Anesthesia

The decision for the type of anesthesia to be used in your surgery, like the decision to perform the surgery itself, is one of risks and benefits. It is usually a joint decision between you and your anesthesiologist, as well as your surgeon. For hip surgery, a combination of general and spinal anesthetics is recommended. For knee surgery, spinal with sedation is recommended.

GENERAL ANESTHESIA
During general anesthesia the patient is unconscious. Light general anesthesia allows the patient to breath on his own; deep anesthesia requires ventilation of the patient by the anesthesiologist. A short case can be done with a mask, but is usually done with an endotracheal tube, which is placed through the mouth or nose into the trachea. Both intravenous and gaseous agents can be used to provide general anesthesia. These agents work on the brain rather than on the spinal cord, as in spinal anesthesia.

The benefits of general anesthesia are that the patient is not aware of what is transpiring and the anesthesia can be prolonged as long as necessary for the procedure. It is also somewhat safer in regards to maintaining adequate oxygenation, when the patient is intubated (has a tube put in the trachea, as discussed above).

Some risks and side effects should be considered. The general anesthetic gaseous agents and the endotracheal tube cause mild irritation of the airway and can cause breathing difficulties after surgery, including a small risk of pneumonia. There is also some grogginess and lethargy as the anesthesia agents slowly clear over several hours post-operatively. General anesthesia can also cause precipitous drops in blood pressure. These can usually be prevented by adequate hydration, but may be a problem in some patients with compromised cardiovascular systems. This lowered blood pressure and possibly lowered perfusion of the brain and heart, can cause (in a very small number of patients) a heart attack or stroke. Post-operative nausea can also occur while the anesthetic agents are cleared from the body over the first few hours following the procedure. This can usually be managed by other medications.

SPINAL ANESTHESIA
This type of anesthesia will completely numb the patient from the waist down. In a spinal anesthetic, a long, thin needle is passed between the vertebrae and enters the spinal canal. The skin and the tract that the needle follows are numbed by the anesthesiologist with a local anesthetic (Lidocaine). Once the spinal canal is entered, a small amount of spinal fluid is withdrawn to be sure that the needle is within the spinal canal. The anesthetic agent is then injected (either Lidocaine, Marcaine or Pontocaine). In addition, for post-operative pain control, a narcotic agent can be injected (Duramorph, Astromorph) and the needle is then withdrawn. The numbing medicine sets up quickly, within a few minutes, and the anesthesiologist checks to see the level of anesthesia which is usually up to approximately the waist level. Depending on the spinal anesthetic used, the numbing effect will usually last three to six hours. The narcotic agent, however, will provide pain control for approximately 12 to 18 hours.

Use of sedatives with amnesic properties given intraveneously allows the patient to be unaware of the procedure and have no memory of the time during the surgery.

Spinal anesthesia has been shown to decrease the blood loss in hip surgeries and possibly decrease the chance of post-operative blood clot formation in the deep veins of the legs and pelvis.

A spinal anesthetic does carry a small risk of spinal headache. This occurs when there is a small leak of spinal fluid through the puncture of the dura. This is uncommon when very fine needles are used. If a spinal headache occurs, the treatment is usually bed rest with the head flat for approximately 24 hours. If the headaches persist, a "blood patch" can be performed by the anesthesiologist where a small amount of the patient’s own blood is injected in the epidural space and this helps to seal-off a dura leak.

The two common side effects from spinals are nausea and itching. Each of these occur approximately 20% of the time and can usually be controlled with other medications.

EPIDURAL ANESTHESIA
This is similar to spinal anesthesia but instead of entered the spinal canal, the needle is place near the canal and a catheter is inserted and the needle removed. The anesthetic and analgesic medications are injected through the catheter and must diffuse through the covering of the spinal canal (the "dura"). Leaving the catheter in place allows for repeat dosing of pain relieving medications after surgery.

We do not use epidural anesthesia for two reasons. First, we have not found it to be as predictably effective as spinal anesthetic. Second, because we start blood thinning medication (i.e. Coumadin) the night before surgery, we are concerned about bleeding around the catheter if it is left in place post operatively. This could cause paralysis.

COMBINATION ANESTHESIA
Using a combination of spinal and general anesthesia can take advantage of the benefits of each and limit the side effects. If a spinal anesthetic is used in addition to a general anesthetic, the amount of general anesthesia required is quite small, because the patient is already numb from the waist down and not receiving any stimulation from the surgery. Therefore, the patient can receive the benefits of spinal anesthesia, such as decreased blood loss, decreased chance of blood clot formation in the deep veins, and post-operative pain control, as well as achieve the safety benefits of general anesthesia, i.e., maintaining adequate ventilation and oxygenation. After the procedure, the patient that has had a combined anesthetic usually wakes up quickly with less of the "hangover" effects of general anesthesia. There is also less irritation to the lungs from the anesthetic agents, resulting in less chance of breathing difficulties and pneumonia afterwards.

There is one increased risk of combined anesthesia and that is an increased chance of having a transient drop in blood pressure. This occurs because of the pooling of the blood in the deep veins caused by the spinal anesthetic, combined with the usual transient drop in blood pressure on induction of general anesthesia. This can usually be avoided in patients with normal cardiovascular systems by maintaining adequate hydration and fluids intravenously. In patients with compromised cardiovascular systems, however, this combination technique may be contraindicated. In these cases, a spinal procedure can be performed, but the narcotics instilled only for postoperative pain management, skipping the anesthetic agent that might cause problems when combined with the general.

PATIENT CONTROLLED ANALGESIA (PCA)
The advent of PCA has significantly improved the management of post-operative pain following all types of major surgery. PCA allows the patient to control when and if pain medication is desired. Standard "on call" pain medication must first be requested by the patient. Then, the nurse must check the orders and time to be sure it is all right to give the medication and determine what dose to give. It usually takes 10-30 minutes to obtain the medication.

The PCA device is a computer controlled injection system that is hooked up to a standard IV line used in all hip and knee replacement patients for routine fluid administration. The device is triggered by the patient, using a push button, when he or she desires pain medication. The devise is programmed by the anesthesiologist (or surgeon) to administer a dose of morphine or demerol on demand by the patient. In addition, a basal rate of constant infusion can be used to give some level of continuous pain relief.

If the medication is not effective, the anesthesiologist (or surgeon) can order an adjustment to the programmed settings as needed. The computer program will determine the timing and frequency of the dose. All the patient has to do is determine if and when he wants pain medication, and push the button. Since the medication is administered through the IV, it will take affect within minutes.

The benefits of PCA are more effective pain control after surgery. The risks are few but deserve mention. Although the chances of over dosage are greatly reduced with PCA, it can still occur. Over dosage can cause breathing difficulties, so while using PCA you will be given oxygen to breathe and the nurse will monitor your respiration and degree of sedation. Nausea and itching can also occur but are usually well managed with other medications. Urination can be difficult when using PCA, so a catheter is placed in the bladder at the time of your surgery and maintained until the PCA is discontinued.

Drs’ Bargar and Blumenfeld usually use PCA as an adjunct following spinal and/or general anesthetics. The spinal narcotics are effective post operatively for 12-18 hours. Therefore if a spinal anesthetic was used, the PCA is usually started at 12 hours following surgery. For general anesthesia alone, PCA is started as soon as you leave the recovery room. It is continued until the second or third post-operative day as needed by the patient.

HIP SURGERY
If you are having a hip replacement procedure, both Drs. Bargar and Blumenfeld feel that general anesthesia is mandatory. This is because you are in a rather confined position during the procedure when you are turned on your side, and it is difficult to maintain adequate ventilation using spinal anesthesia alone. Many other surgeons do perform hip replacement using spinal anesthesia alone, but there is an increased risk of ventilation problems that can be life threatening. Consequently, Drs. Bargar and Blumenfeld strongly recommend the use of general anesthesia for both primary and revision hip surgery. In order to obtain the benefits of spinal anesthesia, it is recommended that hip surgery patients have a combined anesthetic approach as described above. If for some reason the patient does not desire spinal anesthesia, then the hip surgery can be performed with general anesthesia alone.

KNEE SURGERY
If you are having knee surgery, your procedure can be performed under spinal anesthesia, general anesthesia or combined. In these cases, Drs. Bargar and Blumenfeld usually recommend spinal anesthesia alone (with sedation). This is because the patient is in the supine position during the procedure and can ventilate on their own safely. If for some reason there were breathing difficulties, the patient could easily be intubated by the anesthesiologist and the procedure continued with the combination of general and spinal anesthesia.

SUMMARY
In summary, spinal anesthesia has significant advantages in that it can lower blood loss at surgery, decrease the chance of blood clot formation, and provide for post-operative pain control. General anesthesia renders the patient unconscious and, therefore, not aware of the procedure or the passage of time. It also is considered safer in providing controlled ventilation when the patient is placed on his side during hip surgeries.
Drs. Bargar and Blumenfeld recommend a combined anesthetic using general plus spinal for hip surgeries and spinal alone (with sedation) for knee surgery.

The above description of general and spinal anesthesia represents a general description and discussion from the surgeon's viewpoint. The ultimate decision is between the patient and the anesthesiologist. A more complete description of the pros and cons of different types of anesthesia can be provided by a discussion with the anesthesiologist. In most cases, the anesthesiologist will see the patient in the pre-operative holding area just prior to the procedure. Some anesthesiologists call the patient the night before to discuss anesthesia over the phone. If you have particular questions prior to surgery about your anesthesia, an anesthesiologist will meet with you, go over your particular case and make his or her recommendations.