheter-associated emboli has not been examined previously. Recently, however, Powers and Swyer, l! using v e n o u s occlusion plethysmography, measured lower extremity blood flow in a group of infants 29 to 135 days after umbilical artery catheterization. They found no significant difference in blood flows between legs in which the iliac arteries had been catheterized and the opposite, noncatheterized extremities. In 1972, Tooley 9 described a follow-up study of 693 children who had umbilical artery catheters as infants. He observed no difference in gaits or clinically measured leg lengths or circumferences. Our re-examination of 14 children, ten of w h o m as neonates had umbilical catheter-associated arterial thrombi demonstrated by pull-out aortography, also failed to demonstrate any long-term sequelae. Gaits, radiologically determined leg lengths, clinically measured leg circumferences, and pulse pressures were not significantly different from one extremity to another, and could not be correlated with earlier aortography findings. In addition, femoral and tibial bone lengths were within the normal range for age with the exception of one child with Noonan syndrome. We presume that the activation of fibrinolytic systems and perhaps the recruitment of collateral arterial channels combine to ensure extremity blood flow adequate to allow normal growth. Our observations and those of Powers and Swyer TM and Tooley '~ suggest that the ever-present umbilical artery catheter-associated thrombus has little long-term effect on lower extremity blood flow or size. REFERENCES
1. Harris AM, Segel N, and Bishop JM: Blalock-Taussig anastomosis for tetralogy of Fallot: A ten-to-fifteen year follow-up, Br Heart J 26:266, 1964. 2. Curranino G, and Engle MA: The effects of ligation of the subclavian artery on the bones and soft tissues of the arms, J P~mATR 67:808, 1965. 3. Bassett FH, Lincoln CR, King TD, and Canent RV: Inequality in the size of the lower extremity following cardiac catheterization, South Med J 61:1013, 1968. 4. White JJ, Talbert JL, and Haller JA: Peripheral arterial injuries in infants and children, Ann Surg 167:757, 1968. 5. Neal WA, Reynolds JW, Jarvis CW, and Williams H J: Umbilical artery catheterization: Demonstrations of arterial thrombosis by aortography, Pediatrics 50:6, 1972. 6. Green WT, Wyatt GM, and Anderson M: Orthoroentgenography as a method of measuring the bones of the lower extremity, J Bone Joint Surg 28:61, 1946. 7. Anderson M, Messner MB, and Green WT: Distribution of
976
8.
9. 10.
11.
Boros et al.
lengths of the normal femur and tibia in children from one to eighteen years of age, J Bone Joint Surg 46-A:1197, 1964. Strauss AW, Escobedo M, and Goldring D: Continuous monitoring of arterial oxygen tension in the newborn infant, J PEDIATR 85:254, 1974. Tooley WH: What is the risk of an umbilical artery catheter? Pediatrics 50:1, t972. Boros SJ, Thompson TR, Reynolds JW, Jarvis CW, and Williams HJ: Reduced thrombus formation with silicone rubber (silastic) umbilical artery catheters, Pediatrics (in press). Rudolph N, Wang H, and Dragutsky D: Gangrene of the
The Journal of Pediatrics December 1975
12.
13.
14. 15. 16.
buttock: A complication of umbilical artery catheterization, Pediatrics 53:106, 1974. Wigger HJ, Bransilver BR, and Blanc WA: Thrombosis due to catheterization in infants and children, J PEOIATR 76:1, 1970. Ford KT, Teplick SK, and Clark RE: Renal artery embolism causing neonatal hypertension: A complication of umbilical artery catheterization, Radiology 113:169,. 1974. Aziz EM, and Robertson AF: Paraplegia: A complication of umbilical artery catheterization, J PEDIATR 82:1051, 1973. Winter RB: Personal communication. Powers WF, and Swyer PR: Limb blood flow following umbilical artery catheterization, Pediatrics 55:248, 1975.
