Unilateral Biportal Endoscopy (UBE) is a fluid medium surgery. Continuous saline output is critical Hydrostatic pressure. Managing the fluid is the key to successful surgery. It use the principle of Bernauli’s and Pascal law. Explore the water dynamic of UBE surgery.

1. cka
SURESH BISHOKARMA, MCH
CONSULTANT NEUROSURGEON
UPENDRA DEVKOTA MEMORIAL NATIONAL INSTITUTE OF NEUROLOGICAL
AND ALLIED SCIENCES
WATER DYNAMICS IN UBE

2. UBE is fluid-medium surgery
INTRODUCTION
Ingress: Saline
Paraspinal well
chamber
Egress from outlet

3. Continuous saline output is critical
Hydrostatic pressure
Managing the fluid is the key to successful surgery.
INTRODUCTION

4. HYDRAULIC POWER

5. cka
Why to Understand Water dynamics?
Maintaining stable water dynamics is the first step in UBE.
Working space
&
Haemostasis

6. Why to Understand Water dynamics?
Under Pressure
Over Pressure

7. Why to Understand Water dynamics?
Under Pressure
• Bleeding
• Narrow working space
• Cautery burn

8. Why to Understand Water dynamics?
Over Pressure
• Muscle edema
• Intraspinal space bleeding
• Thecal sac compression: transient
Para cauda equina

9. 30 mmHg
(Kim 2019)
Kim JE et al. 2019. Biportal endoscopic spinal surgery for lumbar spinal stenosis. Asian Spine J.
WATER PRESSURE FOR UBE

10. The water supply can be secured by preparing a sufficient inlet, operation field,
and outlet.
ERGONOMICS
Irrigation Inlet
Dynamics within the Water chamber system is governed by two rules.
Outlet
Operation Field

11.  Pascal's law (aka principle of transmission of fluid-pressure) is a principle
in fluid mechanics that states “a pressure change at any point in a confined
incompressible fluid is transmitted throughout the fluid such that the same
change occurs everywhere”
PASCAL'S LAW

12. BERNAULI’S EQUATION
 P1-P2=1.2ƍ (V2
2-V1
2)
 A1V1= A2V2
 Therefore,
 A1<A2, V1>V2 and
 V1>V2, P1<P2
Decreasing area = Increasing Velocity
Increasing Velocity = Decreasing Pressure
Inverse Relation to proportionate

13. BERNAULI’S EQUATION
IV fluid pressurised through the small pipe, this force is multiplied and disperse in
all direction within the chamber.
P2 >>>> P1 Pressure.
 P1-P2=1.2ƍ (V2
2-V1
2)
 A1V1= A2V2
 Therefore,
 A1<A2, V1>V2 and
 V1>V2, P1<P2
Decreasing area = Increasing Velocity
Increasing Velocity = Decreasing Pressure
Inverse Relation to proportionate

14.  Bernoulli's principle controls dynamic of hydraulic fluid.
 Pressure is inversely proportion to velocity.
 The speed of fluid within the chamber is low which will increase the intra
chamber pressure creating the positive pressure working space
 Positive pressure creates haemostasis.
 Egress fluid in same gradient manner will satisfy the principle of water use in
UBE.
CLINICALAPPLICATION

15. Bernoulli’s equation and Pascal’s law can be applied to the water
dynamics in UBE, which can be affected by
the area of the inlet and outlet,
the difference in height,
mass resistance,
and injection pressure.
BERNOULLI’S EQUATION AND PASCAL’S LAW

16. ILLUSTRATION OF LAW
Factors influencing water pressure in the endoscopic spine surgery model.
The height difference, obesity, and a short cannula can contribute positively.
Bernoulli’s equation and Pascal’s
law can be applied to the water
dynamics in UBE, which can be
affected by
the area of the inlet and outlet,
the difference in height,
mass resistance,
and injection pressure.

17.  Considering the structure of the UBE system, the irrigation fluid pressure is
started from the tip of the endoscope.
 This ensures that the inlet always remains patent; however, a small incision and
small outflow can cause water congestion, and these impaired water dynamics
can cause muscle edema and ascites.
PRACTICAL SCENARIO

18.  Structure of the UBE system is a balance adequate chamber system.
BALANCE ADEQUATE CHAMBER SYSTEM

19.  Structure of the UBE system is a balance adequate chamber system.
BALANCE ADEQUATE CHAMBER SYSTEM
Ingress Egress
Working Chamber
Ingress:
Saline
Paraspinal
well
chamber
Egress from
outlet

20.  INGRESS:
 WORKING CHANNEL:
 EGRESS
DETERMINANTS
Ingress: Saline
Paraspinal well
chamber
Egress from outlet

21.  INGRESS:
DETERMINANTS
Gravity and pressure
Volume, Height, Pressure

22.  INGRESS:
 WORKING CHANNEL:
DETERMINANTS
oIf chamber is created inadequate,
oHigh velocity in the system will not create a pressure in the paraspinal
system.
oBleeding and Narrow work space
oIf the working chamber is created large,
oThe intra chamber pressure increases due to reduced velocity due to
stagnation.

23.  INGRESS:
 WORKING CHANNEL:
 EGRESS
DETERMINANTS
If the egress channel has large and long tube
The velocity will reduce and cause increase pressure in the chamber.

24. cka
PRACTICALAPPLICATION
 Ingress reservoir inlet:
 100cm (one arm) above my head.
 Gravity is pushing it down and height is pushing it down.
 This force is transmitted to the operative field chamber (reservoir is paraspinal space)
 Maximum pressure gradient created inside the well of paraspinal muscle provides the
clear vision field, this is the principle of all hydraulic system..
 If bleeding increase in the operative field, what we do is increase the pressure with the
help of increasing cuff pressure by assistant.
Ingress:
Saline
Paraspinal well
chamber
Egress

25.  Local factors : Length of the cannula
 Systemic factors include BMI, skin-to-dura depth, height, and body weight.
 Overall, the local factors showed higher ORs than the systemic factors.
CONFOUNDERS

26.  From the beginning of the procedure, the physician should monitor the
anaesthesia.
 The type of anaesthesia can change the intraspinal pressure and the patient’s
level of consciousness; therefore, proper pain control and continuous sedation
have been recommended.
PRE OP OPTIMISATION

27. • Intraspinal space bleeding
• Thecal sac compression
• Muscle edema
• Para cauda equina like transient sacral numbness
• Ascites
• Convulsion on table
• Temp blindness and visual loss following high intracranial pressure.
• Retroperitoneal collection of fluid in rare cases with pressure on ICV and poor
cardiac filling. Risk to life.
• Abdominal distention and discomfort
COMPLICATIONS

28. 1. Kim JE et al. Biportal endoscopic spinal surgery for lumbar spinal stenosis.
Asian Spine J. 2019
2. Malcolm Pestonji. Keynote.key. Fluid Management in UBE. 2022
3. Heo DH, Park CW, Son SK, Eum JH. Editors. Unilateral Biportal Endoscopic
spine. Springer. Singapore. 2022
4. Hong YH, Kim SK, Hwang J, Eum JH, Heo,DH Suh DW, Lee SC. Water
Dynamics in Unilateral Biportal Endoscopic Spine Surgery and Its Related
Factors. World Neurosurgery. 2021
WATER DYNAMICS IN UBE
References
THANK YOU

29. cka
SURESH BISHOKARMA, MCH
CONSULTANT NEUROSURGEON
UPENDRA DEVKOTA MEMORIAL NATIONAL INSTITUTE OF NEUROLOGICAL
AND ALLIED SCIENCES
WATER DYNAMICS IN UBE
THANK YOU