ANESTH ANALG 815
Intraoperative Hypoxemic Spells in Tetralogy of Fallot
An Echocardiographic Analysis of Diagnosis and Treatment
William J. Greeley, MD, Thomas E. Stanley 111, MD, Ross M. Ungerleider, MD,
and Joseph A. Kisslo, MD
Key Words: ANESTHESIA-cardiovascular. patient was premedicated with meperidine 2 mgikg,
HEART, CONGENITAL DEFECTS-tetralogy of Fallot. pentobarbital 4 mg/kg, and diazepam 0.1 mgikg
orally 90 minutes before the induction of anesthesia.
Systemic arterial oxygen saturation in patients with Anesthesia was induced with oxygen, nitrous oxide,
tetralogy of Fallot is influenced by changes in the and halothane by mask and maintained with fentanyl
dynamics of right ventricular outflow tract obstruc- IV (75 pgikg). Indwelling arterial and central venous
tion or changes in systemic vascular resistance (1). catheters were placed for continuous pressure moni-
Intraoperative decreases in systemic vascular resis- toring. Ventilation was controlled and neuromuscu-
tance due to hypotension or increases in right ven- lar blockade was maintained using incremental doses
tricular outflow tract obstruction due to increased of pancuronium. Pulse rate (115-140 beatsimin),
sympathetic stimulation are associated with an in- blood pressure (90-120160-75 mm Hg), systemic arte-
crease in right-to-left shunting and a decrease in rial oxygen saturation (91-97%) as measured by pulse
systemic arterial hemoglobin oxygen saturation oximetry, and central venous pressure (6-8 mm Hg)
(Sao,), producing a hypoxemic or “tet” spell during remained stable during skin incision and sternotomy.
anesthesia and surgery (2). The precise mechanisms After placement of the arterial cannula of the extra-
of these spells and their treatment have been hypoth- corporeal circuit into the ascending aorta, blood pres-
esized but never demonstrated. We report two chil- sure gradually decreased to 70140 mm Hg over a 1-2
dren with tetralogy of Fallot who had acute hypox- min interval. The decrease in blood pressure was
emic spells during anesthesia and surgery where accompanied by a decrease in central venous pres-
dynamic changes in shunting and the effects of sure and a marked reduction in Sao, to 75%. Epicar-
propranolol and phenylephrine therapy were ob- dial echocardiography with CFI demonstrated a net
served for the first time by intraoperative two- right-to-left shunt through the ventricular septa1 de-
dimensional echocardiography with color flow imag- fect (VSD) (Fig. 1). Diagnoses of hypovolemia and a
ing (CFI). secondary hypoxemic spell due to increased right-
to-left shunting were made. Phenylephrine 25 pg,
administered IV, resulted in an immediate increase in
Case 1 systemic arterial pressure (110i74 mm Hg) and an
increase in Sao, to loo%, and an epicardial echocar-
An 18-month-old male with tetralogy of Fallot (TOF) diography with CFI that showed a reversal of shunt-
was anesthetized for complete repair of his defect. At ing with a net left-to-right ventricular shunt (Fig. 2).
the time of his operative procedure, the patient The patient was subsequently given a bolus of lac-
required no previous medical or surgical therapy for tated Ringer’s solution and the remainder of the case
his cardiac lesion and had no other medical illnesses. proceeded uneventfully.
Preoperative laboratory studies were normal. The
Received from the Division of Cardiothoracic Anesthesiology,
Departments of Anesthesiology, Medicine, and Surgery, The Duke Case 2
Heart Center, Duke University Medical Center, Durham, North
Carolina. Accepted for publication July 6, 1988. A 3-year-old male with TOF was anesthetized for
Address correspondence to Dr. Greeley, Department of Anes-
thesiology, Box 3046, Duke University Medical Center, Durham, complete repair of his defect. At the time of his
NC 27710. operative procedure, the patient required no prior
01989 by the lnternat~onalAncsthes~aResearch Soc~ety
816 ANESTH ANALG CLINICAL REPORTS
Figure 1. Doppler color flow map (left) and schematic diagram (right) of a modified long-axis view illustrating right-to-left shunting (blue
jet) across the ventricular septa1 defect during systole. RV, right ventricle; LV, left ventricle.
medical therapy, had had no surgery for his congen- mm Hg and was accompanied by an increase in heart
ital heart defect, and had no other medical illnesses. rate and a marked reduction in Sao, to 75%. Epicar-
Preoperative laboratory studies were normal except dial echocardiography and CFI demonstrated a net
for a hemoglobin of 16 gidL and a hematocrit of 49%. right-to-left shunt at the site of the VSD, as in Case 1.
Premedication consisted of meperidine 2 mgikg, pen- Increased sympathetic tone due to a light plane of
tobarbital 4 mgikg, and diazepam 0.1 mgikg orally 90 anesthesia with a secondary hypoxemic spell because
minutes before the induction of anesthesia. Anesthe- of an increase in dynamic right ventricular outflow
sia was induced with oxygen, nitrous oxide, and tract obstruction was suspected. Propranolol (0.25
halothane by mask and maintained with fentanyl (15 mg) was immediately administered IV and the halo-
pgikg) and halothane (0.25-1.0%). Ventilation was thane concentration was increased. Sao, gradually
controlled and neuromuscular blockade was main- increased to 9570, systemic arterial pressure de-
tained using incremental doses of pancuronium. creased to 90158 mm Hg, and heart rate decreased to
Pulse rate, blood pressure, Sao, (90-95%), and cen- 125 beatsimin. During these maneuvers epicardial
tral venous pressure remained stable during skin echocardiography with CFI showed a reversal of
incision and sternotomy. During dissection of the shunting with a net left-to-right ventricular shunt.
aorta and placement of the arterial cannula of the The remainder of the anesthetic and operative course
bypass circuit, blood pressure increased to 1351100 proceeded uneventfully.
CLINICAL REPORTS ANESTH ANALG 817
Figure 2. Doppler color flow map (left) and schematic diagram (right) of a modified long axis view illustrating left-to-right shunting (red
jet) across the ventricular septa1 defect during systole.
Echocardiographic Methodology and Results Color flow imaging is accomplished by electroni-
As part of a routine approach to the intraoperative cally separating the reflected ultrasound waves into
assessment of congenital heart defects at our institu- those defining anatomic targets and those defining
tion, epicardial echocardiography with CFI was per- flow within the chambers (5). Images of flow are
formed at specific intervals in these two patients. A created when sound waves are reflected from moving
5.0-MHz short-focus transducer was used and con- red blood cells and provide blood flow information,
nected to a Hewlett-Packard echocardiograph (77020 recorded in color. Therefore, cardiac structures are
CF) incorporating a color-imaging module. In each dispIayed in a monochrome mode, whereas blood
patient the transducer was topically sterilized and flow velocity is presented in color. Using CFI the
then passed into the operative field where it was entire cardiac image can be scanned along several
ensheathed in a sterile plastic sleeve before epicardial lines of sight within the sector arc of the two-
use. This phased array transducer, containing 64 dimensional echocardiographic image. Because blood
elements, provided high-resolution black and white flow toward and away from the transducer have
images recorded from the epicardial surface and different Doppler frequency shifts, direction of blood
displayed on a video screen. The same ultrasound flow can be identified and assigned specific colors. By
transducer was used simultaneously for color flow convention, blood flowing away from the transducer
imaging. is shown in blue, and flow toward the transducer is
818 ANESTH ANALG CLINICAL REPORTS
red (Figs. 1, 2). The magnitude of the flow velocity is namic alterations, and low incidence of side effects
indicated by the brightness of color and turbulence, (2). Although certain dynamics of the relief of hypox-
representing varying velocities of blood, and appears emic spells are known, the precise demonstration of
as a mosaic pattern of color. shunting and the precise pharmacologic effects on
In Case One with the transducer positioned on the shunting have not been demonstrated.
epicardial surface, systolic flow through the ventric- We report two cases of intraoperative hypoxemic
ular septa1 defect is seen as a blue jet indicating flow spells in patients with tetralogy of Fallot in whom
away from the transducer (Fig. 1). This represents two-dimensional echocardiography with CFI was
flow from the right ventricle to the left ventricle, i.e., used to document blood flow patterns before, during,
a net right-to-left shunt associated with hypotension and after therapeutic interventions. In Case One, the
and systemic oxygen desaturation. Immediately after hypoxemic spell was a direct result of hypotension
phenylephrine was administered to the patient in where a decrease in systemic vascular resistance
Case One, continuous two-dimensional echocardiog- augmented right-to-left shunting and a fall in Sao,.
raphy with CFI demonstrated reversal of shunt flow The administration of phenylephrine to this patient
(Fig. 2 ) . In Figure 2, blood flow direction through the immediately improved Sao, by increasing systemic
VSD now appears as a red hue, indicating flow arterial pressure and, presumably, systemic vascular
toward the transducer with flow directed from the resistance, with a resultant increase in pulmonary
left ventricle to the right ventricle. This change in blood flow. In Case Two, the hypoxemic episode was
shunting to a left-to-right shunt was associated with a result of a light plane of anesthesia where surgical
increases in blood pressure and Sao,. Not shown, stress increased sympathetic tone and dynamic right
similar changes in shunting before and after propran- ventricular outflow tract obstruction, augmenting
0101 were observed in Case Two by CFI. right-to-left shunting and causing a decrease in sys-
temic oxygen saturation. The administration of pro-
pranolol and deepening the level of anesthesia imme-
diately increased systemic arterial saturation by
Discussion reducing right ventricular outflow tract obstruction
Patients with cyanotic congenital heart disease un- with P-adrenergic blockade and decreasing sympa-
dergoing surgical procedures are at risk for worsen- thetic tone, augmenting pulmonary blood flow. In
ing right-to-left shunting and for developing hypox- both cases, we observed net right-to-left shunting
emia. This is especially true in patients with tetralogy through the VSD associated with systemic arterial
of Fallot where the interventricular communication, oxygen desaturation by two-dimensional echocar-
i.e., VSD, is large and nonrestrictive, and where the diography with CFI. Furthermore, after therapeutic
relative resistances of the pulmonary and systemic interventions, shunt reversal, i.e., net left-to-right
outflow tracts and vascular beds are the major deter- shunting, was demonstrated and was associated with
minant of shunt flow (4). In these patients, a decrease improvements in Sao,. Several mechanisms for such
in systemic vascular resistance and/or an increase in changes in shunting relating to the pharmacologic
right ventricular outflow tract obstruction due to manipulation of the relative resistances of the sys-
sympathetic stimulation produces an increase in temic vascular bed and the right ventricular outflow
right-to-left shunting and a decrease in Sao,. These tract have been suggested but never demonstrated.
changes have been suggested as mechanisms for the Heretofore speculated, we directly observed the re-
production of hypoxemic or "tet" spells (5). sults of these manipulations on the direction and
The treatment of the hypoxemic spells has been extent of shunting.
directed at increasing systemic vascular resistance Doppler CFI is a method for imaging blood flow
using an a-receptor agonist, decreasing dynamic through the heart by displaying flow data on the
right ventricular outflow tract obstruction using P- two-dimensional echocardiographic image (8,9). Us-
adrenergic blockade, controlling respiratory drive ing this technology the characteristics of blood flow,
and hyperpnea with morphine, and correcting any i.e., direction, velocity, and size, are displayed on the
metabolic acidosis using sodium bicarbonate. Phen- cardiac image by means of color encoding of the
ylephrine or propranolol have been effective in reliev- Doppler-generated flow signal. The intraoperative
ing these hypoxemic spells and are the current meth- use of CFI has recently been reported using a trans-
ods of treatment (6,7). Phenylephrine or propranolol esophageal approach (10). In the cases reported here
are preferred for the intraoperative management of the color flow images recorded from the epicardial
hypercyanotic spells because of their ease of admin- surface of the heart provided immediate information
istration, rapidity in onset of correcting the hemody- about blood flow direction that permitted specific
CLINICAL REPORTS ANESTH ANALG 819
therapeutic interventions and an assessment of ther- 2. Hickey PR, Wessel D. Treatment of Congenital Heart Disease.
In: Kaplan ]A, ed. Cardiac anesthesia. New York: Grune &
apy. Stratton, 1987:625-723.
In conclusion, the present case reports offer the 3. Kisslo J, Adams D, Belken RN. Doppler color flow imaging.
first direct evidence of net right-to-left shunting dur- New York: Churchhill Livingstone, 1988.
ing a hypoxemic episode (tet spell) where shunt 4. Berman W Jr. The hemodynamics of shunts in congenital heart
reversal and augmented systemic oxygen saturation disease. In: Johansen KM, Burggren WW. Cardiovascular
shunts: phylogenetic, ontogenetic, and clinical aspects. New
were observed after therapeutic interventions. These York: Raven Press, 1985:399410.
findings support the hypothesis that an increase in
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systemic vascular resistance relative to right ventric- sympathetic blockade on arterial oxygen saturation in Fallot’s
ular outflow obstruction augments pulmonary blood tetralogy. Circulation 1964;30:501-10.
flow and relieves hypoxemic spells. The pharmaco- 6. Nude1 DB, Berman MA, Talner NS. Effects of acutely increas-
logic effects of phenylephrine and propranolol ac- ing systemic vascular resistance on oxygen tension in tetralogy
of Fallot. Pediatrics 1976;58:24%51.
count for the changes in shunt reversal observed. The
7. Ponce FE, Williams LC, Webb HM, Riopel DA, Hohn AR.
use of two-dimensional echocardiography with CFI Propranolol palliation of tetralogy of fallot: experience with
provided a reliable method of assessing these long-term drug treatment in pediatric patients. Pediatrics 1973;
changes in intracardiac blood flow. 52:100-8,
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9. Omoto R. Color atlas of real-time two dimensional doppler
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1. Rudolph AM. Congenital Diseases of the Heart. Chicago: Year esophageal color flow mapping: initial experience. Anesth
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