Cardiac Arrhythmias during Peritoneoscopy under Local Anesthesia JACK R. G R O O V E R , MD, a n d J A M E S L. B I E R F E L D , MD
Thirty consecutive patients undergoing diagnostic' peritoneoscopy using carbon dioxide (COO pneumoperitoneum with local anesthesia were studied to determine the incidence and types of cardiac arrhythmias occurring during the procedure. All patients received heavy sedation with diazepam intravenously and parenteral analgesics when necessary, but no general anesthesia. There was no mortality or unusual morbidity resulting from the procedure. None of the patients developed serious cardiac arrhythmias despite the presence of underlying cardiovascular disease in 16 of them, and none of the patients developed significant carbon dioxide retention or hypoxemia. A potentially dangerous finding was temporary diastolic hypertension occurring in 6 patients. It is concluded that if properly pelformed, peritoneoscopy with carbon dioxide pneumoperitoneum in the conscious patient, despite heavy sedation and analgesia to combat peritoneal irritation, produces no dangerous cardiac arrhythmias. Previous reports of cardiac arrhythmias occurring during the same procedure performed under general anesthesia are discussed.
A 17% incidence of cardiac arrhythmias, mainly ventricular extrasystoles, has been observed during laparoscopy under general anesthesia using carbon dioxide to insufflate the abdomen (1). It has been assumed that these arrhythmias were related to the hypercarbia produced by carbon dioxide pneumoperitoneum (1, 2) and that they can probably be prevented by either substituting nitrous oxide as the insufflating gas or by using controlled hyper: ventilation while the patient is under general anesthesia (3). Internists frequently use peritoneoscopy as a diagnostic tool in patients who are seriously ill and would not tolerate general anesthesia. The avoidance of general anesthesia also simplifies the procedure by eliminating the need for operating-
room time and the presence of an anesthesiologist. The safest agent for the induction of pneumoperitoneum is carbon dioxide because it does not support combustion and is rapidly absorbed. Under local anesthesia, however, carbon dioxide produces significant peritoneal irritation in conscious patients and heavy sedation and analgesics are often required. The present study was undertaken to determine the incidence and types of cardiac arrhythmias occurring during periotoneoscopy with carbon dioxide pneumoperitoneum under local anesthesia rather than general anesthesia.
From the Divisions of Gastroenterology & Cardiology, Department of Medicine, University of Miami School of Medicine, and Veterans Administration Hospital, Miami, Florida. Dr. James L. Bierfeld's present address is Division of Cardiology, University of Miami School of Medicine, Jackson Memorial Hospital, 1700 N.W. Tenth Avenue, Miami, Florida 33136. Dr. Jack R. Groover's present address is Division of Gastroenterology, University Hospital of Jacksonville, 655 West Eighth Street, Jacksonville, Florida 32209. Address for reprint requests! Dr. Bierfeld, Division of Cardiology, University of Miami School of Medicine, Jackson Memorial Hospital, 1700 N.W. Tenth Avenue, Miami, Florida 33136.
A total of 30 patients underwent peritoneoscopy using carbon dioxide to insufflate the abdomen and xylocaine local anesthesia. An American cystoscope fiberoptic pel:itoneoscope (1 cm in diameter) was used in al! patients in conjunction with a WlSAP CO2 [nsufflato~"providing continuous monitoring of intraabdominal pressure and volume of CO2 insufflated. The average duration of the procedure from local anesthetic through wound closure was 45 min with a range of 30--95 min. The actual duration of instrumentation ranged from 15 to 40 rain. 18 of 30 patients had liver biopsies and 4 had peritoneal biopsies.
Digestive Diseases, Vol. 21, No. 6 (June 1976)
MATERIALS AND METHODS
465
GROOVER AND B I E R F E L D TABLE 1. ARRHYTHMIAS DURING PERITONEOSCOPY--FINDINGS IN 10 PATIENTS UNDERGOING TAPE-RECORDED ECG MONITORING*
Patient & age
l. O.K., 25 2. J.F., 46 3. C.W., 50 4. M.M., 59 5. M.H., 54 6. N.N., 54 7. R.W., 62 8. C.M., 50 9. C.S., 78 10. L.A., 58
Diagnosis
Previous heart disease
Chronic hepatitis Cirrhosis; ascites Cirrhosis; carcinoma Hepatitis Chronic hepatitis; COPD Cirrhosis; ascites Ca rectum; cirrhosis TB; peritonitis Cirrhosis; hepatoma; ascites Cirrhosis
Control Pco2
Operative Pco2
None
45 mm Hg
38 mmHg
None
33 mm Hg
33 mm Hg
Old MI
35.8 mm Hg
37.5 mm Hg
Old MI angina Angina pectoris
Not done
Not done
31.5 mm H.g
34 mm Hg
None
32.5 mm Fig
36 mm Hg
HCVD
33 mm Fig
36 mm Hg
None
25 mm Hg
31 mm Hg
CHF
29 mm Hg
40 mm Hg
None
32 mm Hg
36.5 mm Hg
Avionics findings
Sinus tachycardia Sinus tachycardia Sinus tachycardia NSR throughout Sinus tachycardia NSR throughout NSR throughout Sinus tachycardia Sinus bradycardia w/blocked PACs NSR throughout
* Abbreviations: NSR--normal sinus rhythm; MI--myocardial infarction; COPD--chronic obstructive pulmonary disease; TB--tuberculosis; CHF--congestive heart failure; PACs--premature atrial contractions; HCVD--hypertensive cardiovascular disease.
No e of the study patients were receiving antiarrhythmic medications at the time of the procedure; however, 12 were on maintenance digoxin therapy and 22 of 30 were receiving diuretics. Almost all patients wei-e premedicated with diazepam (3-25 mg) intravenously to the point of slurred speech or drowsiness unless contraindicated. In addition, Demerol (25-100 mg) was given parentally as necessary in some patients because of the peritoneal irritation related to the CO2 insufftation, The cardiac activity of the first 20 patients was continuously monitored by observation of electrocardiogram lead 2 on an oscilloscope equipped with a memory loop for immediate printout of any observed arrhythmias. The last 10 consecutive patients were monitored continuously from 30 min prior to the start of the procedure until at least 60 min after the procedure had terminated, by an Avionics Model 350 Electrocardiocorder, providing a continuous record on magnetic tape of all electrocardiographic activity. Standard 12-lead electrocardiograms were obtained before and after the peritoneoscopy procedure in all patients.
Arterial blood gas measurements (pH, Pao2 and Paco2) were obtained prior to premedication and again just prior to deflating the abdomen in 20 patients. In addition, heart rate and blood pressure determination were monitored at 5-rain intervals in 19 patients throughout the procedure. The medical histories of the 10 patients monitored by continuous tape-recorded electrocardiography are summarized in Table 1 and represent a reasonable cross section of the remaining 20 patients. Of the total 30 patients, 16 had prior cardiovascular disease as evidenced by angina pectoris, previous myocardial infarction, left Ventricular hypertrophy, bundle branch block or congestive heart failure. Of these 16 patients, one (M.M.) had undergone aortocoronary bypass one year earlier for disabling angina pectovis. One patient (C.S.) had chronic, premature atrial contractions before peritoneoscopy. 14 other patients had no evidence of cardiac disease. A l l 30 patients were in normal sinus rhythm prior to the procedure, and all cardiac patients were stable.
TABLE 2. MEAN VALUES --+ SD OF PH, Paco2 AND Pao2 OF 20
All 30 p a t i e n t s r e m a i n e d in s i n u s r h y t h m t h r o u g h o u t p e r i t o n e o s c o p y . 5 p a t i e n t s d e v e l o p e d sinus t a c h ycardia, and one patient (C.S.) with preexisting prem a t u r e atrial c o n t r a c t i o n s d e v e l o p e d a s h o r t segm e n t o f sinus t a c h y c a r d i a w i t h b l o c k e d p r e m a t u r e atrial c o n t r a c t i o n s . F u l l 12-iead e l e c t r o c a r d i o g r a m s postperitoneoscopy were unchanged from preo p e r a t i v e t r a c i n g s in all 30 p a t i e n t s . T h e m o s t signif-
CASES RECEIVING CARBON DIOXIDE PNEUMOPERITONEUM UNDER LOCAL ANESTHESIA
pH Pacoz Pao2
466
Before +- SD
During • SD
7.40 -+ 0.04 33.8 • 6.2 79.8 + 16.3
7.38 -+ 0.03 36.0 +- 5.3 81.5 + 14.9
RESULTS
Digestive Diseases, Vol. 21, No. 6 (June 1976)
CARDIAC ARRHYTHMIAS
DURING
PERITONEOSCOPY
icant finding, however, was the absence of any sign of ventricular irritability in any of the patients during and immediately postperitone0scopy. The blood gas observations are summarized in Table 2. There was no significant carbon dioxide retention during peritoneoscopy in any patient. On only two occasions did the Paco2 level rise above 40 mm Hg during the procedure (46 mm Hg and 43 mm Hg). The acid-base balance and the level of oxygenation also remained normal. Of the 19 patients monitored frequently (every 5 min) during the procedure, 6 became significantly hypertensive (diastolic pressure ranging from 100 to 140 mm Hg) returning to normal within 10 min after termination of the procedure. There was no correlation between those who became hypertensive and any observable change in blood gases or preexisting hypertension. 3 of these 6 patients had a rise in diastolic pressure above 30 mm Hg over baseline values. DISCUSSION This study shows that no serious cardiac arrhythmias occurred during peritoneoscopy under local anesthesia with carbon dioxide pneumoperitoneum as opposed to a 17% incidence of arrhythmias previously reported under general anesthesia (1). The choice of a gas to produce peritoneal distention during peritoneoscopy has generally been either room air, oxygen, carbon dioxide, or nitrous oxide. Each of these has its own advantages and disadvantages; however, carbon dioxide is probably the safest due to its rapid absorption in cases of inadvertent air embolism, subcutaneous emphysema, or pneumothorax. Intravenous carbon dioxide has been used diagnostically by cardiologists in amounts up to 100 cc without serious injury in the past (4). In dogs, up to the equivalent of I liter in humans can be given before cardiac output is profoundly altered (4). If the patient is monitored by precordial auscultation during initial insufflation, the typical "mill-wheel" murmur should warn of inadvertent vascular insufflation in time to take appropriate action. This, combined with its inability to support combustion, makes it an ideal agent for peritoneoscopy under general anesthesia. Although Scott and Julian (1) found a significant increase in ventricular irritability using CO., during spontaneous ventilation (under general anesthesia), this may be avoided by meticulous attention to continuous hyperventilation (3). Scott and Julian demonstrated that the use of nitrous oxide also prevents Digestive Diseases, !/ol. 21, No. 6 (June 1976)
CO2 retention and ventricular arrhythmias (1) but, unfortunately, nitrous oxide supports combustion to the same degree as oxygen. The major drawback to carbon dioxide pneumoperitoneum under local anesthesia, in our experience, has been the significant incidence of peritoneal irritation (30-50%). In order to combat the abdominal pain associated with this peritoneal irritation, moderately large doses of sedation and analgesics are required. Nevertheless, our data would indicate that despite these amounts of sedation, no significant CO2 retention or ventricular irritability occurred. The unexpected finding of significant hypertension in 6 patients studied should be evaluated further, however. This observation has also been noted by others, including Smith et al (5) and Peterson (2), but has usually been ascribed to CO,, retention occurring during the procedure. Elevated carbon dioxide levels dilate blood vessels directly and serve as a myocardial depressant, but also stimulate a sympathoadrenal response, which has been postulated to offset the direct effects, resulting in systemic hypertension (6). In our study there seemed to be no correlation between the hypertension occurring and blood gas abnormalities, suggesting that the rise in blood pressure may have been simply a response to painful stimuli. Nevertheless, when using carbon dioxide pneumoperitoneum, significant hypertension may be a potential hazard in certain patients with coronary arteriosclerosis or cerebral vascular disease. Although nitrous oxide may ultimately be the agent of choice for pneumoperitoneum under local anesthesia since it produces no peritoneal irritation, carbon dioxide with sedation and analgesia appears to be a safe alternative. REFERENCES 1. Scott DB, Julian DG: Observations on cardiac arrhythmias during laparoscopy. Br Med J 1:411413, 1972 2. Peterson EP: Anesthesia for laparoscopy. Fertil Steri122:695698, 1971 3. Gordon NLM, Smith L, Swapp GH: Cardiovascular effects of peritoneal insufflation of carbon dioxide for laparoscopy. Br Med J 1:525, 1972 4. Durant TM, Stauffer HM, Oppenheimer MJ, Paul RE: The safety of intravascular carbon dioxide and its use for roentgenologic visualization of intracardiac structures. Ann Intern Med 47:191-301, 1957 5. Smith I, Benzie RJ, Gordon LM, Kelman GR, Swapp GH: Cardiovascular effects of peritoneal insufltation of carbon dioxide for laparoscopy. Br Med J 3:410-411, 1971 6. Tenney SJ: The effect of carbon dioxide on neurohumoral and endocrine mechanisms. Anesthesiology 21:674-688, 1970
467
Thirty consecutive patients undergoing diagnostic' peritoneoscopy using carbon dioxide (COO pneumoperitoneum with local anesthesia were studied to determine the incidence and types of cardiac arrhythmias occurring during the procedure. All patients received heavy sedation with diazepam intravenously and parenteral analgesics when necessary, but no general anesthesia. There was no mortality or unusual morbidity resulting from the procedure. None of the patients developed serious cardiac arrhythmias despite the presence of underlying cardiovascular disease in 16 of them, and none of the patients developed significant carbon dioxide retention or hypoxemia. A potentially dangerous finding was temporary diastolic hypertension occurring in 6 patients. It is concluded that if properly pelformed, peritoneoscopy with carbon dioxide pneumoperitoneum in the conscious patient, despite heavy sedation and analgesia to combat peritoneal irritation, produces no dangerous cardiac arrhythmias. Previous reports of cardiac arrhythmias occurring during the same procedure performed under general anesthesia are discussed.
A 17% incidence of cardiac arrhythmias, mainly ventricular extrasystoles, has been observed during laparoscopy under general anesthesia using carbon dioxide to insufflate the abdomen (1). It has been assumed that these arrhythmias were related to the hypercarbia produced by carbon dioxide pneumoperitoneum (1, 2) and that they can probably be prevented by either substituting nitrous oxide as the insufflating gas or by using controlled hyper: ventilation while the patient is under general anesthesia (3). Internists frequently use peritoneoscopy as a diagnostic tool in patients who are seriously ill and would not tolerate general anesthesia. The avoidance of general anesthesia also simplifies the procedure by eliminating the need for operating-
room time and the presence of an anesthesiologist. The safest agent for the induction of pneumoperitoneum is carbon dioxide because it does not support combustion and is rapidly absorbed. Under local anesthesia, however, carbon dioxide produces significant peritoneal irritation in conscious patients and heavy sedation and analgesics are often required. The present study was undertaken to determine the incidence and types of cardiac arrhythmias occurring during periotoneoscopy with carbon dioxide pneumoperitoneum under local anesthesia rather than general anesthesia.
From the Divisions of Gastroenterology & Cardiology, Department of Medicine, University of Miami School of Medicine, and Veterans Administration Hospital, Miami, Florida. Dr. James L. Bierfeld's present address is Division of Cardiology, University of Miami School of Medicine, Jackson Memorial Hospital, 1700 N.W. Tenth Avenue, Miami, Florida 33136. Dr. Jack R. Groover's present address is Division of Gastroenterology, University Hospital of Jacksonville, 655 West Eighth Street, Jacksonville, Florida 32209. Address for reprint requests! Dr. Bierfeld, Division of Cardiology, University of Miami School of Medicine, Jackson Memorial Hospital, 1700 N.W. Tenth Avenue, Miami, Florida 33136.
A total of 30 patients underwent peritoneoscopy using carbon dioxide to insufflate the abdomen and xylocaine local anesthesia. An American cystoscope fiberoptic pel:itoneoscope (1 cm in diameter) was used in al! patients in conjunction with a WlSAP CO2 [nsufflato~"providing continuous monitoring of intraabdominal pressure and volume of CO2 insufflated. The average duration of the procedure from local anesthetic through wound closure was 45 min with a range of 30--95 min. The actual duration of instrumentation ranged from 15 to 40 rain. 18 of 30 patients had liver biopsies and 4 had peritoneal biopsies.
Digestive Diseases, Vol. 21, No. 6 (June 1976)
MATERIALS AND METHODS
465
GROOVER AND B I E R F E L D TABLE 1. ARRHYTHMIAS DURING PERITONEOSCOPY--FINDINGS IN 10 PATIENTS UNDERGOING TAPE-RECORDED ECG MONITORING*
Patient & age
l. O.K., 25 2. J.F., 46 3. C.W., 50 4. M.M., 59 5. M.H., 54 6. N.N., 54 7. R.W., 62 8. C.M., 50 9. C.S., 78 10. L.A., 58
Diagnosis
Previous heart disease
Chronic hepatitis Cirrhosis; ascites Cirrhosis; carcinoma Hepatitis Chronic hepatitis; COPD Cirrhosis; ascites Ca rectum; cirrhosis TB; peritonitis Cirrhosis; hepatoma; ascites Cirrhosis
Control Pco2
Operative Pco2
None
45 mm Hg
38 mmHg
None
33 mm Hg
33 mm Hg
Old MI
35.8 mm Hg
37.5 mm Hg
Old MI angina Angina pectoris
Not done
Not done
31.5 mm H.g
34 mm Hg
None
32.5 mm Fig
36 mm Hg
HCVD
33 mm Fig
36 mm Hg
None
25 mm Hg
31 mm Hg
CHF
29 mm Hg
40 mm Hg
None
32 mm Hg
36.5 mm Hg
Avionics findings
Sinus tachycardia Sinus tachycardia Sinus tachycardia NSR throughout Sinus tachycardia NSR throughout NSR throughout Sinus tachycardia Sinus bradycardia w/blocked PACs NSR throughout
* Abbreviations: NSR--normal sinus rhythm; MI--myocardial infarction; COPD--chronic obstructive pulmonary disease; TB--tuberculosis; CHF--congestive heart failure; PACs--premature atrial contractions; HCVD--hypertensive cardiovascular disease.
No e of the study patients were receiving antiarrhythmic medications at the time of the procedure; however, 12 were on maintenance digoxin therapy and 22 of 30 were receiving diuretics. Almost all patients wei-e premedicated with diazepam (3-25 mg) intravenously to the point of slurred speech or drowsiness unless contraindicated. In addition, Demerol (25-100 mg) was given parentally as necessary in some patients because of the peritoneal irritation related to the CO2 insufftation, The cardiac activity of the first 20 patients was continuously monitored by observation of electrocardiogram lead 2 on an oscilloscope equipped with a memory loop for immediate printout of any observed arrhythmias. The last 10 consecutive patients were monitored continuously from 30 min prior to the start of the procedure until at least 60 min after the procedure had terminated, by an Avionics Model 350 Electrocardiocorder, providing a continuous record on magnetic tape of all electrocardiographic activity. Standard 12-lead electrocardiograms were obtained before and after the peritoneoscopy procedure in all patients.
Arterial blood gas measurements (pH, Pao2 and Paco2) were obtained prior to premedication and again just prior to deflating the abdomen in 20 patients. In addition, heart rate and blood pressure determination were monitored at 5-rain intervals in 19 patients throughout the procedure. The medical histories of the 10 patients monitored by continuous tape-recorded electrocardiography are summarized in Table 1 and represent a reasonable cross section of the remaining 20 patients. Of the total 30 patients, 16 had prior cardiovascular disease as evidenced by angina pectoris, previous myocardial infarction, left Ventricular hypertrophy, bundle branch block or congestive heart failure. Of these 16 patients, one (M.M.) had undergone aortocoronary bypass one year earlier for disabling angina pectovis. One patient (C.S.) had chronic, premature atrial contractions before peritoneoscopy. 14 other patients had no evidence of cardiac disease. A l l 30 patients were in normal sinus rhythm prior to the procedure, and all cardiac patients were stable.
TABLE 2. MEAN VALUES --+ SD OF PH, Paco2 AND Pao2 OF 20
All 30 p a t i e n t s r e m a i n e d in s i n u s r h y t h m t h r o u g h o u t p e r i t o n e o s c o p y . 5 p a t i e n t s d e v e l o p e d sinus t a c h ycardia, and one patient (C.S.) with preexisting prem a t u r e atrial c o n t r a c t i o n s d e v e l o p e d a s h o r t segm e n t o f sinus t a c h y c a r d i a w i t h b l o c k e d p r e m a t u r e atrial c o n t r a c t i o n s . F u l l 12-iead e l e c t r o c a r d i o g r a m s postperitoneoscopy were unchanged from preo p e r a t i v e t r a c i n g s in all 30 p a t i e n t s . T h e m o s t signif-
CASES RECEIVING CARBON DIOXIDE PNEUMOPERITONEUM UNDER LOCAL ANESTHESIA
pH Pacoz Pao2
466
Before +- SD
During • SD
7.40 -+ 0.04 33.8 • 6.2 79.8 + 16.3
7.38 -+ 0.03 36.0 +- 5.3 81.5 + 14.9
RESULTS
Digestive Diseases, Vol. 21, No. 6 (June 1976)
CARDIAC ARRHYTHMIAS
DURING
PERITONEOSCOPY
icant finding, however, was the absence of any sign of ventricular irritability in any of the patients during and immediately postperitone0scopy. The blood gas observations are summarized in Table 2. There was no significant carbon dioxide retention during peritoneoscopy in any patient. On only two occasions did the Paco2 level rise above 40 mm Hg during the procedure (46 mm Hg and 43 mm Hg). The acid-base balance and the level of oxygenation also remained normal. Of the 19 patients monitored frequently (every 5 min) during the procedure, 6 became significantly hypertensive (diastolic pressure ranging from 100 to 140 mm Hg) returning to normal within 10 min after termination of the procedure. There was no correlation between those who became hypertensive and any observable change in blood gases or preexisting hypertension. 3 of these 6 patients had a rise in diastolic pressure above 30 mm Hg over baseline values. DISCUSSION This study shows that no serious cardiac arrhythmias occurred during peritoneoscopy under local anesthesia with carbon dioxide pneumoperitoneum as opposed to a 17% incidence of arrhythmias previously reported under general anesthesia (1). The choice of a gas to produce peritoneal distention during peritoneoscopy has generally been either room air, oxygen, carbon dioxide, or nitrous oxide. Each of these has its own advantages and disadvantages; however, carbon dioxide is probably the safest due to its rapid absorption in cases of inadvertent air embolism, subcutaneous emphysema, or pneumothorax. Intravenous carbon dioxide has been used diagnostically by cardiologists in amounts up to 100 cc without serious injury in the past (4). In dogs, up to the equivalent of I liter in humans can be given before cardiac output is profoundly altered (4). If the patient is monitored by precordial auscultation during initial insufflation, the typical "mill-wheel" murmur should warn of inadvertent vascular insufflation in time to take appropriate action. This, combined with its inability to support combustion, makes it an ideal agent for peritoneoscopy under general anesthesia. Although Scott and Julian (1) found a significant increase in ventricular irritability using CO., during spontaneous ventilation (under general anesthesia), this may be avoided by meticulous attention to continuous hyperventilation (3). Scott and Julian demonstrated that the use of nitrous oxide also prevents Digestive Diseases, !/ol. 21, No. 6 (June 1976)
CO2 retention and ventricular arrhythmias (1) but, unfortunately, nitrous oxide supports combustion to the same degree as oxygen. The major drawback to carbon dioxide pneumoperitoneum under local anesthesia, in our experience, has been the significant incidence of peritoneal irritation (30-50%). In order to combat the abdominal pain associated with this peritoneal irritation, moderately large doses of sedation and analgesics are required. Nevertheless, our data would indicate that despite these amounts of sedation, no significant CO2 retention or ventricular irritability occurred. The unexpected finding of significant hypertension in 6 patients studied should be evaluated further, however. This observation has also been noted by others, including Smith et al (5) and Peterson (2), but has usually been ascribed to CO,, retention occurring during the procedure. Elevated carbon dioxide levels dilate blood vessels directly and serve as a myocardial depressant, but also stimulate a sympathoadrenal response, which has been postulated to offset the direct effects, resulting in systemic hypertension (6). In our study there seemed to be no correlation between the hypertension occurring and blood gas abnormalities, suggesting that the rise in blood pressure may have been simply a response to painful stimuli. Nevertheless, when using carbon dioxide pneumoperitoneum, significant hypertension may be a potential hazard in certain patients with coronary arteriosclerosis or cerebral vascular disease. Although nitrous oxide may ultimately be the agent of choice for pneumoperitoneum under local anesthesia since it produces no peritoneal irritation, carbon dioxide with sedation and analgesia appears to be a safe alternative. REFERENCES 1. Scott DB, Julian DG: Observations on cardiac arrhythmias during laparoscopy. Br Med J 1:411413, 1972 2. Peterson EP: Anesthesia for laparoscopy. Fertil Steri122:695698, 1971 3. Gordon NLM, Smith L, Swapp GH: Cardiovascular effects of peritoneal insufflation of carbon dioxide for laparoscopy. Br Med J 1:525, 1972 4. Durant TM, Stauffer HM, Oppenheimer MJ, Paul RE: The safety of intravascular carbon dioxide and its use for roentgenologic visualization of intracardiac structures. Ann Intern Med 47:191-301, 1957 5. Smith I, Benzie RJ, Gordon LM, Kelman GR, Swapp GH: Cardiovascular effects of peritoneal insufltation of carbon dioxide for laparoscopy. Br Med J 3:410-411, 1971 6. Tenney SJ: The effect of carbon dioxide on neurohumoral and endocrine mechanisms. Anesthesiology 21:674-688, 1970
467
