Maintenance of the Surgical Plane
of Anesthesia.
In order to conduct a narcosis scientifically one must know the signs of sufficient anesthesia and the signs of awakening.
Respiration
The respiration is studied by watching the movements of the chest or abdomen, by placing the hand in the vicinity of the nostril to feel the respiratory current of air, or, best of all, for the respiration is rarely noiseless, by listening to the breathing. The quality of the breathing is noted. The faintest indication of a snoring respiration means that the surgical degree has been reached. Any change in the quality of the breathing compels the questions “Has the patient escaped from the proper surgical plane?” “Is the anesthesia too deep or too superficial?” or “Is the change simply a respiratory reflex induced by the surgeon’s manipulations?”
Color
The color of the ear is a most useful guide. This does not hold good of the color of the forehead. The forehead in some individuals becomes cyanotic with slight changes of posture. The ear is not so subject to postural influences and is therefore a less misleading indicator of the venous condition of the blood. Even a slightly bluish tinge of the ear demands attention. Usually, crowding is the cause, and a little more air allows the normal red flush to return. Slight pallor developing during the course of the narcosis should always be regarded as a danger sign. It means that the patient is in profound anesthesia, and that the heart is threatening collapse. The mask should be removed promptly and the patient allowed to breathe pure air. As long as the pulse is not weak or irregular one need not worry about the outcome.
Pulse
There are some advantages in choosing the temporal pulse as the guide, instead of the radial pulse, which is ordinarily followed; occasionally the temporal can still be felt when the radial has become impalpable. The pulsation of the temporal artery is best felt by placing the index finger flat over the tragus into the depression at the root of the ear. The pulse is important because it tells how the heart reacts towards the anesthetic and the surgeon’s manipulations. The frequency is not very important. Exceptionally, it may be 120 or 130 during the greater part of an anesthesia without vital significance, if the quality is good. A diffuse and weakening pulse is a signal that the narcosis is too profound and that the heart is in danger of collapse. A somewhat irregular pulse may immediately precede or accompany the act of vomiting, and it is not a cause for alarm.
Accessory to the respiration, color and pulse, but of lesser significance, are the pupil, the cornea and eyelid, and the secretions.
Pupil