The opinion
TRAYNOR, C. J.
I concur in the judgment.
Since there is substantial evidence to support a verdict for plaintiffs, I agree that the judgments notwithstanding the verdict must be reversed. I likewise agree that the orders granting a new trial must be affirmed because there is substantial evidence to support a verdict for defendants. I cannot agree, however, that the doctrine of res ipsa loquitur is applicable or that verdicts could be sustained on certain other theories of negligence invoked by the majority opinion.
“As a general rule, res ipsa loquitur applies where the accident is of such a nature that it can be said, in the light of past experience, that it probably was the result of negligence by someone and that the defendant is probably the person who is responsible. ... In determining whether such probabilities exist with regard to a particular occurrence, the courts have relied on both common knowledge and the testimony of expert witnesses.” (Siverson v. Weber, 57 Cal.2d 834, 836 [ 22 Cal.Rptr. 337 , 372 P.2d 97 ].)
Since the possible causes of cardiac arrests are not a matter of common knowledge (cf. Davis v. Memorial Hospital, 58 Cal.2d 815, 817 [ 26 Cal.Rptr. 633 , 376 P.2d 561 ]), expert testimony is required before a conditional res ipsa loquitur instruction would be proper. Expert testimony that it is more *171 probable than not that negligence is the cause of cardiac arrests, if believed, would permit the jury to draw an inference of negligence solely from the fact that the arrest occurred. In deciding whether an instruction on the doctrine should be given, it is therefore irrelevant that there may be facts other than the occurrence itself to suggest that the arrest was caused by negligence. Although such facts, if present, might be independent proof of negligence, they have no bearing on the question whether the jury should be permitted to draw an inference of negligence on the happening of the cardiac arrest alone. Hence reliance on evidence that the defendants may have failed properly to appreciate plaintiff’s apprehension and temperature is misplaced. The only question relevant to determining whether a res ipsa loquitur instruction should be given is: Has evidence been offered by expert testimony that when cardiac arrests occur, they are more probably than not caused by negligence ?
No such expert testimony appears. Plaintiffs rely on testimony of both defendant doctors that, when due care is used, cardiac arrests do not ordinarily occur. This testimony, however, fails to establish anything with respect to the question whether, among the possible causes, negligence is the more probable one when these arrests do occur. It is true that cardiac arrests do not ordinarily occur when due care is used because, as all the testimony makes clear, a cardiac arrest is a rare occurrence. As stated in Siverson v. Weber, supra, 57 Cal.2d 834, 839 , however, “The fact that a particular injury suffered by a patient as the result of an operation is something that rarely occurs does not in itself prove that the injury was probably caused by the negligence of those in charge of the operation.” The record shows that plaintiffs’ counsel was fully aware of this holding in the Siverson case. He could easily have framed his questions to elicit testimony as to the probability of negligence when cardiac arrests occur, but he did not do so.
Plaintiffs also rely on expert testimony “that 90 percent of the deaths occurring in patients under anesthesia are due to improper management of the airway.” This testimony, however, cannot reasonably be interpreted to mean that when cardiac arrests occur, it is more probable than not that they are caused by negligence. Thus, this percentage covers deaths other than those following cardiac arrests. The expert who offered this estimate testified that deaths may occur under anesthesia from disturbances that are at least as likely to *172 happen as cardiac arrests. He did not testify that 90 percent of cardiac arrests were caused by improper management of the airway. Moreover, his testimony makes clear that by “improper management” he did not mean faulty or negligent management. He defined “improper management” as any failure “to maintain the free movement of air.” Although he admitted that such failures could be prevented in many instances by an anesthesiologist exercising due care, he denied that mismanagement by the anesthesiologist is necessarily involved, and could not say that it is probably the cause when cardiac arrests occur. 1
Defendant anesthesiologist testified that the most common cause of cardiac arrest is direct or indirect stimulation of the vagus nerve. He added that in his opinion such stimulation was the cause of this cardiac arrest. He testified further that there were several stimuli that might have been operative. This testimony, however, sheds no light on whether negligence is more probably than not the cause of bringing any of these stimuli into play. Moreover, the record presents abundant uncontradicted evidence that the medical profession is in doubt as to the causes that ultimately bring about the physiological events leading to cardiac arrest. In view of such evidence, the most that can reasonably be concluded from the medical testimony with respect to the probabilities of negligence as a cause of cardiac arrest is that negligence will increase the risk of its occurrence. There is no expert testimony that when it does occur, negligence is more probably than not the cause. Accordingly, plaintiffs are not entitled to invoke the doctrine of res ipsa loquitur.
The question remains whether there is any evidence that defendants failed to possess and exercise that reasonable degree of skill, knowledge, and care ordinarily possessed and exercised by members of their profession under similar circumstances. (Si nz v. Owens, 33 Cal.2d 749, 753 [ 205 P.2d 3 , 8 A.L.R.2d 757 ].)
There is no evidence that defendant doctors were negligent in making the initial decision to operate. Although the child *173 was “very appreliensive” and “very agitated” on the morning of the operation, undisputed medical testimony rejected the view that this condition contraindicated surgery. The hospital records show that preoperative medication, 2 administered in part to allay the patient’s apprehension, was “unsatisfactory.” Defendant anesthesiologist testified that “unsatisfactory” did not mean “not sedated to the extent he should be.” It meant only not “sedated to the extent I should like to have [him] sedated.” The testimony of the Chairman of the Department of Anesthesiology of the University of California at San Francisco confirmed that many children are “very apprehensive” 3 just prior to an operation and that an attempt to reduce this apprehension by further sedation might dangerously depress circulation and respiration. This expert also testified that he would have administered anesthesia “under those circumstances” and that standard practice did not require the anesthesiologist to postpone it. Plaintiffs introduced no other testimony that would permit a jury to evaluate the significance of “very apprehensive,” “very agitated,” and “unsatisfactory” in a medical context. Hence, even if the jury did not believe the explanations offered, plaintiffs would not have met their burden of proof.
The record of the child’s temperature adds no more. The temperature had risen to 100.6 on the eve of surgery. Defendant ophthalmologist investigated the fever and found that the rise was not due to any infection that would increase the risk of complications under anesthesia. Plaintiffs offered no evidence to the contrary. The hospital chart shows that the child’s temperature was below normal on the morning of surgery. Medical experts testified that such a sequence of events would not contraindicate surgery. Although a hand *174 writing expert testified that a relevant part of the temperature chart showed signs of an erasure, he also testified that there “was no indication under the microscope of what had been erased nor precisely where it was. ’ ’ Moreover, on cross-examination he “couldn’t positively say” that there had been any writing beneath the erasure. No jury could reasonably make a finding of negligence on the basis of such testimony.
There is also no evidence that defendant ophthalmologist was under a duty either to possess the skill to perform a thoracotomy in the event of a cardiac arrest, or to see to it that a competent surgeon was in the operating room at all times. Every medical witness testified that it was standard practice to call in a thoracic or general surgeon in the event of cardiac arrest. No medical witness testified that it was standard practice for an ophthalmologist to possess such skill. It is true that one surgeon, who otherwise agreed with these conclusions, said on cross-examination, “Anybody, any surgeon who is operating in a hospital, ... in dire circumstances should be able to do an open chest operation.” Yet he added, “However, if he has any choice whatsoever and he has never done this, and he has anyone better qualified in the immediate vicinity he is well advised to have them do it.” The rest of this surgeon's testimony indicates that by “immediate vicinity” he did not mean that a competent surgeon ought always to be present in the operating room itself. Moreover, this expert testified that he had been active in the local campaign designed to alert all specialists to the possibility of cardiac arrest and to inform them about the procedure of thoracotomy. Yet he testified that despite this campaign most specialists could not be expected to perform the operation. Hence his statement that any operating surgeon should be able to open a chest can reasonably be interpreted only as an expression of an ideal that had not yet become a standard of care. Hence no jury could reasonably conclude that defendant ophthalmologist failed to meet the standard of care by not performing the thoracotomy himself or not insuring the presence of a competent surgeon in the operating room at all times.
There is evidence, however, that defendants were negligent in failing to make reasonable preparation for the possible occurrence of a cardiac arrest. (See Harper and James, The Law of Torts (1956) §16.11, p. 939; Prosser on Torts (3d ed. 1964) pp. 173, 343-344.) Both defendant doctors knew that cardiac arrest was an inherent risk of surgery under *175 anesthesia. Both testified that when an arrest occurs every second counts. Both doctors had good reason to believe that a general surgeon would be readily available in the area surrounding the operating room. It may be inferred, however, that they did not confer before the operation to plan an efficient procedure for summoning such a surgeon in response to a possible emergency. Thus, defendant ophthalmologist testified that he could not remember any conversation with the anesthesiologist, although “frequently we have a conversation about the operation prior to surgery. ’ ’ Moreover, defendant anesthesiologist was apparently unaware of the inability of defendant ophthalmologist to perform a thoracotomy, for when the arrest occurred he did not immediately send for a general surgeon. Instead, after it became apparent that external massage had failed, precious time elapsed while the ophthalmologist came to the table, revealed his inability to open the chest, and went to the door to get the general surgeon. More time passed while the general surgeon entered the room and put on gloves before making the incision. Although the record does not specify how much time these steps entailed, a jury could reasonably conclude from defendant ophthalmologist’s testimony that the additional loss of time was enough to cause the brain damage. This time might have been saved had preparations been made for summoning the general surgeon as soon as a cardiac arrest was suspected, so that he could be ready to open the chest at the moment it became apparent that external massage had failed.
Although there is no expert testimony that the prevailing medical standard of care requires such preparation for a possible cardiac arrest, expert testimony is not required when scientific enlightenment is not necessary to show that failure to make such preparations is unreasonable. (Ales v. Ryan, 8 Cal.2d 82, 100 [ 64 P.2d 409 ]; Barham v. Widing, 210 Cal. 206, 214 [ 291 P. 173 ]; see Lawless v. Calaway, 24 Cal.2d 81, 86 [ 147 P.2d 604 ]; Bruce v. United States, 167 F.Supp. 579, 583 ; Prosser on Torts (3d ed. 1964) p. 167.) On that basis alone, I would reverse the judgments notwithstanding the verdicts.
The testimony in question is as follows:
“Q. What do you mean by improper management of the airway? A. It has not been managed to maintain the free movement of air. ’ ’
“Q. That is due to the anesthesiologist’s mismanagement? A. No, that doesn’t mean that, necessarily. It means that sometimes it is impossible to do this.”
”Q. In most instances it is preventable in the exercise of duo care by the anesthesiologist, isn’t it, Doctor? A. In many instances it is.”
Defendant anesthesiologist offered undisputed testimony that nembutal was administered to allay apprehension; atropine, to depress reflexes and decrease secretions. Although the dosage of atropine was twice that given at the first operation, there is no evidence connecting that increase with the possible causes of cardiac arrest. On the contrary, defendant anesthesiologist testified that atropine is used specifically to decrease the sensitivity of the vagus nerve to reflexes that may occur during anesthesia. Moreover, expert testimony is nncontradieted that the child was prepared for the operation according to standard procedures.
Neither party asked this expert any questions about the significance of ‘' very agitated.' ’ Defendant anesthesiologist, who used this term in his post-operative report, testified that he used it as a synonym for “very apprehensive.” He also testified that he used “very apprehensive ’ ’ to summarize the fact that the child was crying and uncooperative.