Exam 3 Flashcards
At what spinal level would we find innervation to the kidneys and ureters?
T8-L2
At what spinal level would we find innervation to the pelvic organs?
Primarily lumbosacral with some lower thoracic input
At what spinal level would we find innervation to the bladder?
T11-L2 (Dome), S2-S4 (Neck)
At what spinal level would we find innervation to the prostate?
T11-L2 and S2-S4
How many thoracic nerves do we have?
12
How many lumbar nerves do we have?
5
What plexus does T11 and S2 come from?
Hypogastric
How much of the CO does the Kidneys receive?
25%
What makes the kidneys an endocrine organ?
Secretion of renin, erythropoietin and 1,25-dihydroxycholecalciferol
Where is the medulla of the kidneys located?
Central region, located under the kidney capsule
Where is the papilla of the kidney located?
Inner most tip of the inner medulla
What is the functional unit of the kidney?
Nephron
Describe the renal tubules
Lined with epithelial cells which serve the functions of reabsorption and secretion
What does a nephron consist of?
Glomerulus and a renal tubule
Describe superficial cortical nephrons
Glomeruli in the outer cortex, short loops of henle which descend only into the outer medulla
Describe juxtamedullary nephrons
Glomeruli near the corticomedullary border, larger nephrons with higher GFR, long loops of henle that descend deep into the inner medulla and papilla
Where does the glomerulus emerge from?
Afferent arterioles
What surrounds the glomerulus?
Bowman’s capsule
What is the goal in the OR in regards to BP and renal function?
Maintain a good BP because urine output is not a good indicator of renal fx
What consideration do we make with insufflation in regard to the kidneys?
Insufflation can compress blood flow to kidneys
3 Renal Vasoconstrictors
- Sympathetic nerves (catecholamines)
- Angiotensin 2
- Endothelin (21 amino acid peptide)
6 Renal Vasodilators
- PGE2
- PGI2
- Nitric Oxide
- Bradykinin
- Dopamine
- Atrial Natruiretic Peptide
What are the afferent and efferent arterioles innervated by?
SNS fibers that produce vasoconstriction by activating alpha 1 receptors
What does increased sympathetic nerve activity cause when acting on the afferent arteriole?
Decrease in RBF and GFR
What does the baroreceptor response in situations like blood loss cause?
Increased SNS activity and reduced GFR
Describe Angiotensin 2 in regards to the kidneys (2)
- A potent vasonstrictor of both afferent and efferent arterioles
- Constricts both arterioles, increases resistance, and decreases blood flow
Describe ANP in regard to the kidneys (2)
- Cause dilation of afferent arterioles and constriction of efferent arterioles
- Because dilatory effects on afferent is greater than constrictor effect on efferent arterioles, there is an overall decrease in renal vascular resistant and resulting increase in RBF
Describe Prostaglandins in regards to the kidneys (2)
- Several are produced locally in the kidneys (PGE2, PGI2)
2. Cause vasodilation of both afferent and efferent arterioles
Describe dopamine in regards to the kidneys (2)
- Dopamine, a precursor of norepinephrine, has selective actions on arterioles
- At low levels, dopamine dilates cerebral, cardiac, splanchic, and renal arterioles, and it constricts skeletal muscle and cutaneous arterioles
5 Things in the evaluation of renal function
- Hx and physical
- Estimates of disease duration
- Urinalysis
- Assessment of GFR
- Laboratory Tests
Describe GFR (2)
- GFR is the best measure of glomerular function
2. Normal GFR is 125 mL/min
Describe BUN (2)
- BUN is a less specific indicator of kidney function and is a reflection of ingested protein and muscle catabolism
- Elevated BUN can be precipitated by protein intake, TPN, steroids, fever, dehydration, and GI bleed
Describe creatinine and creatinine clearance (2)
- Creatinine is a product of muscle metabolism and the most specific indicator of renal function
- Normal values are 0.5 to 1.5 mg/100 mL
Describe Urine Specific Gravity (3)
- Measures the concentration of solutes in urine
- Provides information on the kidney’s ability to concentrate urine
- The reference range is 1.005-1.030
Describe protein excretion (3)
- Without renal disease may excrete 150mg/day
- Greater amounts of protein can be excreted after strenuous exercise
- Massive proteinuria (>750mg/day) is always abnormal and usually indicates severe glomerular damage
Describe glucose and the kidneys (2)
- Glucose is filtered at the glomerulus and is reabsorbed in the proximal tubule
- Glycosuria signifies that the ability of the renal tubules to reabsorb glucose has been exceeded by an abnormally heave glucose load and is usually indicative of DM
When do electrolyte tests become abnormal in regards to the kidneys?
When frank renal failure is present
When does hyperkalemia usually occur with patients and kidney disease?
Not usually until patients are uremic
What would a doubled creatinine level indicate?
50% reduction in renal function
What is indicative of oliguria?
400 cc/day urine output
Describe Prerenal acute kidney injury
Caused by reduction in effective circulating volume and renal perfusion or bilateral arterial occlusion (hypotension, decreased CO)
Describe Intrarenal acute kidney injury
Caused by glomerular or renal tubular injuries, or intrarenal vascular disruption
Describe Postrenal acute kidney injury
Caused by obstruction of the urinary tract or bilateral renal veins
What is pre renal acute kidney injury the direct result of?
- Hypoperfusion
2. Complete lack of blood flow to the kidneys for 30-60 minutes can result in irreversible cell damage
What does Acute Tubular Necrosis (ATN) involve?
Specific injury to the renal tubules and is most commonly the result of ischemia secondary to reduced RBF
5 Renal toxins
- Contrast dye
- NSAIDS
- Aminoglycoside ABX
- Cocaine
- Rhabdo pigment
What part of the EKG do we wait for before performing a lythotripsy?
R-wave
Examples of obstructions from the tubules to the urethra that can cause post renal kidney injury?
- Kidney stones
- Uric precipitate (gout)
- Kinking of urinary catheter
- Prostatic Hyperplasia
Anesthesia considerations in acute kidney injury (5)
- Anesthesia and surgery decrease RBF and GFR
- Catecholamines released during surgery cause reduction in RBF and GFR
- Long periods of hypotension decrease RBF
- Vasopressors reduce GFR
- Neuraxial blockade effects are variable depending on degree to which BP and CO drop
What is the best anesthetic approach for TURP/TURB?
Neuraxial anesthesia
At what spinal level are the cardio-accelerator nerves found?
T1-T4
Describe chronic renal failure (3)
- Progressive, irreversible deterioration of renal function
- DM is leading cause of ESRD followed by HTN in the US
- GFR to less than 25 mL/min eventually progressing to dialysis or transplantation
Clinical presentation of ESRD
- Anemia d/t decreased erythroproeiten
- Increased bleeding time d/t platelet dysfunction, but platelet count is not decreased
- Hyperkalemia and hypermagnesemia
Preop Anesthesia Considerations for pts with ESRD (9)
- Evaluate serum creatinine trend
- Compare body weight before and after dialysis, monitor vital signs (BP and HR)
- Glucose management
- BP well controlled before surgery
- ACE-i and ARBS d/c day of surgery to reduce risk of intraop hypotension
- K+ should not exceed 5.5 mEq/L day of sx
- Gastric aspiration prophylaxis
- H2 receptor blockers excreted renally so adjust dose
- Dialysis within 24 hours preceding elective sx
Induction considerations for patients with ESRD (4)
- Safe with most IV drugs, watch cardio effects of propofol
- Many ESRD respond to induction as if they were hypovolemic
- RSI with succinylcholine if K+ less than 5.5 mEq/L
- Short onset non-depolarizers such as roc at lower doses, nimbex is renal friendly
How much K+ does lactated ringers contain?
4 mEq/L
What is generally considered a urine output to maintain?
0.5mL/kg/hr
What consideration do we give intraop urine output in regards to post-op renal insufficiency?
Intraop-UO has not been shown to be predictive of post-op renal insufficiency
What is the most likely cause of oliguria and how do diuretics play into this setting?
Inadequate circulating fluid volume and admin of diuretics in this setting may further compromise renal function
Describe Fenoldopam
It is a dopamine-1 agonist, may provide renal protection in patients at high risk who are undergoing cardiac, vascular, or transplant surgery
When should we consider blood transfusion in ESRD patients?
If oxygen-carrying capacity must be increased or if blood loss is excessive
What is a useful tool to guide fluid replacement?
CVP
Regional anesthesia considerations for ESRD patients
- Neuraxial anesthesia can be considered
- Sympathetic blockade of T4-T10 by attenuating catecholamine-induced renal vasoconstriction and suppressing the surgical stress response
- Platelet dysfunction effects of residual heparin must be considered (aPTT and ACT)
- Adequate intravascular fluid volume must be maintained
Describe dermatome levels
Skin area innervated by a given spinal nerve
What dermatome landmark is used for S1?
Lateral aspect of foot
What dermatome landmark is used for L1?
Inguinal ligament area
What dermatome landmark is used for T10?
Umbilicus
What dermatome landmark is used for T6?
Xiphoid Process
What dermatome landmark is used for T4?
Nipple
What dermatome landmark is used for T1-T2?
Inner aspect of the arm and the forearm
What dermatome landmark is used for C8?
Fifth finger
Where is the phrenic nerve located?
C5
What do we know if a patient is feeling numbness of their thumb and how should we respond?
This corresponds to C6 and this will eventually move up to C5, we will raise the HOB and give O2
Dermatome level targeted for peri-anal surgery considered to be a “saddle block”?
S2-S5
Dermatome level targeted for foot and ankle surgery?
L2
Dermatome level targeted for Vaginal delivery and uterine procedure?
T10
Dermatome level targeted for lower abdominal procedures?
T6
Dermatome level targeted for for upper abdominal surgery such as a C-section?
T4
What is the problem with blocks placed at T4?
Problems with cardiac accelerator nerves, so have neo and ephedrine ready
Post-op management of ESRD patients?
- Caution with IV opioids due to hypoventilation even if small doses
- Admin naloxone may be necessary if depression of ventilation is severe
- EKG monitor for hyperkalemia
- O2 especially if anemia is present
- Check levels of electrolytes, BUN, Creatinine and Hct
What is the gold standard procedure for BPH?
TURP
What is the transurethral procedure for kidney stones?
Extracorporeal Shock Wave Lithotripsy
Which procedure do we do biopsy of the bladder?
TURBT
What is a serious intraoperative complication during a TURB?
Bladder perforation by the rigid cystoscope due to unexpected patient movement
Which nerve may be stimulated during a TURBT causing ipsilateral contraction of the thigh muscle?
Obturator nerve
What is the highest spinal level we use for regional anesthesia in TURBT which will prevent the obturator reflex?
T9
Describe post-op pain from TURBT
Postoperative pain is usually minimal and responds well to nonopiate and opiate medications
What position do we place patients in for TURBT procedures?
Lithotomy
What do we need to make sure to do when positioning patients for TURBT?
Adequate padding of pressure points and avoidance of common perineal nerve compression
What is the most common lower body nerve injury?
Common perineal nerve compression
What side of leg does the common perineal nerve lie?
Lateral (outside) side of the lower leg
What nerve damage is common in almost all surgical procedures?
Ulnar nerve damage
Describe TURP (4)
- Prostate removal of BPH
- Resectoscope is very rigid, inserted into the urethra
- SAB is preferred @ T10 for neuro assessments
- GETA is possible, but does not allow for neuro checks
Which patient populations are TURPs likely to be performed in?
Elderly and those with serious comorbidities such as DM, so we need to monitor CV and pulmonary status
What intraoperative changes are elderly and those with serious comorbidities respond to the most?
Intravascular volume change
Which patients undergoing TURP would we prefer GETA over spinal anesthesia?
Those on anticoagulant therapy
How long prior to regional procedures should we d/c ASA?
7 days
By what degree and time period does body temp decrease during surgery?
1 degree Celsius per hour
What percentage of patients who receive room-temperature irrigation fluids does shivering occur in?
16%
What percentage of patients undergoing TURP require transfusions?
2.5%
What is the average blood loss per minute during a TURP?
2 to 4 mL/min
What lab should we monitor with 4 to 6 hour surgeries?
Serial hemoglobin levels
What is the purpose of irrigation solutions in TURP?
- Continuous fluid to irrigate the bladder and the prostate
2. Improves visualization during surgery
Where is irrigation solution absorbed?
open venous sinuses of the prostate and a portion is absorbed in the systemic circulation
What are two possible side effects of irrigation solution being absorbed into systemic circulation?
- Circulatory overload
2. Toxicity for the solutes of the fluid
Whats the absorbed volume per time of irrigation solution?
10-30 mL/min
How does resection time of a TURP affect complication rate?
The longer the reception time the more complications
What must the resection time in a TURP be limited to?
1 hour
Describe the changes of height of the irrigation solution
Height of the irrigation solution must be 30 cm above the OR table at the beginning of the case then dropped to 15 cm at the end of the case
Relate the number of venous sinuses open to reabsorption rate
Too many open venous sinuses increases intravascular reabsorption
What is the ideal irrigation solution?
great visibility, clear, isotonic, free of toxicity, electrically inert and inexpensive (this does not exist)
What is the problem with 0.9% saline and LR for irrigation?
They are good choices but are very ionized and good conductors of electricity