Cutaneous blood flow in the TRAM flap

OURNAL OF PLASTIC SURGERY

Cutaneous blood flow in the TRAM flap

H. P. Tuominen, S. Asko-Seljavaara. N. E. Svartling and M. A. Harma

Departments of Plastic Surgery and Anaestkesia, Tiiiilii Hospital, Helsinki University Central Hospital. Helsinki, Firdand

SUMMARY. Changes in the cutaneous blood flow of the pedicled TRAM flap for breast reconstruction were studied in 15 patients with laser Doppler flowmetry (LDF) and transcutaneous oxygen tension (ptc0,). One patient was excluded from the study. The LDF value increased to 127 k 15 % of the base line on the random and to 151 f 13 % (p < 0.01) on the axial side after dissection of the random side of the flap. Ligation of the deep inferior epigastric artery caused a decrease to 57+8% (p < 0.001) on the random and to 78 + 11% on the axial side.

The random side ptc0, decreased from 48 f 2 mmHg 16.4 + 0.3 kPa] to 17 f 5 mmHg (2.3 f 0.7 kPa] (p < 0.001) after dissection of the flap and remained near zero for one week. Eight patients developed minor cutaneous necrosis on the random side, probably because the superior epigastric system could not adequately nourish the TRAM flap. Low LDF and ptc0, values after pedicle ligation and a negative response to oxygen stimulation predicted skin necrosis.

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The transverse rectus abdominis musculocutaneous (TRAM) flap for breast reconstruction was first introduced by Robbins (1979) and later popularised by Hartrampf with coworkers (1982). A natural, soft breast can be created with the TRAM flap without using any foreign material. Sometimes the method is unpredictable, with a moderate risk of complications. One of the major complications is partial skin necrosis, which has been reported in 2-28% of TRAM flap operations (Bunkis et al., 1983 ; Hartrampf and Bennett, 1987; McGraw et al., 1987; Petit et al., 1987; Slavin and Goldwyn, 1988).

The vascular anatomy of the superior and inferior epigastric systems has been described in detail (Boyd et al., 1984; Taylor et al., 1984; Kaufman et al., 1985; Costa rt al., 1987; Miller rt al., 1988; Taylor, 1988; Moon and Taylor, 1988; Taylor et al., 1990). However, no clinical haemodynamic studies have been made of the TRAM flap. It is not known how well the superior epigastric system can maintain blood flow on both cutaneous sides of the TRAM hap after the inferior epigastric vessels have been ligated. If the TRAM flaps which have a high risk for disturbances in cutaneous blood flow could be identified intraoperatively, some procedures to enhance the circulation could be considered.

Our study was designed to evaluate cutaneous blood flow in the TRAM flap during and after the operation by using laser Doppler flowmetry (LDF) and transcutaneous oxygen tension (ptc0,). We also compared LDF and ptc0, as monitors of cutaneous microcirculation. and as predictors of developing skin necrosis in flap surgery.

Patients and methods

Fifteen females who had undergone a mastectomy for breast cancer 1.5-7 (mean 4.8) years earlier were

scheduled for breast reconstruction using a pedicled transverse rectus abdominis musculocutaneous flap based on the contralateral rectus muscle and the superior epigastric vascular system. Informed consent was obtained from the patients. The study was approved by the Tiiiilij Hospital Ethical Committee. One patient was excluded from the study because of technically unsuccessful LDF measurements.

The age of the patients varied from 3 1-6 1 (46 + 8 : mean f SD) years, weight from 52--76 (64 + 8) kg and height from 158-l 73 ( 163 + 4) cm. One of the patients smoked. One of the patients took metoprolol for mild hypertension and thyroxine for postoperative hypo- thyroidism. One patient took timolol for mild hypertension. Two of the patients took tamoxifen because of axillary metastases found at the primary operation. The patients were otherwise healthy.

The patients were operated on under general anaesthesia as recommended for microvascular operations (Robins, 1983 ; Macdonald, 1985). Ventilation was controlled (Servo Ventilator 900, Siemens-Elema, Stockholm, Sweden) and the anaesthesia was maintained with nitrous oxide in oxygen and isoflurane. After induction the patients were given 500 ml of 6 % hydroxyethylstarch (Plasmafusin,“, Leiras, Turku. Finland) and Ringer acetate solution (Ringersteril R. Medipolar. Oulu, Finland) to maintain stable haemodynamics and to obtain mild hypervolaemic haemo- dilution. Haematocrit was kept at 0.30-0.35 by trans- fusing whole blood as needed. 1000 ml Dextran 40 (RheomacrodexR‘. Kabi Infusion A/S, Norway) was infused postoperatively until the next morning.

Heart rate, electrocardiogram, invasive blood pressure, endtidal CO,, inspiratory 0, and peripheral (index finger) and central temperatures were recorded continuously throughout the anaesthesia. Arterial blood was sampled for haematocrit and blood gas determina- tions as needed.

262 British Journal of Plastic Surgery

Table 1 The measuring times

Phase 1 Phase 2 Phase 3 Phase 4 Phase 5 Phase 6 Phase 7 Phase 8 Phase 9 Phase 10

On the preoperative day Patient anaesthetised, before incision Contralateral side of flap elevated The whole flap elevated and rectus muscle cut Inferior epigastric artery ligated Inferior epigastric vein ligated Recovery room First postoperative day Third postoperative day Seventh postoperative day

Intraoperative heat loss was prevented by using a warming mattress, maintaining the ambient temperature at 24 “C and warming the infusion fluids.

All patients were operated on by the same surgeon using a standardised technique. A predesigned skin paddle, mainly below the umbilicus, was first elevated on the random side as far as the linea alba. The ipsilateral (axial) side of the TRAM flap was dissected leaving 3 cm of the anterior rectus sheath on the flap. The rectus abdominis muscle was cut above the arcuate line. At this stage the flap had a double circulation through the inferior and the superior epigastric vessels. Next the inferior epigastric artery was ligated and the vein thereafter. The flap was tunnelled under the upper abdominal skin to the mastectomy wound. The breast was shaped by rotating the flap 180 degrees so that the medial side of the breast represented the random side of the flap. The distal portion of the random side (zone 4) was discarded. The abdominal wall was recon- structed without foreign material using nonabsorbable continuous sutures to the fascia.

Measurements

Measurements were taken perioperatively at different predetermined times (Table 1).

The cutaneous blood flow of the TRAM flap was monitored with a laser Doppler flowmeter (Periflux 2B, Perimed, Stockholm, Sweden). A standard probe was used. One probe holder was attached on the axial (ipsilateral) side and one on the random (contralateral) side of the flap skin, both the same distance from midline, approximately 5-7 cm depending on the form of the flap (Fig. 1). The probe holders were detached during skin disinfection and later attached at the same sites. After that the probe holders remained at the site until the last measurement on the seventh postoperative day. Each measurement lasted for at least 10 min.

PtcO, was measured with a transcutaneous oxygen tension monitor (Transcom 807, Novametrix Medical Systems, Inc., Conn., USA) about 1 cm cranially to the LDF measuring sites (Fig. 1). The probe was calibrated before each replacement against an oxygen free zero solution and ambient pressure. The temperature of the probe was 43.5 “C. Burn injuries were not observed on the skin under the probe. The ptc0, probe was left on the contralateral side after measurements at phase 2 and kept in place until transfer of the flap to the chest. The ipsilateral values were not

Fig. 1

Figure l-Laser Doppler (black circles) and transcutaneous oxygen tension (white circles) measuring sites on the TRAM flap skin (A) before and during and (B) after the operation. The ipsilateral side of the flap is over the rectus muscle.

measured from phase 3 to phase 6 due to the time consuming calibration needed before each replacement of the probe. At phases 1, 2 7, 8, 9 and 10 the ptc0, values were taken from both sides of the flap.

The inspired oxygen concentration was 2 1% during the pre- and postoperative measurements and 35 % intraoperatively.

Cutaneous Blood Flow in the TRAM Flap 263

An oxygen stimulation test was performed after each postoperative measurement with the patient breathing 60 % oxygen for 15 min. A minimum rise of 50% in the ptc0, value was considered a positive result in the oxygen test.

Sterility of the LDF and ptc0, probes was maintained during the operation.

Recta1 and peripheral temperatures were measured continuously using thermocouple probes (Exacon MC 8700, Exacon, Copenhagen, Denmark). The values taken after induction (phase 2). when the contralateral side of the flap was elevated (phase 3), 3 h after induction and at the end of operation were included in the study. Arterial oxygen tension was measured at phase 3-3 h after induction. in the recovery room and during the oxygen stimulation test.

Wound healing was observed clinically postoperatively and the patients were divided in two groups : those who developed a minor skin necrosis on the random side during the one week’s hospital stay and those who healed without skin complications. A skin area that was clinically without circulation and markedly darker than the rest of the TRAM flap was regarded as necrosis.

Statisticd arial?*sis

The LDF values were obtained in arbitrary units. Because values from different persons and even from different sites of the same person vary widely (Tenland. 1982) we expressed the red cell flux at each measuring time as a percentage of the reference value at each site. The measurements in phase 2 are regarded as reference values. because the LDF probe holders were detached from the skin after phase I and were kept at the same site only after phase 2.

The ptc0, values were measured in mm of mercury (mmHg). The respective values in kPa are given in brackets. The ptc0, measurement in phase 2 is regarded as the reference value.

The characteristics of the patients and the operation are given as mean&SD. All the other values are

LDF change

Go-, **

-v v --T r **

*** ***

Table 2 Characteristics of the patients and the operations (mean + SD).

Duration of operation (min) Ringer acetate given

intraoperatively (1) Whole blood given (units) Preoperative haemoglobin

concentration (g/l) Postoperative haemoglobin

concentration (g/l) PaO, at phase 3 (kPa) PaO, 3 h after induction PaO, in recovery room PaO, during the oxygen test T,..,., at phase 2 (“C) T,,.,,, 3 h after induction T,,,., at the end of operation T ,,Prl,Ih at phase 2 T pPrlph 3 h after induction T PPr,Ph at the end of operation

niean + SD rmg

184 + 34 225 330 2.9kO.7 2.S1.5

1.9iO.7 o- 3 135*x 115m 149

107*7 95 117

21.9+ 3.4 15.629.1 23.1k2.8 16.627.5 10.7+ 1.9 8.413.6 36. I k 13.5 20.243.X 36. I +0.5 35.1-36.X 35.4kO.7 34.4 36.6 35.4kO.7 34.4-36.7 34.0+ I .2 30.6 34.9 34.3kO.6 33.635.1 3’.4+‘.2 _- 27.lm 34.4

PaO, = arterial oxygen tension T,,,,, = rectal temperature (I3 measurements)

TSN,,,, = peripheral temperature (13 measurements)

expressed as mean f SEM. The statistical significance of differences between means was tested using Student’s t-test for dependent and independent series. P values of 0.05 or less were considered significant.

Results

The characteristics of the patients and the operations are expressed in Table 2.

The LDF dues

The changes in the LDF values are illustrated in Figure 2. The dissection of the contralateral side of the TRAM flap (phase 3) caused an increase in the contralateral LDF value to 127 &- 15 % and a significant increase in the ipsilateral value to 151 F 13 % (p < 0.0 1) from the base line level. When the whole flap was

20 I I I 1 1 T

2 3 4 5 6 7 8 9 10

measuring time Fig. 2

Figure 2-Change in the LDF value as a percentage of the initial value (phase 2) on the ipsilateral and contralateral sides of the TRAM flap. ** represents p i 0.01 and *** p < 0.001 for difference from initial value on each side of the flap. Measuring times as in Table I. Values represent mean k SEM.

264

W4 (mmHg)

100

i

**

80

British Journal of Plastic Surgery

60 --

40 --

*** *** ***

20 --

O-

1 2 3 4 5 6 7 8 9

measuring time

Fig. 3

Q

** *** IL 10

Figure Change in the transcutaneous oxygen tension (ptc0,) on the ipsilateral and contralateral sides of the TRAM flap. ** represents p c 0.01 and *** p < 0.001 for difference from initial value (phase I) on each side of the flap. $ represents p < 0.01 for difference between the ipsilateral and contralateral sides at each measuring time. Measuring times as in Table 1.

elevated and the inferior part of the rectus muscle cut (phase 4), the blood flow returned to the base line level on both sides. After ligation of the inferior epigastric artery (phase 5) the contralateral LDF value decreased significantly to 57 f 8 % (p < 0.001) and the ipsilateral value to 78 + 11% (not significant) of the base line level. Ligation of the vein (phase 6) did not cause a change from phase 5 in the LDF values. In the recovery room (phase 7) the contralateral LDF values were Iow, 62 + 8 % (p < 0.01) of the reference value, while the ipsilateral LDF values were near the base line level, 89 + 9 % (not significant). During phases 8, 9 and 10 the LDF values were near the base line level on both sides of the flap.

lateral ptc0, values were on the first postoperative day (phase 8) 15 +4 mmHg [2 f0.5 kPa] vs. 2 f 1 mmHg [0.3 f 0.1 kPa], on the third postoperative day (phase 9) 17 + 3 mmHg [2.3 +9.4 kPa] vs. 8 f2 mmHg [l. 1 f 0.3 kPa] and on the seventh postoperative day (phase 10) 25+4mmHg [2.3&0.4kPa] vs. 12+3 mmHg [I .6f0.4 kPa], (p < 0.01 at all times).

Oxygenation of the patients was maintained stable during the operation (Table 2).

The patients with necrosis

The ptc0, values

The ptc0, values are illustrated in Figure 3. On the contralateral side the ptc0, value increased significantly from 48 + 3 mmHg [6.4+0.4 kPa] to 72 f 6 mmHg [9.6 f 0.8 kPa] (p < 0.0 1) when the patient was anaesthetised (phase 2). The ptc0, value returned to base line at phase 3. It decreased significantly compared to the base line to 17+ 5 mmHg [2.3 f0.7 kPa], (p < 0.001) when the whole flap had been elevated and the rectus muscle cut (phase 4) and remained near zero until the third postoperative day (phase 9) when it increased to 8 If: 2 mmHg [ 1.1 & 0.3 kPa].

On the ipsilateral side the ptc0, values increased significantly from 44 + 4 mmHg [5.8 & 0.5 kPa] to 77 f 11 mmHg [10.2f 1.5 kPa] after induction of anaesthesia (phase 2). In the recovery room (phase 7) the ipsilateral ptc0, was low compared to the base line, 11 f 3 mmHg [ 1.5 f 0.4 kPa] and it remained below the reference level during phases 8, 9 and 10.

During the hospital stay 8 of the 14 patients developed skin necrosis. The width of the necrosis varied between 5 and 50 mm. Two patients had a 50 mm wide cutaneous necrosis. Both of these patients sustained other complications: one had a postoperative deep vein thrombosis in the right leg, verified with phleb- ography. Liver metastases were detected later by ultra- sound. She had been operated 1.5 years earlier for a T,N,M, infiltrating ductal carcinoma. The other patient with a broad necrosis developed marked postoperative atelectasis, verified clinically and by chest X-ray. She had been operated 3 years earlier for a T,N2M, adenocarcinoma with lumbar spine metastases treated with radiotherapy. Both of these patients were taking tamoxifen preoperatively. Three of the eight patients with skin necrosis needed surgical revision. The smaller areas of necrosis healed spon- taneously. There was no significant difference between the patients with and without necrosis regarding age, weight, height, duration of operation, transfusions needed, haemoglobin or arterial oxygen tension values. The only patient who smoked did not develop necrosis.

Postoperatively, during phases 7, 8. 9 and 10 the ipsilateral ptc0, values were significantly higher than

The contralateral LDF values were significantly

the contralateral values, but were still low on the lower in the necrosis group compared to the non-

seventh postoperative day. The ipsilateral vs. contra- necrosis group during phase 5 (43 + 7 % vs. 74 + 7 %, p < O.Ol),phase6(50~6%r~s.76~8%,p < O.Ol)and

Cutaneous Blood Flow in the TRAM Flap

LDF change

% INO- A

160- ----t- contra necrosis

265

l *

measuring time

LDF change

80-

20 2 3 4 5 6 7 8 9 IO

measuring time

Fig. 4

Figure 4--Change in the LDF value as a percentage of the initial value (phase 2) on the (A) contralateral and(B) ipsilateral sides of the TRAM flap in patients with and without necrosis. * represents p < 0.05 and ** p < 0.01 for difference between the patients with and without necrosis at each measuring time. Measuring times as in Table 1.

phase8(82+8% L’S. 114+ 11 %,p < O.Ol).Thecontra- lateral LDF values were lower in the necrosis group compared to the non necrosis group also during phases 3, 7, 9 and 10, but the changes were not significant (Fig. 4A).

The LDF value on the ipsilateral side was significantly lower in the necrosis group compared to the patients without necrosis during phase 5 (69&- 1% r’s, 90 k 9 %, p < 0.05) and phase 7 (78 + 12 % VS. 101 t_ 5 %, p < 0.01). The changes were not significant during phases 3. 4, 6, 8, 9 and 10 (Fig. 4B).

The contralateral ptc0, values were near zero after ligation of the artery (phase 5) in the necrosis group and at a slightly higher level in the flaps without necrosis. The ptc0, values in the necrosis group were significantly lower compared to the non-necrosis group during phase 9 (1 +O mmHg LO.1 +O kPa] W. 19f4 mmHg [2.5 +0.5 kPa]) and during phase 10 (5 +_ 3 mmHg [0.7 kO.4 kPa] z‘s. 21 f 2 mmHg [2.8 +0.3 kPa]) (Fig. 5A). The ipsilateral ptc0, values were significantly lower in the necrosis group compared to the patients without necrosis during phase 7 (2t2 mmHg [0.3&-0.3 kPa] rs. 23F4 mmHg

[3.1+0.5 kPa]), phase 8 (8_t3 mmHg [l.l F0.4kPa] 24+ 7 mmHg [3.2+0.9 kPa]). phase 9

yf; +3 mmHg [1.5+0.4kPa] L’S, 27 t2 mmHg [3.6+0.3 kPa]) and phase 10 (17+5 mmHg [2.3 + 0.7 kPa] VS. 36 + 5 mmHg [O. 13 + 0.7 kPa] (Fig. 5B).

The oxygen stimulation test was done at phases 7-10. The results are shown in Table 3. The oxygen test on the contralateral and ipsilateral sides of the flap was more often negative in the patients developing a contralateral skin necrosis than in the patients without necrosis, but the difference was not significant. In the two patients with a 50 mm necrosis the oxygen test was negative on both sides of the flap in all hut one measurement

Discussion

The most important finding of this study is the decrease of the LDF value after the inferior artery ligation and its slow rise to the base line level in the patients developing a cutaneous necrosis. The high risk of


WA (mmW 120 A

80

60

40

20

0 I: 1

I L 2 3 4 5 6 7 8 9 10

measuring time

n ipsi no necrosis

ipsi necrosis

1 2 3 4 5 6 7 8 9 10

measuring time Fig. 5

Figure Change in the transcutaneous oxygen tension @co,) on the (A) contralateral and (B) ipsilateral sides of the TRAM flap in patients with and without necrosis. * represents p < 0.05, ** p < 0.01 and *** at each measuring time. Measuring times as in Table 1.

p < 0.001 for difference between the patients with and without necrosis

Table 3 Results of the oxygen stimulation test. Contralateral and ipsilateral measurements are represented separately in patients with and without necrosis. An increase of at least 50 % of the initial (room air) ptc0, value after the patient breathing 60% oxygen for 15 min is considered a positive result (+ )

Coniralaieral Ipsilateral

Necrosis No necrosis Necrosis No necrosis n=8 n=6 n=8 n=6

Measuring time f _ + - + - + -

Recovery room 1 7 3 3 2 6 5 1 1st postoperative day 2 6 2 3* 5 2’ 5 1 3rd postoperative day 2 5* 3 1 2 6 4 1* 7th postoperative day 2 6 5 1 5 3 5 1

* represents a missing measurement


circulatory complications in the TRAM flap becomes more understandable when we learn more about the haemodynamics of the flap.

In anatomical studies the superior and deep inferior epigastric vascular systems have been widely described (Boyd rt al., 1984; Taylor et al., 1984; Costa et al., 1987; Miller et al., 1988; Taylor, 1988; Moon and Taylor. 1988 ; Taylor et al.. 1990). It has been shown that the deep inferior epigastric artery nourishes a larger abdominal skin area than does the superior epigastric artery (Boyd et al., 1984). The pedicled TRAM flap is based on its nondominant pedicle, the deep superior epigastric artery. In the pedicled TRAM flap the axial skin island receives direct paraumbilical and infraumbilical perforators from the deep inferior epigastric artery, which fills in a retrograde fashion from the superior epigastric system by means of the reduced-calibre corkscrew vessels, “choke vessels” (Boyd et al., 1984). The contralateral (random) skin area gets its blood supply through anastomotic chan- nels crossing the midline in the subdermal plexus (Taylor et al.. 1984) and by means of distinct arteries in the subcutaneous fat tissue superficially to the fascia (Kaufman et al.. 1985). These distinct arteries rarely reach the lateral zone of the TRAM flap (zone 4).

The venous drainage of the TRAM flap skin is through paraumbilical perforators, as on the arterial side, to the deep inferior epigastric veins and then to the deep superior epigastric veins. The deep inferior epigastric veins have valves that prevent retrograde flow. Midline crossover is through several branches of the superficial and deep epigastric veins (Costa et al.. 1987; Taylor et al., 1990).

In the present study we used both transcutaneous oxygen tension and laser Doppler flowmetry as monitors of skin blood flow. The laser Doppler flowmeter is a noninvasive, continuous monitor of microcirculation. Some authors have been sceptical about LDF being reliable (Hickerson et al.. 1990; Banic et al., I990), but generally it is considered a good indicator of changes in blood flow in clinical plastic surgery (Heden et al., 198.5; Svensson etal., 1985a, b; Klitzman, 1990). The blood flow or flux is expressed as a relative value in arbitrary units. No absolute blood flow value is obtained. The LDF value is influenced only minimally by wide differences in oxygen tensions. LDF provides blood flow information from the superficial layer of the skin (about 1 mm from the skin surface), including the capillary loops of the dermal plexus. The technical properties of LDF have been described by Nilsson et al. (1980). Tenland (1982) and Svensson et al. (1983). The LDF level varies greatly between individuals and between measuring sites. Daily LDF level variations of 20-30 % occur frequently. A LDF value measured continuously or repeatedly at exactly the same site of a person is considered reliable (Tenland, 1982).

In the present study an increase in the LDF value is observed on the skin of the TRAM flap when the random side is elevated, more pronounced on the ipsilateral side. One possible reason for the hyperaemia is opening up of the choke vessels originating from the superior epigastric artery. The dissection of the random side of the TRAM flap causes a temporary decrease of flap skin blood flow since the subdermal

blood vessels from the surrounding areas are cut; this might cause the choke vessels to open up and thus an increase in the blood flow noted on both sides of the flap. Boyd et al. (1990) assumed that transient hypoxia in muscle and skin causes an opening of existing arterioles. A similar hyperaemia was observed in musculocutaneous flaps of dogs by Gottrup rt al. (1984). They assumed that the hyperaemia was mostly due to humoral or neural influences.

Another cause for changes in flap skin blood flow is the patient’s temperature. According to Awwad et al. (1983) the flap blood flow varies directly with temperature. During our study there were no marked changes in the rectal and peripheral temperatures of the patients. Ambient temperature was maintained at 24 “C and the patients were kept warm with several methods.

In this study ligation of the deep inferior epigastric artery caused a significant decrease in the LDF value on the contralateral side. probably because the inferior artery is the dominant artery of the TRAM flap. Skin blood flow on the random side of the flap did not return to the initial level until the first postoperative day. This indicates that the superior system is able slowly to increase blood flow in the flap by keeping the choke vessels open. Young (1982) pointed out that in random pattern flaps the forming of new vessels at the healing margins causes augmentation of blood flow postoperatively.

It has been thought that venous stasis is an important reason for impaired circulation in the TRAM flap. In this study we noted that ligating of the deep inferior epigastric vein seemed to have no effect on the skin blood flow.

Transcutaneous oxygen tension has been used for flap monitoring (Achauer et al., 1980; Harrison et al., 1981; Svedman ef al., 1982; Smith et al., 1983). PtcO, is an indirect indicator of blood flow. PtcO, reflects oxygen delivery and consumption in the skin (Achauer and Black, 1984).

In this study the contralateral transcutaneous oxygen tension fell to a low level after dissection of the whole skin flap and remained near zero till the seventh postoperative day, when the measurements were finished. In spite of the low postoperative ptc0, values most of the flaps healed without major problems; three of them needed surgical excision of skin necrosis. Very low ptc0, values have been found in surviving flaps postoperatively (Achauer et al., 1980: Svedman et al., 1982; Gottrup et al., 1984). Raskin et al. (1983) and Hjortdal et al. ( 1991) concluded that elevation of island flaps results in sympathetic denervation of the microcirculation, which leads to opening up of arteriovenous shunts that partially bypass the subdermal plexus and this is observed as low ptc0, values. It has been postulated that a low oxygen tension is an indirect measure of increased metabolic rate in the skin (Achauer and Black, 1984). We assume that the intraoperative decrease in the ptc0, value is a sign of diminished skin blood flow caused by arteriovenous shunts opening up. Postoperatively the ptc0, values remain low, especially on the less nourished contralateral side, probably because of an increased consumption of oxygen needed for healing of the flap.


In this study 8 of the 14 patients developed a minor area of necrosis on the random (contralateral) side skin of the TRAM flap. These eight patients had a marked decrease in the contralateral LDF value or a ptc0, level near zero after the deep inferior epigastric artery was ligated. It seems that LDF and ptc0, measurements during the operation can predict cutaneous skin necrosis of the TRAM flap. If the patients likely to develop necrosis could be identified intraoperatively, techniques to increase the circulation could then be used. Adding a microsurgical anastomosis to the pedicled TRAM flap (Harashina et ai., 1987; Scheflan, 1988) or making a free microvascular TRAM flap (Holmstrdm, 1979; Friedman et al., 1985; Arnei et al., 1988, 1991) could theoretically increase the blood flow in the TRAM flap. Further studies are needed on these subjects.

A response of ptc0, to increased inspired oxygen concentration has been claimed to be a sign of intact circulation and flap survival (Achauer et al., 1980). In the present study a negative oxygen test was observed in the two patients with the broadest (50 mm) necrosis areas. In the other six patients with smaller necrosis areas the oxygen test gave contradictory results. A possible cause for this is that the ptc0, probes were not exactly over the contralateral edge where the necrosis developed but a little more centrally in the flap.

According to our results it seems that, compared to LDF, ptc0, is not sensitive to minor changes in the circulation of the most superficial layer of the skin, especially when the circulation decreases to very low levels. We find LDF a more suitable technique than ptc0, to monitor haemodynamic changes during the TRAM flap operation. LDF and ptc0, measurements cannot be recommended for routine intraoperative monitoring of conventional TRAM flap operations, since they prolong the operation. However, they may be useful in some circumstances, e.g. when a pedicled TRAM flap with additional anastomosis is planned and in monitoring microvascular TRAM flaps.

In conclusion, this haemodynamic study of breast reconstruction with the pedicled TRAM flap shows that ligation of the deep inferior epigastric artery causes a significant decrease of the cutaneous blood flow, especially on the random side. In half of the patients the circulation recovers, presumably by means of the choke vessels, and the nondominant superior epigastric system is able to nourish both sides of the flap adequately. However, in the other half of the patients the blood flow of the random side depends more on the inferior artery, and these patients there- fore have a greater tendency to develop necrosis of the skin. Ligation of the deep inferior veins, according to this study, has no effect on the blood flow in the flap. More haemodynamic studies on the different TRAM flap variations, such as the free TRAM flap, are needed to optimise the TRAM flap for breast reconstruction.

Acknowledgement

The skilful assistance of MS Sisko Asp, MSc, in analysis of the data is gratefully acknowledged.

References

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The Authors

Hanna P. Tuominen, MD, Consultant Anaesthetist Sirpa Asko-Seljavaara, MD, Assistant Professor, Head of the

Department of Plastic Surgery Nils E. Svartling, MD, Consultant Anaesthetist Markku A. Hiirml, MD, Consultant Plastic Surgeon

Departments of Plastic Surgery and Anaesthesia, Tljiilti Hospital. Helsinki University Central Hospital. Topeliuksenkatu 5, 00260 Helsinki. Finland.

Requests for reprints to Dr H. Tuominen.

Paper received I1 October 1991. Accepted 2 January 1992, after revision.

This research was supported by a grant from the Association for Development and Education of Plastic Surgery and Burn Treatment in Finland.

Cutaneous blood flow in the TRAM flap

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