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The development of a hydrostatic compensating dual system for accurate intrauterine pressure determination
Volume Number
118 8
Food and Drug Administration-approved package insert, the recommended maximum dose of lidocaine was exceeded in the second case reported above and probably also was exceeded in the first case. The possibility of intravascular injection of the anesthetic agent must be considered in both of the reported cases. In the first patient hemorrhage in the area of the broad ligament observed on postmortem examination supports this hypothesis. In the second patient, aspiration prior to injection was performed. However, the failure to aspirate blood does not eliminate the possibility that vascular entry may have occurred. It has been demonstrated previously that paracervical block anesthesia during labor may result in direct vascular entry of the local anesthetic, despite the failure to obtain blood on aspiration prior to injection.8 Perhaps this results from advancement of the needle tip into a blood vessel during injection. Although no controlled study has been performed to confirm this, it seems likely that utilization of a paracervical block technique in which the anesthetic is injected just beneath the mucosa, such as described by Walden” for elective abortion procedures, would help reduce the likelihood of inadvertent injection into the uterine vasculature. Although intravascular entry of local anesthetic agents may not always be avoidable, strict adherence to the manufacturer’s current directions regarding the maximum dose of the drug would help reduce the likelihood of toxic reactions. In view of the increasing number of firsttrimester abortions being performed and the concomitant increasing number of patients exposed to local anesthesia, it is important to reduce even further the incidence of toxic reactions if similar deaths are to be prevented in the future. We wish to acknowledge the contribution of Dr. Edwin D. Lyman, Director of Health, and the staff of the Kansas State Department of Health, Topeka, Kansas. REFERENCES
1. Bonica, J. J.: Principles and Practice of Obstetric Analgesia and Anesthesia, Philadelphia, 1966, F. A. Davis Company, vol. 1, p. 508. 2. Nyirjesy, I., Hawks, B. L., Hebert, J. E., Hopwood, J. G., and Falls, F. C.: AM. J. OBSTET. GYNECOL. 87:231,1963. 3. Sinclair, J. C., Fox, H. A., Lentz, J. F., Fuld, G. L., and Murphy, J.: N. Engl. J. Med. 273: 1173, 1965.
Communications
in brief
1143
Rosefsky, J. B., and Petersiel, M. E.: N. Engl. J. Med. 278: 530, 1968. Tietze, C., and Lewit, S.: Personal communication. Smith, E. B., Hare, F. W., and Hiss, 0. W.: Anesth. Analg. 43: 476, 1964. Goodman, L: S., and Gilman, A.: The Pharmacoloeical Basis of Theraueutics. New York. 1970, Macmillan Publish& Co.,‘Inc., p. 72: 8. Chastain, G. M.: J. Med. Assoc. Ga. 58: 426, 1969. 9. Walden, W. D.: Obstet. Gynecol. 41: 473, 1973.
The development of a hydrostatic compensating dual system for accurate intrauterine pressure determination JORGE RODRIGUES LIMA, M.D. CARLOS ANTONIO BARBOSA MONTENEGRO, M.D. RONNEY BERNARDES PANERAI, M.Sc. JORGE DE REZENDE, M.D., F.A.C.S. Maternidade Escola (Head Prof. Jorge de Rezende), Federal University of Rio de Janeiro, Rio de ]aneiro, Brazil
T HE DETER M IN AT10 N 0 F illtI2UtWiIle resting pressure by conventional hydraulic transmission methods, generally used in clinical and investigation studies,‘3 2 can be significantly altered by artifacts. Inaccurate leveling and unobserved altimetric variations of the uterus frequently occur and must be constantly watched for and corrected. A hydrostatic pressure-free system was devised based on the subsequent philosophy: (1) If two identical membrane transducers are leveled and communicate through a hydraulic system with an open container and the container’s liquid surface is leveled with the transducers’ membranes, the readout is “0” in both preamplifiers. (2) If the container is lowered or elevated, a negative or positive hydrostatic pressure will develop and the Reprint requests: Dr. Jorge Rodrigues Escola, Federal University of Rio de Laranjeiras 180, Rio de Janeiro, Brazil.
Lima, Maternidade Janeiro, Rua das
1144
Communications
April IS, 1974 Am. J. Obstet. Gynecol.
in brief
This study was made with two pressure transducers* and two identical amplifiers made in our electronic laboratories calibrated to have an output of 100 mv. per millimeter of mercury. Both strain gauges and preamplifiers were mounted together in a box that stayed close to an oscillographt; and the reference container, kept near the patient, was attached to the obstetric bed. Instructions follows. 1. Calibrate
to
operate
the
the
empty
systems.
system
are
as
2. Fill the systems with sterilized water, keeping the container leveled with the transducers. 3. Recalibrate both preamplifiers to “0.” 4. Without withdrawing the tubes, secure the container to the patient’s bed or operating table at mid-uterus level. 5. Bring both pens of the oscillograph to the “0” position. 6. Connect the oscillograph as shown in Fig. 1. The left channel (corrected for hydrostatic
Fig. 1. Schematic
drawing of the dual compensating system. The transducer marked REF measures exclusively hydrostatic pressure, and the transducer marked UC measures intrauterine pressure and hydrostatic pressure. The polygraph channel marked COR reads the corrected intrauterine pressure: Intrauterine pressure and hydrostatic pressure (UC) are connected to the upper contact and hydrostatic pressure (REF) is connected to the middle contact. The ground is connected to the lower contact. The polygraph channel marked EST reads the uncorrected intrauterine pressure. The estimated intrauterine pressure is adjusted by shifting the “0” position and bringing the basal line to the corrected level, similar to the COR tracing. preamplifiers will give identical readings different from “0.” (3 ) If the two preamplifiers are connected to a differential amplifier, the resultant will be always “0” despite hydrostatic pressures. In order to measure intrauterine pressure, one of the tubes is kept in the container, and the other is attached to the intrauterine catheter. The differential oscillograph’s channel connected to both preamplifiers will measure the exact intrauterine pressure at the level of the container’s liquid surface level.
pressure) will read “0.” The right channel will assimilate the value of the hydrostatic pressure between the transducer’s membrane and the container’s liquid surface. 7. Connect the right-side tube to the intrauterine catheter and keep the left-side tube in the container. The oscillograph will record corrected intrauterine pressure in the left channel and an erroneous uncompensated measurement in the right channel (intrauterine pressure Ir hydrostatic pressure). 8. If a comparative
study
of the
compensating
qualities is desirable, reset the right channel to the values given by the left channel by moving the “0” adjustment knob. With a dual pressure system, the delicate transducers and cables are kept out of the way and integrate the electronic block free from mechanical vibrations, bumps, and shocks that unavoidably occur to the parts in the patient’s vicinity. Two very fine, pliable, unexpensive tubes connect the patient and the reference container to the electronic equipment and are easier to handle than the conventional thick and stiff shielded electric cable. Leveling of the liquid surface is very
easily
checked.
*Gauge P-23, Statham Instruments, Inc., 2230 Statham Blvd., Oxnard, California 93030. tCould Brush Mark 220, Brush Instruments Div., Clenite Corp., 3631 Perkins Ave., Cleveland, Ohio 44114.
Volume Number
118 8
Communications
in brief
1145
Fig. 2. Intrauterine pressure tracings of the end of the first stage and expulsion. The upper tracing (A) is corrected for hydrostatic pressure. The lower tracing (B) is uncorrected. The double arrow at C marks the moment when the obstetric table was elevated and the patient was prepared for delivery. The increase of hydrostatic pressure caused by the elevation of the table simulates hypertony. A small rise in the tonus can be seen in Channel A. For better visualization, tracings were run at 50 mm. Hg full scale, with double the usual sensitivity used for clinical monitoring of labor. Time is referred to in minutes, in a regressive counting from the moment of birth
The “cleaner” hydrostatic
graphs obtained by this method and have less mechanical artifacts, compensation is made with the
are and great-
est accuracy. REFERENCES
1. 2.
Alvarez, Ginecol. Csapo, 493,
H., and Caldeyro-Barcia, Obstet. 7: 3, 1948. A. I.: AM. J. OBSTET.
R. : GYNECOL.
Arch. 90:
1964.
A long-term follow-up of passively immunologically sterilized rats JOHN
P.
GUSDON,
JR.,
M.D.
Department of Obstetrics and Gynecology, Bowman Gray School of Medicine, Winston-Salem, North Carolina YEARS AGO, we published data which showed that the passive administration of a rabbit antibody against a specific human placental protein resulted in the destruction of SEVERAL
Supported by the Rockefeller Foundation and United States Public Health Service Grant 12197-02. Reprint requests: Dr. John P. Gusdon, Jr., Department of Obstetrics and Gynecology, Bowman Gray School of Medicine, Winston-S&m, North Carolina 27103.
that We
pregnancy learned
by
and failure continued
to deliver observation
any of
pups1 these
animals that, though their estrous cycles essentially returned to normal and they were frequently sperm positive, they never did give birth to any pups. Some cycles were prolonged. In our original paper, it was shown that those animals treated with rabbit anti-human placental lactogen developed a marked intrauterine inflammatory response with a destruction of fetal tissues following a normal appearance through the twelfth day of gestation. The remaining 18 animals have been observed over a 2 year period. Intermittently, some of the animals were killed for study. During this period of time, no animals gave birth, but all had been impregnated many times. They all appeared healthy up to the time they were killed. Three of the treated rats killed at 2 years of age were found to have developed basophilic or chromophobe adenomas of the pituitary. However, 5 of 20 control animals from the same original group were also found to have the same type of tumor. It is apparently not an uncommon development in certain female rats reaching an elderly age.2 No other type of pituitary pathology was found. Two animals in each group died from pneumonia. Of interest also is the fact that 3 control animals developed mammary carcinoma during this period of time. None of the
118 8
Food and Drug Administration-approved package insert, the recommended maximum dose of lidocaine was exceeded in the second case reported above and probably also was exceeded in the first case. The possibility of intravascular injection of the anesthetic agent must be considered in both of the reported cases. In the first patient hemorrhage in the area of the broad ligament observed on postmortem examination supports this hypothesis. In the second patient, aspiration prior to injection was performed. However, the failure to aspirate blood does not eliminate the possibility that vascular entry may have occurred. It has been demonstrated previously that paracervical block anesthesia during labor may result in direct vascular entry of the local anesthetic, despite the failure to obtain blood on aspiration prior to injection.8 Perhaps this results from advancement of the needle tip into a blood vessel during injection. Although no controlled study has been performed to confirm this, it seems likely that utilization of a paracervical block technique in which the anesthetic is injected just beneath the mucosa, such as described by Walden” for elective abortion procedures, would help reduce the likelihood of inadvertent injection into the uterine vasculature. Although intravascular entry of local anesthetic agents may not always be avoidable, strict adherence to the manufacturer’s current directions regarding the maximum dose of the drug would help reduce the likelihood of toxic reactions. In view of the increasing number of firsttrimester abortions being performed and the concomitant increasing number of patients exposed to local anesthesia, it is important to reduce even further the incidence of toxic reactions if similar deaths are to be prevented in the future. We wish to acknowledge the contribution of Dr. Edwin D. Lyman, Director of Health, and the staff of the Kansas State Department of Health, Topeka, Kansas. REFERENCES
1. Bonica, J. J.: Principles and Practice of Obstetric Analgesia and Anesthesia, Philadelphia, 1966, F. A. Davis Company, vol. 1, p. 508. 2. Nyirjesy, I., Hawks, B. L., Hebert, J. E., Hopwood, J. G., and Falls, F. C.: AM. J. OBSTET. GYNECOL. 87:231,1963. 3. Sinclair, J. C., Fox, H. A., Lentz, J. F., Fuld, G. L., and Murphy, J.: N. Engl. J. Med. 273: 1173, 1965.
Communications
in brief
1143
Rosefsky, J. B., and Petersiel, M. E.: N. Engl. J. Med. 278: 530, 1968. Tietze, C., and Lewit, S.: Personal communication. Smith, E. B., Hare, F. W., and Hiss, 0. W.: Anesth. Analg. 43: 476, 1964. Goodman, L: S., and Gilman, A.: The Pharmacoloeical Basis of Theraueutics. New York. 1970, Macmillan Publish& Co.,‘Inc., p. 72: 8. Chastain, G. M.: J. Med. Assoc. Ga. 58: 426, 1969. 9. Walden, W. D.: Obstet. Gynecol. 41: 473, 1973.
The development of a hydrostatic compensating dual system for accurate intrauterine pressure determination JORGE RODRIGUES LIMA, M.D. CARLOS ANTONIO BARBOSA MONTENEGRO, M.D. RONNEY BERNARDES PANERAI, M.Sc. JORGE DE REZENDE, M.D., F.A.C.S. Maternidade Escola (Head Prof. Jorge de Rezende), Federal University of Rio de Janeiro, Rio de ]aneiro, Brazil
T HE DETER M IN AT10 N 0 F illtI2UtWiIle resting pressure by conventional hydraulic transmission methods, generally used in clinical and investigation studies,‘3 2 can be significantly altered by artifacts. Inaccurate leveling and unobserved altimetric variations of the uterus frequently occur and must be constantly watched for and corrected. A hydrostatic pressure-free system was devised based on the subsequent philosophy: (1) If two identical membrane transducers are leveled and communicate through a hydraulic system with an open container and the container’s liquid surface is leveled with the transducers’ membranes, the readout is “0” in both preamplifiers. (2) If the container is lowered or elevated, a negative or positive hydrostatic pressure will develop and the Reprint requests: Dr. Jorge Rodrigues Escola, Federal University of Rio de Laranjeiras 180, Rio de Janeiro, Brazil.
Lima, Maternidade Janeiro, Rua das
1144
Communications
April IS, 1974 Am. J. Obstet. Gynecol.
in brief
This study was made with two pressure transducers* and two identical amplifiers made in our electronic laboratories calibrated to have an output of 100 mv. per millimeter of mercury. Both strain gauges and preamplifiers were mounted together in a box that stayed close to an oscillographt; and the reference container, kept near the patient, was attached to the obstetric bed. Instructions follows. 1. Calibrate
to
operate
the
the
empty
systems.
system
are
as
2. Fill the systems with sterilized water, keeping the container leveled with the transducers. 3. Recalibrate both preamplifiers to “0.” 4. Without withdrawing the tubes, secure the container to the patient’s bed or operating table at mid-uterus level. 5. Bring both pens of the oscillograph to the “0” position. 6. Connect the oscillograph as shown in Fig. 1. The left channel (corrected for hydrostatic
Fig. 1. Schematic
drawing of the dual compensating system. The transducer marked REF measures exclusively hydrostatic pressure, and the transducer marked UC measures intrauterine pressure and hydrostatic pressure. The polygraph channel marked COR reads the corrected intrauterine pressure: Intrauterine pressure and hydrostatic pressure (UC) are connected to the upper contact and hydrostatic pressure (REF) is connected to the middle contact. The ground is connected to the lower contact. The polygraph channel marked EST reads the uncorrected intrauterine pressure. The estimated intrauterine pressure is adjusted by shifting the “0” position and bringing the basal line to the corrected level, similar to the COR tracing. preamplifiers will give identical readings different from “0.” (3 ) If the two preamplifiers are connected to a differential amplifier, the resultant will be always “0” despite hydrostatic pressures. In order to measure intrauterine pressure, one of the tubes is kept in the container, and the other is attached to the intrauterine catheter. The differential oscillograph’s channel connected to both preamplifiers will measure the exact intrauterine pressure at the level of the container’s liquid surface level.
pressure) will read “0.” The right channel will assimilate the value of the hydrostatic pressure between the transducer’s membrane and the container’s liquid surface. 7. Connect the right-side tube to the intrauterine catheter and keep the left-side tube in the container. The oscillograph will record corrected intrauterine pressure in the left channel and an erroneous uncompensated measurement in the right channel (intrauterine pressure Ir hydrostatic pressure). 8. If a comparative
study
of the
compensating
qualities is desirable, reset the right channel to the values given by the left channel by moving the “0” adjustment knob. With a dual pressure system, the delicate transducers and cables are kept out of the way and integrate the electronic block free from mechanical vibrations, bumps, and shocks that unavoidably occur to the parts in the patient’s vicinity. Two very fine, pliable, unexpensive tubes connect the patient and the reference container to the electronic equipment and are easier to handle than the conventional thick and stiff shielded electric cable. Leveling of the liquid surface is very
easily
checked.
*Gauge P-23, Statham Instruments, Inc., 2230 Statham Blvd., Oxnard, California 93030. tCould Brush Mark 220, Brush Instruments Div., Clenite Corp., 3631 Perkins Ave., Cleveland, Ohio 44114.
Volume Number
118 8
Communications
in brief
1145
Fig. 2. Intrauterine pressure tracings of the end of the first stage and expulsion. The upper tracing (A) is corrected for hydrostatic pressure. The lower tracing (B) is uncorrected. The double arrow at C marks the moment when the obstetric table was elevated and the patient was prepared for delivery. The increase of hydrostatic pressure caused by the elevation of the table simulates hypertony. A small rise in the tonus can be seen in Channel A. For better visualization, tracings were run at 50 mm. Hg full scale, with double the usual sensitivity used for clinical monitoring of labor. Time is referred to in minutes, in a regressive counting from the moment of birth
The “cleaner” hydrostatic
graphs obtained by this method and have less mechanical artifacts, compensation is made with the
are and great-
est accuracy. REFERENCES
1. 2.
Alvarez, Ginecol. Csapo, 493,
H., and Caldeyro-Barcia, Obstet. 7: 3, 1948. A. I.: AM. J. OBSTET.
R. : GYNECOL.
Arch. 90:
1964.
A long-term follow-up of passively immunologically sterilized rats JOHN
P.
GUSDON,
JR.,
M.D.
Department of Obstetrics and Gynecology, Bowman Gray School of Medicine, Winston-Salem, North Carolina YEARS AGO, we published data which showed that the passive administration of a rabbit antibody against a specific human placental protein resulted in the destruction of SEVERAL
Supported by the Rockefeller Foundation and United States Public Health Service Grant 12197-02. Reprint requests: Dr. John P. Gusdon, Jr., Department of Obstetrics and Gynecology, Bowman Gray School of Medicine, Winston-S&m, North Carolina 27103.
that We
pregnancy learned
by
and failure continued
to deliver observation
any of
pups1 these
animals that, though their estrous cycles essentially returned to normal and they were frequently sperm positive, they never did give birth to any pups. Some cycles were prolonged. In our original paper, it was shown that those animals treated with rabbit anti-human placental lactogen developed a marked intrauterine inflammatory response with a destruction of fetal tissues following a normal appearance through the twelfth day of gestation. The remaining 18 animals have been observed over a 2 year period. Intermittently, some of the animals were killed for study. During this period of time, no animals gave birth, but all had been impregnated many times. They all appeared healthy up to the time they were killed. Three of the treated rats killed at 2 years of age were found to have developed basophilic or chromophobe adenomas of the pituitary. However, 5 of 20 control animals from the same original group were also found to have the same type of tumor. It is apparently not an uncommon development in certain female rats reaching an elderly age.2 No other type of pituitary pathology was found. Two animals in each group died from pneumonia. Of interest also is the fact that 3 control animals developed mammary carcinoma during this period of time. None of the