Ether (diethyl ether) is a colorless, highly volatile, and flammable liquid that was first used as an anesthetic in the mid-19th century. It should be stored at temperatures >25°C in tightly sealed dark bottles or cans. These protect the ether from light, which may decompose it. Ether is a poor anesthetic at altitudes over 2000 meters (6000 feet), although it has been used at altitudes up to 3500 meters (~11,000 feet).21
Ether is probably the most widely used inhalational anesthetic in the world.22 Where the supply of medical-grade ether is limited, industrial-grade ether can be used instead.23 Industrial ether is the same as anesthetic ether, only much less expensive. But, since it comes in drums, it must be poured into dark bottles or sealed cans for use.24 Common types of ether for anesthesia, many of which can be found in industrial settings, include trifluoroethyl vinyl, ethyl vinyl, divinyl, diethyl, and dichloro-difluoroethyl methyl.25 Of these, ethyl vinyl ether is the safest and most potent, and has the most rapid onset of anesthesia and the shortest recovery time, while divinyl ether is the least potent agent for surgical anesthesia and the most likely to produce respiratory arrest.26
Ether (divinyl [anesthetic] and ethyl/diethyl ether) can easily be produced locally since ethanol and sulfuric acid are available nearly everywhere.27 However, non-chemists should try to produce ether only in the most desperate situations, and then only after consulting a reputable organic chemistry text and, if possible, a real chemist.
The substances involved in ether production are highly volatile; the risk of explosion is very real. Essentially, the process is to dehydrate ethyl alcohol with sulfuric acid. Here's how: (a) Obtain ethyl alcohol (i.e., drinking alcohol), since other alcohols will not produce diethyl ether and will be very dangerous. (b) Obtain sulfuric acid, which can often be taken from a lead-acid battery. If necessary, sulfuric acid can be made by burning sulfur and saltpeter (potassium nitrite) together, although this may prove more difficult than finding it premade. The sulfuric acid is reusable and catalyzes the process. (c) Heat the ethanol-sulfuric acid mixture in a glass distillation chamber (such as from any basic chemistry lab). This produces ether vapor, which condenses to liquid. It has to be maintained within a certain temperature range for the reaction to occur. The process is essentially a continuous one with repeated addition of further alcohol.28
The main advantage to using ether is that it has proved to be very safe, especially in unskilled hands, with a wide margin between satisfactory anesthesia and a lethal overdose.21,27,29,30 Another advantage is that with a vaporizer and mask—or just the ether and a makeshift mask—ether can be used whenever a general anesthetic is needed. Ether is considered one of the anesthetics of choice for major operations requiring intubation and for poor-risk cases (using a low dose), and it is the volatile agent of choice when general anesthesia is needed but no oxygen is available.30
Unlike many modern anesthetics, ether provides intrinsic analgesia, so it does not require the simultaneous use of N2O. It also provides intrinsic neuromuscular relaxation, is a bronchodilator, rarely potentiates the dysrhythmic effect of sympathomimetic agents, causes little uterine relaxation, stimulates blood flow (helpful in shocky patients), and stimulates respiration (useful if no oxygen is available). Even if the patient receives enough ether to depress respirations, cardiac function remains good, and so ether has a wide safety margin.
The classic slow changes of anesthesia depth—the "stages" (see Table 15-3) with their attendant physical signs—are easily observed, suggesting that when one does not have the necessary monitoring equipment and needs to use an inhalation anesthetic, ether is the best choice.21,27,30–33
Disadvantages and Side Effects
Disadvantages associated with using ether are that it has an unpleasant smell (that both the patient and the staff notice) and slow induction and recovery times. In addition, the vapor irritates the bronchial tree, which bothers many patients, and often is accompanied by postoperative nausea, vomiting, and drowsiness.24,27 It helps to get the patient accustomed to the ether smell before anesthesia begins.34
Laryngeal spasm is common during induction and when the anesthesia is too light. Stop surgery and deepen the anesthesia; add oxygen, if available, until the patient breathes normally.21 Administer atropine to prevent excess secretion production.
Patients may vomit during ether induction, usually during the delirium stage when anesthesia is light. Since laryngeal reflexes persist at this stage, tilt the table head down, turn the patient on his side, and clean out the mouth and pharynx. As long as the patient's breathing, pulse, and color are normal, the patient probably has not aspirated and it is safe to continue anesthetizing him. If apnea develops, consider whether the patient has received too much ether, has an airway obstruction, is breath-holding, or is in cardiopulmonary arrest. Treat the problem.21
Nausea and vomiting after ether anesthetic are due to a central emetic effect caused either by prolonged deep-stage anesthesia or by gastritis from ether dissolving in the patient's saliva. Premedicate the patient with atropine or give ether through an ET tube to lessen the chance of this occurring.21
Ether also potentiates non-depolarizing neuromuscular blocking agents and may cause myocardial depression in patients on beta-blockers. Transient postoperative effects include liver function impairment and leukocytosis.33
Operating room staff, including the surgeon and anesthetist, may complain about the ether smell and claim that it gives them headaches or makes them sleepy. Some symptoms improve over time; others may require efficient "scavenging" (i.e., redirecting excess ether). For example, if using a non-rebreathing valve, fit an exhaust tube to the valve and vent the exhaust gases to the floor.21,30 Also, if the end of the scavenging tube is placed on the floor (away from any possible sources of ignition), then the heavy ether vapor will remain at floor level.24 When using open-drop ether, the best choice is to have air circulating in the room.
Contraindications and Risks
While there are no absolute contraindications to using ether, it is best avoided in patients with moderate or severe preeclampsia, with liver or renal failure, with increased cerebrospinal fluid pressure, or who have pheochromocytoma.30,33
Ether is highly flammable in air and explosive when mixed with oxygen or N2O. It is not explosive when mixed with air.21 "Under clinical conditions, it is difficult to ignite and almost impossible to explode air-ether mixtures." That is because ether vapor at a 2% or 3% concentration in air will not burn. As soon as it escapes from the vaporizer circuit or beyond the ether mask, it is diluted beyond the limit of flammability. Even if it is not diluted, it only burns slowly. But, if as little as 1 L/min of oxygen or N2O is added, ether becomes explosive. The risk of flames and explosions is greatest close to the expiratory valve.35
The safe distance between ether vapor and potential heat or spark sources is unknown, but the ether vapor "zone of risk" may be up to 100 cm (~40 inches). Ether vapor is heavier than room air, so the floor up to a height of 50 cm must be clear of any electrical appliances, sockets, and plugs. Electrical sockets and switches situated within 1 meter of the floor should be spark-proof. No potential source of combustion or sparking should be allowed within 30 cm of an expiratory valve emitting ether vapor.23,27,33
Particularly in a very dry atmosphere such as in hot-dry or very cold climates, make all anesthetic equipment conductive, including all surgical booties and stretcher wheels, so that any electric charges go to ground.21,33 In tropical countries, the high humidity (above 50%) offers added protection against static electricity build-up.27
Being able to identify the stages of ether anesthesia (Fig. 16-1) makes the induction, maintenance, and emergence much more elegant. Identifying these stages is relatively easy, since they were developed for use specifically with ether.
Ether anesthesia is given in one of three ways: (a) Using ether without any adjuvant drugs. This requires enough medication to reach deep ("too deep") Stage 3 to provide the muscle relaxation required for intra-abdominal surgery. (b) Using ether with 10% to 20% of the normal neuromuscular block (NMB) dose. Moderately deep Stage 3 can be achieved. Patients usually resume breathing spontaneously without the need to reverse the neuromuscular blockade. (c) Using ether with 50% of the normal NMB dose. Light ether anesthesia can be maintained, but patients may need NMB reversal to resume normal breathing.27 The second and third methods require both an NMB and controlled ventilation, which usually will not be available in austere situations.
Stage 1 anesthesia is useful for obstetrics and minor painful procedures. It can be self-administered. Give the patient a face mask delivering 2% to 3% ether and ask the patient to take deep breaths when he or she has pain. Tie the mask to their wrist; if they drop the mask, ether administration ceases.
Titrating ether's effects on spontaneously breathing patients is vital to be able to get them to and keep them at the right level. When you touch the patient's eyelash and the lid no longer contracts when touched, the patient is unconscious and is ready for surgery.31 If the patient struggles and is difficult to control, holds his breath or moves slightly as a surgical incision is made, or moves his eyes about, the anesthesia is too light. Re-induce the patient steadily. Don't give the patient a sudden high concentration of ether or he may start to cough.21,31
If the patient's pupils become steadily larger, his chest falls on inspiration, and a "tracheal tug" develops (the patient's diaphragm contracts causing a "tug" on his trachea), the patient is too deeply anesthetized.21,31 An overdose leads to severe medullary depression, with respiratory failure. Promptly stop ether administration and assist the patient's breathing; spontaneous respiration usually resumes quickly.33
Open-Drop Ether Anesthesia
The first method of administering inhalational anesthesia, now a relic of bygone days, is very safe and requires the least amount of equipment to administer.
When working in a major disaster or in other settings where resources are extremely limited, those giving general anesthesia may "have to confine themselves to the simplest possible method … that meant ‘rag and bottle' with ether as the main volatile agent."36 A benefit of ether anesthesia is that it is effective for most patients and most surgical procedures, except craniotomy and thoracotomy, just by dripping it on a gauze mask. "Without an anesthesia machine or ketamine, open-mask [open-drop] ether may be the safest way to administer anesthesia."37
When giving open-drop ether, premedicate the patient with atropine or scopalamine to reduce salivary and bronchial secretions. While the open-mask technique is very wasteful of ether, it needs only a dropping bottle and a "Schimmelbusch mask," which is merely a few thicknesses of gauze held in a wire frame (Fig. 16-2). Unfortunately, a smooth ether anesthetic is difficult to give with an open mask, especially in a large adult.37 Since diethyl ether is a weak anesthetic with a slow uptake, induction may be tedious and prolonged in a robust patient because it is difficult to reach more than 14% concentration. All the patient's inspired air must pass through the mask.
Schimmelbusch mask. (Source: Unknown original source. Illustration from 1894.39)
To improvise a "dropping bottle," use "any clean glass bottle with a rubber stopper. Two tubes should pass through the stopper; one is for ether to come out and the other for air to enter the bottle" (Fig. 16-3). An alternative is to cut two slits in the bottle's stopper, inserting a cloth (the proverbial "rag") through one opening and leaving the other slit open to allow air to pass into the bottle. If the ether is in a can with a rubber top, "put a safety pin horizontally through the rubber stopper. The ether then drips from the pin."38 (See Fig. 16-4.)
Safety-pin-through-ether-can drip delivery system. Drawn from original photograph. (Adapted from De Lee.38)
Administer open-drop ether by dripping it onto a piece of cloth (gauze or other absorbent material) held over the patient's face with a wire frame. The frame is to facilitate airflow and to prevent the ether from coming in direct contact with the eyes and skin, which could cause serious burns. Cover the rest of the patient's face and eyes with gauze to protect them and, if available, apply petroleum jelly to exposed skin.
Make an improvised mask (preferably two) by stretching gauze over a small kitchen sieve, a large coffee strainer, a tea strainer (often an excellent infant mask), or a piece of screen that has been bent and sewed into the desired shape. The ideal mask just fits over the patient's mouth and nose and should look like the classic Schimmelbusch mask (shown in Fig. 16-2). Place 6 or 7 layers of gauze (depending on the size of their mesh) over the masks. Have extra gauze; it may need to be changed frequently because, when the ether evaporates, a "frost" forms on the gauze that interferes with its effectiveness. You should be able to see light through the full thickness of the gauze; otherwise, sufficient air will not pass through it.21,40 Do not place the mask directly on the patient's face; use cotton padding around the edges. Otherwise, the metal mask may get very cold and burn the patient.
The first part of giving the anesthetic is to induce the patient, or make the patient unconscious. To do this, the patient must receive as much ether as he can tolerate, which depends on how well the patient is breathing and his reaction to the ether. Ether is irritating, so too much will make the patient cough, gag, and hold his breath. Thus, induction with ether alone often takes 20 minutes.21
Either parenteral or inhalational agents can be used to smooth and speed inductions with ether, provided that the dose is small enough so that it does not depress respiration. Ketamine (1 mg/kg IV or IM) or a benzodiazepine (e.g., diazepam 0.1 to 0.2 mg/kg IV) eliminates slow induction.21,27 An alternative is to drop 3 mL of halothane slowly onto the mask from a glass or nylon syringe. (Some disposable plastic syringes dissolve if used with these liquids.)21 Then, immediately begin the ether maintenance. Don't let the surgeon start until the patient is at the surgical stage of anesthesia.
Take a thick piece of cotton or several layers of gauze and cut a hole for the patient's nose and mouth. Hold the mask above the gauze, and drop ether onto it (12 drops/min for 2 minutes, then 1 drop/sec until the patient loses consciousness—usually within 5 minutes). Drop ether sparingly at first to accustom the patient to the irritating vapor. Never place the mask directly on the face of a conscious patient, or he will feel suffocated. Wait until his eyelash reflex has gone, and then put on the mask. As soon as he begins to tolerate the ether, drop it on faster. Keep the stream of ether drops moving steadily over the mask to avoid freezing. Listen to every breath and make adjustments for any airway problem. Don't pour it on so fast that it makes the patient cough. If the patient does cough or hold his breath, give him a breath of air. You may have given him too much ether too quickly, given it irregularly, or have a poor fit between the mask and his face. As things settle down, adjust the rate to provide the required depth of anesthesia. Give a few breaths of air and continue more slowly. Deep levels of surgical anesthesia cannot be achieved with this technique in less than 20 to 30 minutes.21,33
Ether is a weak anesthetic, so a patient must breathe a high concentration of vapor. In adults, it is useful to increase the ether concentration by using the "ether chimney." Improvised by prisoners of war (POWs) during World War II, the ether chimney is a metal column that sits over the mask, increasing the vapor concentration close to the face, which in turn increases the inspired concentration of ether. You won't need this for a child.
Construct an ether chimney using two cans that fit into one another (Fig. 16-5). Place one can over the patient's mouth and nose. Three (not more) layers of gauze go between the cans, and the second can fits into the first, holding the gauze. For use during long operations, make some side holes in the lower can to increase the air flow; tape them up during shorter operations.21,31
Keeping patients at the right anesthetic stage is a difficult art that must be individualized to the patient and the circumstances. "Most anesthetists like to err on the side of being just-too deep. If the patient becomes too light, regaining control will not be easy."21 Table 16-5 presents a rough guide to open-drop ether use.
Table 16-5 Guide to Ether Maintenance Dosing ||Download (.pdf)
Table 16-5 Guide to Ether Maintenance Dosing
after 30 min
When the mask becomes so cold that it is covered with frost, change it for a fresh one. To diminish the amount of ether escaping into the atmosphere and affecting the anesthetist and surgical team, put two layers of gauze over the mask after pouring the ether. Replace it with fresh (non-etherized) gauze each time that additional ether is poured.21
During long operations, if oxygen is available and all the precautions are in place to avoid an explosion (see the previous text), feed a small oxygen tube under the mask with a flow of 2 to 5 L/min.
To avoid a prolonged recovery, discontinue ether administration about 20 minutes prior to closure. After a long operation (with more saturation of the tissues), stop giving ether 15 minutes before the last stitch. If conditions allow, assist ventilation to promote ether washout and make recovery faster and to help decrease the incidence of nausea/vomiting.27 Put the patient in the recovery position (on his side); don't send him back to the ward until it is safe to leave him alone: The patient should be able to talk, be breathing quietly and easily, and have warm hands and a good pulse.21,30
Special Situations: Pediatrics and Obstetrics/Gynecology
Open-drop ether administration is one of the safest inhalation methods for children, especially if you lack specialized pediatric equipment. The anesthetic stages in children are the same as in adults. Take care not to administer more ether than necessary. An additional sign in babies is that they relax their grip as they become anesthetized.21
In febrile children, exposure to ether increases the risk of potentially fatal seizures. If seizures occur, immediately stop ether administration and lower the child's body temperature by sponging the child with tepid water. Administer small doses of a benzodiazepine or thiopental until convulsions cease.33
Use ether during pregnancy only when the need outweighs any possible risk to the fetus. However, at term, ether is especially useful for C-sections because the baby tolerates it and the uterus contracts well.30 Use low concentrations (no more than 4%) in obstetric procedures to avoid loss of uterine tone, excessive postpartum hemorrhage, and neonatal respiratory depression.33
Intravenous Ether Anesthesia
Intravenously administered ether is an excellent anesthetic, especially for procedures not needing profound relaxation, such as intra-abdominal surgery. Using this method, both adults and children can be anesthetized to Stage 3, Plane 1 anesthesia—in which there is a normal or increased rate and depth of respirations (see Table 15-3). Intravenous ether anesthesia at this stage has been successfully used for head and neck surgeries, including bronchoscopy, laryngoscopy, tonsillectomy, and oral surgery. Not only are the necessary tools for this anesthetic technique readily available, but they are also quite inexpensive.41
Begin by preparing a 5% ether solution. Dissolve 50 mL diethyl ether in 1 L 5% glucose solution (D5W). Cool the mixture to about 4°C (40°F) in a refrigerator to facilitate dissolving the ether. Shake the mixture vigorously for about 1 minute to mix it thoroughly, which is necessary to obtain good anesthesia. Keep the solution at 4°C until it is used. Shake it again before use to obtain thorough mixing.41
To anesthetize the patient, attach the bottle with the ether solution to a D5W IV using a three-way stopcock or Y-tubing. After inducing the patient into a light sleep with an IV induction agent, open the ether solution to its maximum flow (with a "macro drip"); increase the flow by raising the bottle or by using a pressure cuff on the bag. Keep the ether solution flowing "wide open" during induction. By the time 100 to 400 mL of the solution is administered over the first 5 to 10 minutes, the patient is usually well anesthetized. The patient reaches a surgical level of anesthesia in about 10 minutes. As the operation progresses, control the flow rate to maintain Stage 3, Plane I anesthesia. If available, administer oxygen continuously.41
The patient usually sleeps quietly. Jaw relaxation is adequate for oral surgery or endoscopy without the need to use a neuromuscular blocker. If necessary, use an airway. Should there be unwanted motion of the extremities or the head, give a small additional dose of the IV induction medication. Prolonged postanesthesia nausea and vomiting is rare.41