The Life of P.I. (PERFUSION INDEX)🐾

🚤 Reduction of plethysmographic pulse wave amplitude (PPWA) has been proven to be a reliable method for detecting the IV injection of an exogenous vasopressor ( for e.g. The adrenaline in epidural test dose)

🚤 Currently, a numerical value has been added to new pulse

oximeters indicating the PPWA, termed the perfusion index (PI), to augment its clinical applicability.

🚤i.e. PI is the numerical value of the amplitude of the

plethysmographic pulse wave that is displayed on

many pulse oximeters.

🚤 Using pulse oximetry, a variable amount of light is absorbed by pulsating arterial flow (AC) and a constant amount of light is absorbed by nonpulsating blood and tissue

(DC). The pulsating signal indexed against nonpulsating signal and expressed as ratio is commonly referred to as the perfusion index

🚤 It depends on the distensibility of the vascular wall and the intravascular pulse pressure. Usually the effect of autonomic impulses upon distensibility is so strong that it predominates the opposite effect of pulse pressure.

🚤 Decreases in PI resulting from pain and other stressful stimuli are due to vasoconstriction of the finger arterial bed rather than changes in the pulse pressure

Reference: The Efficacy of Perfusion Index as an Indicator for Intravascular Injection of Epinephrine-Containing Epidural Test Dose in Propofol-Anesthetized Adults, Anesth Analg 2009;108:549 –53) 

ROBOTIC🤖 PROSTATECTOMY: #Anesthesia CONCERNS

🏈FACTS ABOUT THE SURGERY

▪️There is a master console; surgeon sits here & controls the robotic surgical manipulator, once it has been docked

▪️Robot is bulky and is positioned over the chest and abdomen

▪️Patient is positioned in lithotomy with a steep Trendelenberg tilt

▪️Needs immobility of the patient till the robot is undocked

▪️Table position should not be altered until the surgical instruments are disengaged

▪️Discharge may occur as early as within 24 hours after surgery

🏈ADVANTAGES

▪️Better continence & erectile function 

▪️Less pain and hence less analgesic requirements 

▪️Less blood loss

▪️Shorter hospital stay

🏈ANESTHESIA CONCERNS

▪️Since immobility is very important, it can be established by continuous infusion of a non depolarizing muscle relaxant

▪️As the procedure may take long time, it's better to use agents with rapid offset

▪️Because patient is positioned in steep head-down position 

➖Ensure pressure points are protected adequately 

➖Fluids are infused cautiously to reduce chances of cerebral and laryngeal oedema ( N.B.: Rule out cerebral oedema in case of delayed emergence )

➖As the position of the robot interferes with resuscitation, prior practice-drills and good communication are necessary to manage such a situation effectively 

➖Epidural analgesia, if at all required, are used only postoperatively, as the steep head-down position will increase the risk of high block

Reference: Irvine M, Patil V. Anaesthesia for robot-assisted laparoscopic surgery. Contin Educ Anaesth Crit Care Pain. 2009; 9(4): 125–129.