Venous air embolism and cesarean sections

Maternal position during caesarean section for preventing maternal and neonatal complications

BACKGROUND

During caesarean section mothers can be in different positions. Theatre tables could be tilted laterally, upwards, downwards or flexed and wedges or cushions could be used. There is no consensus on the best positioning at present.

OBJECTIVES

We assessed all available data on positioning of the mother to determine if there is an ideal position during caesarean section that would improve outcomes.

SEARCH METHODS

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (20 August 2012), PubMed (1966 to 20 August 2012) and manually searched the references of retrieved articles.

SELECTION CRITERIA

Randomised trials of woman undergoing caesarean section comparing different positions.

DATA COLLECTION AND ANALYSIS

Two review authors assessed eligibility, trial quality and extracted data.

MAIN RESULTS

We identified 22 studies with a total of 857 women included. We included 11 studies and excluded 11. Included trials were of variably quality with small sample sizes. Most comparisons had data from single trials. This is a shortcoming and applicability of results is limited.The incidence of air embolism was not affected by head up versus horizontal position (average risk ratio (RR) 0.85; 95% confidence interval (CI) 0.28 to 2.57; Tau² = 0.50; I² = 74%).We found no change in hypotensive episodes when comparing left lateral tilt (RR 0.11; 95% CI 0.01 to 1.94), right lateral tilt (RR 1.25; 95% CI 0.39 to 3.99), a right lumbar pelvic wedge (RR 0.85; CI 0.53 to1.37) and head down tilt (RR 1.07; 95% CI 0.81 to 1.42) with horizontal positions. We found no change in hypotensive episodes when comparing full lateral tilt with 15-degree tilt (RR 1.20; 95% CI 0.80 to 1.79). Hypotensive episodes were decreased with manual displacers (RR 0.11; 95% CI 0.03 to 0.45), and increased with a right lumbar wedge compared with a right pelvic wedge (RR 1.64; 95% CI 1.07 to 2.53) and increased with a right lateral tilt compared with a left lateral tilt (RR 3.30; 95% CI 1.20 to 9.08).Position did not affect systolic blood pressure when comparing left lateral tilt (MD 2.70; 95% CI -1.47 to 6.87) or head down tilt (MD -3.00; 95% CI -8.38 to 2.38) with horizontal positions, or full lateral tilt with 15-degree tilt (MD -5.00; 95% CI -11.45 to 1.45). Manual displacers showed decreased fall in mean systolic blood pressure compared with left lateral tilt (MD -8.80; 95% CI -13.08 to -4.52).Position did not affect diastolic blood pressures when comparing left lateral tilt versus horizontal positions (MD-1.90; 95% CI -5.28 to 1.48). The mean diastolic pressure was lower in head down tilt (MD -7.00; 95% CI -12.05 to -1.95) when compared with horizontal positions.There were no statistically significant changes in maternal pulse rate, five-minute Apgars, maternal blood pH or cord blood pH when comparing different positions.

AUTHORS' CONCLUSIONS

There is limited evidence to support or clearly disprove the value of the use of tilting or flexing the table, the use of wedges and cushions or the use of mechanical displacers. A left lateral tilt may be better than a right lateral tilt and manual displacers may be better than a left lateral tilt but larger studies with more robust data are needed to confirm these findings.

Maternal position during caesarean section for preventing maternal and neonatal complications

BACKGROUND

During caesarean section mothers can be in different positions. Theatre tables could be tilted laterally, upwards, downwards or flexed and wedges or cushions could be used. There is no consensus on the best positioning at present.

OBJECTIVES

We assessed all available data on positioning of the mother to determine if there is an ideal position during caesarean section that would improve outcomes.

SEARCH STRATEGY

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (September 2009), PubMed (1966 to 14 September 2009) and manually searched the references of retrieved articles.

SELECTION CRITERIA

Randomised trials of woman undergoing caesarean section comparing different positions.

DATA COLLECTION AND ANALYSIS

Two authors assessed eligibility, trial quality and extracted data.

MAIN RESULTS

We identified 17 studies with a total of 683 woman included. We included nine studies and excluded eight studies. Included trials were of variably quality with small sample sizes. Most comparisons had data from single trials. This is a shortcoming and applicability of results is limited.The incidence of air embolism was not affected by head up versus horizontal position (risk ratio (RR) 0.91; 95% confidence interval (CI) 0.65 to 1.26). We found no change in hypotensive episodes when comparing left lateral tilt (RR 0.11; 95% CI 0.01 to 1.94), right lateral tilt (RR 1.25; 95% CI 0.39 to 3.99) and head down tilt (mean difference (MD) -3.00; 95% CI -8.38 to 2.38) with horizontal positions or full lateral tilt with 15-degree tilt (RR 1.20; 95% CI 0.80 to 1.79). Hypotensive episodes were decreased with manual displacers (RR 0.11; 95% CI 0.03 to 0.45), a right lumbar wedge compared to a right pelvic wedge (RR 1.64; 95% CI 1.07 to 2.53) and increased in right lateral tilt (RR 3.30; 95% CI 1.20 to 9.08) versus left lateral tilt.Position did not affect systolic blood pressure when comparing left lateral tilt (MD 2.70; 95% CI -1.47 to 6.87) or head down tilt (RR 1.07; 95% CI 0.81 to 1.42) to horizontal positions, or full lateral tilt with 15-degree tilt (MD -5.00; 95% CI -11.45 to 1.45). Manual displacers showed decreased fall in mean systolic blood pressure compared to left lateral tilt (MD -8.80; 95% CI -13.08 to -4.52).Position did not affect diastolic blood pressures when comparing left lateral tilt versus horizontal positions. (MD-1.90; 95% CI -5.28 to 1.48). The mean diastolic pressure was lower in head down tilt (MD -7.00; 95% CI -12.05 to -1.95) when compared to horizontal positions.There were no statistically significant changes in maternal pulse rate, five-minute Apgars, maternal blood pH or cord blood pH when comparing different positions.

AUTHORS' CONCLUSIONS

There is limited evidence to support or clearly disprove the value of the use of tilting or flexing the table, the use of wedges and cushions or the use of mechanical displacers. Larger studies are needed.

Complete recovery after near-fatal venous air embolism during cesarean section

During replacement to the abdomen of the exteriorized uterus at cesarean section under epidural block, a previously healthy woman developed cardiorespiratory arrest. Tracheal intubation revealed low end-tidal carbon dioxide concentration suggesting embolization. Resuscitative efforts were successful. Uterine exteriorization - as well as the Trendelenburg position - significantly increase the risk of air embolization so that routine use of appropriate monitors is indicated to facilitate early diagnosis.

Amniotic fluid embolus

A case report of a 27-yr-old healthy patient for Caesarean section under epidural anaesthesia is presented. The patient suffered an acute cardiorespiratory collapse when the infant's head was being delivered through the anterior abdominal wall. The patient remained cyanosed after proper tracheal intubation and pulmonary ventilation with 100% O2. Hypotension was difficult to treat but returned to normal 25 min after the event. A pulmonary artery catheter inserted three hours after the event showed normal pressures and a high cardiac output. The patient suffered permanent neurological damage. The differential diagnosis is discussed and current concepts of the aetiology and management of amniotic fluid embolism reviewed.

Venous emboli occurring caesarean section: the effect of patient position

The effect of position, horizontal versus 5 degrees reverse Trendelenburg's, on the incidence of venous emboli during Caesarean section was evaluated in 207 patients. Venous emboli were diagnosed using precordial ultrasonic Doppler monitoring. In the horizontal position, 44% (60 of 134) parturients had venous emboli compared with 1% (1 of 73) parturients in the 5 degrees reverse Trendelenburg's position (P less than 0.0001). Epidural anaesthesia was performed in 171 patients, and 36 patients had general anaesthesia. In the epidural group, pulse oximetric haemoglobin oxygen desaturation and complaints of chest pain and/or dyspnoea were associated with the venous emboli. Venous emboli, probably air, occur frequently during Caesarean section with the patient in the horizontal position. This occurrence was minimized by placing the patient in the 5 degrees reverse Trendelenburg's position.

Precordial Doppler diagnosis of haemodynamically compromising air embolism during caesarean section

This is a report of a 39-year-old parturient who had a haemodynamically compromising venous air embolism during a repeat Caesarean section under lumbar epidural anaesthesia. The embolism occurred immediately after surgical incision during surgery in the superficial subcutaneous tissues. The diagnosis was made using intraoperative precordial ultrasonic Doppler monitoring which allowed early and successful treatment.

Fatal air embolism as a complication of laser-induced hyperthermia

Laser-induced hyperthermia is a new treatment modality for malignancies. When large tumors are treated with laser thermia, relatively high laser powers (4-6 W) must be used to accomplish destruction of the cancerous cells. Overheating and burning of the laser fibers and contact tips during laser thermia treatment must be prevented by using coaxial gas or fluid flow. The present report describes a case of fatal air embolism as a complication of laser thermia using coaxial gas. The authors warn all surgeons performing this procedure not to use coaxial air flow for cooling the contact tips because of the potential risk of air embolism.