Changes of circulating blood volume incoronary arterial graft surgery withand without cardiopulmonary bypass

To the Editor:We evaluated the circulating blood volume (BV) ofpatients who underwent cardiac surgery with or with-out cardiopulmonary bypass (CPB) by using the newpulse dye-densitometry (PDD) method,1–3 to measurewhether there are differences in circulating BVchanges during and after surgery.

After approval by our Institutional Ethics Committeeand informed consent, anesthesia for patients with(n=12) and without (n=12) CBP was induced by mida-zolam, fentanyl, and vecuronium. Anesthesia was thenmaintained with midazolam and fentanyl, and/orsevoflurane. Before (preoperative) and after surgery(postoperative), including arrival in the intensive careunit, at 9:00 a.m. (POD 1) the morning after surgery,and two days afterwards at 9:00 a.m. (POD 2), BV wasmeasured by the usual PDD methods using a DDG ana-lyzer (Nihon Kohden Co., Tokyo, Japan). No significantdifferences between the CPB vs the non-CPB groupwere observed in age, weight, height, duration of opera-tion and anesthesia. The changes of BV and fluid balancevalues are shown at the four different times measured, inthe accompanying Table. BV in the CPB groupdecreased postoperatively and during POD 1, whereasBV in the non-CPB group did not change. A significantdifference in BV was observed between the CPB andnon-CPB groups at POD 1.

Our results suggest that the BV of patients undergo-ing coronary arterial graft surgery with CPB decreasesafter surgery and gradually recovers to its preoperative

level, whereas the BV in patients undergoing surgerywithout CPB does not change postoperatively.

Mitsuaki Yamazaki MD

Kiyoshi Shakunaga MD

Koki Hirota MD

Toyama, Japan

RReeffeerreenncceess1 Iijima T, Aoyagi T, Iwao Y, et al. Cardiac output and

circulating blood volume analysis by pulse dye- densit-ometry. J Clin Monit 1997; 13: 81–9.

2 Haruna M, Kumon K, Yahagi N, et al. Blood volumemeasurement at bedside using ICG pulse spec-trophometry. Anesthesiology 1998; 89: 1322–8.

3 Iijima T, Iwao Y, Sankawa H. Circulating blood vol-ume measured by pulse dye-densitometry. Comparisonwith 131 I-HSA analysis. Anesthesiology 1998; 89:1329–35.

Identification of the thoracic epiduralspace by the running infusion driptechnique

To the Editor:Location of the thoracic epidural space between T3 andT7 is difficult because of the extreme caudad angulationof the long posterior spinous processes at these levels.Also, above L2, the epidural space gradually becomessmaller because of the size of the spinal cord.

The loss-of-resistance technique is the most fre-quently used method for locating the epidural space.However, because of the difficulty of identification of

CORRESPONDENCE 935

TABLE Changes of BV and in-out balance values

Preoperative Postoperative POD 1 POD 2

BV (L)CPB 5.11 ± 1.64 3.73 ± 1.02a 3.81 ± 0.49a 4.73 ± 1.13non-CPB 5.29 ± 0.97 4.23 ± 1.16 5.21 ± 1.21* 5.44 ± 1.24

Prepost Post-POD 1 POD1–POD 2

Fluid balance (mL)CPB 4890 ± 1572 478 ± 526 290 ± 694non-CPB 3188 ± 773* -59 ± 754 -789 ± 607*

BV=circulating blood volume, fluid balance=fluid transfusion volume-blood loss-urine output; Prepost=fluid balance during anesthesia;Post-POD 1=fluid balance from postoperative to POD 1; POD 1–POD 2=in-out balance from POD 1 to POD 2; CPB=cardiopulmonarybypass.a: different from preoperative (ANOVA, P <0.05).*Different from CPB group (non-paired t test, P <0.05).Results are mean ± SD.

the epidural space in the thoracic region as well as thepossibility of inadvertent dural puncture resulting inintrathecal administration of the local anestheticand/or spinal cord injury, an objective technique foridentification of the thoracic epidural space must beconsidered as an alternative for the subjective loss-of-resistance technique.

Thirty years ago, I reported the use of the runninginfusion technique for identification of the lumbarepidural space.1 The technique has also proved to bevery useful for identifying the thoracic epidural space.Patients are positioned in the sitting position and,after scrubbing and draping the skin, a Tuohy epidur-al needle is inserted in the midlle line at the desiredthoracic level, with an upward angulation of 45–60angle to the skin. The needle is advanced through theskin, subcutaneous tissue, supraspinous ligament andinterspinous ligament. The stylet is then removed, andthe sterile end of a saline infusion drip tubing is care-fully connected to the hub of the needle. The drip isthen left open. The infusion sometimes drips slowlywhen the tip of the needle is in the loose interspinous

ligament. However, when the needle engages the lig-amentum flavum, marked resistance is felt and theinfusion always stops running. The needle is thenadvanced very slowly through the ligamentum flavum.As soon as the bevel of the needle enters the epiduralspace, the infusion starts to flow, thus identifying theepidural space (Figure). The rate of the drip variesfrom patient to patient, due to possible variations inthe epidural pressure. Entry into the space is usuallyassociated with a “give way” feeling and advancementof the needle is stopped immediately. The infusion isthen detached from the needle. If no cerebrospinalfluid drips from the needle, injection of 3 mL of lido-caine plus epinephrine 1:200,000 is used as a testdose. The injection without resistance, as well as theabsence of tachycardia or spinal anesthesia confirmproper epidural localization.

Anis Baraka MD FRCA

Beirut, Lebanon

RReeffeerreennccee1 Baraka A. Identification of the peridural space by a

running infusion drip. British Journal of Anaesthesia1972; 44: 122.

Gauging the depth of venipuncture dur-ing internal jugular vein cannulation

To the Editor:Right internal jugular vein (IJV) is the preferred sitefor central venous cannulation. During the procedurethere are chances of complications like arterial punc-ture, hematoma formation, pneumothorax, thoracicduct injury, arteiovenous fistula, and brachial plexusinjury due to the inability to judge the appropriatelength that the large bore needle traverses in order todo the venipuncture.1 Complications can be lifethreatening and may be avoided if the depth from skinto vein is measurable.

In an attempt of safer and accurate cannulation ofIJV, we devised a venipuncture and a 24-gauge guidepuncture needle with centimetre-highlighted mark-ings (Figure). The guide puncture determines thedirection of IJV and centimetre markings on it givethe exact distance at which IJV is hit. Then thevenipuncture needle is introduced in the same direc-tion as the guide puncture needle. As the distancefrom skin entry to the IJV is measured on the guidepuncture needle, the venipuncture needle is intro-duced to the prefixed distance to hit the IJV.

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FIGURE A saline infusion set is positioned approximately onemetre above the site of proposed epidural anesthesia and connect-ed to the hub of the epidural needle. As soon as the needle piercesthe ligamentum flavum, and enters the peridural space, the infu-sion starts to drip due to the hydrostatic pressure differencebetween the infusion and the peridural space.