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A SIMPLIFIED METHOD OF DIRECT MEASUREMENT OF ARTERIAL BLOOD PRESSURE FOR USE IN EXTRACORPOREAL CIRCULATION
A SIMPLIFIED METHOD OF DIRECT MEASUREMENT OF ARTERIAL BLOOD PRESSURE FOR USE IN EXTRACORPOREAL CIRCULATION Thomas F. Boyd, M.D.* Boston, Mass.
W
ITH the increasing use of cardiovascular surgery, a need has developed for an accurate, safe, sterile, and inexpensive method of direct measurement of arterial blood pressure during the operative procedure. This is most important during open-heart surgery when the circulation is maintained by a heartlung machine and auscultatory methods cannot be used. However, even in poor risk candidates for closed-heart surgery (for example, Class IV patients with mitral stenosis), there is a crucial time during which the patient is under anesthesia but the heart or aorta are not visible or palpable. Once the patient has been given a muscular relaxant, such as succinylcholine, if the anesthesiologist cannot palpate the pulse and the chest is not open, "cardiac arrest" must be assumed. The electrocardiograph is useless in monitoring the patient for, after effective myocardial contractions have ceased, electrical activity continues. In the animal laboratory, we have always used a simple U-tube mercury manometer to record the mean arterial pressure in dogs undergoing cardiac surgery. As soon as the animal has been anesthetized, the femoral artery in the groin is exposed and a plastic catheter is inserted into the proximal artery and threaded cephalad into the abdominal aorta. Thereafter, the pressure is recorded as a mean pressure which normally is 160-130 mm. Hg for dogs and 90-70 mm. Hg for humans. Prior to transferring our attempts at open-heart surgery from the laboratory to the operating room, it was necessary to have a reliable method of measuring arterial blood pressure in humans. Statham-type pressure transducers, attached to a recording system of the Sanborn or Offner type, have been used for this purpose, but such a system requires the services of someone, not a member of the operating team, to balance, calibrate, and monitor the equipment during the surgical procedure. The addition of personnel and the heavy outlay of funds for the recording equipment adds greatly to the expense of this type of surgery. An additional disadvantage is that the pressure transducer cannot be autoelaved. From the Third (Boston University) Surgical Research Laboratory, Boston City Hospital, Boston, Mass. Received for publication March 26, 1962. •Assistant Director, Third (B.U.) Surgical Service and Research Laboratory, Boston City Hospital; Assistant Professor of Surgery, Boston University, School of Medicine. 240
Vol. 45, No. 2
February, 1963
MEASUREMENT OF ARTERIAL BLOOD PRESSURE
241
I t seemed logical that the mercury-filled U-tube manometer which we had used satisfactorily in the laboratory should be modified for use in the operating room. Accordingly, a model* was made which served so well in both the laboratory and the operating room that a description is herein presented to the everincreasing audience of cardiovascular surgeons. DESCRIPTION OF APPARATUS
The entire apparatus is autoclavable. The mercury to fill the U-tube manometer is autoclaved separately in a 50 ml. Erlenmeyer flask. The top of the flask is covered with a single thickness of heavy filter paper which is held in position with a rubber band, and the flask is autoclaved on its side, with the mouth down, for one hour in a standard autoclave at 250° P. and at a pressure of 15 pounds per square inch.
Pig:. 1A.—Autoclavable
simple apparatus for direct measurement of arterial blood pressure. Schematic diagram of appartus.
The apparatus itself (Fig. 1) consists of a plate of heavy (3 mm. thick) stainless steel, measuring 11 by 22 cm. (A). Mounted in the midline of this plate, 4 cm. from the right, is a vertical plate of stainless steel (2.5 mm. thick) measuring 5 by 22 cm. '(B). This is held in position by suitable stainless steel screws. Mounted on this plate is a stainless steel centimeter rule (C). On each side of the rule are the two vertical arms of a standard U-tube manometer made from standard laboratory glass tubing (D). The manometer is held in position on the vertical plate by flexible stainless steel clamps (E). On the left side of the base plate are four flexible stainless steel brackets {F), so positioned that they will firmly hold a Pyrex glass 500 ml. flask with a side-arm close to the top (G). The bottle is fitted with a single-holed No. 7 black rubber stopper (H). •Available from Edward A. Olson Company, Union Street, Ashland, Massachusetts.
BOYD
242
J. Thoracic and Cardiovas. Surg.
Through the single hole is threaded a piece of standard laboratory glass tubing bent at an angle of 90 degrees. The end of the tubing which enters the flask should extend approximately 4 cm. above the flask before reaching the angle, but within the flask, it should be approximately 1 cm. from the bottom (7). The stopper is securely held in the flask by means of a Hassan clamp* ( J ) .
Fig. IB.—Photograph of apparatus.
From the end of the glass tubing emerging from the stopper, a piece of standard rubber tubing (inner diameter, 3/1(i in.; wall thickness, Vio in.) (K) leads to the side-arm of a three-way, Luer-tip stopcock (L). From the non-Luer (female) end of the stopcock (L), another piece of identical rubber tubing (M) leads to the glass U-tube. The Luer-end of the stopcock (L) is attached to another Luer stopcock (N) which is identical. From the side-arm of the flask, a long piece (180 cm.) of the standard rubber tubing (0) leads from the operative field to the anesthesiologist who connects a standard blood pressure cuff valve to it and keeps this end in his possession. METHOD
We have used this system primarily by open exploration of the femoral artery and insertion of the recording tubing through a tiny stab wound in its anterior wall. We have used a 90 cm. length of small autoclavable polyvinyl tubing t for insertion into the femoral vessel and have advanced it cephalad for •Available from Edward A. Olson Company. tVx044 polyvinyl tubing, available from Becton, Dickinson, and Company, Rutherford, New Jersey.
Vol. 45, No. 2
February, 1963
MEASUREMENT OF ARTERIAL BLOOD PRESSURE
243
approximately 45 cm. so that it was well up in the abdominal aorta. An 18 gauge Ran-Fac adapter (P),* which is simply a standard needle hub with a short needle-like projection without any sharp edges, fits this tubing well and attaches to the Luer-end of the stopcock (2V), thus connecting the vascular tree to the recording system. In use, the recording system is assembled by the scrub nurse. The flask is filled to a point just below the side-arm with 0.85 per cent saline solution and 50 mg. of heparin is added to the flask. The U-tube is then filled half full with the sterilized mercury. The heparinized saline from the flask is used to fill the side of the U-tube from the mercury surface to the stopcock end of the rubber tubing (M). The stopper is inserted into the flask and secured with the Hassan clamp (
A slight drawback is that the inlying polyvinyl tubing must be removed by a sterile procedure at the bedside. The artery is repaired by tying the pursestring suture as the tubing is removed. The groin wound is closed in layers. This •Available as 18 gauge adapter for plastic tubing- from Randall Faichney Corporation, 299 Marginal Street, Boston 28, Massachusetts.
BOYD
244
J. Thoracic and Cardiovas. Surg.
particular difficulty perhaps can be overcome by the use of the Seldinger needle technique 2 and introduction of the plastic catheter percutaneously. However, the problem of the sterile removal from the groin wound at the bedside has been such a slight one that we have not used this Seldinger technique. The system is set up by the scrub nurse. It is easily read and used by the bedside nursing staff who also take arterial blood samples for analysis. These factors of convenience and ease override the slight difficulty of its removal by a small procedure at the bedside. REFERENCES
1. Ito, I., Faulkner, W. R., and Kolff, W. J . : Metabolic Acidosis and Its Correction in Patients Undergoing Open-Heart Operation, Cleveland Clin. Quart. 24: 193-203, 1957. 2. Seldinger, S. I.: Catheter Replacement of the Needle in Percutaneous Arteriograpliy: A New Technique, Acta radiol. 39: 368-376, 1953.
W
ITH the increasing use of cardiovascular surgery, a need has developed for an accurate, safe, sterile, and inexpensive method of direct measurement of arterial blood pressure during the operative procedure. This is most important during open-heart surgery when the circulation is maintained by a heartlung machine and auscultatory methods cannot be used. However, even in poor risk candidates for closed-heart surgery (for example, Class IV patients with mitral stenosis), there is a crucial time during which the patient is under anesthesia but the heart or aorta are not visible or palpable. Once the patient has been given a muscular relaxant, such as succinylcholine, if the anesthesiologist cannot palpate the pulse and the chest is not open, "cardiac arrest" must be assumed. The electrocardiograph is useless in monitoring the patient for, after effective myocardial contractions have ceased, electrical activity continues. In the animal laboratory, we have always used a simple U-tube mercury manometer to record the mean arterial pressure in dogs undergoing cardiac surgery. As soon as the animal has been anesthetized, the femoral artery in the groin is exposed and a plastic catheter is inserted into the proximal artery and threaded cephalad into the abdominal aorta. Thereafter, the pressure is recorded as a mean pressure which normally is 160-130 mm. Hg for dogs and 90-70 mm. Hg for humans. Prior to transferring our attempts at open-heart surgery from the laboratory to the operating room, it was necessary to have a reliable method of measuring arterial blood pressure in humans. Statham-type pressure transducers, attached to a recording system of the Sanborn or Offner type, have been used for this purpose, but such a system requires the services of someone, not a member of the operating team, to balance, calibrate, and monitor the equipment during the surgical procedure. The addition of personnel and the heavy outlay of funds for the recording equipment adds greatly to the expense of this type of surgery. An additional disadvantage is that the pressure transducer cannot be autoelaved. From the Third (Boston University) Surgical Research Laboratory, Boston City Hospital, Boston, Mass. Received for publication March 26, 1962. •Assistant Director, Third (B.U.) Surgical Service and Research Laboratory, Boston City Hospital; Assistant Professor of Surgery, Boston University, School of Medicine. 240
Vol. 45, No. 2
February, 1963
MEASUREMENT OF ARTERIAL BLOOD PRESSURE
241
I t seemed logical that the mercury-filled U-tube manometer which we had used satisfactorily in the laboratory should be modified for use in the operating room. Accordingly, a model* was made which served so well in both the laboratory and the operating room that a description is herein presented to the everincreasing audience of cardiovascular surgeons. DESCRIPTION OF APPARATUS
The entire apparatus is autoclavable. The mercury to fill the U-tube manometer is autoclaved separately in a 50 ml. Erlenmeyer flask. The top of the flask is covered with a single thickness of heavy filter paper which is held in position with a rubber band, and the flask is autoclaved on its side, with the mouth down, for one hour in a standard autoclave at 250° P. and at a pressure of 15 pounds per square inch.
Pig:. 1A.—Autoclavable
simple apparatus for direct measurement of arterial blood pressure. Schematic diagram of appartus.
The apparatus itself (Fig. 1) consists of a plate of heavy (3 mm. thick) stainless steel, measuring 11 by 22 cm. (A). Mounted in the midline of this plate, 4 cm. from the right, is a vertical plate of stainless steel (2.5 mm. thick) measuring 5 by 22 cm. '(B). This is held in position by suitable stainless steel screws. Mounted on this plate is a stainless steel centimeter rule (C). On each side of the rule are the two vertical arms of a standard U-tube manometer made from standard laboratory glass tubing (D). The manometer is held in position on the vertical plate by flexible stainless steel clamps (E). On the left side of the base plate are four flexible stainless steel brackets {F), so positioned that they will firmly hold a Pyrex glass 500 ml. flask with a side-arm close to the top (G). The bottle is fitted with a single-holed No. 7 black rubber stopper (H). •Available from Edward A. Olson Company, Union Street, Ashland, Massachusetts.
BOYD
242
J. Thoracic and Cardiovas. Surg.
Through the single hole is threaded a piece of standard laboratory glass tubing bent at an angle of 90 degrees. The end of the tubing which enters the flask should extend approximately 4 cm. above the flask before reaching the angle, but within the flask, it should be approximately 1 cm. from the bottom (7). The stopper is securely held in the flask by means of a Hassan clamp* ( J ) .
Fig. IB.—Photograph of apparatus.
From the end of the glass tubing emerging from the stopper, a piece of standard rubber tubing (inner diameter, 3/1(i in.; wall thickness, Vio in.) (K) leads to the side-arm of a three-way, Luer-tip stopcock (L). From the non-Luer (female) end of the stopcock (L), another piece of identical rubber tubing (M) leads to the glass U-tube. The Luer-end of the stopcock (L) is attached to another Luer stopcock (N) which is identical. From the side-arm of the flask, a long piece (180 cm.) of the standard rubber tubing (0) leads from the operative field to the anesthesiologist who connects a standard blood pressure cuff valve to it and keeps this end in his possession. METHOD
We have used this system primarily by open exploration of the femoral artery and insertion of the recording tubing through a tiny stab wound in its anterior wall. We have used a 90 cm. length of small autoclavable polyvinyl tubing t for insertion into the femoral vessel and have advanced it cephalad for •Available from Edward A. Olson Company. tVx044 polyvinyl tubing, available from Becton, Dickinson, and Company, Rutherford, New Jersey.
Vol. 45, No. 2
February, 1963
MEASUREMENT OF ARTERIAL BLOOD PRESSURE
243
approximately 45 cm. so that it was well up in the abdominal aorta. An 18 gauge Ran-Fac adapter (P),* which is simply a standard needle hub with a short needle-like projection without any sharp edges, fits this tubing well and attaches to the Luer-end of the stopcock (2V), thus connecting the vascular tree to the recording system. In use, the recording system is assembled by the scrub nurse. The flask is filled to a point just below the side-arm with 0.85 per cent saline solution and 50 mg. of heparin is added to the flask. The U-tube is then filled half full with the sterilized mercury. The heparinized saline from the flask is used to fill the side of the U-tube from the mercury surface to the stopcock end of the rubber tubing (M). The stopper is inserted into the flask and secured with the Hassan clamp (
A slight drawback is that the inlying polyvinyl tubing must be removed by a sterile procedure at the bedside. The artery is repaired by tying the pursestring suture as the tubing is removed. The groin wound is closed in layers. This •Available as 18 gauge adapter for plastic tubing- from Randall Faichney Corporation, 299 Marginal Street, Boston 28, Massachusetts.
BOYD
244
J. Thoracic and Cardiovas. Surg.
particular difficulty perhaps can be overcome by the use of the Seldinger needle technique 2 and introduction of the plastic catheter percutaneously. However, the problem of the sterile removal from the groin wound at the bedside has been such a slight one that we have not used this Seldinger technique. The system is set up by the scrub nurse. It is easily read and used by the bedside nursing staff who also take arterial blood samples for analysis. These factors of convenience and ease override the slight difficulty of its removal by a small procedure at the bedside. REFERENCES
1. Ito, I., Faulkner, W. R., and Kolff, W. J . : Metabolic Acidosis and Its Correction in Patients Undergoing Open-Heart Operation, Cleveland Clin. Quart. 24: 193-203, 1957. 2. Seldinger, S. I.: Catheter Replacement of the Needle in Percutaneous Arteriograpliy: A New Technique, Acta radiol. 39: 368-376, 1953.