Transcutaneous CO2/O2 and CO2/air suction in patients undergoing cataract surgery with retrobulbar anaesthesia

The effect of a forced-air warming blanket on patients' end-tidal and transcutaneous carbon dioxide partial pressures during eye surgery under local anaesthesia: a single-blind, randomised controlled trial

Surgical drapes used during eye surgery are impermeable to air and hence risk trapping air underneath them. We investigated the effect of a forced-air warming blanket on carbon dioxide accumulation under the drapes in patients undergoing eye surgery under local anaesthesia without sedation. Forty patients of ASA physical status 1 and 2 were randomly assigned to either the forced-air warmer (n = 20) or a control heated overblanket (n = 20). All patients were given 1 l.min(-1) oxygen. We measured transcutaneous and end-tidal carbon dioxide partial pressures, heart rate, arterial pressure, respiratory rate, temperature and oxygen saturation before and after draping, then every 5 min thereafter for 30 min. The mean (SD) transcutaneous carbon dioxide partial pressure in the forced-air warming group stayed constant after draping at 5.7 (0.2) kPa but rose to a maximum of 6.4 (0.4) kPa in the heated overblanket group (p = 0.0001 for the difference at time points 15 min and later). We conclude that forced-air warming reduces carbon dioxide accumulation under the drapes in patients undergoing eye surgery under local anaesthesia.

Effect of Single-Dose fentanyl on the cardiorespiratory system in elderly patients undergoing cataract surgery

STUDY OBJECTIVES

To evaluate the effects of fentanyl on the cardiorespiratory system in elderly patients undergoing cataract surgery with phacoemulsification method.

DESIGN

Randomized, prospective, double-blind study.

SETTING

University hospital.

PATIENTS

70 ASA physical status I, II, and III patients (>60 years) who underwent cataract surgery with topical anesthesia.

INTERVENTIONS

Patients were randomly divided into two groups. The fentanyl group (35 patients) received fentanyl in 0.7 microg/kg bolus doses in a 2-mL balanced salt solution prior to surgery. The control group (35 patients) received a 2-mL balanced salt solution without any analgesic drug.

MEASUREMENTS AND MAIN RESULTS

Systolic (SBP), diastolic (DBP), mean arterial pressure (MAP), heart rate (HR), peripheral oxygen saturation (SpO(2)), respiratory rate (RR), end-tidal carbon dioxide (ETCO(2)), inspired CO(2) concentration, and sedation scores were measured preoperatively and at 5, 10, 15, 20, and 30 minutes intraoperatively. Postoperatively, patients were questioned about the presence of intraoperative pain. In the fentanyl group, no significant differences were observed in SPB, DBP, MAP, RR, or peripheral SpO(2). In the control group, RR was higher than baseline values at 10, 15, and 20 minutes. Diastolic blood pressure was higher than baseline values at 20 minutes. End-tidal CO(2) and inspired CO(2) levels were higher than baseline levels in both groups at all measurement times. Intraoperative ETCO(2) levels were higher in the fentanyl group than the control group (p < 0.01). Finally, no hypoxemia was observed in either group.

CONCLUSION

Fentanyl can be used safely in 0.7-microg/kg dosages in elderly patients to improve patient comfort without any cardiorespiratory side effects, when undergoing cataract surgery with topical anesthesia.

Effectiveness of oxygenation and suction in cataract surgery: is suction of CO2-enriched air under the drape during cataract surgery necessary?

PURPOSE

To investigate the effectiveness of aspiration of expired air by a suction system on peripheral oxygen saturation (SpO(2)) and end tidal carbon dioxide (EtCO(2)) during cataract surgery.

MATERIALS AND METHODS

In total, 160 pre-medicated patients aged between 40 and 70 years (ASA I-III, classification of patients according to the American Society of Anesthesiologists) scheduled for cataract surgery under retrobulbar or peribulbar block were examined in a randomised, single-blind manner. The patients were sedated with 3 mg midazolam i.v. 15 min before operation and were monitored with an anaesthesia monitor. Heart rate (HR), non-invasive mean arterial pressure (MAP), SpO(2) and EtCO(2) were continuously measured using a standardised monitor. The first group (non-suction group, n = 80) received 4 L min(-1) O(2) with nasal cannule while the second group (suction group, n = 80) received 4 L min(-1) O(2) with nasal cannule, and the expired air was aspired with a Y-piece suction system. EtCO(2) was measured with the line of the sampling tube in the anaesthesia monitor. Respiratory rate (RR) was counted for a period of 1 min at each measurement time with thoracic excursions. The results were evaluated by unpaired t-test and analysis of variance.

RESULTS

Severe reduction of SpO(2) and raising of EtCO(2) were observed significantly in the first group during the operation. RR, HR and MAP increased due to hypoxaemia. In the second group, SpO(2) was stabilised at high levels and EtCO(2) did not increase. RR, HR and MAP levels remained within the normal limits. Differences between the two groups were statistically significant (P < 0.05).

CONCLUSION

During cataract surgery with local anaesthesia, SpO(2) decreases and RR, HR and MAP increase because of reinspiration of expired air under the drape. Insufflation of O(2) and aspiration of expired air with a suction system have prevented severe reduction of SpO(2) and raising of EtCO(2). It was suggested that O(2) delivery and use of an aspiration system decreased the risk of hypoxaemia significantly in the patients undergoing the cataract surgery.

A simple and inexpensive nasal cannula to prevent rebreathing for spontaneously breathing patients under surgical drapes

IMPLICATIONS

A new nasal cannula that provides oxygenation and suctioning simultaneously prevents rebreathing during surgery in spontaneously breathing patients under surgical drapes. When air is not suctioned, inspired CO(2) levels increase significantly, whereas suctioning prevents this increase. Expiratory CO(2), respiratory rate, heart rate, and arterial blood pressure remain stable regardless of suctioning.

Oxygen application by a nasal probe prevents hypoxia but not rebreathing of carbon dioxide in patients undergoing eye surgery under local anaesthesia

BACKGROUND/AIM

Hypoxia and carbon dioxide rebreathing are potential problems during eye surgery in spontaneously breathing patients. The aim of the present study was to determine effectiveness of nasal application of oxygen to prevent hypoxia and carbon dioxide accumulation in spontaneously breathing patients undergoing cataract surgery.

METHODS

Oxygenation and carbon dioxide rebreathing were examined in 40 elderly patients using two different methods of oxygen supply-nasal v ambient air-with a constant flow of 2 l/min. Partial pressure of carbon dioxide under ophthalmic drapes, transcutaneous pressure of carbon dioxide, and the respiratory rate were measured during 25 minutes while oxygen was supplied via a nasal cannula or into the ambient air under the drapes.

RESULTS

In both groups carbon dioxide accumulation under the drapes, carbon dioxide rebreathing, tachypnoea, and an increase in peripheral oxygen saturation occurred. No significant differences were found between the two methods.

CONCLUSION

Nasal application of oxygen prevented hypoxia but did not prevent carbon dioxide accumulation in patients undergoing eye surgery under retrobulbar anaesthesia. Additionally, as a side effect when using nasal probes, irritation of the nose was described in half of the patients investigated.

New equipment to prevent carbon dioxide rebreathing during eye surgery under retrobulbar anaesthesia

BACKGROUND

Carbon dioxide concentration under ophthalmic drapes increases during eye surgery under local anaesthesia. A new prototype has been designed which combines continuous suction of carbon dioxide enriched air and continuous oxygen insufflation under ophthalmic drapes to prevent carbon dioxide accumulation in spontaneously breathing patients undergoing cataract surgery.

METHODS

In a prospective randomised single blind study the effectiveness of this new prototype was examined in 50 unpremedicated elderly patients. In 25 patients suction was applied under ophthalmic drapes, whereas in the other 25 patients no suction was used. In all cases oxygen was insufflated under the drapes at a constant flow of 2 l/min. Carbon dioxide concentration in the ambient air surrounding the patient's head under ophthalmic drapes, transcutaneous partial pressure of carbon dioxide, respiratory rate, and oxygen saturation were measured.

RESULTS

Carbon dioxide concentration under the drapes, transcutaneous partial pressure of carbon dioxide, and respiratory rate remained unchanged in the suction group, whereas in the non-suction group these values increased significantly. Oxygen saturation rose significantly in both groups without differences between the groups.

CONCLUSION

Application of this new prototype for continuous aspiration of carbon dioxide enriched air prevents carbon dioxide rebreathing and subsequent hypercapnia associated with an elevated respiratory rate. This new equipment may therefore be useful in patients undergoing ophthalmic surgery under retrobulbar anaesthesia.

Accumulation of carbon dioxide under ophthalmic drapes during eye surgery: a comparison of three different drapes

Carbon dioxide accumulation under ophthalmic drapes is caused by their impaired permeability to exhaled carbon dioxide in spontaneously breathing patients. Three different ophthalmic drapes were examined under clinical conditions. Sixty unpremedicated patients of each gender, aged over 60 years and with an ASA status of I-III undergoing cataract surgery under retrobulbar anaesthesia were included in the study. Patients with known pulmonary diseases were excluded. The patients were divided into three groups of 20 patients each. In all groups, oxygen was insufflated under the drapes at a constant flow of 21.min-1. Carbon dioxide concentration in the inspired air, transcutaneous carbon dioxide pressures, respiratory rate and oxygen saturation by pulse oximetry were measured. Accumulation of carbon dioxide under the drapes, increase of partial pressure of transcutaneous carbon dioxide and hyperventilation were observed in all three groups. An oxygen supply of 21.min-1 prevented hypoxaemia but not hypercapnia. Therefore, producers of ophthalmic drapes are encouraged to look for further ways to increase the carbon dioxide permeability of their drapes with the aim of reducing carbon dioxide accumulation and hyperventilation in spontaneously breathing patients undergoing eye surgery.