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improved outcomes in colon and rectal surgery
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25. Stellato TA, Danziger LH, Gordon N. Antibiotics in elective
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3
Anesthesia and intraoperative positioning
Lebron Cooper and Larry R Hutson
CHALLENGING CASE
A 47-year-old male is undergoing a transanal excision of a rectal
villous adenoma under intravenous sedation and local infiltration
of xylocaine. During the procedure the patient complains of lightheadedness and numbness of the tongue. The anesthesiologist
notices bradycardia and hypotension.
CASE MANAGEMENT
Xylocaine toxicity is suspected. The patient should be moved to
the supine position and supported with supplemental oxygen via
mask. The patient’s blood pressure is supported with intravenous
fluid and epinephrine.
INTRODUCTION
The American Society of Anesthesiologists (ASA) defines anesthesiology as a discipline within the practice of medicine that specializes in the (1) medical management of patients who are rendered
unconscious and/or insensible to pain and emotional stress during
surgical, obstetric, and certain other medical procedures; (2) protection of life functions and vital organs under the stress of anesthetic,
surgical, and other medical procedures; and (3) management of
problems in pain relief (1). In this chapter, we will be discussing the
various kinds of anesthesia used in the operating room for colorectal surgery, including their relative benefits and risks. Additionally,
we will be discussing new treatments for postoperative pain relief,
as well as one of the more visible risks of anesthesia—awareness
under anesthesia. We will also discuss the new Surgical Care
Improvement Project (SCIP), including prophylactic antibiotic
administration within 1 hour of surgical incision, and the proper
positioning and padding of patients for colorectal surgery.
ANESTHESIA
Local Anesthesia
The earliest local anesthetic used was cocaine (prepared in weak
solutions and injected in high volumes) for field block at the turn
of the 19th century.(2) However, the toxicity of cocaine, its irritant
properties, and its strong potential for physical and psychological
dependence led to the development of alternative local anesthetics.
Many of these—such as lidocaine—are still used today, as much as
half a century after their introduction.(3)
While there are relatively few instances in colorectal surgery
where it is used as the sole anesthetic, local anesthesia still has a
place. It requires, however, a cooperative patient who can remain
immobile for both the infiltration of the local anesthetic, as well
as for the actual procedure itself.
It is important to be cognizant of the patient’s underlying
health status and the position that the patient will be in for the
procedure. A healthy patient in their mid-20s can tolerate the
prone jack-knife position much better than an obese geriatric
patient with a pulmonary history who uses supplemental oxygen. Bear in mind that while the patient may only be receiving
local anesthesia in an office setting, the patient may be under
self-administered mild sedation. Any degree of sedation blunts
the body’s response to hypoxia and hypercarbia, and while a restless patient may simply be a restless patient, there is always the
possibility that the patient is agitated due to relative hypoxia or
hypercarbia.
One must always keep in mind the possibility of local anesthetic
toxicity when using these drugs. The typical doses used for local
infiltration in colorectal procedures are far below the threshold
needed for systemic toxicity (Table 3.1). However, accidental intravenous or intraarterial injection could result in systemic toxicity.
As such, it is important to recognize the signs and symptoms of
systemic toxicity when they first appear, as toxicity progresses in a
dose-dependent fashion.
At lower plasma concentrations, the patient begins to experience central nervous system (CNS) toxicity characterized by lightheadedness, tinnitus, and numbness of the tongue. As plasma
concentrations increase, the patient begins to experience CNS
excitation, resulting in seizures, followed by unconsciousness,
coma, and respiratory arrest. At higher plasma concentrations,
cardiovascular (CV) toxicity occurs, as the local anesthetic blocks
sodium channels of the myocardium.
Relative potency of the local anesthetic plays a role here.
Lidocaine toxicity will result in bradycardia and hypotension before cardiac arrest, while the longer acting, more potent
bupivicaine often results in sudden cardiovascular collapse due to
ventricular dysrhythmias. Maintenance of perfusion and ventilation through prolonged cardiopulmonary resuscitation (CPR)
is the key, as the patient will not convert into a life-sustaining
cardiac rhythm until the local anesthetic has had a chance to
completely dissociate from the sodium channels of the conducting system of the heart. Cardiopulmonary bypass may even be
considered. Dissociation of local anesthetic from sodium channels has been shown to take a considerable length of time, and
prolonged, intensive, and continuous support is warranted.
Table 3.1 Local anesthetic drugs.
Agent
Tetracaine 30 seconds 30–60 minutes 400 mg
Lidocaine 2–5 minutes 30–45 minutes 5 mg/kg 7 mg/kg
Mepivacaine 7–15 minutes 2.5 hours 400 mg
Prilocaine 2 minutes 2.5 hours 80 mg
Bupivicaine 30 minutes 2 hours 2 mg/kg 4 mg/kg
Procaine 5–10 minutes 15–30 minutes 10 mg/kg
Onset
Duration
Maximum
Dose
Maximum Dose
with Epinephrine
improved outcomes in colon and rectal surgery
Treatment of CNS toxicity, including the cessation of seizure
activity, is with the use of benzodiazepines, propofol, or thiopental.
Treatment of CV toxicity is supportive in nature, and may require
electric cardioversion, epinephrine, and magnesium.(4)
Systemic toxicity following local anesthetic administration is
thankfully rare. More common, however, is inadequate analgesia
following local anesthetic infiltration. This can be multifactorial in
nature. Inadequate analgesia resulting from insufficient quantities
placed in the correct location is easily resolved with the addition
of further local anesthetic at the site. Inadequate analgesia can also
result from tachyphylaxis to local anesthetics, which is defined as
repeated injection of the same dose of local anesthetic leading to
diminishing efficacy. Additionally, inadequate analgesia can be a
consequence of the tissue pH into which the local anesthetic is
injected. Local anesthetics exist in both an ionized and nonionized state; it is only in the nonionized state that local anesthetics
can penetrate the nerve sheath, thus producing analgesia. In an
acidic environment (i.e., an infected pilonidal cyst), more of the
anesthetic is converted into the ionized state, leading to far less
of the nonionized form available to produce analgesia. It is not
uncommon for infected tissues to prove nearly impossible to be
rendered totally insensitive despite more than adequate amounts
of local anesthetic infiltration.
A perianal block (Figure 3.1) can be performed with the
patient in either the prone or lithotomy position and provides
relaxation of the sphincter as well as anesthesia. The anesthetic
solution of choice is infiltrated in a fan fashion from the lateral
positions to superficially encompass the anal margin. Emphasis
should be placed in the posterolateral positions where the greatest
concentration of nerves is found. A finger or retractor is placed
within the canal. At the anterior, posterior, and lateral positions
anesthetic is injected submucosally or intramuscularly through
the previously infiltrated tissue. The needle is held parallel to the
finger, with care to avoid entering the canal.
(a)
(b)
Monitored Anesthetic Care (MAC)
MAC is defined by the ASA as “a procedure in which an anesthesiologist is requested or required to provide anesthetic services,”
and includes (1) the diagnosis and treatment of clinical problems
during and immediately following the procedure; (2) the support
of vital functions; (3) the administration of sedatives, analgesics,
hypnotics, anesthetic drugs, or other medications necessary for
patient safety; (4) physical and psychological comfort; and (5)
the provision of other services as needed to complete the procedure safely (5). When it comes to the care of a patient undergoing
MAC, all of the precautions and equipment needed to perform
a safe general anesthetic must be present, as it is always possible
that an escalation of care will be needed. While uncommon, it is
possible that a patient cannot safely undergo a MAC for a specific
procedure. Most commonly this is due to the inability to safely
prevent a patient from moving in response to painful stimuli
without producing oversedation and/or apnea. Some patients,
when undergoing MAC, tend to have no middle ground between
moving in response to stimuli and airway obstruction or complete apnea, requiring intervention by the anesthesiologist.
The same limits of positioning and patient tolerance that were
discussed with local anesthetics apply to procedures under MAC
Figure 3.1 Technique for anal block. (A) perianal view of submucosal injection.
(B) saggital view of injection of anal canal.
as well. While most patients will be able to tolerate a lithotomy
or prone position without problem, there are some patients who
are unable to tolerate these positions without endotracheal intubation, positive pressure ventilation, and high oxygen concentrations. Additionally, there are those patients who are unable to
understand or comply with the requirement that they must remain
immobile. Young children, mentally challenged, or extremely ill
patients are prime examples of poor candidates for MAC.
There is an erroneous perception on the part of patients—and
even physicians—that a patient undergoing MAC is at decreased
anesthesia and intraoperative positioning
risk for serious anesthesia-related complications when compared
to general anesthesia, that MAC is safer. This can best be appreciated by examining the ASA Closed Claims Project database.
The ASA Closed Claims Project is a structured evaluation of all
adverse anesthetic outcomes obtained from the closed claim files
of 35 professional liability insurance companies in the United
States. A 2006 review showed more than 40% of claims associated with MAC involved death or permanent brain damage,
which was similar to the percentage seen in claims associated with
general anesthesia. Respiratory depression was the most common
(21%) damaging mechanism, nearly half of which were judged to
be preventable through better monitoring.
Cardiovascular events comprised another 14% of the claims
made in patients undergoing MAC, which was similar in frequency
to that seen following general anesthesia. The average payment
made to a plaintiff in these cases was $159,000 (U.S.).(6) So, while
we would like to think that MAC is safer than a general anesthetic
for patients, in fact the risk of significant injury and death are
similar between the two anesthetic types.
Regional Anesthesia
Central Neuraxial Blockade
Regional anesthesia encompasses a wide variety of peripheral and
central neuraxial blocks, many of which do not pertain to colorectal surgery. The most common regional anesthesia technique
applied in colorectal surgery is the spinal, or intrathecal, blockade. The spinal block is relatively easy to place, has a fast onset
of sensory and motor blockade, and has a predictable length of
efficacy. This is a very old technique, dating back to the late 1800s,
when it was performed using cocaine as the anesthetic agent, to
great amazement of surgeons of the day.(2)
With the advent of newer local anesthetics, we can now tailor
the duration of the spinal blockade to the projected length of the
surgery by varying the type and amount of local anesthetic used.
The goal is to provide adequate analgesia for the duration of the
procedure, yet allowing safe ambulation and encouraging urination
within a short time frame after cessation of surgery.
There are three different densities of the medications used:
hyperbaric, isobaric, and hypobaric. Hypobaric local anesthetics
are less dense than normal cerebrospinal fluid (CSF), which allows
these medications to rise in the CSF following injection. This is
commonly used for perineal procedures that will be performed
in the prone jack-knife position. The local anesthetic is injected
into the intrathecal space, and the patient is immediately placed
in the jack-knife position to allow the hypobaric solution to drift
upward, or caudad. After approximately 5 minutes, the spinal
anesthetic will have “set up”, meaning the uptake and distribution
of the local anesthetic across nerve membranes has occurred. No
further migration of the drug should occur at this point.
By adding a small amount of glucose to the local anesthetic used,
the solution will become hyperbaric. The density of the solution will
cause it to sink in relation to the CSF.(7) An alternative approach
to perineal analgesia performed in the prone jack-knife position is
performing the intrathecal block using a hyperbaric solution, then
keeping patients in the sitting position for 5 minutes to allow the
spinal anesthetic to sink caudad, thus blocking the lumbosacral
nerves. Once the block has “set up,” the patient is placed in the
prone jack-knife position. These two techniques have allowed the
use of significantly less local anesthetic for the spinal anesthesia,
compared to isobaric solutions, which have the same density as CSF.
Isobaric solutions require a higher dose of local anesthetic to evenly
distribute throughout the CSF, resulting in a larger volume needed
to achieve the same blockade of the lumbosacral nerves. The benefits related to reducing the total amount of local anesthetic injected
are a decreased risk of toxicity, along with providing adequate
analgesia,and allowing faster recovery of motor function.
A caudal anesthetic is the placement of a local anesthetic and/
or narcotic into the epidural space from an approach through
the sacral hiatus. This is typically performed in either the prone
or lateral position. While uncommon in adults, this procedure is
used frequently in children, where the caudal space is more easily
accessible and a relatively safe and easy approach to infuse local
anesthetic and/or narcotic for postoperative analgesia while still
under general anesthesia.
The third and final type of central neuraxial block is the
epidural anesthetic. While epidural anesthesia can be used as the
sole anesthetic for colorectal procedures, it is more common to
place a catheter within the epidural space to provide analgesia
during and after the procedure. The location of the block is determined by the anesthesiologist based on several anatomic factors;
however, a thoracic approach has been shown to be more effective in reducing postoperative ileus and early return of bowel and
bladder function than a lumbar approach.(8)
Most commonly, patients will receive a postoperative continuous infusion of a local anesthetic and narcotic mixture through the
epidural catheter. In addition, they may be given the opportunity
to provide themselves small amounts of analgesia through their
epidural catheter on demand. This is termed patient-controlled
epidural analgesia (PCEA), and it provides excellent pain control
while minimizing the undesirable side effects typically seen with
intravenous narcotics. Provided the patient does not manifest signs
of systemic infection, the epidural catheter can remain in place for
several days following surgery if needed to control pain. This benefit must be weighed against the risk of withholding anticoagulant
prophylaxis and a possible resultant thromboembolic event.
While initial studies examining PCEA were performed using
lumbar epidural, more recent studies have examined the impact of
thoracic epidural analgesia on patients undergoing elective colorectal surgery. In a study in 2001, Carli et al. reported 42 patients
undergoing open large bowel resection, randomized to receive
either an intravenous Patient Controlled Analgesia (ivPCA) morphine or a thoracic (T7-8) epidural with bupivicaine and fentanyl.
Patients who received thoracic epidural had distinctly superior
analgesia as compared to the ivPCA morphine group; time to first
flatus and first bowel movement occurred, on average, 36 hours
sooner in the epidural group, and time to readiness to discharge
was the same in both groups.(8) In 2007, Taqi et al. examined thoracic epidural analgesia compared to postoperative intravenous
morphine for laparoscopic colectomy. Recovery from postoperative ileus occurred sooner in the epidural group by 1 or 2 days, and
a full diet was resumed earlier. The epidural group experienced
significantly less pain at rest, with coughing, and with ambulation.(9) These studies demonstrate the effectiveness of thoracic
epidural analgesia and its superiority in allowing early return of
improved outcomes in colon and rectal surgery
bowel function, ability to resume a full diet, and early ambulation,
as compared to intravenous narcotics.
All three of these techniques—spinal, caudal, and epidural—
have one thing in common: contraindications. Specifically, absolute contraindications to neuraxial techniques include patient
refusal, infection at the planned site of needle puncture, elevated
intracranial pressure, and bleeding diathesis. There are also several
relative contraindications. Bacteremia raises the concern that the
needle puncture site of the neuraxial block might allow an epidural
abscess or meningitis to develop; however, a clinical scenario may
exist where the need to avoid a general anesthetic might outweigh
the small risk of such occurring.
While chronic back pain is not a contraindication to neuraxial
techniques, patients with underlying neurological disease should
be considered carefully, as neuraxial blockade might exacerbate their condition, such as in multiple sclerosis. The presence
of cardiac disease also indicates that caution should be applied,
as patients who receive a neuraxial block typically experience
a sudden decrease in lower extremity vascular tone, leading to
rapid vasodilation and a significant decrease in systemic vascular
resistance. The resultant precipitous drop in systolic and diastolic
blood pressure can be extremely dangerous, or even deadly, in
patients with severe coronary artery disease, aortic stenosis, and
idiopathic hypertrophic subaortic stenosis (IHSS). It is still arguable whether the presence of IHSS or aortic stenosis is an absolute
contraindication to neuraxial blockade, and many centers avoid
them in the presence of these coexisting morbidities.
The final relative contraindication is abnormal coagulation status. Patients with abnormal coagulation—either due to endogenous
factors such as liver disease or thrombocytopenia, or due to the
administration of anticoagulants—must be considered carefully.
Additionally, patients who are receiving or will be receiving anticoagulants postoperatively have different needs than patients who
receive a general anesthetic alone. For spinal and caudal anesthesia,
the greatest risk of spinal hematoma (a neurosurgical emergency)
occurs at the time the block is placed. For epidural anesthesia, the
risk of hematoma formation is just as great at the time of epidural
catheter removal as during placement. As a result, certain guidelines
should be instituted in order to reduce the risk of spinal hematoma
formation upon removal of the epidural catheter.
Heparin is often administered perioperatively as prophylaxis
against deep vein thrombosis formation. While the effect of
intravenous heparin administration is immediate, subcutaneous
administration requires 1–2 hours to effect a change on coagulation. Small doses of heparin administered before surgery for DVT
prophylaxis are not a concern in terms of risk of spinal hematoma
formation.(10) Postoperatively, subcutaneous DVT prophylaxis
dosing twice daily of heparin while an epidural catheter is in place
is acceptable. The catheter is removed 2 hours before the next
heparin dosing to maximize safety.
Therapeutic heparin, however, is a different matter. Ruff et al.
demonstrated that neuraxial procedures performed <1 hour after
heparin therapy is discontinued resulted in a 25-fold increase in
spinal hematoma.(11) The effect is even more pronounced if the
patient also received aspirin.
Low-molecular weight heparin (LMWH) was introduced in
1993 as an alternative to heparin prophylaxis for prevention of
DVT. There have been numerous reports of spinal hematoma in
patients receiving LMWH with a neuraxial blockade. For patients
receiving low-dose LMWH for thromboprophylaxis preoperatively, it is recommended that neuraxial anesthesia occur at least
12 hours after the last dose. In patients who are receiving highdose LMWH, neuraxial anesthesia should be delayed for 24 hours
after the last dose. Postoperatively, the typical prophylactic twicedaily dosing of LMWH should only begin 24 hours after the neuraxial block, and any epidural catheter should be removed before
initiation of twice-daily dosing. Once-daily thromboprophylactic
dosing, however, can safely occur with an epidural catheter in
place, provided that the first dose occurs at least 8 hours following the initial blockade and that any epidural catheter is removed
12 hours after the last dose before its removal.(12)
Warfarin therapy is another concern. Warfarin anticoagulation
must be stopped 4–5 days before surgery, and the PT/INR assessed
before surgery. Anticoagulation with warfarin can be used for
thromboprophylaxis in patients with an indwelling epidural
catheter, though the catheter should be removed while the INR is
still <1.5. Typically, this is approximately 36 hours following the
initial administration of warfarin. Neurologic and motor testing
should be routinely performed on these patients.(12)
All three of the neuraxial techniques have possible side effects.
Patients can become hypotensive, as their systemic vascular
resistance decreases. This is due to the sympathectomy caused
by blockade of sympathetic fibers along the thoracic sympathetic
chain. Rarely, patients can develop an unintentionally high spinal
anesthetic, leading to bradycardia, apnea, and even loss of consciousness. This “high spinal” must be treated as a general anesthetic, with immediate securing of the airway with endotracheal
intubation and supportive therapy until the local anesthetic is
metabolized.
Some patients can experience mild back pain at the site of
needle placement, especially when multiple attempts are needed
to place the block. Post Dural Puncture Headache (PDPH) can
occur, typically following inadvertent dural puncture with an
epidural needle—a ‘wet tap’. These headaches are characterized
by a slow leak of CSF from the puncture, leading to a headache
that is strongest when standing and lessened when lying. They
are often treated conservatively with oral fluid therapy, oral caffeine, and remaining recumbent. Should there be no relief after a
couple of days of conservative treatment, an epidural blood patch
can be performed. 20 mL of sterile, autologous blood is injected
into the epidural space, resulting in thrombus formation, sealing
of the dura, and cessation of CSF leak. If the diagnosis of PDPH is
correct, there is typically immediate relief of symptoms. Epidural
abscess and meningitis are possible if proper sterile technique is
not used, or if systemic infection is present.(7)
Transversus Abdominis Plane (TAP) Block
The TAP block is a relatively new procedure for blocking the
abdominal wall afferent nerves by way of the lumber triangle of Petit. It can be performed using a landmark technique or
under ultrasound guidance; 20 mL of 0.375% of bupivicaine or
levobupivicaine is then injected into the transversus abdominis
neurofascial plane.(13, 14, 15) In a prospective, randomized
controlled trial, McDonnell et al. reported patients undergoing
anesthesia and intraoperative positioning
large bowel resection who received the TAP block required 75%
less morphine in the first 24 hours, and had significantly lower
pain scores at all time points over the first 24 hours. Additionally,
these patients experienced significantly less postoperative nausea
and vomiting.(13) This is an excellent block for patients having
smaller abdominal procedures, e.g., ventral hernia repair, on an
outpatient basis.
Ilioinguinal and Iliohypogastric Nerve Block
These are field blocks of the terminal branches of the lumbar plexus,
primarily from the L1 root. These blocks are relatively simple to
perform and provide anesthesia in the inguinal and genital region.
A 22-gauge needle is inserted 3 cm medial and 3 cm inferior to the
anterior superior iliac spine, in a cephalolateral direction through
the abdominal muscles until contact is made with the iliac bone. As
the needle is removed, local anesthetic solution is injected. This is
repeated 1–2 more times to cover a fan-shaped area, for a total of
approximately 10–20 mL of local anesthetic.(16)
Awareness Under Anesthesia
Awareness under anesthesia is a rare complication of anesthesia,
but one which has risen to prominence in the public eye recently.
Studies of large numbers of patients in Sweden demonstrated an
overall incidence of 0.16%.(17) One can imagine that this would
be a distressing event; the frequency of posttraumatic stress disorder (PTSD) in the 2 years following an incident of awareness
under anesthesia approached 50%, even if the patient was not
initially distressed by the incident. A similarly large study in
the United States found an overall incidence rate for confirmed
intraoperative awareness of 0.13%, and a rate of 0.24% of possible awareness.(18) It has long been known that awareness occurs
with greater frequency in emergent trauma surgery cases, cases
involving cardiopulmonary bypass, and emergency caesarean
sections. These are situations where patients may experience significant hypotension, requiring a reduction in volatile anesthetic
agents below the level that ensures amnesia. If there is a question whether a patient has had an episode of awareness under
anesthesia, it is imperative the anesthesiologist be contacted, and
the patient reassured. Psychiatric evaluation is usually necessary
to help the patient deal with the potentially distressing nature of
this complication.
A device available that attempts to determine the depth of
consciousness is the bispectral index (BIS), a monitor of anesthetic depth approved by the Food and Drug Administration in
the United States. The frontal EEG is measured, processed using
proven algorithms, and reported on an arbitrary scale of 0–100.
A total of 100 equates to completely awake and responsive, and
zero represents complete electrical silence of the brain. A BIS of
<60 is generally considered a safe level to ensure adequate depth
of anesthesia and lack of awareness under anesthesia. In the
B-Aware trial, patients at high risk for awareness under anesthesia were randomized to two groups, either routine care or a
BIS-guided anesthetic. While the incidence of awareness among
even high-risk patients was very low, the BIS-guided group had a
reduced risk of awareness by 82%.(19)
However, there is controversy surrounding the reliability of the
BIS monitor. Use of the BIS monitor and maintenance within the
proper depth of anesthesia (as indicated by the BIS algorithm)
is still no assurance that the patient will not have an episode of
awareness, as there are numerous reports to the contrary.(20)
Additionally, there are numerous conditions that can influence
the BIS, causing BIS levels that are paradoxically high, such as
ketamine administration or the use of halothane, or paradoxically low, such as following nitrous oxide termination.(21) An
analysis of the ASA Close Claims Project database demonstrates
that between the years of 1961 and 1995 there were 79 claims for
awareness made in the United States; 18 claims for awake paralysis, i.e., the inadvertent administration of a muscle relaxant to an
awake patient, and 61 claims for recall under general anesthesia,
i.e., recall of events while receiving general anesthesia. Most of
the claims for awake paralysis represented substandard care; less
than half of the claims for recall were the result of substandard
care. The majority of patients experienced temporary emotional
distress; 10% of patients were later diagnosed with PTSD. The
awareness of sound without pain was the most common intraoperative event; 21% of patients experienced pain while aware
under anesthesia.(22)
POSITIONING
Supine
This is the most common surgical position; it results in the least
hemodynamic and ventilatory changes and is frequently the best
position for surgical exposure. The supine position is not perfect,
of course, as it creates certain pressure points that, given time,
result in ischemia over certain bony prominences, such as the
heels, sacrum, and back of the head. The head should rest on a
soft support to spread the pressure, decreasing the incidence of
pressure points, thus preventing alopecia. Particular care must be
given to the arms, including careful padding of the elbows and
wrists. Abduction of the arms must not exceed 90 degrees from
the body to prevent compromising blood flow to the distal arm.
(23) Trendelenburg positioning while supine has several anesthetic implications, as it causes the diaphragm to move cephalad,
causing increased airway pressures and possibly advancing the
endotracheal tube into an endobronchial position.
Shoulder braces are sometimes used to prevent the patient from
sliding off the table during extreme Trendelenburg positioning,
though this can cause injury by compressing the brachial plexus.
(24) The most common upper extremity injury is to the ulnar
nerve, which is 3 times more likely in men who undergo general
anesthesia. This seems to occur despite padding of the extremity.(25) Other nerves at risk due to positioning are illustrated in
Figure 3.2.
Prone
Even when a procedure is planned in the prone position, induction of general anesthesia and intubation of the trachea should
occur in the supine position. The patient is then turned prone,
taking care to keep the cervical spine and head in-line with the
rest of the body. There are several different pillow types that allow
for proper positioning of the head in a neutral position with the
remainder of the body, while keeping the eyes, nose, and chin free
from pressure.
3
improved outcomes in colon and rectal surgery
side of the body in a neutral position, with careful padding of the
elbows to prevent injury. Alternatively, the arms can be positioned
along side the head, taking care that the arms are not abducted
>90 degrees to prevent injury to the brachial plexus.(23, 24) Great
care must be taken to not inadvertently dislodge the endotracheal
tube while prone, as it is exceedingly difficult to reintubate or mask
ventilate a patient in the prone position.
Lateral Decubitus
Just as with prone positioning, it is imperative that the head be kept
in a neutral positioning while turning the patient. Additionally,
extra cushioning is needed under the head to keep the cervical
and thoracic spines in line. An axillary roll needs to be placed
just caudad to the dependent axilla in order to prevent compression injuries to the brachial plexus. It should not be placed in the
axilla, as the purpose is for the weight of the thorax to be borne
by the chest wall. The dependent arm is extended perpendicular
to the body on a padded armboard, while the nondependent arm
is similarly extended on an armrest suspended in such a way that
the arm is not abducted >90 degrees from the body. Additionally,
the arm should not be raised superior to the level of the deltoid.
A pillow or cushion should be placed between the knees.(23, 24)
Figure 3.2 Nerves at risk for injury during positioning for a surgical procedure.
There is a low, but significant risk that pressure on the eye or
surrounding orbit will lead to increased intraocular pressure,
decreased retinal artery blood flow, and resultant blindness, if
the intraocular pressure exceeds systemic pressure. Although this
is a rare complication associated with the prone position, it is
nevertheless, devastating. Extreme care must be taken to avoid
this life-changing occurrence.
The thorax should be supported with chest rolls that extend
from the clavicle to the iliac crest. The arms can be placed at the
Lithotomy
The lithotomy position is very common in colorectal surgery. The
hips are flexed 80–100 degrees from the trunk, and the legs are
abducted 30–45 degrees from midline. It is important that the legs
always be moved simultaneously to prevent lumbar spine torsion,
and that the legs be carefully padded to reduce the risk of injury.
In a retrospective review of patients undergoing surgery in the
lithotomy position, Warner et al. found that the most common
lower extremity nerve injury was to the common peroneal nerve,
accounting for 78% of nerve injuries. It was postulated that the
cause was compression of the nerve between the leg support and
the lateral head of the fibula.(26)
While rare (1 in 8,720), the incidence of compartment syndrome
of the lower extremities is markedly higher in the lithotomy position than all other surgical positions. Compartment syndrome
occurs when high tissue pressure builds within the closed space of
the anterior compartment. Ischemia of the tissue in the compartment results in edema of the interstitium, thereby raising compartment pressure. Since perfusion is dependent on compartment
pressure being lower than mean arterial pressure to allow tissue
perfusion, any situation where increased compartment pressure
and/or decreased arterial flow into the tissue can result in ischemia.
The result is capillary endothelial damage and even greater interstitial edema. Unfortunately, it is not completely understood why
some patients develop a compartment syndrome, while others
do not. As a result, no safe maximum time limit can be defined.
(27) Early diagnosis and treatment with fasciotomy is imperative.
Analysis of closed claims in cases of compartment syndrome due
to the lithotomy position during colorectal surgery demonstrated
an average indemnity payment of $426,000.
Great care must be taken in the positioning and padding,
as patients themselves cannot express any pain or discomfort
they may be experiencing while under general or regional
anesthesia.
anesthesia and intraoperative positioning
SURGICAL CARE IMPROVEMENT PROJECT
Process and Outcome Measures
The Surgical Care Improvement Project (SCIP) of the United
States is a national quality initiative involving the American
Society of Colorectal Surgeons, the American College of Surgeons,
the American Society of Anesthesiologists, the American Hospital
Association, the Association of Perioperative Registered Nurses,
and a host of governmental agencies dedicated to improvement
in healthcare.(28) The goals of the SCIP partnership are to reduce
the incidence of surgical complications by 25% by the year 2010,
and to promote the use of evidence-based care processes known
to reduce surgical complications.
Out of approximately 40 million major operations each year,
postoperative complications account for up to 22% of preventable
deaths among patients, depending on the complication. These
complications accounted for 2.4 million additional hospital days
and $9.3 billion (USD) in additional charges each year.(29)
SCIP focuses on areas where the incidence and cost of the most
common and preventable complications are high:
Surgical Site Infections (SSIs)
Adverse Cardiac Events
Venous Thromboembolism
Postoperative Pneumonia
Although not limited to anesthesia care, the anesthesiologist and
colorectal surgeon must partner in attempts to meet the expectations set by the national SCIP initiative.
One such initiative is the administration of prophylactic antibiotics within 1 hour of surgical incision. Although not typically
considered “anesthetic agents”, antibiotics may best be given
within 1 hour of incision if administered by the anesthesia provider. Frequent operating room and turnover delays may result
in an antibiotic administration well-before the 1 hour limit if
given by in the preoperative holding area. Late patient arrivals for
same-day admit surgery or administrative paperwork delays may
result in inadequate or insufficient time to infuse the antibiotic
before going to the operating room (OR), with the result of no
antibiotic being given or being given only if the “missed dose” is
noticed by someone in the OR.
Although no longer reportable as public information, prophylactic antibiotic selection for surgical patients is monitored, as is
discontinuation of the antibiotic within 24 hours after the surgery
end time (48 hours for cardiac surgery patients). If an antibiotic
if felt to be needed beyond the allowed 24 hours, the colorectal
surgeon must document, in the medical record, the reason for the
continuation of the antibiotic.
Another SCIP initiative that is frequently met or monitored
by the anesthesiologist is perioperative beta blockade. By having
patients see an anesthesiologist preoperatively for assessment
and clearance for anesthesia, the anesthesiologist can begin beta
blockers on all patients who are not already on them.
Venous thromboembolism was discussed above, and involvement of the anesthesiologist and associated regional anesthesia
play a significant role here. As previously mentioned, an epidural
catheter must be removed at an appropriate time surrounding the
initiation and discontinuation of heparin, LMWH, or warfarin.
The risks of inadequate venous thromboembolism prophylaxis
must be weighed against the benefits of regional anesthesia for
colorectal surgical patients.
Postoperative pneumonia is a complication where the cause is
multi-factorial. Ventilator management and weaning protocols
for patients requiring postoperative mechanical ventilation may
fall under the purview of the anesthesiologist.
CONCLUSION
Although the sum total of anesthesia practice can hardly be related
in a textbook chapter, we have attempted in the preceding pages
to highlight areas in anesthesia practice of which the colorectal
surgeon should be aware. Improved patient satisfaction through
reduction of postoperative pain, earlier ambulation, and quicker
return of bowel function and diet will have a marked impact
on surgical outcomes. Thoracic epidural anesthesia/analgesia is
becoming a standard for many colorectal surgical procedures,
whether as the sole anesthetic, or in conjunction with general
anesthesia.
Awareness under anesthesia is a rare, but serious concern, highlighted more recently in the media and receiving much greater
appreciation among surgical patients. Supportive care, including
psychological counseling may improve outcome and reduce the
incidence of posttraumatic stress disorder.
Oversedation resulting in hypoventilation, hypoxemia, and
hypercarbia can produce devastating results. Extreme caution must
be given to the patient who is restless, but sedated. Loss of airway is
the ultimate disaster under general anesthesia, and is a surgical, as
well as anesthetic, emergency.
Proper positioning requires the vigilance of the anesthesia
provider, the colorectal surgeon, and the operating room nurses.
Severe nerve injuries can generally be avoided with the use of
padding. Although even with appropriate padding, there is an
increased incidence of neurologic injury with the use of stirrups
in the lithotomy position.
Extra care must be taken of the patient in the prone position,
as neck injuries from improper turning, endotracheal tube dislodgement, or perioperative blindness from periorbital pressure
can all result in devastating outcomes.
Partnership of the surgeon and the anesthesiologist may help
improve outcomes, reduce surgical site infections, improve perioperative cardiac morbidity and mortality, and reduce the incidence of
venous thromboembolism. Whether in the office setting, outpatient
center, or surgical hospital, safe anesthesia practice is paramount.
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1. Stoelting RK, Miller RD. Scope of Anesthesia Practice in
Basics of Anesthesia. Fifth Edition. Philadelphia: Churchill
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2. Hutson LR, Vachon CA, Dr. Rudolph M. Innovator and pio-
neer in anesthesiology. Anesthesiology 2005; 103(4): 885–9.
3. Stoelting RK, Miller RD. Local Anesthetics in Basics of
Anesthesia. Fifth Edition. Philadelphia: Churchill Livingstone
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4. Barash PG, Cullen BF, Stoelting RK et al. Local Anesthetics in
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Basics of Anesthesia. Fifth Edition. Philadelphia: Churchill
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6. Bhananker SM, Posner KL, Cheney FW et al. Injury and
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Anesthesia. Fifth Edition. Philadelphia: Churchill Livingstone
Elsevier, 2007: 273–90.
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4
Sepsis
Steven Mills and Michael J Stamos
CHALLENGING CASE
Six days after a low anterior resection with diverting loop ileostomy for rectal cancer, the patient is febrile and has a leukocytosis
with a left shift. His vital signs remain stable, but he had a borderline low urine output overnight.
CASE MANAGEMENT
You increase the patient’s intravenous fluids, start him on broad
spectrum antibiotics and obtain a computed tomography scan of the
abdomen and pelvis. The study reveals evidence of an anastomotic
leak with an associated collection of fluid and gas in the pelvis. After
consultation with interventional radiology, the patient undergoes
percutaneous drainage with a 7-French pig tail catheter.
INTRODUCTION
The postoperative patient with sepsis is concerning to any surgeon. There are different causes of sepsis following an operation,
from soft tissue infections to intraabdominal infections and pelvic sepsis, not to mention those causes not directly related to the
surgical procedure, such as line sepsis, urinary tract infection, or
pneumonia. Each can produce a response along a physiologic
spectrum, from minimal systemic effects to multisystem organ
dysfunction. For the surgeon, knowledge of prevention, identification, and treatment of each type and cause of postoperative
sepsis is necessary.
Recognizing a postoperative patient in trouble is critical for any
surgeon. Changes in certain physiologic parameters may indicate a
problem, or may be a normal response to surgery (e.g., tachycardia
due to pain). The systemic inflammatory response syndrome (SIRS)
is a constellation of findings suggestive of “systemic inflammation”
without a defined cause (i.e., either infectious or noninfectious). In
contrast, sepsis is this same physiologic response with an identified
infectious etiology. A patient with SIRS exhibits two or more of the
following: tachycardia, tachypnea, fever, and a leukocytosis.(1) Any
patient who qualifies for SIRS by this definition should be carefully
evaluated to search for infectious causes of the systemic response,
including wound infections, urinary tract infections, pneumonia,
abdominal, or pelvic abscesses, etc. As each of these may be treated
differently, or indeed, there may be another cause for the patient’s
systemic inflammatory response, the surgeon needs to evaluate systematically the patient to determine whether or not any interventions are required.
SURGICAL SITE INFECTIONS
Skin and soft tissue infections are a risk of any operation. The
skin functions as a natural barrier to protect our body from invasion by bacteria in the environment. As we violate this protective
shield during surgery, a bacterial inoculum occurs at the surgical
site, and the host defenses must fight to overcome this bacterial
load. Over the past century, surgeons have worked diligently on
methods to decrease the risk of surgical site infections, including improved surgical technique and antimicrobial prophylaxis.
If a wound infection does occur, decisions must be made on how
appropriately to manage the complication.
In an effort to predict the expected risks of infection for a patient
before surgery, various scales have been devised to categorize and
risk stratify. More recently, some of these same scales have been
used to “grade” or trend outcomes. Many of these are based upon
a wound classification scale which divides wounds into categories:
clean, clean-contaminated, contaminated, and dirty. Predictions
of wound infection risk have been based upon this classification.
An inclusive classification scheme was devised in 1985 by Haley
et al. (2) They described additive factors for wound infection risk
which include (in order of importance): abdominal operations,
operations >2 hours, contaminated or dirty wounds, and three
or more associated medical diagnoses (complicated patients).
The lowest risk operations had infection rates of <1% whereas
the riskiest procedures carried up to 27% risk of surgical site
infection. The National Healthcare Safety Network (NHSN) (formerly known as the National Nosocomial Infections Surveillance
(NNIS) System) is regarded as one of the strongest predictors of
surgical site infections (SSI).(3) To predict SSI, ASA score, wound
class, and surgery duration were evaluated. A “point” is added for
each positive category, with cutoffs based upon specific type of
surgery being performed (e.g., colon, hepatobiliary, etc.). More
recently, the surgical approach has been factored in, with laparoscopic operations having a “point” deducted due to lower risk of
infection observed in NHSN’s database.
Prophylactic antibiotics given before surgical incision have
become standard of care for colon and rectal operations. Most
surgeons agree that prophylactic antibiotics will decrease the risk
of surgical site infections, though specific choice of agent(s), and
their timing and length of use are somewhat more controversial.
Nichols et al. described the use of oral antibiotics to decrease the
levels of intracolonic bacteria (4) in patients without any intestinal pathology. The same investigative group then followed this
with a look at colonic resection and a comparison of mechanical
prep alone versus mechanical and oral erythromycin base/neomycin preparation.(5) This study showed a dramatic drop in wound
infection rate in the group receiving the oral antibiotics. A followup Veteran’s Administration study (6) showed an improvement
from 43% overall septic complications with mechanical bowel
prep to 9% with mechanical prep and oral antibiotics. However,
with improvements in intravenous antibiotics, the routine use of
oral antibiotics has been called into question. In a 2003 survey of
members of the American Society of Colon and Rectal Surgeons,
49% felt prophylactic oral antibiotic to be essential, 41% deemed
them doubtful and 10% considered oral prophylaxis unnecessary; however, 75% of the surgeons routinely used oral antibiotics, 11% used them selectively and 13% omitted oral prophylaxis.
(7) A more recent randomized trial evaluating the efficacy of
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