Anesthesiology

Knee arthroscopy

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What the Anesthesiologist Should Know before the Operative Procedure.

Arthroscopic knee surgery is primarily used as an elective surgical procedure. Its’ primary use is in diagnostic studies and soft tissue repairs of the knee joint. As such there are few critical issues surrounding this procedure. The surgery is usually accomplished minimally invasively producing few physiologic perturbations. Younger patients suffering sports injuries generally have few co-morbidities, in contrast to some of the older patients undergoing diagnostic procedures for osteoarthritis who lead sedentary lives and may have other systemic diseases. Diagnostic arthroscopy, if truly diagnostic, may cause minimal pain. If used for diagnostic and treatment purposes, post-operative pain may become a major issue.

1. What is the urgency of the surgery?

What is the risk of delay in order to obtain additional preoperative information?

Knee arthroscopy is never an emergent procedure. Orthopedic procedures that are to be performed on an emergent basis involve osseous injury. The nature of the injury and the treatment requirements prevent them from being adequately treated with an arthroscope. On occasion, it can be used as an urgent treatment modality. Primarily knee arthroscopy is an elective procedure.

There are no indications for emergent arthroscopy; consequently there are no related issues.

Urgent and elective arthroscopies carry few related specific issues. The primary concerns associated with these procedures surround the patient’s underlying medical issues.

2. Preoperative evaluation

Most patients presenting for knee arthroscopy have suffered trauma, either from an acute event or from repetitive use. Acute traumas may be an isolated injury, as in sports related accidents, or may have been part of a constellation of poly-trauma, with knee injuries coming to light only after major injuries have been treated. The athlete with an isolated knee injury may have few, if any, associated medical problems. Patients with injury to the knees secondary to chronic repetitive use may present with medical issues (cardiac, pulmonary, renal, etc.), which are well controlled but must, nevertheless, be considered when constructing an anesthetic plan.

Patients who have suffered poly-trauma may, in addition to pre-injury medical issues, have developed new concerns. These would include conditions such as new onset seizure disorders, spine injuries, and neurologic deficits. All could potentially change anesthetic plans and management.

Since knee arthroscopy is essentially an elective procedure, there should be no unstable medical conditions that require further evaluation and work up. It is conceivable that a patient with no history of cardiac disease, yet with significant coronary artery stenosis, for example, develops acute ECG changes due to adrenergic drive secondary to anxiety. It is also possible that a patient may present to have surgery after being sedentary for a prolonged period of time after a knee injury, have an unrecognized DVT and develop a pulmonary embolus. Another possibility is the patient who presents for arthroscopy and during the course of the anesthetic interview, a history that suggests the possibility of a bleeding disorder is revealed. These are rare and unlikely events.

The patients listed above are appropriate to have their surgery delayed or postponed to allow further investigation and possible treatment. It is also appropriate to delay surgery if the patient has violated the NPO time frame. This would protect the patient allowing for safe anesthesia and surgery. Another reason to delay or cancel the procedure is if the patient has second thoughts about having surgery or if the patient is excessively fearful of the surgery and states that he/she cannot proceed with the surgery. These patients should not be forced or coerced into a procedure.

3. What are the implications of co-existing disease on perioperative care?

Perioperative evaluation

- Being essentially an elective procedure, most preexisting medical conditions should be optimized by the time the patient arrives for surgery. There are no significant comorbidities associated with conditions for which knee arthroscopy is required.

Perioperative risk reduction strategies

- Patients who present with a knee injury requiring diagnostic arthroscopy or arthroscopic intervention with no coexisting medical problems will require no risk reduction strategies. They are frequently only taking pain medication with the possible addition of medications to relieve muscle spasms. These patients can continue to take these medications up to the time of surgery. Those patients who present with coexisting medical problems will need to have their medications reviewed. A decision must be made weighing the risks versus benefits of continuing a particular medication. For example, diabetics taking metformin should be asked not to take this medication prior to surgery due to the possibility of developing metabolic acidosis. Patients who have cardiac disease should be advised to continue their medications. Those who have had drug-eluting stents placed need to be free from Plavix with an enoxaparin bridge prior to surgery. Those patients treated with warfarin for arrhythmias or CVAs need to have the medication stopped sufficiently in advance of surgery to assure adequate hemostatis at the time of the planned operation. Patients who have disorders of blood coagulation, such as hemophilia or other factor deficiencies, should be evaluated by a hematologist prior to surgery and recommendations made as to the proper factor infusions needed for safe surgery.

b. Cardiovascular system

Acute/unstable conditions:

Patients with acute or unstable conditions should not be scheduled for elective knee arthroscopy.

Baseline coronary artery disease or cardiac dysfunction - Goals of management:

Patients with significant cardiac conditions fall into one of three basic groups. The first group consists of patients with significant coronary disease, but with normal ventricular function. These patients will require careful attention being paid to the patient's heart rate and blood pressure throughout the course of the case. Significant reductions in diastolic pressures, in particular, risk critically lowering the trans-myocardial perfusion head. Allowing excessive heart rates risks decreasing diastolic filling times, often to the point where cardiac output can diminish significantly. This is particularly accentuated in patients who have concomitant hypertension with thickened myocardiums. The second group consists of patients with valvular disease. This group can be subdivided into stenotic, regurgitant, and mixed valvular dysfunction categories. Volume status and rate regulation are paramount in this class of heart disease. The final group is those patients with cardiomyopathies. Special consideration must be paid to the ejection fraction in these patients with regard to the ventricular chamber size. Those patients with large chambers and low ejection fractions may still have good cardiac outputs and, therefore, adequate organ perfusion. Those with small ventricular chamber size and poor ejection fractions could have inadequate cardiac outputs and poor perfusion.

c. Pulmonary

COPD:

Patients with COPD should be queried about their activity limitations due to their poor pulmonary function. Their requirement for home oxygen use needs assessment, as does their ability to lay flat. Inability to lay supine will make anesthetic options slim if the surgeon is unwilling to modify the procedure to accommodate the patient's medical condition. If intubation is required, there is a possibility the patient may not be able to separate from the ventilator, and may need to be admitted to an acute care unit. If possible, a regional technique would most likely be the best anesthetic choice for the patient. Which regional technique would be best tailored to this patient is debatable. If a peripheral nerve block is used, the possibility of a high spinal requiring intubation is obviated. The patient will have a period of postoperative analgesia from the blocks, which will allow him/her to use less opioid medications. If the patient develops a toxic response from intravascularly injected local anesthetics this may lead to intubation. If, however, a spinal anesthetic technique is utilized, barring a high spinal, postoperative analgesia may require the use of opioids that may cause respiratory depression in a patient that has marginal pulmonary reserve.

OSA:

Patients with sleep apnea should have the severity of the disease assessed, and appropriate strategies developed to reduce the potential for post-operative exacerbation of their disease by opioid-induced respiratory depression. They should continue the use of their CPAP therapy in the peri-operative period. Those patients with diagnosed and treated sleep apnea who present for arthroscopy should bring their CPAP machines on the day of surgery. Usually an anesthetic strategy can be devised that will avoid or minimize opioid use. Spinal anesthesia, epidural, and peripheral nerve blocks can be good options for these patients. Usually the patients can be discharged home after an appropriate stay in the PACU. If however the patient must be admitted for pain control or other surgically related issues, the patient will have his CPAP available for use on the surgical floor. The patient who is undiagnosed but is suspected of having OSA based on history and symptoms poses a dilemma. Should the patient be admitted after arthroscopy on merely the suspicion of OSA or should the risk of sending him/her home be taken? It is most likely in the best interest of the patient's safety to have them plan on being admitted after surgery for overnight monitoring and observation. Further, if the patient is suspected of having OSA, he/she should be counselled about the medical dangers of untreated sleep apnea and should be advised to be tested.

Reactive airway disease (Asthma):

Patients with reactive airway disease should be questioned about their history of inhaler use, need for steroid treatment, hospitalization, and the frequency of exacerbations, emergency room visits, and hospitalizations. It is important to know if medications are taken daily or if on a PRN basis. In these patients it is often helpful to choose an anesthetic technique that will avoid manipulation of the airway. In those patients who are triggered by anxiety or stress, it is helpful to provide preoperative sedation. Those who are taking oral steroids should receive IV stress steroids.

d. Renal-GI:

Patients with renal dysfunction span a broad spectrum ranging from mild insufficiency to complete failure requiring dialysis. The patient with mild insufficiency will not require care that is different from patients that have renal function indices that are normal. At the other end of the continuum, patients with dialysis dependent renal failure must be questioned about the days they are dialyzed and the last date of dialysis. Electrolyte analysis, particularly potassium, is important to obtain. Several medicines, which are usually eliminated by the kidneys, should be avoided. Examination of their dialysis access must be made for thrills and bruits and documented prior to and after surgery. Care must be taken when positioning these patients so their dialysis fistulas/shunts do not become obstructed by pressure from poor positioning. Finally, care must be used when treating patients who have had renal transplants. Attention must be given to the immunosuppressant regimen. Those who are taking prednisone should be considered for stress doses of steroids during their arthroscopy.

e. Neurologic:

Neurologic status is of concern during knee arthroscopy primarily from peripheral nerve injury in the distribution of an intended nerve block. The patients need to be made aware that there may be a potential for worsening neurologic function if a block is used. Additionally, some neurologic conditions may predispose patients to develop catastrophic neurologic deficits even in the face of no pre-existing nerve dysfunction. These patients should most likely be advised against peripheral nerve blocks. Additionally, if neuraxial procedures are considered for a patient, spinal stenosis, previous corrective spinal surgery, and uncorrected spinal deformities may be deterrents. Finally other neurologic issues such as seizures, traumatic brain injury and past strokes must be taken into account when developing an anesthetic plan.

f. Endocrine:

There are no significant endocrine medical problems that will impact knee arthroscopy. The only consideration would be diabetes and any associated neuropathies. The neural deficits would need to be documented and the possibility of worsening neural function in the distribution of any blocks needs to be delineated to the patient. Naturally, the patient’s blood glucose would need to be followed throughout the course of the surgery and during their recovery phase.

g. Additional systems/conditions which may be of concern in a patient undergoing this procedure and are relevant for the anesthetic plan (eg. musculoskeletal in orthopedic procedures, hematologic in a cancer patient)

Since regional anesthesia, either neuraxial or peripheral nerve blocks, is frequently used as the anesthetic for knee arthroscopy, one must be careful when dealing with patients with clotting abnormalities. Most commonly, the clotting abnormalities are secondary to medications, which will be covered in a later segment. On occasion, the anesthesiologist will be dealing with a patient who has a genetic deficiency in a clotting factor. These patients will be at risk for intra and post-operative bleeding. Usually the patient will already have been identified and followed by a hematologist. A close working relationship needs to be developed between the hematologist and the anesthesiologist. Recommendations should be obtained regarding which factor(s) need to be transfused, how much of each factor and amount, and frequency of post-operative transfusions. In addition, recommendations will be made with respect to the number of days the transfusions must be continued. With such coordination, patients with significant inborn errors of coagulation can be safely guided through surgery.

Patients who have never had an operation, but have a suspicious history for a bleeding disorder, would be well served by being seen in consultation by a hematologist. This may postpone elective surgery, but could potentially spare the patient significant post-operative morbidity.

4. What are the patient's medications and how should they be managed in the perioperative period?

Most medications that a patient is taking who presents for knee arthroscopy will not affect the anesthetic. It is therefore not necessary to stop taking these. There are a few, however, that will impact the planned anesthetic. Most of these medications affect coagulation in some aspect. Non-steroidal analgesics and aspirin are platelet inhibitors. Surgeons will often request that the patient refrain from taking these medications. According to the ASRA guidelines, they need not be held prior to neuraxial or peripheral nerve block techniques. If the patient is receiving clopidogrel and/or aspirin to reduce the chance of re-stenosis of intracoronary stents, then discussion with the cardiologist and surgeon in necessary to develop an appropriate peri-operative anticoagulation strategy.

Low molecular weight heparin medications, such as lovenox, must be held twelve hours prior to neuraxial or peripheral nerve blocks. Performing these anesthetic techniques in the presence of these medications risks significant bleeding. If this occurs in the epidural space after performing a spinal, blood accumulating in this space can cause progressive cord compression. If not dealt with expeditiously, paralysis can result.

Patients taking Coumadin should have this medication held far enough in advance to allow the INR to return to 1.4 or less. Again, according to the most recently published ASRA guidelines, an INR of 1.4 is safe for performing spinal anesthetics as well as peripheral nerve blocks.

Some over the counter medications can theoretically affect clotting. These are the four “G” medications: ginseng, gingko, garlic, and goldenrod.

Diabetic patients taking metformin should not take this medication on the day of surgery due to the risk of developing metabolic acidosis.

There is some controversy surrounding patients taking ACE inhibitors or ARB inhibitors. It is not clear if these medications need to be held on the day of surgery or if they are safe to take. Traditionally, these medications have been held.

h. Are there medications commonly seen in patients undergoing this procedure and for which should there be greater concern?

There are no specific medications associated with pathologies that require knee arthroscopy that need special consideration. Most of the medications that are taken specifically for knee pathology are pain medications. These will have no direct consequences on arranged anesthetic plans for arthroscopy.

i. What should be recommended with regard to continuation of medications taken chronically?

Recommendations regarding medications patients are taking chronically who are presenting for knee arthroscopy is fairly straightforward. Patients should take most of their chronic medications up to and including the day of surgery. Since knee arthroscopy anesthetic plans often include the use of regional techniques, anticoagulation medications should be held. If there is medical reason for not discontinuing the anticoagulation medications, and the orthopedic surgeon is willing to proceed with the operation, the anesthetic plan must be changed to a general technique avoiding regional anesthetics.

j. How To modify care for patients with known allergies -

Patients presenting for knee arthroscopy are treated no differently than patients presenting for other types of surgery in terms of known allergies. Triggering agents must be avoided. Allergies that are significant in relation to anesthetics for knee arthroscopy are those to tape, antibiotics, local anesthetics, pain medications, and soy or egg products (components in propofol).

Patients allergic to tape should be queried about the specifics of their allergy. Often there is a specific type of tape that the patient is allergic to allowing the safe use of other, non-allergic reaction producing, tape to be used. If the history is unclear, the use of an LMA without being secured by tape is an option. If an endotracheal tube is used, tracheal ties are reasonable options.

Patients are usually given prophylactic antibiotics for these procedures. The primary organisms being covered are skin flora. A cephalosporin (usually cephazolin) is used to provide protection against these organisms. Patients allergic to cephalosporins, and those allergic to penicillins (10-15 % cross reactivity), can receive clindamycin or vancomycin.

Pain medication allergies are occasionally a concern for patients undergoing knee arthroscopy. Issues surrounding these medications revolve around true allergies versus adverse responses. Adverse responses are often designated as allergies making post-operative and occasionally intra-operative pain control challenging. In clinical practice today there are several pain medications that can be used to provide relief for patients. These include non-steroidal anti-inflammatory agents, but also opioids as well as local anesthetics used for local infiltration/field blocks or conductive peripheral nerve blocks.

If a patient receives a regional technique for his/her anesthetic it is often combined with sedation. The most common agent used is propofol. Propofol is also commonly used as part of a general anesthetic. Occasionally a patient is allergic to soy or lecithin (components of propofol) and, therefore, should avoid this medication. Alternatives to propofol sedation include dexmedetomidine, versed, and ketamine.

Although they are alternatives, they may be associated with significant side effects. For instance, dexmedetomidine may in addition to its sedative and analgesic properties produce bradycardia, hypotension, nausea, and dry mouth. Ketamine, in addition to producing a dissociative state, can produce excessive salivation and involuntary limb movements, which are particularly unwanted when precise surgery is being attempted through small portals.

Perhaps the most disturbing side effect of ketamine is the occurrence of emergence delirium. This can be quite frightening to the patient, staff and family. Unwanted side effects of midazolam include a lack of coordination, motor function impairment, blurred vision, and occasionally, and nausea and vomiting. All these undesired side effects can slow the through-put of a busy operating room, particularly a busy ASC In addition, they can adversely affect a patient's anesthetic and operative experience, an important factor in patient satisfaction.

k. Latex allergy- If the patient has a sensitivity to latex (eg. rash from gloves, underwear, etc.) versus anaphylactic reaction, prepare the operating room with latex-free products.

Latex allergies are fairly common due to extensive exposure to rubber products. As a result, particular caution needs to be used when anesthetizing these patients. Because of heightened awareness of this, most products used in the operating room are latex/rubber free. However, there are still some medications that are bottled with latex stoppers. The tops to these medications must be removed and the drug drawn up directly from the glass or plastic container. If the medication is aspirated through the latex stopper, there is a possibility that when the drug is administered to the patient an allergic reaction can be induced.

l. Does the patient have any antibiotic allergies-

Since antibiotics are commonly administered when performing knee arthroscopies, a history of allergic reactions to these medications must be elicited. The usual antibiotics used will cover skin flora. The most commonly used antibiotic is ancef, a cephalosporin. If the patient has never been exposed to cephalosporins in the past a history of penicillin allergy should be sought since there is an incidence of cross sensitivity. If the patient has a history of penicillin allergy but no prior cephalosporin exposure, a decision need be made as to the risk of an allergic response to the ancef versus the benefit of its bacterial coverage. If the patient has a documented cephalosporin allergy, a different class of antibiotic should be used. Alternative antibiotics include clindamycin and vancomycin.

m. Does the patient have a history of allergy to anesthesia?

Querying the patient about allergic responses to anesthesia can yield a variety of answers, some of which can be helpful, but some of which are vague and unhelpful. It is difficult to know what is meant when a patient states they have been told they have had an allergic response to anesthesia since they had a prolonged wake-up time. It is, however, helpful if a patient has been exposed to various anesthetic agents and has had an adverse reaction to one, or some, of these. Also helpful is a history of a documented allergic response to any of the agents commonly used for anesthetics in knee arthroscopy. This can include local anesthetics, sedatives, induction agents, analgesics, and antibiotics.

Malignant hyperthermia:

Patients with documented malignant hyperthermia can usually be safely managed by avoiding triggering agents. Succinylcholine and volatile anesthetics need not be used for those undergoing knee arthroscopy. Alternatives to these agents for patients who do not desire regional techniques include the use of all standard sedatives, induction agents, non-depolarizing neuromuscular blocking agents, as well as opioids. Induction agents such as propofol, along with remifentanil infusions, can be used for TIVA, obviating the need for volatile anesthetics. Patients who are willing to have a regional technique as their anesthetic (neuraxial or peripheral nerve blocks) will also avoid exposure to triggering agents. All local anesthetics are safe to use in patients with this disorder of calcium metabolism.

Those patients who present for surgery who do not carry a diagnosis of malignant hyperthermia, but have family members who either have documented MH or have an anesthetic history suspicious for malignant hyperthermia are most likely best managed with a strategy that avoids triggering agents. They can be sent for testing at a later time, however, this may have implications about medical insurance if testing is positive.

Local anesthetics/ muscle relaxants:

Since regional anesthesia is a large component of the anesthetic plan for knee arthroscopies, care must be taken to avoid local anesthetics that patients are allergic to. It is uncommon for patients to be allergic to amide types of local anesthetics. These are the most common types of local anesthetics used in clinical practice today. However, some patients are allergic to amide containing solutions. This could be due to the added preservative methylparaben. It is difficult to determine, from history alone, if an allergic reaction to a local anesthetic solution administered was a preservative free solution, or one with a preservative. In this circumstance it is best to proceed with an ester type of local (chloroprocaine or procaine). If these agents are used, it must be realized that the duration of action is short and the length of the surgical procedure must be accounted for. If the surgeon can complete his procedure within one half to one hour, the ester local anesthetic can be used for spinal anesthetics. Sensitivity to the ester class of local anesthetics is more common than that seen with amide types of locals. This may relate to preservatives that had been used in the past. There is a new formulation used in clinical practice that is void of the preservatives used previously, which seems to have reduced the number of adverse reactions. Finally, some local anesthetics are premixed with epinephrine, and epinephrine is often added to local anesthetics. Allergic responses to the epinephrine may be due to the sulfite stabilizer added to the epinephrine preparation and not the epinephrine itself. Regardless of the allergic response, it is best to avoid those medications, even if the response is weak or the allergic reaction description is questionable for a true allergy. If the patient has what seem to be allergies to both classes of local anesthetics, an alternative anesthetic plan must be devised.

5. What laboratory tests should be obtained and has everything been reviewed?

Knee arthroscopy is not a highly invasive surgical procedure. As such, few laboratory tests and physiologic function tests will need to be obtained. There are, however, a few exceptions. Patients who present with chronic renal insufficiency should have laboratory data evaluating their potassium, BUN, and creatinine levels. In addition, those patients who require dialysis should be asked about their dialysis frequency and when their last dialysis was. The dialysis site, if a shunt or fistula, should be investigated for thrills and bruits and documented.

Patients with endocrinopathies should be optimized. This includes management of diabetics to assure well-controlled blood glucose levels as well as documentation of the HbA1C. Those with thyroid dysfunction should be checked for thyroid function and corrected to be euthryoid.

Finally, patients on anticoagulants should have their clotting parameters checked. This includes primarily PT and INR since testing for the effect of many of the newer antiplatelet agents is difficult and expensive. These medications are best managed by a prescribed interval of time where they are not taken allowing the drug’s effect to dissipate. Those who have any abnormal results should be rescheduled at a time when abnormalities have been corrected and physiological derangements optimized.

Intraoperative Management: What are the options for anesthetic management and how to determine the best technique?

Knee arthroscopy can be performed with general, regional, or monitored anesthesia care.

a. Regional anesthesia

Regional anesthesia for knee arthroscopy can be divided into two broad categories, neuraxial and peripheral nerve blocks.

Neuraxial

  • Benefits--Benefits of neuraxial anesthetics include ease of performance, reliability of a dense block, the assurance of a painless procedure, and a relaxed joint for the surgeon to work with. There are several agents that can be used (chloroprocaine, mepivacaine, ropivacaine, and bupivacaine) which will afford the surgeon varying times in which to complete the procedure. The duration of each local anesthetic can be manipulated to a certain degree by using additives (epinephrine or clonidine).

  • Drawbacks--There are several drawbacks to using a spinal technique. The first drawback is that the proposed procedure can often be changed based on what is seen on the initial arthroscopic survey. If this occurs, the procedure can either be shorter or longer than initially planned. Consequently the anesthetic will either last too long or not last long enough. Both are undesired events. If the spinal lasts too long, the surgery can be completed using this modality, but the patient may need to stay for a prolonged period of time after the completion of the case. If the spinal does not last as long as the surgery, a secondary plan needs to be initiated. This usually requires conversion to general anesthesia. On most occasions this in not a significant problem, but on other occasions it becomes a problematic process. This is particularly highlighted, for example, in the patient with a difficult airway.

Issues --Another problem is that the patient must wait for the regression of the anesthetic to the point where he/she can urinate and ambulate before discharge. There can be significant patient variation in the time of regression. Since most arthroscopies are performed as an outpatient procedure this can cause undue delays in the throughput of the patients. Prolonging PACU stays can not only slow the patient’s discharge, but also overburden the nursing staff.

Peripheral Nerve Block

  • Benefits--Peripheral nerve blocks can be highly effective for knee arthroscopy. The procedure can be completed using the block only or can be combined with sedation. To assure complete knee anesthesia, at least the femoral and sciatic nerves need to be blocked, and on rare occasion, the obturator nerve also needs to be blocked. The advantage of these blocks is that they can provide good surgical conditions as well as good anesthesia and a still field, depending on the doses used. The anesthesia is unilateral; there is minimal recovery time and a rapid time to discharge if the procedure is performed on an outpatient basis. The blocks can also provide prolonged analgesia (up to 24 hours, and in some outlier cases 36 hours) after discharge.

  • Drawbacks--The disadvantage to this approach is that the block will render the leg immobile needlessly for a prolonged period of time.

  • Issues-- In addition there are several other potential problems associated with nerve blocks. The two major potential risks are vascular injections, or rapid absorption and neural damage. Intravascular injections are uncommon particularly with the use of ultrasound, but do occur. Even the most serious consequences, seizures and arrhythmias, primarily ventricular fibrillation can now be successfully managed with the use of intralipids. Nerve injury is also relatively uncommon, 0.02-0.1 %, and possibly higher. Most nerve injuries recover, however, the time course may be protracted (up to a year) and on rare occasion, there is never a full recovery. Most of the injuries are of a sensory nature. Occasionally these result in hyperalgesia, which are intolerable for the patient. Some injuries involve motor neurons and result in weakness. These injuries can be devastating particularly to patients who rely on their legs for a living, for example, professional dancers and athletes.

    Selective nerve blocks of the articular branch of the saphenous nerve can be very effective for knee arthroscopy. This is purely a sensory nerve and can provide adequate coverage for the port insertion sites. Local anesthetic supplementation by the surgeons may be required, as well as sedation. The drawback to this approach is that this nerve is difficult to visualize, therefore, making the technique impossible on a reliable basis. A saphenous nerve block is a reasonable alternative. This permits the patient to become mobile quickly and have an expedited discharge from the PACU.

b. General Anesthesia

  • Benefits--The benefit of general anesthesia for knee arthroscopy is that it can be tailored to meet the time required by the surgeon to complete the procedure. General anesthetic techniques for knee arthroscopies are usually straightforward, simple, and uncomplicated. Though general anesthesia requires control of the airway, it does not necessarily require the use of neuromuscular blocking agents. LMAs can be used, including the LMA supreme with a gastric suction port for decompressing the stomach. If intubation is required, this can be accomplished by deepening the patient and placing the endotracheal tube without the use of muscle relaxants. This obviates the need for reversal of non-depolarizing agents, and avoids the potential muscle aches commonly associated with the use of depolarizing agents.

  • Drawbacks--Drawbacks of general anesthesia include an increased incidence of post-operative nausea and vomiting, a somewhat longer PACU stay and a longer time to discharge readiness.

  • Other issues--Another potential concern with general anesthesia is the unmasking of malignant hyperthermia in a patient with no history and no previous surgeries. Though rare, this is a possibility, and one must be ready to respond to this emergency.

  • Airway concerns--Additionally, patients undergoing general anesthesia require securing the airway. This can, in some patients, be quite difficult and on occasion surprisingly result in a “can’t intubate, can’t ventilate” situation despite a preoperative evaluation indicating a straightforward airway.

c. Monitored Anesthesia Care

Monitored anesthesia care is often not feasible for knee arthroscopy since the surgical stimulation is usually too great. However, it is possible to perform arthroscopy using a combination of local anesthetic infiltration at port sites as well as an intraarticular local anesthetic injection. Adjuvants such as epinephrine and opioids can also be administered intraarticularly along with the local anesthetic to prolong the desired effect. This is then combined with varying degrees of sedation, from none to heavy sedation. When this type of anesthetic is to be employed several factors need to be considered.

First, is the expected length of the planned procedure. If the procedure is to be quite lengthy, and if the exposure is difficult and extensive knee distraction is applied for prolonged periods for adequate exposure, the patient may become very uncomfortable and intolerant of the procedure. The second consideration is the speed or proficiency of the surgeon. Again, if the surgeon is slow and has difficulty gaining adequate exposure the patient may become intolerant. Finally, the patient's expectations must be considered. The patient must be made aware of what he/she will experience during the procedure. With proper patient and procedure selection in the hands of an efficient surgeon, this type of anesthetic can be effective in terms of patient satisfaction, rapid recovery from the anesthetic, and early discharge from the hospital/ASC.

6. What is the author's preferred method of anesthesia technique and why?

My preferred anesthetic for knee arthroscopy is a saphenous nerve block combined with a medium acting local anesthetic for a spinal and light sedation. Though lidocaine can be used as a medium acting spinal anesthetic, I prefer to use 1.5 % mepivacaine.The incidence of TNS is lower with this local anesthetic and ultimately patient satisfaction will be greater. Patients will benefit from a densely senseless extremity during the operative procedure with good postoperative pain control with a functional leg. The surgeon will benefit from a still, relaxed field making the completion of the procedure easier.

The propofol used for sedation has an added benefit of aiding in the prevention of postoperative nausea and vomiting. I use a medium acting local anesthetic since it provides a cushion of time if the surgeon unexpectedly finds something needing repair that would not have been possible to complete if using a shorter acting local for the spinal. I accept that I may be trading a potentially needed time cushion for a longer stay in the PACU or second stage recovery.

However, if a surgeon is very quick and the surgical procedure is one that can be completed quickly, a short acting local anesthetic such as 2-chloroprocaine can be used for the spinal anesthetic. This will eliminate the time cushion previously mentioned, but will afford a more rapid through-put and earlier patient discharge. This allows the operating rooms and PACU to run more efficiently. Because of a shorter PACU stay, there will be a decrease in total expense, and there can potentially be greater patient satisfaction.

Finally, using a purely regional technique I am able to avoid manipulating the airway. This prevents the potential occurrence of sore throats and the rare, but potentially catastrophic, difficult airway.

Though this is my preferred technique, I will modify my plan to meet the needs and comfort level of the patient.

What prophylactic antibiotics should be administered?

Ancef is the standard antibiotic used since it has good skin flora coverage. They must be administered less than one hour prior to the time of incision. However, the aim of prophylactic antibiotics is to have a tissue level at the site of surgery at the time of incision. Since a tourniquet is almost invariably used for knee arthroscopies to produce a bloodless field, the timing of the administration of the antibiotics is crucial. They must be started well in advance of the tourniquet inflation, but within the sixty-minute pre-incision window.

What can I do intraoperatively to assist the surgeon and optimize patient care?

There are no significant parts of the surgical technique that impact anesthetic care. Equally, there is no special anesthetic technique that needs to be employed to help facilitate the surgical procedure.

What do I need to know about the surgical technique to optimize my anesthetic care?

There are no significant parts of the surgical technique that impact anesthetic care. Equally, there is no special anesthetic technique that needs to be employed to help facilitate the surgical procedure.

What are the most common intraoperative complications and how can they be avoided/treated?

There is rarely any complication associated with knee arthroscopy. Most of the patients are relatively healthy, the procedure is minimally invasive, and does not involve a major body cavity. There is usually no significant blood loss or major fluid shifts. Consequently, there is insignificant physiologic perturbation. The primary intraoperative issues surround the control of episodic transient hypertension associated with surgical stimulation when a patient is receiving general anesthesia or purely a peripheral nerve block. These patients can be managed with small doses of opioids as well as increasing the inhalational agent in those undergoing general anesthesia and increasing the propofol for those having a PNB with sedation. Another approach for treating the adrenergic response to surgical stimulation in patients under general anesthesia is with beta-blockers. A potential problem associated with neuraxial anesthetics is the tendency for hypotension. This can be treated successfully with pressers such as ephedrine and phenylephrine. Another potential problem associated with spinal anesthesia is the rare occurrence of a high spinal requiring the securing of the airway. This can be achieved with an LMA or an endotracheal tube depending on whether the patient has a history of gastric reflux.

Cardiac complications

- There is always the possibility of a rare patient who develops acute ECG changes consistent with myocardial ischemia, which may progress to a myocardial infarction. Pulmonary emboli and strokes are also possible, but are exceedingly rare.

Pulmonary

- no common complciations.

Neurologic: Unique to procedure-

Nerve injury due to procedure or block.

a. Neurologic:

N/A

b. If the patient is intubated, are there any special criteria for extubation?

If the patient was intubated for the surgery, there are no special criteria for extubation related to the procedure.

c. Postoperative management

What analgesic modalities can I implement?

Postoperative management of knee arthroscopy patients is straightforward. As previously mentioned, these patients are relatively healthy and have not had major physiologic derangements as a result of the surgical procedure.

These patients can be given nonsteroidal anti-inflammatory and opioid medications for pain control. If a patient did not receive a preoperative peripheral nerve block, they can have one offered in the PACU if this option had been discussed and agreed upon prior to surgery in the event of inadequate pain control through other modalities.

What level bed acuity is appropriate?

Most patients do not need hospital admission after this elective, or semi-elective procedure. They are usually discharged home after a brief postoperative PACU or second stage recovery stay. If pain cannot be adequately controlled (which is extremely rare) the patient may need to be admitted to the hospital and provided intravenous pain medication, most commonly via a PCA. If a patient needs to be admitted for pain control he can be admitted to a standard surgical nursing floor.

What are common postoperative complications, and ways to prevent and treat them?

Complications are rare. If a full femoral nerve block is performed, there is a risk of a fall after discharge. In addition, the patient with a femoral nerve block must protect the limb and be cognizant of applying extremely hot or cold items since it is insensate and may result in unrealized serious injury.

What's the Evidence?

Horlocker, TT, Wedel, DJ, Rowlingson, JC, Enneking, FK, Kopp, SL, Benzon, HT, Brown, DL, Heit, JA, Mulroy, MF, Rosenquist, RW, Tryba, M, Yuan, C-S. "Regional Anesthesia in the Patient Receiving Antithrombotic or Thrombolytic Therapy". Regional Anesthesia and Pain Medicine.. vol. 35. 2010. pp. 64-101.

Horlocker, TT, Hebl, JR. "Anesthesia for Outpatient Knee Arthroscopy: Is There an Optimal Technique?". Regional Anethesia and Pain Medicine.. vol. 28. 2003. pp. 58-63.

Dunn, WR, Cordasco, FA, Flynn, E, Jules, K, Gordon, M, Liguori, G. "A Prospective Randomized Comparison of Spinal Versus Local Anesthesia With Propofol Infusion for Knee Arthroscopy". Arthroscopy: The Journal of Arthroscopic and Related Surgery.. vol. 22. 2006. pp. 479-483.

Maldini, B, Miskulin, M. "Outpatient arthroscopic knee surgery under combined local and intravenous propofol aneshtesia in children and adolescents". Pediatric Anesthesia.. vol. 16. 2006. pp. 1125-1132.

Lundblad, M, Kapral, S, Marhofer, P, Lonnqvist, P-A. "Ultrasound-guided infrapatellar nerve block in human volunteers: description of a novel technique". British Journal of Anaesthesia.. vol. 97. 2006. pp. 710-714.

Hadzic, A, Karaca, PE, Hobeika, P, Unis, G, Dermksian, J, Yufa, M, Claudio, R, Vloka, JD, Santos, AC, Thys, DM. "Peripheral Nerve Blocks Result in Superior Recovery Profile Compared with General Anesthesia in Outpatient Knee Arthroscopy". Anesth Analg.. vol. 100. 2005. pp. 976-981.

O'Donnell, BD, Iohom, G. "Regional anesthesia techniques for ambulatory orthopedic surgery". Current Opinion in Anaesthesiology.. vol. 21. 2008. pp. 723-728.

O'Donnell, D, Manickam, B, Perlas, A, Karkhanis, R, Chan, VWS, Syed, K, Brull, R. "Spinal mepivacaine with fentanyl for outpatient knee arthroscopy surgery: a randomized controlled trial". Can J Anesth.. vol. 57. 2010. pp. 32-38.

Barash, P, Akhtar, S. "Coronary stents: factors contributing to perioperative major adverse cardiovascular events". British Journal of Anaesthesia.. vol. 105. 2010. pp. i3-i15.

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