Minimally invasive abdominal & pelvic surgery Flashcards
Anaesthetic considerations for minimally invasive (laparoscopic & robotic) major abdo & pelvic surgery
A: tracheal intubation with cuffed oral tube
carefully tape (risk tube migration R) main bronchus, don’t tie in case of steep head down/impairing venous return )
Care not to inflate stomach w bmv (obscure surg views, may require decompression)
secure tube effectively (tape), check length after positioning & auscultate to confirm
conscious that if steep head down, risk upper airway oedema (consider “air leak” test before extubate)
Pneumoperitoneum is required, physiological effects (“minimal access surgery, maximal cardiopulmonary stress”)- bigger issue for pts with impaired physiological reserve:
-CO2 absorption: SNS stimulation, incr HR/BP, incr PVR, cerebral VD & incr CBF
absorption into blood from peritoneum with reduced elimination (incr alveolar deadspace) may cause hypercapnia & resp acidosis unless increase MV
-CNS: increased cerebral blood flow (=CPP/CVR, CPP= MAP-ICP or JVP, with pneumo esp steep head down MAP rises >JVP) which may increase ICP (Monroe Kellie doctrine) with incr MAP & blood volume (due to transmitted extraperitoneal effects, potentially incr JVP particularly if also steep head down). With raised ICP, may get cerebral oedema if compensatory mechanisms (CSF translocation to spinal cord, increased CSF reabsorption) are exhausted. This raised ICP may be compounded by flow-metabolism uncoupling with high MAC anaesthesia. care w IVT. IOP raised with steep head down also.
Can also get incr IOP- risk corneal abrasion or optic neuropathy.
-Cardiovascular:
impacts of raised IAP are biphasic:
-at low IAP (<=10mmHg), venous return & CO may increase.
-moderate (10-20mmHg) IAP, reduced CO & increased SVR, effect on MAP variable.
-high IAP (>20mmHg) may decr MAP, CO reduced markedly.
-impaired preload (IVC compression) & incr afterload (compression major arteries, incr SVR), SNS stimulation increasing HR & contractility have variable effects depending on pt & anaesthesia- while pts with robust compensation may not have CO or MAP reductions, pts with impaired/blunted baroreceptor reflexes/beta-blockers may have reduced CO (inability to compensate)- may precipitate ventricular failure if pre-existing ventricular function poor.
high IAP can lead to ADH production & RAAS activation (compression of renal vasculature)
-care re: potential hypotension on levelling- preload with IVT & consider vasopressors
-addition of trendendelenburg incr VR & CVP which may incr CO
-Increased venous pooling risks VTE
-Respiratory: reduced FRC, incr airway resistance, reduced compliance
atelectasis, V/Q mismatch & shunt
increased airway pressures & risk barotrauma
may have reduced PaO2 & incr PaCO2, incr PaCO2-PECO2 gradient & reduction in PaO2/FiO2 ratio.
choose strategy based on balance btwn airway pressures (not wanting high peak insp pressures, maintain <35cmH2O) & maintaining CO (avoid excessive PEEP whilst using some as it mitigates atelectasis- 7cmH2O). Incr insp phase could improve oxygenation & CO2 elimination.
-GIT: increased intra-abdominal pressure predisposes to aspiration (need to be well-fasted, cuffed tube with adequate pressures, consider NGT/drainage, ensure eyes well-covered)
-Vascular compression reduces splanchnic visceral perfusion- due to reduced perfusion pressure and increase in geometric resistance. risk for ischaemia or ischaemia-reperfusion injury
-Renal: reduced perfusion & renal function with increased IAP & SNS stimulation
-Prolonged procedure (may be flat, reverse trendelenburg or steep trendelenburg):
-positioning & pressure care
-pad well, esp over AC joint
-care re: LL neuropathy (esp in lithotomy)- lateral femoral cutaneous nerve, CPN, obturator, sciatic
-neutral joints to limit neuropraxia/neuropathy/pressure sores: gel padding, pad connectors, avoid excess stretch (arm board angles)
-care w pt sliding (use non-slip padding/eggshell, straps, supports, beanbags, consider lithotomy)
*AVOID compression stockings given risk of bilateral compartment syndrome (esp lithotomy syndrome)- pad carefully, periodic “levelling out”, monitor foot pulses, use heel/ankle supports
-ensure all lines have long enough extension as do monitors & can access well prior to docking robot, check eyes well covered/protected (particularly as risk aspiration/gastric secretions burning conjunctiva)
-care in particular with ICP & upper airway oedema with prolonged steep head down, also risk well leg/compartment syndrome with prol lithotomy. recheck tube/pressures & positioning/pressure points after each reposition
-fluid balance (aim= near zero fluid balance- maintain homeostasis with 1-4mL/kg/hr). permissive oliguria may be appropriate & not thought to lead to incr AKI given IDC drainage may be poor in steep trendelenburg & major surgery associated with incr ADH production (0.3mL/kg/hr may be appropriate). consider other markers eg. lactate, acid-base, ScvO2. During RALP, bladder opened to access prostate- restrict fluid prior to this point (until anastomosis of bladder & urethra) as excessive urine may disrupt surgical view.
-if prolonged steep trendelenburg care that excess fluids may promote cerebral oedema & upper airway & conjunctival oedema (esp if excess IVT) along with raising ICP & IOP- risk post-extubation resp distress & necessity for emergency re-intubation. Avoid ties but secure well. consider periodic levelling of pt
consider “air leak” test before extubation
-analgesia- while minimal incision & modest requirements for postop analgesia, still require multimodal opioid-sparing (promote early return to PO intake, limit PONV), also want to have effective cough/limit resp depression, misuse potential. Epidural has been compared with spinal or PCA & found to be associated with reduced mobilisation, increased IV fluid requirements, slower return of bowel function & incr LoS in hospital. a popular approach= spinal w IT diamorphine. TAP blocks may decrease opioid consumption, esp if sited before the surgery. Ketamine & IV lignocaine advocated- IV lignocaine reduces opioid requirements, PONV & time to resumption of diet. Postop regular paracetamol, NSAIDs, opioids for breakthrough.
-N2O may cause greater bowel distension for longer procedures (avoid)
may have limited pt access so:
-systems for rapid detection & addressing of complications vital
Main complications=
a) those during surgical access to the abdo (50% of complications occur at this time, eg. small bowel, iliac artery, colon & iliac vein damage- bleeding may not be immediately obvious as bleeding into retroperitoneum may occur. Emergency undocking procedures essential (need to rapidly access pt) for robot, need to regularly practice the undocking protocols with sim)
b) physiological complications of the pneumoperitoneum/pt positioning or other complications eg. subcut emphysema, mediastinal emphysema, PTx, CO2 retention, postop pain related to intra-ado gas, air embolism from venous injury, well leg syndrome/compartment syndrome (prol lithotomy, steep trendelenburg, pneumatic compression stockings, IVT restriction, hypoT, vasoactive meds may reduce perfusion & incr risk LL compartment syndrome), oedema of face, AIRWAY, eyes.
c) surgical complications
d) mechanical failures can also occur with robotic systems eg. uncontrolled movements, spontaneous powering on & off, arcing from diathermy causing burns to surrounding tissue, sometimes out of surgical field of view which may go unnoticed
-ensure happy with pt position before robot docked
-extensions on lines & monitoring devices
-art line likely useful depending on pt, comorbidities, duration, EBL. Useful for reliable monitoring & regular ABGs esp as pt access limited.
always consider the possibility of conversion to open
-Deep NMB (PTC 1-2 twitches vs TOF 1-2 twitches- former= theoretically better operating conditions at lower IAP)- minimising pt movement important to limit harm- fully reverse
-BIS likely useful- avoid excess depth (more likely POCD in comorbid/elderly population)
-multimodal antiemetics based on pt risk
What are benefits of minimally invasive abdominal/pelvic surgery?
reduction in complications (medical & surg incl blood loss, transfusion rates)
shorter recovery period
able to have PO intake earlier (except cystectomy- often ileus) as less bowel handling
reduction in hospital LoS
reduced death rates with minimally invasive surgery
What’s a disadvantage of minimally invasive surgery?
the loss of haptic (sensory) feedback
Why is CO2 used?
inert- doesn’t support combustion if diathermy used
has increased blood solubility cf nitrogen or oxygen, minimising risk of significant venous embolus if inadvertent intravascular insufflation
Conditions considered contraindication for MIS?
severe RV or biventricular failure (where ventricular output declines with significant incr SVR)
R)- to L)- cardiac shunt (may increase as RV pressures increase
hypovolaemic shock (further VR reduction dramatically reduce CO & art pressure)
retinal detachment & raised ICP (raised IOP further injures eye, raised ICP markedly reduces perfusion pressure)
What benefits of lignocaine for laparoscopy have been demonstrated through meta-analyses?
reduces opioid requirements, PONV & time until resumption of diet
awaiting ALLEGRO trial (accelerating GI recovery after colorectal surgery) currently underway
How do outcomes for robotic radical prostatectomy compare with laparoscopic or open? and rectal surgery? evidence re: long-term outcomes?
less blood loss, transfusion rates & hospital LoS with robotic cf laparoscopic (both are superior to open) but higher cost with robotic
for rectal surgery, robotic may reduce LoS but incr costs cf laparoscopic, both superior to open wrt wound infection & LoS
evidence yet to resolved re: differences in long-term oncological outcomes
Is a brachial or radial art line more likely to cause median nerve damage?
brachial- due to proximity of the nerve to the artery @ this point (cf radial where the median nerve is in the carpal tunnel several cm away)
relatively high incidence of median nerve paraesthesia associated with brachial art line
From which cervical nerve root is shoulder tip pain referred?
C4
Should calf compression stockings be used for laparoscopic procedures in trendelenburg?
no- associated with bilateral compartment syndrome
