Femoral vein diameter-a guide to femoral sheath size during peripheral stem cell harvesting in children

 

 

Abstract               Stem cells are undifferentiated biological cells that can differentiate into specialized cells and thus various tissues of the body. These can be harvested form the body and can be utilized in many treatment protocols like in bone marrow depression etc. In one such scenario of harvesting from a child, femoral vein cannulation was done which lead to low amplitude waves and oxygen saturation in corresponding lower limb. The child was later kept on observation and inj. Lignocaine infiltration around femoral artery to relieve spasm. This case led us to think that – Can femoral vein diameter be used as a guide to femoral vein cannulation and thus in turn preventing any untoward pressure on femoral artery? After this particular case we have started measuring femoral vein diameter and thus using femoral sheath accordingly. Key-words: Femoral Vein Diameter, Stem cell harvesting, Femoral Sheath Size

Key Messages: Femoral vein sheath diameter should always be in correspondence with femoral vein diameter for a safe post stem cell harvesting period especially in a child.

 

 

INTRODUCTION

Hematopoietic stem cells from different sources are being used for the reconstitution of lymphohematopoietic function after myeloablative, near-myeloablative, or nonmyeloablative treatment. Harvesting them from peripheral blood requires blood to be withdrawn from a major vein like femoral using a wide sheath which is then processed through a machine to harvest stem cells. There are no fixed guidelines regarding size of femoral sheath to be used in children. Inadequate sized sheath can compress femoral artery and thus compromise peripheral circulation. In that scenario using ultrasound for analyzing femoral vein diameter and thus deciding the adequate sized sheath can be of much help as different children may have different femoral diameter as per their anthropometric measurement. We present below such a case where a child developed compromised peripheral circulation. After that case we have started measuring femoral vein diameter routinely by ultrasound for femoral sheath cannulation in children.

 

CASE HISTORY

A 3 year old 11 kg male child was posted for peripheral blood stem cell harvesting. He was a donor for his elder sister who was undergoing chemotherapy for leukaemia and had bone marrow depression. After thorough history and medical examination, child was prepared for the procedure under general anaesthesia after getting a consent form parents. With 6 hours of fasting, child was shifted to operation theatre. After applying standard American society of anaesthesiologists monitoring, like EKG, pulse probe and NIBP, child was given general anaesthesia with sevoflurane induction, followed by intravenous access and muscle relaxant i.e. injection atracurium 10mg. The child was then intubated with uncuffed number 5 endotracheal tube. Anaesthesia was then maintained with oxygen, sevoflurane and injection atracurium infusion along with neuromuscular monitoring. Dorsalis pedis was palpated in both lower limbs and checked for plethysmograph and oxygen saturation to find out if there is any anomaly. Under all aseptic precautions and ultrasonographic guidance right sided femoral vein was cannulated using 5 french size sheath. This was followed by stem cell harvesting. The complete harvesting took around 4 hours, during this period anaesthesia and adequate relaxation was maintained. After the procedure the child was reversed with injection neostigmine 0.5mg and injection glycopyrrolate 10 microgram and trachea extubated. After extubation, pulse probe application revealed low amplitude waves and low oxygen saturation in right lower limb as compared to other limb. Dorsalis pedis pulsations were also feeble on right lower limb, though there were no signs of ischemia. Immediately a diagnosis of femoral artery compression was considered and femoral sheath was removed. Inj. Lignocaine (2%, 2ml) was infiltrated around the artery to relieve the spasm. Child was then kept under observation with continuous monitoring of plethysmograph for 24 hours. Within 24 hrs plethysmograph returned to normal amplitude and saturation without any complications in the concerned limb. Follow up of the child for next one month revealed no changes with respect to lower limb physiology.

 

DISCUSSION

Stem cells are undifferentiated biological cells that can differentiate into specialized cells and can divide to produce more stem cells and thus various tissues of the body. There are two broad types of stem cells: embryonic and adult stem cells. Third type of stem cells are called as Induced pluripotent stem cells which made from laboratory techniques from adult specialised cell. Adult stem cells can further be harvested form the body and can be utilized in many treatment protocols. Major sites for harvesting in humans are: Bone Marrow, adipose tissue (lipid cells), and blood¹. These stem cells have been applied in the treatment of especially cancers (post chemotherapy patients), blood disorders like thalassemia (post irradiation), and diseases like dementia, stroke, and diabetes. In case of blood disc arias or leukaemia, stem cells can be harvested either via bone marrow or peripheral blood². The process of harvesting stem cells via peripheral blood is known as apheresis. In this process blood is drawn from the donor and passed through aphaeresis machine that extracts the stem cells (CD34+) and returns other portions of the blood to the donor. This journey of blood requires two intravascular access in the donor: withdrawal and transfusion. For transfusion any 16 to 20 G intravenous cannula is adequate depending upon age and venous accessibility which is generally accessed in cubital fossa. For blood with drawl and transfer it to machine a pressured blood flow is required which is generally accessed through femoral vein cannulation. Femoral vein cannulation requires a sheath insertion of various sizes depending upon age. Currently there are no fixed criteria or guidelines available for the use of appropriate sized sheath. In our institute, we generally uses either 4 or 5 french size sheath in children between 3 to 5 years age group and 5 to 6 french above 5 years children. We have already used 5 french sheath in 3 year old children in other cases with no adverse consequences, but this particular incident made us to think about the appropriate size of sheath. There are few studies are available which had measured the femoral vein diameter using ultrasound and thus assessed the size of femoral sheath to be inserted. Fred Warkentine³ had measured the size of femoral vein in paediatric age group and given a relation between femoral vein diameter and femoral sheath size to be used. As per those measurements, 4-5 french sheath can be used in age group of 3 years. Though we cannot standardized these criteria unless thorough research is done but they can guide us to some extent with respect to size of sheath to be used. Also use of ultrasonography while inserting these sheaths can be of much benefit. We can measure the femoral vein diameter in millimetres which can be converted into French diameters to decide the size of sheath to be used. (1 french is exactly 1/3 millimetres. In SI units 1 french is 3.333...x10^-4 meters). Despite the use of appropriate sized sheath, its best to continuously monitor the plethysmograph for any changes in circulation in the limb. After this particular case we have started measuring femoral vein diameter and selecting sheath size accordingly. Also we now use continuous plethysmography measurement in the catheterized limb for post procedure monitoring, so that any variation can be detected early and managed accordingly.

 

REFERENCES

1. https://en.wikipedia.org/wiki/Stem_cell.
2. Mijovic A, Pamphilon D. Harvesting, processing and inventory management of pe-ripheral blood stem cells. Asian Journal of Transfusion Science. 2007;1(1):16-23.
3. Fred H. Warkentine et al. The Anatomic Relationship of Femoral Vein to Femoral Ar-tery in Euvolemic Pediatric Patients by Ultrasonography: Implications for Pediatric Femoral Central Venous Access ACAD EMERG MED • May 2008, Vol. 15, No. 5.