Lack of reactivity of uterine arteries from patients with obstetric hemorrhage

Management of postpartum haemorrhage with uterine balloon tamponade: The way forward

Uterine balloon tamponade has rapidly gained popularity in the management of postpartum haemorrhage. It is a conservative method often utilised before embarking on advanced surgical interventions. The mechanism of action, complications and long-term outcomes are discussed.

Ultrasonographic visualization of balloon placement for uterine tamponade in massive primary postpartum hemorrhage

This case report is the first documentation of ultrasonographic confirmation of positioning of a Sengstaken-Blakemore balloon catheter (SBEC) in the management of massive postpartum hemorrhage. The sonongraphic position, while incorrect according to conventional use of uterine balloon catheters, raises the possibility of an alternative mechanism of action of the balloon: not uterine cavity tamponade but hydrostatic pressure directly around the uterine arteries, a mechanism akin to mechanical uterine artery embolization or ligation. If this hypothesis is correct, it not only elucidates how balloon tamponade works but also challenges current thinking on how postpartum hemorrhage should be managed effectively. Future studies are required to corroborate this hypothesis and we believe that sonographic confirmation of balloon catheter location should be an integral part of uterine balloon tamponade in women with massive primary postpartum hemorrhage.

Preeclampsia selectively impairs endothelium-dependent relaxation and leads to oscillatory activity in small omental arteries

The vascular pathophysiology of preeclampsia, a hypertensive disorder unique to human pregnancy, has been postulated to be due to endothelial dysfunction, primarily manifest as deficient nitric oxide (NO) synthesis. We evaluated contraction (KCl and arginine vasopressin [AVP]) and dilation (acetylcholine and bradykinin) in small resistance-size omental arteries obtained during surgery from women with preeclampsia, postulating that these vessels would exhibit augmented contraction and diminished endothelium-dependent relaxation, most likely due to decreased NO synthesis. For comparison, vessels were also obtained from normotensive gravidas, pregnant women with chronic hypertension, or with chronic hypertension and superimposed preeclampsia, as well as from premenopausal nonpregnant controls. Vessels of approximately 200 micron in internal diameter were studied in vitro using a Mulvany-Halpern myograph. Maximal contraction due to either KCl or AVP was significantly augmented in vessels from women with preeclampsia; these vessels all exhibited endothelium- and cyclooxygenase-dependent phasic oscillations while vessels from all other groups exhibited only tonic contractions. Acetylcholine and bradykinin both led to dose- and endothelium-dependent relaxation which was unaffected by inhibitors of NO synthesis. Responses to bradykinin were similar in vessels from normal pregnant and preeclamptic women while those to acetylcholine were absent in vessels from women with preeclampsia. These data suggest specific defects in resistance-artery endothelium from women with preeclampsia.

Characterization of arginine vasopressin actions in human uterine artery: lack of role of the vascular endothelium

1. The effect of arginine vasopressin (AVP) on human uterine artery rings, both intact and denuded of endothelium, was investigated. 2. Initially, AVP (63 pM-32 nM) induced concentration-dependent contraction of human uterine artery (pD2 = 8.92 +/- 0.01). Removal of the endothelium did not affect the concentration-response curve for AVP (pD2 = 8.83 +/- 0.03). 3. In contrast, human uterine arteries, both intact and denuded of endothelium, did not respond to the addition of 1-desamino-8-D-arginine vasopressin (dDAVP, 1 nM-1 microM). 4. In both types of preparations, [d(CH2)5Tyr(Me)AVP (1-10 nM) and [d(CH2)5,D-Ile2,Ile4]AVP (300 nM-3 microM) produced parallel rightward shifts of the curves for AVP. The Schild plots constrained to a slope of unity gave the following -log KB values: [d(CH2)5Tyr(Me)]AVP vs. [d(CH2)5,D-Ile2,Ile4]AVP 9.66 vs. 6.69 and 9.61 vs. 6.80 for human uterine artery, intact and denuded of endothelium, respectively. 5. The pKA values for AVP itself also did not differ between preparations: 6.56 and 6.43 for human uterine artery with and without endothelium, respectively. In both types of preparations, the receptor reserve (KA/EC50) was considerably greater than unity (intact vs. denuded: 228 vs. 244). 6. It is concluded that, in human uterine artery, AVP induces contractions that are not modulated by the endothelium. It is likely that AVP acts as a full agonist on human uterine artery, regardless of the endothelial condition. On the basis of differential antagonists affinity and affinity of AVP itself, it is probable that vasopressin receptors involved in AVP-induced contraction in human uterine arteries belong to the V1a or V1a-like subtype.

Effect of pregnancy on vasopressin-mediated responses in guinea-pig uterine arteries with intact and denuded endothelium

The effect of pregnancy on vasopressin-induced contraction of guinea-pig uterine arterial rings was investigated. Initially, vasopressin induced contraction (pD2 = 9.14) in pregnant guinea-pig uterine artery with greater potency than in non-pregnant guinea-pig uterine artery (pD2 = 8.77). Removal of the endothelium did not affect vasopressin-induced contractions, regardless of pregnancy status. In all types of preparations, [d(CH2)5Tyr(Me)2]vasopressin (10-100 nM) and [d(CH2)5,D-Ile2,Ile4]vasopressin (300 nM-3 microM) produced parallel rightward shifts of the curves for vasopressin. The Schild plots constrained to a slope of unity gave the following -log KB values: [d(CH2)5Tyr(Me)2]vasopressin vs. [d(CH2)5,D-Ile2,Ile4]vasopressin 8.74 vs. 6.82 and 8.50 vs. 6.72 for non-pregnant guinea-pig uterine artery with intact and denuded endothelium, respectively; 8.38 vs. 6.49 and 8.36 vs. 6.75 for pregnant guinea-pig uterine artery with intact and denuded endothelium, respectively. The pKA values for vasopressin itself also did not differs between preparations: 6.49 and 6.55 for non-pregnant guinea-pig uterine artery with intact and denuded endothelium, respectively; 6.48 and 6.52 for pregnant guinea-pig uterine artery with intact and denuded endothelium, respectively. The receptor reserve (KA/EC50) was significantly greater in preparations taken from pregnant than from non-pregnant animals. It is concluded that vasopressin-induced contractions of guinea-pig uterine artery are not modulated by the endothelium, regardless of pregnancy status. The receptor reserve for vasopressin in guinea-pig uterine artery is increased during pregnancy, that is not related to the changes of vasopressin receptor affinity for vasopressin. It is probable that vasopressin receptors involved in vasopressin-induced contraction of all types of vessels studied belong to the V1A-like subtype.

Stepwise uterine devascularization: a novel technique for management of uncontrolled postpartum hemorrhage with preservation of the uterus

OBJECTIVE

The objective of this study was to test the efficacy of a novel stepwise technique of uterine devascularization for management of uncontrollable postpartum hemorrhage.

STUDY DESIGN

Stepwise uterine devascularization was performed for 103 patients to control intractable postpartum hemorrhage not responding to classic management. This technique entails five successive steps, so if bleeding is not controlled by one step the next step is taken until bleeding stops. The steps were (1) unilateral uterine vessel ligation, (2) bilateral uterine vessel ligation, (3) low uterine vessel ligation, (4) unilateral ovarian vessel ligation and (5) bilateral ovarian vessel ligation.

RESULTS

The procedure was effective in all cases (100%), and hysterectomy was not needed in any case. No complications occurred, and the survival rate was 100%. Among the patients followed up normal menstruation and pregnancy occurred.

CONCLUSION

Stepwise uterine devascularization is an effective and safe alternative to hysterectomy for management of uncontrollable postpartum hemorrhage.